Graft Polymerization of Methyl Methacrylate Onto Polytetrafluoroethylene Free Radicals

GRAFT POLYMERIZATION OF METHYL METHACRYLATE ONTO POLYTETRAFLUOROETHYLENE FREE RADICALS

A Thesis Presented to The Faculty of the College of Engineering and Technology Ohio University

In Partial Fulfillment of the Requirement for the Degree Master of Science

by Karen Ann Donato November, 1985

OHIO UNIVERSITY LIBRARY TABLE OF CONTENTS

List of Tables ••••••••••••••••••••••••••••••••••••••••••••••••••••••••4 Li st of Figures •••••••••••••••••••••••••••••••••••••••••••••••••••••••5

~knowledgement •••••••••••••••••••••••••••••••••••••••••••••••••••••••9

I. Introduction •••••••••••••••••••••••••••••••••••••••••••••••••••10

II. Radiation Effects on Polytetrafluoroethylene 11.1. Effects of Radiation on the Structure of Polymers ••••••12 11.2. The Structure of Polytetrafluoroethylene•••••••••••••••13 11.3. Effects of Radiation on the Structure of Polytetrafluoroethylene••••••••••••••••••••••••••••••••15

III. Methyl Methacrylate Free Radical Polymerization 111.1. Free Radical Chain Polymerization ••••••••••••••••••••••19 111.2. Methyl Methacrylate Homopolymerization •••••••••••••••••21 111.3. ~l Effect •••••••••••••••••••••••••••••••••••••••••••••22

IV. Experimental Apparatus and Procedures IV.l. Kinetics Experiments •••••••••••••••••••••••••••••••••••24 IV.2. Infrared Transmittance Measurements ••••••••••••••••••••26 IV.3. Electron Spin Resonance Measurements •••••••••••••••••••28 IV.4. Differential Scanning Calorimetry••••••••••••••••••••••28 2

V. Results

V.I. Kinetics Data••••••••••••••••••••••••••••••••••••••••••30 V.I.a. Effects of Preheating the Monomer •••••••••••••••••30 V.I.b. Effects of PTFE:MMA Ratio •••••••••••••••••••••••••31 V.I.c Effects of Temperature••••••••••••••••••••••••••••32 V.I.d Effects of Hydroquinone •••••••••••••••••••••••••••32

V.I.e Effects of Different Grades of PTFE •••••••••••••••33 V.I.f Extractions•••••••••••••••••••••••••••••••••••••••34

V.2. DSC Scans ••••••••••••••••••••••••••••••••••••••••••••••34 V.3. Fourier Transform Infrared Scans•••••••••••••••••••••••35 V.4. Electron Spin Resonance ••••••••••••••••••••••••••••••••35

VI. Discussion of Results

VI.I. Kinetics Results •••••••••••••••••••••••••••• e ••••••••••37 VI.I.a. Development of Kinetics Equations •••••••••••••••••37 VI.I.b. Temperature Effects •••••••••••••••••••••••••••••••43 VI.I.c. Ratio Effects •••••••••••••••••••••••••••••••••••••44

VI.I.d. Gel Effect at 353K(80°C) ••••••••••••••••••••••••••45 VI.I.e. Comparison with Literature Values •••••••••••••••••47

VI.2. DSC Results ••••••••••••••••••••••••••••••••••••••••••••49 VI.3. FTIR Results •••••••••••••••••••••••••••••••••••••••••••51 VI.4. Electron Spin Resonance ••••••••••••••••••••••••••••••••52 3

VII Properties of the PMMA-PTFE Graft

VII.I. Physical Appearance ••••••••••••••••••••••••••••••••••••53 VII.2. Stability••••••••••••••••••••••••••••••••••••••••••••••53 VII.3. Moldability••••••••••••••••••••••••••••••••••••••••••••53 VII.4. Possible Applications of the Graft Polymer •••••••••••••54

VIII Summary

VIII.!. Conclusions ••••••••••••••••••••••••••••••••••••••••••••57 VIII.2. Recommendations for Future Work ••••••••••••••••••••••••60

References •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••63

Appendices •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••67

A. Properties of Methyl Methacrylate ••••••••••••••••••••••67 B. Properties of Polytetrafluoroethylene••••••••••••••••••68 c. Summary of Variables •••••••••••••••••••••••••••••••••••69 D. Experiment Codes •••••••••••••••••••••••••••••••••••••••70 E. Sample Codes •••••••••••••••••••••••••••••••••••••••••••71

~stract ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••112 4

List of Tables

Table Page 1. Experiment 3: Reaction data at 333K(60°C) with 1 gram PTFE(L-169):3 milliliters MMA(DuPont) at room temperature ••••••••••••••••••••••••••••••••••••••••••••••72

2. Experiment 4: ~eaction data at 133K(60°C) with 1 gram PTFE(L-169):3 milliliters MMA(DuPont) at the reaction temperature•••••••••••••••••••••••••••••••••••••••••• 7~ 3. Experiment 5: Reaction data at 333K(60°C) with 1 gram PTFE(L-16Q):5 milliliters MMA(DuPont) at the reaction temperature ••••••••••••••••••••••••••••••••••••••73 4. Experiment 6: Reaction data at 353K(80°C) with 1 gram 'PTFE(L-169):3 milliliters MMA(DuPont) at the reaction temperature••••••••••••••••••••••••••••••••••••••73 5. Experiment 7: Effects of hydroquinone on post polymerization:reaction data at 353K(80°C) with 1.5 gram PTFE(L-169):2 milliliters MMA(Fisher) at the reaction temperature ••••••••••••••••••••••••••••••••••••••74 6. Experiment 8: Reaction data at 343K(70°C) with 2 grams PTFE(Polymist~ F 5-A):5 milliliters MMA at 273.2K(O.2°C) •••••••••••••••••••••••••••••••••••••••••••••••••74 7. Experiment 9: Reaction data at approximately 353K(80°C) with different ratios of PTFE( L-171) : MMA( Fi sher) •••••••••••••••••••••••••••••••••••••••74 8. Residue after evaporation of the acetone used for extractions•••••••••••••••••••••••••••••••••••••••••••••••75 9. Results of DSC Scans••••••••••••••••••••••••••••••••••••••••••75 10. Mass Ratios of PMMA to PTFE in the graft polymer as determined by FTIR •••••••••••••••••••••••••••••••••••••••••76 11. Kinetics constants and linear correlation coefficents as defined by equation VI.1.19 ••••••••••••••••••••76 5

List of Figures

Figure Page 1. Schematic diagram of a crystalline sheet of sintered PTFE(not to scale). The striation length includes amorphous material on the hexagonal faces formed by chain ends, irregular folds, and tie molecules (from Reference 9) ••••••••••••••••••••••••••••••••••••••••••••••••••77 2. Models of the PTFE chain above and below the 292K(19°C) transitions(from Reference 8) •••••••••••••••••••••••••••••••••77 3. Experiment 3: Conversion(%) vs. time(min.) at 333K(60°C) with 1 gram PTFE(L-169):3 milliliters MMA(OuPont) at room temperature•••••••••••••••••••••••••••••••78 4. Experiment 4: Conversion(%) vs. time(min.) at 333K(60°C) with 1 gram PTFE(L-169):5 milliliters MMA(OuPont) at the reaction temperature •••••••••••••••••••••••79 5. Experiment 5: Conversion(%) vs. time(min.) at 333K(60°C) with 1 gram PTFE(L-169):5 milliliters . MMA(OuPont) at the reaction temperature •••••••••••••••••••••••80 6. Experiment 6: Conversion(%) vs. time(min.) at 353K(80°C) with 1 gram PTFE(L-169):3 milliliters MMA(OuPont) at the reaction temperature •••••••••••••••••••••••81 7. Experiment 7: Effects of hydroquinone on post polymerization: conversion(%) vs. time(min.) at 353K(80°C) with 1.5 gram PTFE(L-169):2 milliliters MMA(Fisher) at room temperature •••••••••••••••••••••••••••••••82 8. Experiment 8: Conversion(%) vs. time(min.) at 343K(70°C) with 2 grams PTFE(Polymist® F5-A):5 milliliters MMA(OuPont) at 273.2K(O.2°C) ••••••••••••••••••••••83 9. Experiment 8: Conversion(%) vs. 1n time(min.) at 343K(70°C) with 2 grams PTFE(Polymist® F-5A): 5 milliliters MMA(OuPont) at 273.2K(O.2°C) ••••••••••••••••••••84 10. FTIR scan of the residue in the acetone after extraction of graft sample 80-145B made at 353K(80°C) for 145 minutes with 1 gram PTFE(L-169):3 milliliters MMA(OuPont) at the reaction temperature •••••••••••••••••••••••85 6

List of Figures (continued)

11. DSC scan of L-169 •••••••••••••••••••••••••••••••••••••••••••••86 12a. OSC scan of graft sample 80-558 made at 353K(80°C) for 55 minutes with 1 gram PTFE(L-169):3 milliliters MMA(DuPont) at the reaction temperature; first run of melting and recrystallization••••••••••••••••••••••••••••••87 12b. OSC scan of 80-558 (same sample as in figure 12a); second run of melting and recrystallization•••••••••••••••••••88 12c. Duplicate DSC run of the sample 80-558 used in figure 12a ••••••••••••••••••••••••••••••••••••••••••••••••••••89 13a. DSC scan of graft sample 80-908 made at 353K(80°C) for 90 minutes with 1 gram PTFE(L-169):3 milliliters MMA(OuPont) at the reaction temperature •••••••••••••••••••••••90 13b. Duplicate DSC run of sample 80-908••••••••••••••••••••••••••••91 14a. FTIR scan of graft sample 80-1A produced at 353K(80°C) for 1 minute at 1 gram PTFE(L-169):3 milliliters MMA(OuPont) at the reaction temperature •••••••••••••••••••••••92 14b. FTIR scan of graft sample 80-3A produced at 353K(80°C) for 3 minutes at 1 gram PTFE(L-169):3 milliliters MMA(OuPont) at the reaction temperature •••••••••••••••••••••••93 14c. FTIR scan of graft sample 80-20A produced at 353K(80°C) for 20 minutes at 1 gram PTFE(L-169):3 milliliters MMA(OuPont) at the reaction temperature •••••••••••••••••••••••94 14d. FTIR scan of graft sample 80-55A produced at 353K(80°C) for 55 minutes at 1 gram PTFE(L-169):3 milliliters MMA(OuPont) at the reaction temperature •••••••••••••••••••••••95 14e. FTIR scan of graft sample 80-145A produced at 353K(80°C) for 145 minutes at 1 gram PTFE(L-169):3 milliliters MMA(DuPont) at the reaction temperature •••••••••••••••••••••••96 14f. FTIR scan of graft sample 80-1458 produced at 353K(80°C) for 145 minutes at 1 gram PTFE(L-169):3 milliliters MMA(DuPont) at the reaction temperature •••••••••••••••••••••••97 15. FTIR scan of L-169 ••••••••••••••••••••••••••••••••••••••••••••98 7

List of Figures (continued)

16a. ESR scan of L-169.(Gain = 103) ••••••••••••••••••••••••••••••••99 16b. ESR scan of the same L-169 sample as in figure 16a, taken 2 months later.(Gain = 103) •••••••••••••••••••••••••••••99

17a. ESR scan of Polymist® F-5A.(Gain = 2 x 102) ••••••••••••••••••100 17b. ESR scan of the same Polymist® F-5A sample as in figure 17a, taken 2 months later.(Gain = 2 x 102) ••••••••••••100 18. ESR scan of sample 55A run at 353K(80°C) for 55 minutes with 1 gram PTFE(L-169):3 milliliters MMA(DuPont) at the reaction temperature. Curve 1 corresponds to a scan with DPPH in the reference cavity. Curve 2 corresponds to a scan without the DPPH in the reference cavity. (Gain = 104) ••••••••••••••101

19. FTIR scan of sample RT-55A produced at room temperature with 1 gram PTFE(L-169):3 milliliters MMA(DuPont) at room temperature••••••••••••••••••••••••••••••l02 20. FTIR scan of sample 40-55A produced at 311K(40°C) with 1 gram PTFE(L-169):3 milliliters MMA(OuPont) at the reaction temperature ••••••••••••••••••••••••••••••••••103 ,21. Application of equation VI.1.19. to experiment 3; reaction data at 333K(60°C) with 1 gram PTFE(L-169): 3 milliliters MMA(DuPont) at room temperature ••••••••••••••••l04 22. Application of equation VI.l.19. to experiment 4; reaction data at 333K(60°C) with 1 gram PTFE(L-169): 3 milliliters MMA(DuPont) at the reaction temperature••••••••105 23. Application of equation VI.1.19. to experiment 5; reaction data at 333K(60°C) with 1 gram PTFE(L-169): 5 milliliters MMA(DuPont) at room temperature ••••••••••••••••106

24. Application of equation VI.l.19. to exper;~ent 6; reaction data at 353K(80°C) with 1 gram PTFE(L-169): 3 milliliters MMA(DuPont) at the reaction temperature••••••••107 8

List of Figures (concluded)

25. Application of equation VI.1.19. to experiment 8; reaction data at 343K(70°C) with 2 gram PTFE(Polymist® F5-A):5 milliliters MMA(DuPont) at 272.2K(O.2°C) •••••••••••••••••••••••••••••••••••••••••••••108 26. Schematic of the grafting of MMA on to the PTFE free radical matrix••••••••••••••••••••••••••••••••••••••••••109 27. ~ Hmelting of the graft polymer vs. gram graft/gram PTFE. Data were obtained from DSC scans in figures 11 - 13••••••••••••••••••••••••••••••••••••••••••••••••••••••110 28. ~ Hcrystallization of the graft polymer vs. gram graft/ gram PTFE. Data were obtained from DSC scans in figures 11 - 13•••••••••••••••••••••••••••••••••••••••••••111 9

ACKNOWLEDGEMENT

Special thanks are extended to Carleton A. Sperati for guidance and encouragement throughout the course of this research. Thanks are also due to several members of the Ohio University Chemistry Department: to Professor C. C. Houk, for use of his laboratory for the kinetics experiments; to G. Winner and C. Rottell of the chemistry department staff for helping to arrange and maintain the experimental apparatus; to Professor P. D. Sullivan for running and helping to interpret electron spin resonance scans; and to Professor R. R. Williams for use of his Fourier Transform Infrared Spectrometer and his help in interpreting the IR scans. In addition, acknowledgement is made to those people who supplied experimental materials: R. G. Alsup, formerly of DuPont, for methyl methacrylate monomer; A. Matthews of ICI Americas for Fluon® micropowder; and F. Fifoot of Allied for Polymist® micropowder. Most sincere thanks and graditude are extended to my husband, Bruce, for his support and sacrifices throughout the course of this work and for typing, analyzing, and proofreading this manuscript. 10

PART I Introduction

Copolymers are being developed to augment and enhance the favorable properties of each of their constituents. Among the many requirements for these new materials are better environmental resistance, easy processability and machinability, low cost, and a quality appearance. Polytetrafluoroethylene (PTFE), a highly crystalline polymer, is a chemically inert material used in such diverse applications as metal coatings, textile fibers, pipe liners, and wire and cable insulation. When sintered and then subjected to ionizing radiation, the PTFE • degrades to a micropowder that has found extensive use as a lubricant. This micropowder contains PTFE free radicals that have a very long lifetime due to being trapped in the crystalline matrix. Poly(methyl methacrylate) (PMMA) and its homologs are easily processed polymers that can be melt extruded or molded under heat and presssure. PMMA is best known for its optical qualities and is a primary component of safety glass and lighting covers. It recently has found favor as an architectural material for use in kitchens and bathrooms. The purpose of this research was to use the PTFE free radicals in commercially available micropowder to initiate methyl methacrylate (MMA) polymerization. Since the PTFE free radicals have a high molecular weight, the material resulting from this research is a graft 11 polymer of PTFE and PMMA. Because the steady state assumption in the theory of free radical polymerization does not apply to this system, a kinetics mechanism was developed to explain the production of the block copolymer. The amount of graft produced was determined gravimetrically, and data were substantiated by Differential Scanning Calorimetry and Fourier Transform Infared Analysis The kinetics model developed fi,t the data well and its assumptions were supported by electron spin resonance scans. Of special interest are the properties of this graft copolymer, including its stability aand appearance. Samples were molded in a press to qualify its machinability and strength. 12

PART II Radiation Effects on Polytetrafluoroethylene

11.1 Effects of Radiation on the Stucture of Polymers

When exposed to high energy radiation (Y -rays, x-rays, electron beams, etc.), polymer chains undergo two types of reactions:

1) crosslinking, leading to the formation of an infinite network; or 2) scission, resulting in shorter, lower molecular weight chains(l). For some polymers, both reactions occur simultaneously(l), usually with one predominating due to the effects of temperature(2,3), oxygen(l), or other materials(4). For most polymers which crosslink upon irradiation: • Each carbon of the main chain carries at least one hydrogen atom, the repeat unit being

H :1 -[-CH2- C-] 1 R n

Polymers such as polyethylene, polypropylene, polystyrene and polyesters are in this category. • The molecular weight of the polymer increases with dose, due to branching. This results in the formation of a gel which is insoluble in the polymer1s normal solvents. • Radicals form at adjacent sites to allow cross-linking to occur(l). 13

For those polymers which degrade after radiation exposure: •A tetrasubstituted carbon is present in the main chain, the repeat unit being R' t -C-CX2-C-J- I n R where X = H, F, or OH. Polymers which have this structure include poly(methyl methacrylate), polytetrafluoroethylene, cellulose and poly(iso-butylene). Strain in the molecule due to steric repulsion weakens the C-C bond, allowing scission to occur(1,3). • The molecular weight of the polymer decreases with dose as random chain scissions occur. The molecular weight can decrease enough that the polymer is degraded to a very viscous liquid(l,3). • Melting temperatures may decrease due to the lower molecular weight of the material(5). • Recombination is dependent upon the mobility of the radicals. Radicals can recombine if they remain close enough (cage effect) or diffuse to within a distance that allows termination to occur(6).

11.2. The Structure of Polytetrafluoroethylene Polytetrafluoroethylene (PTFE) is a high molecular weight homopolymer of tetrafluoroethylene with a repeat unit of 14

Typical methods of molecular weight determination are not suitable for PTFE since it does not dissolve in common solvents (7,8,9). Radioactive end group counts and a standard specific gravity test (ASTM 01457)(8) set the molecular weight of commerical PTFE at 106 - 107(7,8,9). PTFE is well known for its resistance to chemical attack. Only alkalai metals, fluorine, and strong fluorinating agents at elevated temperature and pressure will cause degradation(9). This chemical resistance is due to the high C-F bond strength, which has a dissociation energy of 460 kJ/mole (8). PTFE is believed to be a linear, unbranched, non-crosslinked polymer due to its sharp melting point (608-618 kelvins(335 - 345°C) for virgin resin and 600K for sintered material), high degree of crystallinity (93-98 per cent) as polymerized, and its ability to be oriented (8,9,10). The molecules assume a helical conformation and fold back on themselves at regular intervals to form a crystalline structure of hexagonal thin sheets, about 1.0 microns thick, with the molecular segments normal to the sheets (Figure 1)(9). Chains in the crystalline region pack tightly and have a higher density of 2.3 Mg/m3(2.3 g/cm3), compared to the randomly oriented chains in the amorphous phase with a density of 2.0 Mg/m 3(2.3 g/cm3)(8,10). The crystalline part of the polymer undergoes solid state transitions at 292K(19°C) and 303K(30°C). The amorphous region is 15

unaffected by these transitions(9). The two transitions combined result in about a 1 per cent increase in the density upon heating. At 292K, the helical structure of the PTFE chain changes from 13 to 15 carbon atoms per 1800 twist and from 1.69 nm to 1.95 nm per repeat unit(9) (Figure 2). Between 292K and 303K, chain segments become disordered from the perfect hexagonal structure (as shown in Figure 1) by small angular displacements about the longitudinal axis. Above 303K, molecular segments oscillate along the longitudinal axis. Higher temperatures cause the chain to twist and untwist. Even above its melting point of 600K(327°C), the sintered polymer retains much of its crystalline structure(8). Properties of PTFE are summarized in Appendix A.

11.3. Effects of Radiation on the Structure of Polytetra fluoroethylene

Despite its chemical stability, PTFE degrades readily upon exposure to ionizing radiation. This degradation is very rapid in the presence of oxygen, but occurs at a significantly lower rate in a vacuum(11,12,13). The degradation is a result of the weakening of the structure near the scission point, plus the effects of the build-up of internal pressure of various gaseous products(16,21). Using electron spin resonance, Siegel and Hedgpeth note the existence of two radicals formed upon degradation in a vacuum(4): 16

1) A propagating radical

2) A chain radical

There are ten times more chain than propagating radicals since the propagating radicals can recombine more easily(10). Both radicals will react with oxygen to form peroxide radicals(14). The hypothesized mechanism for the production of the propagating radical and its peroxide derivative is given in reactions 11.3.1. and

11.3.2.; that for the chain radical is given in 11.3.3. and 11.3.4. (10,15) •

11.3.1.

11.3.2.

11.3.3.

11.3.4. 17

The symbol ~ indicates that the reaction is initiated by ionizing radiation. Other possible reactions are given by Fisher and Corelli in Reference 10. The number of radicals produced in air is proportional to the dose according to an equation developed by Judeikis et. al.(17):

R = 0.87 x 10- 3 (D)0.88 in which R = Radical concentration (micromole/kg) D = Dose (rads)

For degassed samples the 0.88 becomes 1 within experimental error. Scission of the PTFE chain during irradiation is a random process which results in shorter chains and a broadening of the molecular weight distribution, regardless of the original polydispersity of the sample. During the irradiation, the PTFE undergoes a steady weight loss proportional to the dose due to the evolution CF4, C2 F6' C3Fg, and other volatile fluorocarbons(16). When the bonds in the PTFE are broken by the radiation, pairs of chain ends generated in the crystalline regions are prevented from moving due to their close packing in the matrix; therefore, the pairs may readily recombine. In the amorphous region, the chains are loosely packed and may diffuse away before combination can occur; most permanent scission, therefore, must take place in these amorphous 18 regions. A "cage effect" determines if the scission is permanent. If the chain ends remain in the cage, recombination is possible. If the ends become separated, scission is completed(18,19). The lower molecular weight PTFE chains created by the scissions, being more mobile, assume the lower free energy conformation of the crystalline phase. Scissions in the amorphous regions may reduce hindrances, chain entanglements, and other stresses and grant enough mobility to the chains to promote crystallinity(lO). This increase in crystallinity has been proven by NMR work which shows a broadening of the amorphous component of the spectrum. This corresponds to an increase in the hindrance of molecular motion in the amorphous phase, implying that the chains have become more tightly packed. In addition, Differential Thermal Analysis (DTA) (19) and Differential Scanning Calorimetry (DSC) (10) work show a peak on the low temperature side of the irradiated PTFE melting endotherm, which may indicate the presence of imperfect crystallites formed in the amorphous region(lO). In this crystalline conformation, the chains with their free radical ends are rigidly packed and recombination of the radicals is unlikely(3,20). This accounts for the long lifetime of the PTFE free radical of at least many months to years, compared to milliseconds for most other free radicals(15,2l). 19

PART III Methyl Methacrylate Free Radical Polymerization

III .1. Free Radical Chain Polymerization Radical chain polymerization consists of a three step sequence: initiation, propagation, and termination(22,23). The initiation step requires two reactions: the homolytic dissociation of an initiator, I, to yield a pair of radicals, R·,

I 111.1.1. and the addition of the first monomer molecule to produce the chain initiating species Mi '

k·1 R. + M 111.1.2. in which Mrepresents a monomer molecule and kd and ki are the respective rate constants. Reaction 111.2. is assumed to be so fast that it cannot be rate controlling.

In the propagation step, the radical grows by successive additions of monomer molecules:

M. + M ---)r.... M· 111.1.3. 1 2

M. + M M· 111.1.4. n >- n+1 20 in which kp is the propagation rate constant. Growth to high polymer is almost instantaneous for free radical polymerizations. Termination occurs by a bimolecular reaction between radicals to produce dead polymer. Combination simply adds two radicals together:

M. + M. n 111.1.5. n m ------",-.. M+m in which ktc is the rate constant for combination termination. A disproportionation termination results in the formation of one saturated and one unsaturated polymer molecule:

M. + M. ____)-~ Mn + fv\n 111.1.6. n m in which ktd is the rate constant for disproportionation termination. Coupling is a more likely termination scheme, but a combination of coupling and disproportionation also can occur. To simplify the kinetic equations, several assumptions are made. • The radical reactivity is independent of radical size. • The total rate of reaction of the monomer is equal to the rate of reaction of the monomer in the propagation steps alone, neglecting any consumption of monomer in the initiation or the termination steps.

• After a "pre-effectll time, a steady state concentration of free radicals is reached(22). With these assumptions, the kinetics equation for reactions 111.1.1. 111.1.6. can be rearranged to give a useful expression for the rate 21

of propagation, Rp:

111.1.7.

The value "f" is the initiator efficiency, the number of polymer chains formed per initiator fragment, and has a value between a and 1, depending on the initiator, solvent, and conditions used. [M] and [IJ refer to the concentrations of monomer and initiator respectively(23).

111.2. Methyl Methacrylate Homopolymerization The carbon-carbon double bond in methyl methacrylate polymerizes by a free radical chain mechanism to poly (methyl methacryl ate) :

CH3 CH3 I I n CH2=C > -CH2- C, 111.2.1. l ~00CH3_ COOCH3 n Methyl methacrylate (MMA) undergoes a very low rate of uninitiated thermal polymerization(22) of 1.94 x 10-7 mol/l-sec at 273K(OoC). Initators such as benzoyl peroxide and azobisisobutyronitrile have been used to polymerize MMA to a number average molecular weight, 5 6(24). Mn, of up to 10 to 6 x 10 22

In the initial stages of MMA polymerization, the reaction medium increases in viscosity from a mobile liquid to a viscous syrup(25,26). Between about 10 and 50 per cent conversion, the rate of polymerization increases. The ratio of kp/kt increases rapidily due to a large drop in kt• It is during this stage that the "gel" effect occurs(25,26). In the later stages, the polymer radicals have limited mobility. The number of monomer units has decreased and the diffusion of these units to active propagating sites becomes more difficult. Termination becomes, in effect, the cessation of the ability to propagate(25,26). Most termination is by combination, but disproportionation is favored at higher temperatures(27,28,29). Properties of MMA are summarized in Appendix B.

111.3. Ge 1 Effect Using benzoyl peroxide as an initator for MMA, Norrish and Smith(30) noted a rapid increase in the polymerization rate after a particular conversion was reached. This deviation from typical kinetics occurs for vinyl monomers and ;s known as the Norrish-Smith, Trommsdorf, or gel effect(23). The gel effect is due to an increase in the viscosity of the system(31,32) caused by entanglements of high molecular weight propagating radicals and dead polymer(33). These entanglements prevent active free radical ends from diffusing close enough together to terminate(31,34). Propagation and initiation involve small monomer 23 molecules whose mobility is not affected by this increase in the systemls viscositY(31); therefore, the corresponding rapid increase in , conversion is attributed to a drop in the termination rate and kt rather than an increase in the propagation or initiation rates. 24

PART IV Experimental Apparatus and Procedures

IV.I. Kinetics Experiment Polytetrafluoroethylene (PTFE) free radicals, as produced by irradiation, were used as initiators for a methyl methacrylate polymerization. Three different commercially available irradiated PTFE grades were used: Fluon~ L-I69 and L-171 from leI and Polymist~ F-5A from Al lied. Two sources of methyl methacrylate were used: Fisher laboratory grade (inhibited with 25 ppm hydroquinone) and Dupont1s commercial grade (inhibited with 100 ppm hydroquinone). The methyl methacrylate was washed several times with sodium hydroxide until no color change was apparent. Afterward, it was washed repeatedly with distilled water until a clear layer of methyl methacrylate was obtained. Drierite® was added to the methyl methacrylate to remove any traces of the distilled water. For most reactions, the methyl methacrylate was put in a constant temperature bath at the reaction temperature until added to the PTFE. For several runs, the methyl methacrylate was kept in an ice bath or used at room temperature. The temperature of the methyl methacrylate for each run is noted in Tables 1 to 7.

Samples of irradiated PTFE were weighed in test tubes to ~ 0.0001 grams using a Mettler H-IO balance. The samples were placed in a constant temperature bath and heated to the reaction temperature. 25

Methyl methacrylate was added volumetrically to the weighed irradiated PTFE samples using either a graduated cylinder or a graduated pipette. The mixture of irradiated PTFE and methyl methacrylate monomer was returned to the constant temperature bath and the reaction was carried out for a specified amount of time. At the end of the time limit, hydroquinone at approximately I weight per cent of the total reacting mixture was added to the test tube to quench the reaction. All reactions were performed in air at atmospheric pressure. Various temperatures and ratios of PTFE to MMA were used. The contents of the test tubes were transferred to dried, preweighed extraction thimbles. Extractions with acetone were carried out in a Soxleht extraction column until the thimble and its contents reached a constant weight. The amount of poly(methyl methacrylate) grafted onto the polytetrafluoroethylene free radicals was found by using equation IV.I.I.:

Mass of thimble + contents Mass of thimble Mass of irradiated PTFE used Mass of PMMA graft IV.I.I. The definition of conversion is given in equation IV.I.2.:

% conversion = Mass of PMMA graft x 100. IV.l.2. Initial weight of MMA used

A summary of variables is given in Appendix C. Appendix D 26 contains the conditions used for each experiment.

IV.2. Infrared Transmittance Measurements In reflectance spectroscopy, an infrared beam is directed at some fixed angle onto the sample. The energy reflected from the sample is collected, appropriate computer manipulations are made, and the absorbance spectrum is obtained(35). Fourier transform infrared analysis is preferred over conventional infrared studies due to the "multiplex" advantage: in FTIR, all spectral elements contribute simultaneously to the interferogram, whereas in IR, spectral increments of particular wavelengths are measured successively. For this reason, FTIR is considerably faster in generating the same data as conventional IR(3fi). To substantiate the results of the kinetics experiments, Fourier transform infrared spectra of samples of the graft product were made using a Matteson Instruments Sirus 100. The samples were ground in a Wig-L-Bug with a small quantity of potassium chloride to reduce the amount of energy scattered. Since the samples were in powder form, the diffuse relectance attachment was used and KUbelka-Monk functions were generated(37). The Kubelka-Monk function is defined as

F(Roo) = (I-Roo )2/ 2Roo = k/ s IV.2.1. in which 27

F(Roo) = Kubelka-Monk function

Roo = Reflectance of a layer so thick that further increases in thickness fail to change the reflectance k = absorption coefficient

s = scattering coefficient

Roo is further defined as

F(Roo) = R~ sample = k/s IV.2.2. R'oo standard in which

R~ = absolute reflectance of the layer.

In this instance, the sample is either the graft polymer or irradiated, unreacted PTFE and the standard is potassium chloride with

R~ approximately equal to 1. F(R oo) is also related to the molar concentration, C, according to equation IV.2.3.:

IV.2.3.

in which kl is a constant equal to s/2.303t: with E: defined as the extinction coefficient. S;s rendered independent of wavelength by using scattering particles whose size is large in relation to the wavelength used(37). If it ; s assumed that k' is constant for a given 28

sample, then a ratio of Kube1ka-Monk functions at different wavelengths will be equal to the molar concentration of those substituents absorbing at the given wavelengths. If the log F(Roo ) is plotted against the wavelength or wave number, the curve obtained corresponds to the real absorption spectrum of the compound determined by transmission measurements, except for a displacement by (- log s) in the ordinate direction(37,38)

IV.3. Electron Spin Resonance Measurements Electron spin resonance is based upon the absorption by unpaired electrons of electromagnetic radiation which causes transitions between energy levels. The spectra recorded are the first derivative of absorbed power as a function of the applied magnetic field. The number of spins, or free radicals, can be determined from the spectra by the application of quantum mechanics(39). In order to determine the presence of free radicals in the PTFE and in the graft product, ESR scans using a Varian E-15 EPR Spectrometer were made. 1,1-dipheny1(-2-picrylhydrazyl) (DPPH) was used as the reference material. Since the accuracy of measuring absolute quantities of free radicals is very low, no better than ~ 20 per cent(39), ESR scans were used only for qualitative purposes.

IV.4. Differential Scanning Calorimetry Whenever a material undergoes a change in physical state, such as melting, or in chemical composition, such as decompostion, energy is 29 either absorbed or liberated. Differential Scanning Calorimetry measures the heat flow required to maintain a sample and a reference system at the same temperature as this temperature is either kept constant or varied linearly at a predetermined rate(40). When the sample undergoes a thermal transition, a signal proportional to the power difference between the heater of the sample and that of the reference is plotted on the y-axis of the recorder with time recorded on the x-axis. The area under the resulting curve is a direct measure of the heat of transition(41). A Perkin Elmer Model DSC-l Differential Scanning Calorimeter was used to study the heats of melting/fusion of the unreacted irradiated PTFE and the PTFE-PMMA graft polymer. A continuous heating rate of 10 kelvins/minute over a temperature range of about 580-620K (307-347°C) was used for the analysis. 30

PART V Results

V.I. Kinetics Data Tables I - 5 give the data for the kinetics experiments. Included in these tables are the quantities of PTFE and MMA used, the amount of graft formed, the per cent conversion of MMA to graft, and the ratio of the graft to the initial quantity of PTFE. Figures 3 - 9 are graphs of conversion versus time at the various temperatures and conditions studied. No weight increase was noted in samples run in experiment I at oC) 293K(20 or in experiment 2 at 313K(40oC). Sam~les run at 333K(60oC)-353K(80oC) showed an increase in weight, i.e., the production of a poly(methyl methacrylate) graft, at all the time allowed for polymerization, the ratios of the PTFE to MMA, the initial temperature of the MMA, or the grade of irradiated PTFE used.

V.I.a. Effects of Preheating the Monomer

Tables 1 - 3 and Figures 3 and 4 give the data for the reactions at 333K(60oC). Table I and Figure 3 show the data for experiment 3 for PTFE (L-169) and MMA (DuPont) in a ratio of 1 gram of PTFE to 3 milliliters MMA at room temperature. Table 2 and Figure 4 give the data for experiment 4 for PTFE (L-169) and MMA (DuPont) in the same ratio with the MMA volumetrically measured at the reaction temperature. The average conversion expected at each time interval is 31 approximately the same for both experiments; however, experiment 4 gave more consistent results, with a linear correlation coefficient(42), r, of 0.88 versus r=O.76 for the run using unheated MMA. Since prior heating of the MMA gave better results, this step was repeated for most runs.

V.1.b. Effects of PTFE:MMA Ratio Tables 2 and 3 and Figures 4 and 5 describe the effects of the ratio of the irradiated PTFE (L-169) to methyl methacrylate monomer (DuPont) on the conversion to graft polymer. In both instances, the reaction temperature is 333K(60°C). Table 2 and Figure 4 give information for experiment 4 for 1 part by weight PTFE to 3 parts by volume MMA; Table 3 and Figure 5 are for experiment 5 using 1 gram of PTFE to 5 milliliters MMA. About three times more conversion at shorter times and twice as much conversion at the longer times was noted for the 1:3 ratio as compared to the 1 to 5 ratio. Reaction data for experiment 9 run at 353K(80°C) with a different grade of PTFE (L-171) at two different ratios of irradiated PTFE to MMA is given in Table 7. Both runs lasted 60 minuntes. Using three times more PTFE to a constant amount of MMA resulted in three times more conversion of MMA to graft. The ratio of grams of graft to grams of PTFE remained constant despite the change in the PTFE:MMA ratio and is only a function of time. A higher value of grams of graft to grams of PTFE is obtained using L-171 versus L-169 (Table 4), probably due to a larger number of free radicals in L-171 (see section VI.1.). 32

V.l.c. Effects of Temperature The results of experiment 6 at 353K(80°C) with PTFE (L-169) to MMA (DuPont) at a 1 gram: 3 milliliters ratio are given in Table 4 and Figure 6. Average conversion at this temperature is higher than at 333K(60°C) at the same conditions: 8.5 per cent at 353K(80°C) versus 6.4 per cent at 333K(60°C) for the 55 minute runs. The amount of conversion continues to increase with time: about 13 per cent conversion of MMA to graft polymer is obtained at 90 minutes and about 21 per cent conversion at 145 minutes. The conversion at 145 minutes corresponds to a ratio of 0.52 grams of graft to 1.0 gram of PTFE, or about 60 per cent graft by volume.

V.l.d. Effects of Hydroquinone Hydroquinone is a common inhibitor for methyl methacrylate polymerizations. Table 5 and Figure 7 show the effects of hydroquinone addition on the reacting samples. This was used to determine if it was necessary to inhibit the samples chemically to prevent any post-polymerization once the samples were removed from the constant temperature bath. In experiment 7, irradiated PTFE (L-169) and MMA (Fisher) were used in a ratio of 1.5 gram to 2 milliliters with the reaction carried out at 353K(80°C). Inconsistent results were obtained for the shorter reaction times, but for longer periods, a slightly higher conversion was obtained for those samples to which no hydroquinone was added. To avoid complicating the kinetics results by post-polymerization grafting that might occur as the sample cooled 33 or was heated in the extraction column, hydroquinone inhibition at about 1 part per 100 parts monomer was used in all other runs. As noted in the 333K(60°C) runs, the higher ratio of PTFE to MMA results in a greater conversion of MMA to graft. For experiment 7 using 1.5 grams of PTFE to 2 milliliters MMA (Table 5 and Figure 7), conversion was about 19 per cent at 50 minutes compared to R.5 per cent conversion at 55 minutes for experiment 4 for 1 gram of PTFE to 3 milliliters MMA (Table 4 and Figure 6), both at 353K(80°C).

V.1.e. Effects of Different Grades of PTFE Several manufacturers produce irradiated polytetrafluoroethylene. Since these materials are used in different applications, radiation doses are varied to produce a micropowder of the appropriate size. Given in Table 6 and Figure 8 are results of experiment 8 run at 343K(70°C) using Allied's Polymist® F-5A instead of ICI's L-169 or L-171. The Polymist@ to MMA ratio was 2 grams: 5 milliliters. Even though the methyl methacrylate was kept in an ice bath prior to reaction, higher average conversions are noted for this run than for experiment 6 using L-169 at 353K(80°C) (Table 4 and Figure 6) at 1 gram of PTFE to 3 milliliters of MMA. Using the Polymist® resulted in 46 per cent conversion of MMA to graft at 55 minutes. Using the L-169, conversion was 8.5 per cent for 55 minutes. About 1:1 ratio of PTFE to graft is obtained. This corresponds to approximately 74 per cent graft by volume.

Figure 8 gives the percent conversion versus time with r = 0.77. 34

for Unlike the other runs which gave linear correlations, the data a this experiment imply a logarithmic relationship. Figure 9 shows the graph of per cent conversion versus the natural logarithm of time; linear correlation coefficent for this relationship is 0.93.

V.I.f. Extractions Samples of PTFE as received were weighed in thimbles and extracted noted under the same conditons as polymerized samples. No change was . in the PTFE weight. The acetone used for extracting the two graft samples run at was 353K(80°C) for 145 minutes in experiment 6 (Table 4 and Figure 6) evaporated and the residue was weighed. For comparison, the experiment was repeated for pure acetone and acetone to which hydroquinone was added. Results are given in Table 8. The remainder of the residue for the polymerized samples after the amount of of hydroquinone is subtracted has a value equal to about 10 per cent the quantity of graft formed and is due to any impurities in the

acetone, hydroquinon~, methyl methacrylate, or PTFE, or due to the production of a small amount of methyl methacrylate homopolymer. A Fourier transform infrared scan (FTIR) (Figure 10) of this and residue from sample B shows a small amount of PTFE carryover (1200 2400 em-I), C-O groups (1400 - 1600 em-I), C=O groups (1600-1800 em-I), and OH groups (above 2800 em-I). 35

V.2. DSC Scans DSC scans were run on unreacted irradiated PTFE L-169 and graft polymer made in experiment 6 at 353K(80°C) using a 1 gram: 3 milliliters ratio of PTFE:MMA for both 55 minutes and 90 minutes.

The melting peak for PTFE was assumed to correspond to a ~ H melting = 75.3 Joules/gram. Areas of the other melting and fussion peaks were measured relative to the L-169 melting peak, with ~ H proportional to the relative areas. DSC scans are given in Figures 11 - 13. A summary of the heats of melting and fusion are given in Table 9. The sample 80-558 was melted and crystallized twice; all other samples were scanned once.

V.3. Fourier Transform Infrared Scans Samples from experiment 6 at 353K(80°C) were scanned by infrared analysis. These scans are given in Figures 14a - 14f. Sample designation are given in Appendix E. A FTIR scan of unreacted L-169 is given in Figure 15. The peak at approximately 1200 cm- 1(8.333 ~ ) corresponds to the C-F bond in PTFE(41), while the peak at about 1700 cm-1(5.882~ ) corresponds to the C=O bond in the methyl methacrylate (42). Relative areas under the peaks at 1200 cm- 1 and 1700 cm- 1 were taken to be proportional to the molar concentration of C-F to C=O. These molar ratios are given in Table 10. 36

V.4. Electron Spin Resonance ESR scans of L-169, Polymist® F-5A, and the graft polymer made at 353K(80°C) for 145 minutes with 1 gram L-169 : 3 milliliters MMA are given in Figures 16 - 18. The scans were made relative to diphenyl 1,1-diphenyl(-2-picrylhydrazyl) (DDPH). The shape of these curves coresponds well with the results of Siegel and Hedgpeth(14). The L-169 sample was run on a sensitivity (gain) one order of magnitude higher than the Polymist®. Still, the area under the Polymist® curve is larger; therefore, there is at least one order of magnitude more free radicals in the Polymist® than in the L-169. The slight blip in the PTFE curve near the DPPH curve is believed to be a shadow of the signal from the DPPH. The graft polymer was run at a sensitivity one order of magnitude higher than the L-169. Curve 1 corresponds to a scan with DPPH in the reference cavity; for curve 2 the DPPH was removed. The loss of the "blip" substantiates the likelihood of a DPPH shadow in other scans. Running at this higher sensitivity results in more noise in the scan. The area under the resulting PTFE peaks is much lower than for the unreacted L-169 sample, suggesting that there are significantly fewer free radicals present in the graft polymer. The stability of the PTFE free radical is sUbstantiated by comparing Figure 16a to Figure 16b and Figure 17a to Figure 17b. The a and b scans were made 2 months apart and show only a small decrease in the areas under the curves, signifying only a small drop in the number of free radicals present in the samples. 37

PART VI Discussion of Results

VI.I. Kinetics Results vr.i.s. Development of Kinetic Equations

Theory for free radical chain polymerization uses the steady state assumption to simplify the kinetics equations: the rate of initiation is equal to the rate of termination, which means that the the number of free radicals quickly reaches a steady state concentration at which it remains constant for the course of the polymerization(23). Production of free radicals involves the dissociation of the initiator to yield a pair of free radicals (111.1.1), which in turn react with the momomer molecules to produce the polymer chain (111.1.2). In the irradiated PTFE-MMA graft polymerization system, the PTFE free radicals are already present and no more can be produced. The concentration of these radicals starts at a set amount and decreases as the PTFE free radicals are used up; steady state assumptions do not apply. For this reason, the kinetic equations must be modified to model this system. The resulting kinetic steps are given as follow:

Initiation: R· + M ---'7-~ M· VI.l.I. Propagation: M. + M M· VI.l.2. n n+l 38

dead or Termination: M. + M. ______----~~ occluded VI.I.3. n m polymer in which: R· = PTFE free radicals M = Methyl methacrylate monomer M· = PTFE-MMA growing graft radical. Several assumptions are made. (A) Step VI.I.I. is very fast. This step is assumed to be so fast in free radical polymerization kinetics that it cannot be rate controlling, and therefore, does not affect the development of the kinetics. In this system, this step is assumed to be so fast that all initiator (PTFE free radical s) is used up almost immediately; this is substantiated by ESR results (Figure 18). The initial number of M· radicals is then equal to the initial number of PTFE free radicals. A certain activation energy barrier

must also be crossed, as is shown by the dependence of conversion on temperature.

(B) Equal reactivity of all free radicals is assumed for steps VI.I.2. and VI.I.3. (C) Steady state conditions do not apply. (D) Average rate constants, which are not functions of time, are determined from the kinetics. A derivation of appropriate kinetics is similar to that found in Qdian(23) • 39

The rate of disappearance of monomer (-d[MJ/dt) is equal to the rate of initiation (R i) plus the rate of propagation (R p):

-d[M]/dt = Ri + Rp VI.l.4. in which the brackets signify concentration.

The rates of initiation and propagation are defined from steps VI.I.I. and VI.l.2. as

R.1 = VI.I.S.

VI.l_6.

in which ki and kp are the respective rate constants for initiation and propagation_ Substituting into equation VI.l.4. gives

VI.I.7.

Dividing this equation by [M] and multiplying by dt gives

-d[M]/[M] = (ki[RO] + kp[MO])dt VI.I.B.

Assumption (A) says that for time greater than zero, [R·] = 0; therefore, [M-Jo = [R-Jo ' in which the [R·]o ;s the initial concentration of free radicals and the sUbscript zero 40

signifies the condition at time = O. For any time greater than zero,

[R·] = 0 and

-d[M]/[M] = kp[MO]dt VI.I.9.

From the termination step VI.I.3. and assumption (B),

VI.I.IO. in which kt is the rate constant for termination. From this equation, the concentration M· can be determined as a function of time:

VI.I.II.

Integration gives

by assuming that the constant of integration is zero. Assumption (A)

states that [R·]o = [M-J o' and when this is substituted in VI.l.12., the expression for [M·J becomes

VI.l.13. 41

VI.I.9. gives value into equation Substituting this VI.l.14.

show Integration tables(45) VI.I.IS. ~1/(aX +b))dx = I/a In(ax + b) + c

integration the constant of VI.l.14. and setting Using this to solve equal to zero gives VI.1.16.

and [M] is the monomer concentration [M]o is the intial in in which the integration at time t. Completing monomer concentration gives equation VI.l.16. VI.I.17.

greater than 1; set kt[R·]o much Literature values(26) from the the 1 can be dropped first approximation therefore, as a is resulting expression the right. The logarithmic term on VI.I.18. 42

Expanding the logarithmic term on the right side,of VI.I.18. gives

In([M]O/[M]) = (kp/kt)ln(t) + VI.I.19. (kp/kt)ln(kt[RO]o)

When In([MJo/[M]) is graphed versus In(t), equation VI.l.19. defines a straight line with a slope of kp/kt and a y-intercept of (kp/kt)ln(kt[Ro])o Since the exact concentration of PTFE free radicals is difficult to measure, it will be assumed that the number of free radicals in an irradiated PTFE sample is homogenous throughout the sample; therefore, the total mass of the PTFE sample can be used for the kinetics equations since it is directly proportional to the number of free radicals in the sample. All concentrations in VI.I.19. can be changed to a mass basis, relative to the initial mass of MMA, with the resulting kinetic constants having units of grams MMA/grams PTFE-minutes, rather than the typical moles/liter-minutes. The term

[R·]o has the units of grams of PTFE/initial gra~s of MMA. Equation VI.I.19. predicts that for longer periods of time or for larger concentrations of irradiated PTFE initiator relative to MMA monomer, more conversion of MMA to graft will occur. Application of equation VI.I.19. to the data of the PTFE-MMA system is given in Figures 21-25. Rate constants and linear correlation coefficients are summarized in Table 11. 43

VI.I.b. Temperature Effects Temperature plays a significant role in the production of the PTFE-MMA graft. Although no weight gain was noted in samples polymerized with 1 gram L-169 : 3 milliliters MMA at either room temperature or at 313K(40°C) (experiments 1 and 2), the FTIR scans for these conditions (Figures 19 and 20) are slightly different than the scan for unreacted irradiated L-169 (Figure 15). The scan of RT-55A (Figure 19) shows a broad peak at about 1700 cm-l(5.882~), which may be due to the presence of poly(methyl methacrylate). The scan of 40-55A (Figure 20) shows a peak around 900 cm-l(ll.111~ ) which does not appear in the PTFE scan, but does show up in FTIR scans at higher temperatures. A small amount of polymer may have been formed at these lower temperatures, but a more sensitive test than a weight gain would be required to detect its amount. The higher temperatures used for other runs result in higher conversion and, therefore, more grafting (Figure 14a - 14f). The data at the higher temperatures give a good fit to equation VI.l.19(Table 11). Higher temperatures result in a higher conversion; these samples have a larger weight gain that is more easily measured. The nature of the experiment will result in more error at the lower temperatures, and therefore lower conversions, since only a smaller quantity of graft will be produced. 44

VI.I.c. Ratio Effects The presence of more free radicals results in higher conversion of MMA to graft. These can be seen in figures 4 and 5 of experiments 4 and 5 with PTFE:MMA at ratios of 1 gram: 3 milliliters and 1 gram 5 milliliters. This is also noted by the high conversion using Polymist® F 5A at a reaction temperature of 343K(70°C) in experiment 8 (Figure 8), which was shown by ESR scans (Figure 17a and 17b) to contain significantly more free radicals than L-169: the more free radicals, the more sites available for MMA to add on to the PTFE. The data at 333K(60°C) from experiments 3-5 show a better fit to VI.l.19. when the ratio of PTFE:MMA is higher. With more PTFE initiator available, there can be more grafting. As stated above, a larger amount of graft to measure will reduce experimental error of the measurement. The conversion versus time data for experiment 8 using Polymist® F 5-A as given in Table 6 and Figure 25 substantiates that given the same quantity of MMA, the amount of graft depends upon the amount of PTFE free radicals available. ESR scans show a larger amount of free radicals in the Polymist@ compared to the L-169 (Figures 7a and 7b), resulting in a higher conversion. Dropping the 1 from equation VI.I.17. has little effect on the calculated rate constants. For shorter times, ktt[RoJ is approximately equal to 1, but since most data are for longer times than 1 minute and linear regression techniques favor the data at the upper end of the range, this will have little effect on the results. 45 vr.r.a, Gel Effect at 353 kelvins (80°C) The data in experiment 6 at 353K(80°C) imply the onset of a gel effect after about 10 per cent conversion. According to the work of Norrish and Smith(30), this is a reasonable point for the gel effect to occur. The data show a sharp break and linear regression statistics for VI.l.19 for each side of the break result in significant error when used to predict the conversion for the opposite side (Figure 24). Using VI.l.19., the ratio of kt/kp for time less than about one hour is 41.1; for time greater than about one hour, the ratio is 4.9(Table 11). The lower ratio for the higher times implies that the termination is much less likely than for the shorter times. The mechanics of this possible gel effect can be explained by the schematic in Figure 25. As the PMMA chains grow away from the the PTFE matrix, they can terminate by bridging over from one chain to the other, provided that there are no obstacles to sterically hinder them and that there is a near enough neighbor to allow a ready termination to occur. As the chains become longer with the higher conversion, more movement must occur for the chains to be in a favorable orientation to terminate(31,33). More entanglements can occur around the IIbridges" that have already terminated and among the longer chains that are not in a favorable position to terminate. In order to get over the bridges and other obstacles, these longer chains must grow still longer to find another chain, since many of its nearest neighbors have already terminated. This schematic mechanism can explain the decrease in the termination rate constant by a factor 46 of 34, as determined by the y-intercept in equation VI.l.19., at the break in the data in Figure 24. During the gel effect, the propagation rate is not expected to change since the mobility of small monomer molecules is unaffected by the increase in the system's viscosity due to entanglements and conversion. The data collected at 353K(80°C), however, show a decrease hy a factor of four in the propagation rate, as determined from equation VI.l.19. This may be due to a slight shielding of the free radical end in the growing PTFE - graft matrix which would prevent the monomer from easily finding an active propagating site. It is unlikely that the decrease in propagation is caused by decrease in the amount of monomer available, since approximately only 10 per cent conversion has occurred, and therefore, there is still a large amount of MMA available for reaction. Overall, the 34-fold decrease in termination rate shows a tendency toward a gel effect at these conditions, despite the slight decrease in the propagation rate. Even though the higher conversion occurred using the Polymist® F 5-A in experiment 8, no tendency toward a gel effect is noted in the data. This may be due to the presence of more free radicals in the Polymist® F 5-A which allows for the formation of a larger number of shorter chains. In general, a higher quantity of initiator results in Shorter, low molecular weight chains since more active sites are competing for a set amount of monomer(23). The larger number of shorter chains in the Polymist@ - PMMA graft have more near neighbors 47 with which they can terminate before any obstacles sterically prevent their movement; therefore, a gel effect is much less likely in the Polymist® system.

VI.1.e. Comparison with Literature Values Literature values for methyl methacrylate homopolymerization constants at 333K(60°C) are given(23).

k 31/mol-sec P = 0.515 x 10 Ep = 26.4 kJ/mol 7 Ap = 0.087 x 10 l/mol-sec 7 kt = 2.55 x 10 l/mol-sec Et = 11.9 kJ/mol At = 0.11 x 109 l/mol-sec

The subscript p denotes propagation constants, while t is used for termination. A is the frequency or collision factor and E is the activation energy as defined by

k = A exp(-E/RT) VI.1.21 in which R is the gas law constant and T is the absolute temperature. Values for the rate constants for grafting of MMA on to PTFE at 333K(60°C) are taken from Table 11. Application of equation VI.l.19. using data for 55 minutes from experiment 4 at 333K(60°C) and from experiment 5 at 353K(80°C) provides the values of the collision 48 constant and activation energy.

kp = 0.0272 gram MMA/ gram PTFE-min Ep = 31.3 kJ/mol

Ap = 2201 gram MMA/ gram PTFE-min kt = 2.0457 gram MMA/ gram PTFE-min Et = 1.7 kJ/mol At = 3.9 gram MMA/ gram PTFE-min

Literature values are for MMA polymerization in a solvent; whereas, the experimental data for the grafting are for a bulk system. In addition, the experimental values of the rate constants cannot be easily converted to a mole basis since the molecular weight of the PTFE is difficult to measure. It is important to note that these values will be applicable only for the L-169 : MMA system, since different grades of PTFE will have different amounts of free radicals per gram. Useful unformation, however, can be gained by comparing various ratios of the literature and experimental values. The literature 5; value of kp/kt is 2.02 x 10- the experimental value of 2• kp/kt for the graft is 1.33 x 10- The lower value for the literature ratio shows that termination· is much more likely in the solvent system that in the grafting system (Figure 25). The solvent may improve the mobility of the chains, making termination easier. This assumes that the propagation of the MMA graft proceeds according 49 to a typical MMA homopolymerization.

The ratio of Ap/At gives the relative frequency of propagation versus termination. The literature values gives Ap/At = 7.91 x 10-3; the experimental value for grafting gives 568.73 as this ratio. These values also show that termination is much more likely in a solvent rather than in the PTFE-MMA grafting system where more obstacles must be overcome. Once the chain has grown away from the PTFE matrix, it would be expected that the addition of more MMA monomer molecules would proceed at about the same rate and activation energy as in a homopolymeriztion. The literature values of 26.4 kJ/mol for Ep compares favorably with the experimental value of 31.3 kJ/mol. The experimental value may be slightly higher to account for any steric hindrances that would allow propagation to occur from only particular orientations.

The values for Et are not in good agreement: 11.9 kJ/mol for the literature value versus 1.8 kJ/mol for the graft polymer. The lower experimental value may be a result of obstacles and entanglements. Although termination seems to be less likely in the grafting system, once the chains have oriented themselves favorably for termination to occur, other hindrances prevent these chains from easily moving away from each other, and· termination results.

VI.2. DSC Results ~ H values determined from DSC scans are summarized in Table 9. 50

If the average ~ H values of duplicate runs along with the H for unreacted L-169 are graphed versus gram of graft/ gram of PTFE in the sample, regression lines are obtained (Figure 26 and 27).

~Hmelt;ng(J/g) = -31.98(gram graft/gram PTFE) + 76.27 VI.2.1.

~Hcrystall;zt;on(J/g)= -44.99(gram graft/gram PTFE) + 74.16 VI.2.2.

The values of the y-intercepts in both equations compare favorably with a value of 75.31 Joules/gram for unreacted PTFE. Addition of the PMMA graft to the PTFE matrix results in a decrease in the enthalphies of melting and crystallization since less PTFE is present per gram of polymer. Temperatures at which these transitions occurred remained approximately constant, despite the amount of graft. Since the major portion of the polymer by weight is PTFE, transitions occur at conditions similar to those for PTFE. In addition, the ratio of the heights of melting to crystallization peaks remained constant. Sample 80-55B was DSC scanned twice. The increase in disorder caused by melting and recrystallization is shown by a slight decrease in the enthalpies and transition temperatures for subsequent scans. The increase in the ratio of the heights of the melting to crystallization peaks is related to the increased disorder in the system that would cause a broadening of the crystallization peak. With enough data to establish a better linear regression, DSC 51 scans could be used to determine the amount of graft in a sample given the enthalpies of transition.

VI.3. FTIR Scans FTIR scans of several samples agre given in Figures 14a - 14b.

Ratios of -CF 2CF2- in the PTFE to C=O in the poly(methyl methacryalate) graft are given in Table 10. Concentrations as determined by the relative heights of the peaks at 1200cm-1(8.33~) and 1700 cm-1(5.88~ ) are given in the first column. The second column gives the relative concentrations based on the area under the scans at these wavelengths. The results of either method do not correspond well with the data collected gravimetrically for the ratio of PMMA graft to PTFE as shown in the third column. These discrepancies may be a result of the high molecular weight of the polymeric materials: given a set number of moles of PTFE, a molar quantity of MMA will graft. With high molecular weights, increases on a mass basis will show as only slight increases in molar quantities. Kube1ka-Monk functions may not be appropriate to use with high molecular weight materials. Further FTIR work would be required to substantiate this. Despite the methods used for calculations, the value of the ratio for sample 80-1A is much smaller than those for the other polymerization times because only a very small amount of conversion has occurred at this point.

FTIR can be used as a qualitative tool to determine if significant 52 conversion of MMA monomer to graft has occured; however, its usefulness as a quantitative tool is limited unless the molecular weight of the graft and PTFE can be measured accurately.

VI.4. Electron Spin Resonance Electron spin resonance scans demonstrate the presence of free radicals in irradiated PTFE(14) (Figures 16 and 17). The scans show significantly more free radicals in Polymist~ F 5-A (Figure 17a and 17b) than in L-169 (Figure 16a and 16b). This results in a much higher conversion of MMA to graft for the Polymist~ sample since more active sites are available for reaction in this material (Figures 8 and 9).

Graft material made in experiment 6 with L-169 and polymerized for 55 minutes at 353K(80°C) still showed the presence of a slight amount of free radicals, approximately 5 per cent of the quantity seen in as received L-l69 (Figure 18). This substantiates assumption A in section VI.l.a., that the majority of PTFE active sites are used up in the initial stages of the polymerization (less than 10 per cent conversion). 53

PART VII Properties of the PMMA-PTFE graft polymer

VII.I. Physical Appearance The graft polymer, as produced, is white and slightly translucent. At low conversions it has the consistency of a fine powder similar to the irradiated PTFE. At higher conversions, the graft polymer is hard due to the presence of a higher amount of PMMA and assumes the shape of the inside of its reacting vessel.

VII.2. Stability When heated on a McQuinne block, the graft polymer softens at 483K(165°C). At 493 - 498K(220-225°C), the material flattens more easily and shows some elasticity by springing back when sliced with a spatula. At 523 - 533K(250-260°C), the material becomes more malleable, smears, and large pieces can be broken apart easily. Heating to 553K(280°C) resulted in no change of color, no signs of any liquid, and no decrease in weight after extraction, showing that the graft is stable up to this temperature.

VII.3. Moldability When the graft polymer is molded in· a Pasedna Platen Press without heating of the plates, a smooth, waxy-film is produced. This film retains the slippery properties for which PTFE is known. The film ;s brittle and cleaves easily. It will crumble if enough force is applied. 54

Sample 20A produced with 1 gram L-169 : 3 milliliters-MMA: at 353K(80°C) was molded at 1.15 x 10-1 pascals(795 psi) for five minutes with the bottom plate of the press at 463K(190°C) and the top plate at 380K(107°C). A brittle, slightly translucent film was made. This film was put back into the press at 1.73 x 10-1 pascals(1,192 psi) for 20 minutes. The resulting material was slightly less brittle, but more translucent. Water readily beaded on the surface of this film. Two piece of this film were put at right angles to each other and remolded at 5.23 x 106 pascals for 10 minutes with the top plate at 500K(227°C) and the bottom plate at 388K(115°C). The pieces fused well, showing that the graft polymer also had some adhesive properties. Overall, the graft polymer retains the slippery surface of the PTFE and the light transmittance and adhesive nature of the PMMA.

VII.4. Possible Applications of the Graft Polymer The polytetrafluoroethylene-poly(methyl methacrylate) graft may prove useful in several diverse applications due to the strength and durability of the PMMA and the non-stick properties of the PTFE.

Paints and Finishes: Poly(methyl methacrylate) and its homologs are used extensively in paints and finishes due to their durability and pigment uptake. Addition of a PTFE-PMMA graft polymer could enhance these properties by providing a non-stick surface. This should prove useful in household paints that must withstand scrubbing, automobile finishes that must bead water to help maintain a strong shine, and 55 marine paints that must prevent the attachment of barnacles and other sea debris.

Textile Uses: Spinning of the PTFE-PMMA graft into filaments and yarns could increase their wearability and resistance to soiling. The graft polymer would be an integral part of the yarn or filament, rather than an applied film, such as Scotchguard-, that could be worn away. The non-stick surface of the fabric should prevent staining and reduce the friction that causes wear.

Outdoor Applications: PTFE and PMMA are both known for their superior weatherablility. The graft polymer may be especially suitable for greenhouse applications that require translucent, rather than transparent, windows. The graft polymer may also lend itself well to reflectors; the non-stick surface would increase the efficiency of the reflector by preventing a build-up of dirt.

Household Applications: PMMA is useful in many indoor applications, such as countertops and bathtubs. Incorporation of the PTFE-PMMA graft into these products should reduce staining and the build-up of soapy residues, thus reducing both the time and frequency of cleaning.

Moldings: PMMA is very easy to mold; PTFE must be ram extruded since it does not melt under ordinary processing conditions. A graft with a high enough'PMMA content may result in melted PMMA "carryingll the PTFE 56 matrix along with it and allow for easier moldability. Internally lubricated parts, that, in addition, would release from the mold easily, could be produced. Since the graft polymers made to date do not have high strength, additives or a higher molecular weight of the PMMA graft may be required to produce parts with adequate dimensional stability. 57

PART VIII Summary

VIII.I. Conclusions Several researchers are studying graft polymers produced by irradiating a fluoropolymer film in the presence of reactive monomers(46,47). In the research, presented here, temperature, rather than irradiation, was used to drive the reaction to make a graft polymer of polytetrafluoroethylene and methyl methacrylate. The PTFE free radicals in commercially available PTFE micropowders, as formed by irradiation, were used to initiate the reaction. The amount of graft was set equal to the increase in mass of a PTFE sample after being mixed with a given amount of MMA at a certain temperature for a specified time. The amount of conversion of MMA to PMMA graft was a function of concentration, time, and temperature. Given a set amount of MMA, more conversion to PMMA graft occured if more PTFE free radicals were available to initiate the polymerization. These chains, however, were expected to be of a lower molecular weight than those that would result if fewer free radicals were available. Various grades of PTFE will result· in different conversions since they do not have the same amount of PTFE free radicals. For example, Polymist® F 5-A used for a 343K(70°C) reaction resulted in a higher conversion of MMA to graft than did Fluon® L-I69 used at 353K(80°C), 58 since the Polymist® was irradiated at a higher dosage and, therefore, contained more free radicals. Higher reaction temperatures will result in more conversion. Although gravimetric analysis did not show any gain in mass for samples run at lower temperatures (293 and 313K), Fourier transform infrared scans were different for these samples than for unreacted irradiated PTFE. A slight amount of conversion or some type of rearrangement may have taken place at these lower temperatures. Conversion at 353K(80°C) was higher than at 333K(60°C) using the same grade of PTFE. Higher conversion is seen for greater times than for shorter ones. More consistent conversion data were obtained by preheating the MMA to the reaction temperature before adding it to the PTFE. This eliminated a lag time required for heating the reaction system that would have affected the results at shorter times more significantly. Adding hydroquinone after the reaction time also improved the consistency of the data by preventing any post-polymerization that might have occured as the polymer cooled down or was extracted. Initiation in this system is very fast, and the PTFE free radicals are used up almost immediately. Steady-state assumptions do not apply to this initiation system since no more PTFE free radical initiators can be produced. The energy of propagation for this system agrees well with data derived for solvent systems, implying that the propagation of the PMMA graft follows a mechanism similar to that for MMA homopolymerization. Termination in this system is different 59

compared to a solvent system. The ratio of kp/kt for a solvent system is much lower than for the MMA graft polymerization, implying that termination is much more likely in a solvent system than in this one. The graft chains must grow far enough away from the PTFE matrix in order to find each other to bridge over other obstacles and terminate. In a solvent system, mobility is much easier, and termination more favorable. A gel effect was seen in the PTFE - PMMA graft system for those grades of PTFE that have fewer free radicals, and therefore, produce longer chains for a given conversion. The reasons for this gel effect are identical to those for a typical MMA homopolymerization: the system's viscosity was increased so greatly by the presence of high molecular weight polymer and growing polymer free radicals, that mobility was restricted and chains ends could not diffuse easily to favorable termination orientations. In order to satisfy the kinetics of this system, a series of equations was derived that explained the relationship of conversion, time, and concentration at a given temperature. This relationship is defined by the straight line given by equation VI.l.19. All concentrations were set relative to the initial amount of MMA. Since the number of free radicals in the PTFE is dificult to determine, but is homogeneous throughout the sample, the initial weight of the PTFE was used instead of the number of free radicals. Rate constants then have units of grams MMA/ grams PTFE - minutes.

Although conv~rsion data were obtained gravimetrically, 60

differential scanning calorimetry gave a good correlation for ~H versus conversion. It would be necessary, however, to generate more data to define this relationship. Kubelka-Monk functions generated by FTIR did not prove useful on a quantitative basis for this system, probably due to the relatively few end groups for this high of a molecular weight system. Qualitatively, however, the FTIR scans did support the presence of a PMMA graft. ESR scans proved the presence of PTFE free radicals in the micropowder and confirmed the assumption of a very fast initiation that used up the PTFE free radicals almost immediately. The graft polymer made was white and had an appearance ranging from the micropowder to a hard plug, depending on the concentration of the PMMMA. The polymer showed no change in color or formation of liquid up to 453K(280°C); however, it did become more malleable at higher temperatures. When molded, the block copolymer had a smooth, slippery finish that was not wetted by water. Layers of molded polymer adhered to each other with the application pressure and temperature.

VIII.2. Recommendations for Future Work • The feasibility and usefulness of the PTFE-PMMA graft copolymer would need to be demonstrated. Appropriate testing, such as molding, extrusion, weatherability, etc., would be necessary before applications could be proposed. • Production of a greater quantity of the graft copolymer 61

would be necessary before this testing could occur. •A graft polymer composed of a block of any fluoropolymer and a block of any vinyl polymer could be useful in many applications. By using the most suitable fluoropolymer free radical and vinyl monomer, a custom-made block polymer can be produced. To do this would require a study of the kinetics involved for each combination. • In order to determine the usefulness of the kinetics derived for this system to described other non-steadY state cases or those systems for which the steady state assumption is assumed to hold true, appropriate experimentation with other materials would be necessary. • To improve the kinetics equations of the system, a relationship between the dose of irradiation to the fluoropolymer was subjected and the conversion of the vinyl monomer to graft polymer would need to be developed. This relationship would have to account for the decay of the free radicals with time, if the free radicals were to be used immediately after irradiation. • DSC scans could be correlated with conversion to define a better relationship between the heats of the transitions and the amount of graft present. A large amount of time could be saved using DSC since it is much faster than the gravimetric technique used with extractions to constant weight. 62

• If IR analysis is to be used, absorption and transmission scans may prove more useful than Kubelka-Monk functions. 63

References 64

References (continued)

14. ) S. Siegel and H. Hedgpeth, J. Chern. Phys., ~, 3904 (1967). 15. ) N. R. Lerner, J. Chern. Phys., .E.Q., 2902 (1969).

16.) J. H. Golden, J. Po 1ym • Sc i ., 45, 146 (lg60). 17.) H. S. Judeikis, H. Hedgpeth, and S.Siegel, Radiation Research, 65 References (continued)

30. ) R. G• W• No rrish and R. R. Sm i t h, Na t ure, 150 , 336 (1942) • 31.} J. N. Cardenas and K. F. OIDriscoll, J. Polym. Sci., Polym. Chern. Ed.,..!i, 883 (1976).

32•) T. Ma 1avsic, V. 0sredkar, I. An zur , and I. Viz 0 visek, J. Macrornol. Sci. - Chern., A19(7), 987 (1983). 33.) E. Abuin and E. A. Lissi, J. Macromol. Sci. - Chern., A13(8), 1147 (1979). 34.) E. Abuin and E. A. Lissi, J. Macromol. Sci. - Chern., Al1(5), 967 (1977). 35.) H. A. Szymanski, The Theory and Practice of Infrared Spectroscopy, Plenum Press, N. Y. (1964). 36.) H. W.Siesler and K. Holland-Moritz, Infrared and Raman Spectroscopy of Polymers, Marcel Dekker, Inc., N. Y. (1980). 37.} R. W. Frei and J. D. Mac Neil, Diffuse Reflectance Spectroscopy in Environmental Problem Solving, CRC Press, Cleveland, Ohio (1973) • 38.) W. W. Wendlandt and H. G. Hecht, Reflectance Spectroscopy, Interscience Publishers, N. Y. (1966). 39.) M. Symons, Chemical and Biochemical Aspects of Electron Spin Resonance Spectroscopy, John Wiley and Sons, N. Y. (1978). 40.) "Perkin-Elmer Model DSC-l Di fferential Scanning Calorimeter", Perkin-Elmer Instrument Division, Norwalk, Connecticut. 41.) W. K. Fisher, Ph.D. Dissertation, Rensselaer Polytechnical Institute, Troy, N. Y. (1981). 66

References (concluded)

42.) W. L. Gore, Statistical Methods for Chemical ExperiMentation, Interscience Publishers, Inc., N. Y. (1952).

43.) R. E. Moynihan, J. Amer. Chern. Soc., ~, 1045 (1959). 44.) R. T. Morrison and R. N. Boyd, Organic Chemistry, Allyn and Bacon, Inc., Boston, Mass. (1973).

45.) G. B. Thomas Jr., Calcul us and Analytical Geometry, Addison-Wesley PUblishing Company, Reading Mass. (1968).

46.) T. Nenner and A. Fahrasmove, Int. J. Hydrogen Energy, ~, 309 (1984). 47.) E. A. Hegazy, J. Polym. Sci., Polym. Chern. tu., .?l, 493 (1984). 48.) C. A. Sperati, "Fl uoropl astt cs", Modern Plastics Encyclodedia,

~, lOA (1982). 49.) J. Brandrupt and E. H. Immergut, Eds., with W. McDowell, Polymer Handbook, 2nd Ed., Wiley Interscience, N. Y. (1975).

50.) H. Krenz, "Ac ryl t c'", Modern Plastics Encyclopedia,~, IDA, 1982. 67

Appendix A

Properties of Polytetrafluoroethylene

Molecular Weight(8) (commercial material)

Melting Point(48) 600K(327°C) (fabricated material)

Density(8,lO) 2.0 Mg/m3 - 2.3 Mg/m 3 (2.0 g/cm3 -2.3 g/cm3)

Coefficient of friction(48) 0.01 68

Appendix B

Properties of Methyl Methacrylate

CH3 I Structure(44) H2 C=C ~OOCH3

Density of Monomer(49) 291K( 18°C) 0.9558 Mg/m 3(0.9958 g/cm3) 29 3K( 20°C) 0.9535 Mg/m 3(0.9535 g/cm 3)

Density of Polymer(23) 298K( 25°C) 1.179 Mg/m 3(1.1790 g/cm 3)

Volume change upon Polymerization(23) -20.6%

Molecular Weight of Po 1ym er(23) 50,000 - 100,000

White Light Optical Transmi 55ion(50) 92%

WeatherabilitY(50) very hi9h 69

Appendix C

Variables Studied

Variable Range

Temperature 293 - 353K(20 - 80°C)

Time 1 - 145 minutes

Ratio of grams PTFE to milliliters MMA 1:3, 1:5, 1.5:2, 2:5, 1:27, 1:10

PTFE grades Fluon® L-169 and L-171, Polymist® F 5-A

MMA grades Fisher laboratory grade with 25 ppm HQ DuPont commercial grade with 100ppm HQ 70

Appendix D: Experimental Code

Experiment Reaction PTFE MMA grams PTFE: Temperature No. Temperature, mil liters of MMA kelvins,(OC) MMA kelvins(OC)

1 293 (20) L-169 Dupont 1 3 room temp. 2 313 (40) L-169 Dupont 1 3 313 (40)

3 333 (60) L-169 Dupont 1 3 room temp.

4 333 (60) L-169 Dupont 1 3 333 (60)

5 333 (60) L-169 Dupont 1 5 333 (60) 6 353 (80) L-169 Dupont 1 3 353 (80) 7 353 (80) L-169 Fisher 1.5:2 353 (80)

8 343 (70) Polymi st~ Dupont 2 5 273.2(0.2) F 5-A

9 353 (80) L-171 Fisher 1 27 room temp. 1 10 71

Appendix E: Sample Code

Sample Experiment Reaction Time

RT-55A 1 55 40-55A 2 55

80-lA 6 1

80-3A 6 3

80-20A 6 20

80-55A 6 55

80-55B 6 55

80-90B 6 90

80-145A 6 145

80-145B 6 145 72

Tab 1e 1

Reaction Data at 333K(60°C) with 1 gram PTFE(L-169} : 3 milliliters MMA (DuPont) at room temperature

Time PTFE MMA Graft Conversion Graft (min) (g) (ml) (temp K) (g) (g) (~) PTFE 1 4.0119 9.0 303 8.4780 0.0565 0.6664 0.0141 1 2.8401 9.1 303 8.5722 0.0773 0.9018 0.0272 1 3.0195 8.9 298.5 8.4299 0.0036 0.0427 0.0012 1 3.0656 8.9 29A.5 8.4~q9 3 3.0164 9.0 303 8.4780 3 3.2570 8.8 303 8.2896 3 2.9771 9.0 298.5 8.5246 3 2.9805 9.0 299 8.5194 0.0107 0.1~56 0.0036 7 3.0890 9.1 302 8.5827 0.0008 0.0093 0.0003 7 2.9369 9.1 303 8.5722 0.291;1 3.4542 0.1008 7 3.1959 9.1 298.25 8.6219 7 ~.9735 9.1 298 8.6245 0.0167 0.1936 0.0056 20 2.9175 8.9 303 8.3838 0.7340 8.7550 0.2516 20 3.1769 9.1 302 8.5827 0.2~9q 2.6786 0.0724 20 3.0120 9.1 299.25 8.6114 0.0732 0.8500 0.0243 20 2.9461 9.0 299 8.5194 55 2.9707 9.0 303 8.4780 0.4411 5.2029 0.1485 55 2.9999 9.0 303 8.4780 0.4648 5.4824 0.1549 55 2.9452 8.9 299 8.4247 0.5533 6.5676 . 0.1879 55 3.0006 9.0 300 8.5091 O.1i711 6.7116 0.1901

Table 2

Experiment 4: Reaction Data at 333K(600C) w1tB 1 gram PTFE(L-169) .. 3 milliliters HMA at the reaction temperature

Time PTFE MMA Graft Conversion Graft (min) ( g) (m 1) (temp K) (g) (g) (I) ---rnt 1 3.1130 9.0 333.5 8.1623 0.0770 0.9434 0.0247 1 3.4062 9.0 333.5 8.1623 0.0898 1.1002 0.0264 1 2.8508 9.1 334.5 8.2426 0.0732 0.8881 0.0257 3 3.1630 9.0 333.75 8.1597 0.0350 0.4289 0.0111 3 3.1914 9.0 333.5 8.1623 0.0993 1.2166 0.0311 3 2.7378 9.1 334.5 8.2426 0.0282 0.3421 0.0103 3 3.0710 9.1 334.5 8.2426 0.0388 0.4707 0.0126 7 3.5109 9.0 333.5 8.1623 7 3.4612 9.0 333.5 8.1623 0.0374 0.4582 0.0108 7 2.7063 7.4 332 6.7240 0.0552 0.8209 0.0204 7 3.2588 9.1 334 8.2478 0.0383 0.4644 0.0118 20 3.1975 9.0 333 8.1675 0.0703 0.8607 0.9220 20 3.5393 9.0 333.5 8.1623 0.1324 1.6221 0.0374 20 2.7364 9.1 334.5 8.2426 0.1486 4.2292 0.1274 20 3.0906 9.1 334.5 8.2426 0.4035 4.8953 0.1306 55 3.1169 9.1 333 8.2583 0.4353 5.2723 0.1397 55 3.0776 9.0 334 8.1572 0.6212 7.6154 0.2018 73

Table 3

Experiment 5: Reaction Data at 333K(60°C) with 1 gram PTFE(L-169) 5 milliliters MMA (DuPont) at the reaction temperature

Time PTFE MMA Graft Conversion Graft (min) (g) (ml) (temp K) (g) (g) (%) PTFt 1 2.0886 10 333 9.0750 0.0274 0.3019 0.0131 1 2.0010 10 333 9.0750 0.0230 0.2534 0.0115 1 2.2952 10 333.5 9.0693 1 2.1866 10 334.5 9.057R 1 2.1221 10 334 9.0635 1 2.0158 10 333.5 9.0693 0.0484 0.5337 0.0240 3 2.0998 10 334 9.0635 3 1.9173 10 332.5 9.0808 3 2.1427 10 334 9.0635 3 1.9406 10 334.5 9.0578 3 2.0367 10 334 9.0635 3 1.9292 10 334 9.0635 0.1151 1.~699 0.0597 7 1.9406 10 336.5 9.0348 0.0040 0.0443 0.0021 7 2.0848 10 335 9.0520 0.0017 0.0188 0.0008 7 1.9858 10 333.5 9.0693 7 2.1845 10 333.5 9.0693 7 1.8220 10 334 9.0635 7 1.8859 10 334 9.063~ 20 1.9855 10 334 9.0635 20 1.9924 10 335 9.0520 20 2.1770 10 335 9.0520 0.0511 0.5645 0.0235 20 1.9467 10 333 9.0750 0.0776 0.8551 0.0399 20 1.9421 10 333.5 9.0693 20 1.9281 10 333 9.0750 55 1.9903 10 332.5 9.0808 0.3866 4.2573 0.1942 55 1.9415 10 333.5 9.0693 0.3335 3.6772 0.171R 55 1.9462 10 332.5 9.0808 0.3486 3.8389 0.1791 55 1.9952 10 333 9.0750 0.1874 2.01\50 0.09~9 55 1.9855 10 333 9.0750 0.1214 1.3377 0.0611 55 1.9079 10 333 9.0750

Tab 1e 4

Experiment 6: Reaction Data at 353K(80°C) with 1 gram PTFE(L-169) 3 milliliters MMA (DuPont) at the reaction temperature

Time PTFE MMA Graft Conversion Graft ("'Iin) (g) (ml) (temp K) (g) (g) (~) PTFt 1 2.8464 9 353 7.9605 1 2.9903 9 354 7.9502 1 2.9859 9 353 7.9605 0.0370 0.4648 0.0124 1 2.8569 9 355 7.9398 0.0332 0.41R1 0.0116 3 2.8508 9 353 7.9605 3 3.0767 9 353 7.9605 3 3.0606 9 353.75 7.9527 0.0284 0.3571 0.0093 3 3.0936 9 354.5 7.94~ 0.O~25 0.4091 0.0105 7 2.9769 9 352.5 7.9657 0.2068 2.5961 0.0695 7 2.9333 9 353 7.9"05 0.4585 5.7597 0.1563 20 3.1614 9 352.5 7.9651 0.4503 5.6530 0.1424 20 2.987? 9 352.5 7.9657 0.70~3 8.8542 0.?361 55 3.0604 9 352.5 7.9657 0.6653 8.3521 0.2174 55 3.0634 9 353 7.9605 0.7073 8.8851 0.?309 90 9.2067 31.5 338 28.4051 3.6879 12.9832 0.4006 90 9.5245 30 337 27.0870 3.6891 13.6194 0.3873 145 9.4655 30 353 26.5350 5.5058 20.7492 0.5817 145 10.6757 30 353.5 26.5178 5.8298 21.9845 0.5461 74

Table 5

Experiment 7: Effects of Hydroquinone on Post-Polymerization: reaction data at 353K(80°C) with 1.5 grams PTFE(L-l~9) : 2 milliliters MHA(Fisher) at the reaction temperature

Time PTFE HMA HQ* Graft Conversion Graft (min) (g) (ml) (temp K) (9) (9) (g) (I) --pm 1 1.7846 2 303 1.8840 0.065 0.307 16.2q51 0.1720 1 1.6677 2 303 1.8840 0.000 3 1.5922 2 303 1.8840 0.078 3 1.6300 2 303 1.8840 0.000 5 1.5068 2 303 1.8840 0.087 0.3295 17.4894 0.~187 5 1.5609 2 303 1.8840 0.000 0.1463 7.7654 0.0937 10 1.3320 2 303 1.8840 O.OQl 0.1761 9.3471 0.1322 10 1.6271 2 303 1.8840 0.000 0.1763 9.3577 0.1084 25 1.4372 2 303 1.8840 0.074 0.1674 8.A854 0.11fi5 25 1.5087 2 303 1.8840 0.000 0.1967 10.4406 0.1304 50 1.5224 2 303 I.A840 0.092 O.34Q9 1~.5722 0.?298 50 1.5690 2 303 1.8840 0.000 0.3825 20.3025 0.2438

*Measured on a Mettler P-160 Balance

Table 6

Experiment 8: Reaction Data at 343K(70°C) with 2 grams PTFE(Polymiste F-5A) 5 milliliters MMA (DuPont) at 273.2K(0.2°C)

Time PTFE tt4A Graft Conversion Graft (min) (g) (ml) (temp K) (g) (g) (%) PTFt 1 5.9401 15 273.2 14.6441 1 5.8Q51 15 273.2 14.6441 1.7507 11.9550 0.2970 3 6.1659 15 273.2 14.6441 2.2071 15.0716 0.3580 3 5.9942 15 273.2 14.6441 2.8822 19.6R16 0.4808 7 5.7898 15 273.2 14.6441 4.5899 31.3430 0.7928 7 4.5060 15 273.2 14.1;441 5.0419 34.4296 1.1189 20 , 6.6620 15 273.2 14.6441 6.7631 46.1831 1.0152 20 6.2509 15 273.2 14.6441 5.6811 38.7945 0.Q088 55 6.0352 15 273.2 14.6441 7.7386 52.8445 1.2822 55 6.5761 15 273.2 14.6441 5.8351 39.8461 0.8873

Table 7

Experiment 9: Reaction Data at approximately 353K(800C) with different ratios of PTFE(L-171) MMA (Fisher)

Time PTFE HMA Graft Conversion Graft (min) (g) (ml ) (temp K) (g) (g) (%) PTFt 60 1.4980 40 303 37.6800 0.6024 60 1.5987 0.4021 4.5?53 46 303 43.3320 I.R122 4.1821 0.4005 75

Table 8 Residue after evaporation of the acetone used for extrations Acetone used to extract Acetone used to extract Acetone as Acetone as 80-14SA 80';'1458' . " recei ved received + ~droqu1none

grams of Residue 0.8272 0.9367 1.0484 0.0018 grams of Hydroqui none 0.1605 0.1885 1.0459 grams of Remainder 0.6667 0.7482 0.0025 0.0018

Table 9

Results of DSC Scans

MELTING CRYSTALLIZATION MASS Hmelting PEAK TEMP. H CRYSTALLIZATION SAMPLE PEAK TEMP. RATIO OF HEIGHTS OF ir!!9l ~ J&... ~ ill-. MELTING/CRYST. PEAKS PTFE l-169 11.8 75.31 608.5 75.37 590.5 0.75

80-5581-1 8.9 72.08 607 63.17 588 80-5581-2 8.9 0.79 63.17 603 61.87 587 1.02

80-5582 8.9 70.47 608.5 58.41 590.5 0.75

80-90B1 9.4 61.57 606 61.21 588 0.77

80-90B2 9.2 63.36 607 55.82 588 0.78

sample 558 at 0.2309 g graft/g PTFE

Sample 90B at 0.3873 9 graft/g PTFE

$ample 5581 was scanned twice 76

Table 10

Mass ratios of PMMA to PTFE in the graft polymer as detenmined by FTIR. Based on peak Based on area sampl e Based on gravimetric heights under peaks ~

80-1A 0.0040 0.0105 0.0224

80-20A 0.0877 0.0332 0.1424

80-55A 0.1014 0.0289 0.2174

80-145A 0.1037 0.0349 0.5817

80-145B 0.1573 0.0387 0.4445

Table 11

Kinetic Constants and linear Correlation coefficients as Defined by equation VI.l.19.

Temp. PTFE:MMA ""'A Temp. s ~A g ~~A Experiment K(OC) g:ml K(OC) 9 PTFE-mi n 9 PTFE-mi n r Conwnents 3 333{ 60) 1:3 303(30) 0.0275 1.q858 0.81 4 333{ 60) 1:3 333(60) 0.02fi9 2.1509 0.73 3&4 333(60) 1:3 0.0272 2.0457 0.77 All data at 333K PTFE:MMA: : 19:3ml 5 333(60) 1:5 333(60) 0.264 4.0343 0.70 6 353(80) 1:3 353(80) 0.0546 1.3369 0.89 All data at 353K 6 353(80) 1:3 353(80) 0.0516 2.1209 0.92 Data at 353K up to 71 min

6 353(80) 1:3.2 353(80) 0.0129 0.0632 0.99 Data at 353K from 77 min 8 343(70) 2:5 273.2(0.2) 0.6891 4.8990 0.92 PTFE = Poymi st- F-5-A ~ lLJ ~ c: LLc o c: t-O • 0 0... QJ ..f-J.s::: )( s; r- ..... (,/) ttJ..f-J 0 U c, .r- C'l L.. .r- -010"'"QJ.,... QJ c, c: a.E LL-o u >, ..f-JQJa. CUCU c: o ttJ V') r- ", r-4 ....., +-J ", o ...J CItS r-4 -~ .,... E -- en en Q) (/)""0 s: '+- ::;, r ..f-J 000..c '+ ~ V) ~ C. o c: Q)LL r- CUOttJ QJ o .s:::.Er .D L (,/)",;:, U en "C .... CUCl)Q) c: E CQ)L ~ .,... L QJV') o "'0 CU (/) ~ r- ::;,.,... U U E QJ r- r- E c: 0 > c: 0 U ", L. o ItS U - 10 L. 0 ..f-J+-) .J:) )( ....,C(/) ..f-l~ CI) .,... -c 0'\ (/) (/) ~ o (/) (/) ...... ,... en L.. >. c: .,... C") L..c Q) 0c: c: o, Clc: ~ c::( o, U+J ~c:( 0 c:( C\ c: ,...... f-l ", ", c· .... ItSLO ItS 0'\ s: Q) aJ • U ..c Q)1tS CU • CO ~ \4- ,.... .c. 0-\.0 u 0.0' aJr-4 lJJ Cl o ~r-4 0::: c: c: LL QJ Eo>, .- ItS ...... 0 a... ~ • L+-J QJeo r- 0l1tS'"O sz »:» IO 10·,... Q) ....., .,... L E ~(/) V) -c....,L. ~o c: ~ (/)0 0·,... L U \t ....., U ..... CU ...., ..r::.(/) (J).,... ",..-cu r- (J) E U CU c: ,... CU ItS ""0'" .. .c:: • \4- o L OE U~ :E~ V') CU • ,.... r-ItS ~ ItS CO' U 0""-'" Cl)C')CI) N ,..... ItSCU ox,..... QJ CU~CU::;, L L s: U :::J ~.f-J Q) en t:nOQ),...... ,... c:.t::. 0 l.L LL ""-"'~E 78

Figure 3: Conversion(%) vs. time(min.) at 333K(60°C) with 1 gram PTFE (L-169) : 3 milliliters MMA (DuPont) at room temperature

9 D

7 B 6 z 0 ~ ~ 5 ~ Z 0 4 0 ~ D 3

0 0 20 ~ ~ nME(m~)

Linear Regression Line: y = 0.IOD8x + 0.7637 r = 0.70 79

Figure 4: Experiment 4: Conversion(%) vs. time(min.) at 333K(60°C) with 1 gram PTFE(L-lfi9) : 3 milliliters MMA (DuPont) at the reaction temperature.

8 D 7

z 5 0 a iii I[ ~ D 0 0 ~ 3

2 a

0 0 20 40 60 TIME (min)

Linear regression line: y = 0.113x + 0.4050 r = 0.88 80

Figure 5: Experiment 5: Conversion(%) vs. time(min.) at 333K(60°C) with 1 gram PTFE(L-169) 5 milliliters MMA (DuPont) at the reaction temperature.

4.5 D 4 D D 3.~

3 z 0 iii II: 2.5 l&I >z 0 2 D 0 ~ 1.5 D 0

0.5 D a

O.....--a...... ---...,.-.--.....----..-----w------I o 20 60 TIME (min)

Linear Regression Equation: y = 0.0511x + 0.1458 r = 0.84 81

Figure 6: Experiment 6: Conversion(%) vs. time(min.) at 353K(80°C) with 1 gram PTFE(L-169) 3 milliliters MMA (DuPont) at the reaction temperature.

z 14 0 Ii I: 12 III ~ 0 10 U D ~ 8 D

6 D D

0 0 20 40 60 80 100 120 140 TIME (min)

Linear Regression Equation: y = O.1341x + 1.7870 r = 0.97 82

Figure 7: Experiment 7: Effects of Hydroquinone on post-polymerization: conversion(%) vs. time(min.) at 353K(80°C) with 1.5 grams PTFE(L-169) : 2 milliliters MMA(Fisher) at room temperature.

21 ..,..------20 19 18 D 17 16 a z o 15 Ii I: 14 ~ o 13 o 12 • 11 10 • 9 8 7 6-+-----....----...... ---...------... o 20 nME (min) D No HQ + HQ:f.tMA::1 :4 .=ffi

Linear Regression Equations: No Hydroquinone y = 0.1308x + 10.5310 r = 0.50 HQ:MMA::l:4; y = 0.0397x + 13.3962 r = 0.17 R3

Figure 8: Experiment 8: Conversion(%) vs. time(min.) at 343K(70°C) with 2 grams PTFE(Polymist® F 5-A) : 5 milliliters MMA (DuPont) at 273.2K(O.2°C).

55 D 50

0 45

40 D Z a 0 iii I: 35 D bJ >z 0 30 0 ~ 25

20 D

15 D

D 10 0 20 40 60 nME (min)

Linear Regression Equation: y = O.5006x + 22.7269 r = 0.77 84

Figure 9: Experiment 8: Conversion(%) vs. time(min.) at 343K(70°C) with 2 grams PTFE(Polymist~ F 5-A) : 5 milliliters MMA (DuPont) at 273.2K(O.2°C).

55 D 50

D 45

40 z 0 iii ~ 3S ~ 0 30 0 " 25

20 D

15 a

10 0 2 3 4 LH nME (min)

Linear Regression Equation: y = 9.5053x + 11.0154 r = 0.93 85

Figure 10: FTIR scan of the residue in the acetone after extraction of graft sample 80-1458 made at 353K(80°C) for 145 minutes with 1 gra~ PTFE(L-169) : 3 milliliters MMA(DuPont) at the reaction temperature (experiment 6).

I- ----~:::;-t-I I ! •L .a• I ~ i e> I • I

: ~ ~ I I ~ ~ ~ ~..~ ~ ~. ~ II ; ~ 86

Figure 11: DSC scan of L-169

590.5

608.5

600 610 620 610 600 590 580 570

Temperature(kelvins) 87

Figure 12a: DSC scan of graft sample 80-558 made at 353K(80°C) for 55 minutes with 1 gram PTFE(L-169) : 3 milliliters MMA(DuPont) at the reaction temperature; first run of melting and recrystallization.

607 588

600 610 620 610 600 590 580

Temperature(kelv;ns) 88

Figure 12b: Same sample as in Figure 12a; second run of melting and recrystallization.

603 587

590 600 610 600 590 580

Temperature(kelvins) 89

Figure 12c: Duplicate OSC scan of the sample used in Figure 12a.

608.5

590.5

590 600 610 620 600 590 580 570

Temperature(kelvins) 90

Figure 13a: DSC scan of graft sample 80-90B made at 353K(80°C) for 90 minutes with 1 gram PTFE(L-169) : 3 milliliters MMA(OuPont) at the reaction temperature (experiment 6).

588

580 600 610 620 600 590

Temperature(kelvins) 91

Figure 13b: Duplicate DSC scan of sample 80-90B (experiment 6).

588

607

590 600 610 620 600 590 580

Temperature(kelvins) 92

Figure 14a: FTIR scan of graft sample 80-1A produced at 353K(80°C) for 1 minute with 1 gram PTFE(L-169) : 3 milliliters MMA(OuPont) at the reaction temperature (experiment 6).

I...

I ! • .! I ; ~ I » I I .... 1ft fit N 1ft ... ~ . I •. II .., • I . ~ ...... II 93

Figure 14b: FTIR scan of graft sample 80-3A produced at 353K(80°C) for 3 minutes with 1 gram PTFE(L-ln9) : 3 milliliters MMA(DuPont) at the reaction temperature (experiment 6).

I-

I...

IN°

•L

I te •a> I • I I N N .. •. . • •. . N .. N N N .. - - - •. •. . . 94

Figure 14c: FTIR scan of graft sample 80-20A produced at 353K(80°C) for 20 minutes with 1 gram PTFE(L-169) : 3 milliliters MMA(DuPont) at the reaction temperature (experiment 6).

I...

•L .a• I I •a> I • I I .., N .... ••...... •..1ft ...... 95

Figure 14d: FTIR scan of graft sample 80-55A produced at 353K(80°C) for 55 minutes with 1 gram PTFE(L-169) : 3 milliliters MMA(DuPont) at the reaction temperature (experiment 6).

I I- I- I ! •~ I ~ I~ I • I I • N ~ • N ~ • N • N • •~ •~ ~ ~ • • N •. •.. . - .. •. . . N N N - -- - 96

Figure 14e: FTIR scan of graft sample 80-145A produced at 353K(80°C) for 145 minutes with 1 gram PTFE(L-169) : 3 milliliters MMA(OuPont) at the reaction temperature (experiment 6).

~ • • ~ • ~ ~ ...... • . N. ~. 97

Figure 14f: FTIR scan of graft sample 80-1458 produced at for 145 353K(80°C) minutes with 1 gram PTFE(L-169) : 3 milliliters MMA(OuPont) at the reaction temperature (experiment 6).

I- I- I ! •Ii I 1 •~

In. 98

Figure 15: FTIR scan of L-169.

I...

I.. I

IN }• I •~ > 0 I • I I .. . • .. N til •• .. N N •. •. ....N •. •. ... N...... ,.; ,.; N tV tV N ......

~z LL..:)cu.,,·... Oc: 99

Figure 16a: ESR scan of L-169. (Gain = 103).

DPPH

0 Gain = 1.25 x 10

Figure 16b: ESR scan of the same L-169 sample as in Figure 16a, taken 2 months later. (Gain = 103).

\ ~

DPPH 100

Figure 17a: ESR scan of Polymist~ F 5-A. (Gain = 2 x 102).

o Gain = 1.25 x 10

Figure 17b: ESR scan of the same Polymist~ F 5-A sample as in Figure 17a, taken 2 months later. (Gain = 2 x 102).

DPPH 101

Figure 18: ESR scan of sample 80-55A run at 353(80°C) for 55 minutes with 1 gram PTFE(l-169) : 3 milliliters MMA(DuPont) at the reaction temperature (experiment 6). Curve 1 corresponds to a scan with DPPH in the reference cavity. Curve 2 corresponds to a scan without DPPH in the reference cavity. (Gain = 104).

Curve 2

Gain = 1.25 x 100 102

Figure 19: FTIR scan of sample RT-55A produced at room temperature for 55 minutes with 1 gram PTFE : 3 milliliters MMA(DuPont) at room temperature (experiment 1).

I ! L• G ~ I ~ G a> I ~ I I • • • • N ~ • • • N N • • • N • • N. ~ M ~ M N N N N ~. ~. ~..~ - .. . . 103

Figure 20: FTIR scan of sample 40-55A produced at 313K(40°C) for 55 minutes with 1 gram PTFE(L-169) : 3 milliliters MMA(DuPont) at the reaction temperature (experiment 2).

•L i• ~ a> ~

• ~ ~ ~ N ~ ~ •• ~ • n ~ ~ N ~ ~ ~ ~ ~ ~ ~ ...... 104

Figure 21: Application of equation VI.1.19. to experiment 3; reaction data at 333K(60°C) with 1 gram PTFE(L-169) : 3 milliliters MMA(OuPont) at room temperature.

0.07 ------..,,---,

0.06 D D O.OS

"~ 0.04 <, 0 ~ D 'J z 0.03 .J D

0.02

0.01 n

O...... - ...... ----r=--r----liir---,----r--.--,--..., o 2 3 4 LN nME (min)

Linear Regression Line: y = O.0139x - 0.0049 r = 0.81 105

Figure 22: Application of equation VI.l.19. to experiment 4; reaction data at 333K(60°C)with 1 gram PTFE(L-169): 3 milliliters MMA(DuPont) at the reaction temperature.

0.08

0.07

0.06

0.05 "~ -, 0 ~ 0.04 '-' Z .J O.OJ

0.02 D

0.01 D 0 B D 0 0 2 3 4 LN TIME (min)

Linear Regression Line: y = O.0125x -0.0035 r = 0.73 106

Figure 23: Application of equation VI.l.19. to experiment 5; reaction data at 333K(60°C)with 1 gram PTFE(L-169): 5 milliliters MMA(DuPont) at the reaction temperature.

0.045 D

0.04 D D 0.035

0.03

~ ~ , <, 0.025 0 ~ '-' D z 0.02 .J

0.015 D

0.01 D

0.005 D

0 0 2 3 ... L.N nME (min)

Linear Regression Line: y = 0.0066x - 0.0008 r = 0.70 107

Figure 24: Application of equation VI.l.19. to experiment 6; reaction data at 353K(80°C)with 1 gram PTFE(L-169): 3 milliliters MMA(DuPont) at the reaction temperature.

0.26

0.24

0.22 0.2

0.18

0.16 '"~ <, 0.14 0 ....,:J 0.12 z .J 0.1 D / 0.08

0.06 D 0.04

0.02

0 0 2 4 l.N TIME (min)

Linear Regression Line: y = 0.0243x + 0.0056 to 77 minutes r = 0.92

Linear Regression Line: y = O.204Bx - 0.7788 above 77 minutes r = 0.99 108

Figure 25: Application of equation VI.l.19. to experiment 8; reaction data at 343K(70°C)with 2 grams PTFE(Polymist® F 5-A): 5 milliliters MMA(DuPont) at 273.2K(O.2°C).

0.8 D 0.7

D 0.6

D 0.5 D "~ <, 0 D :! 0.4 \,J z .J 0.3

0.2

0.1

0 0 2 3 4 LN nME (min)

Linear Regression Line: y = 0.1407x - 0.0946 r = 0.92 109

Figure 26: Schematic for the grafting of MMA on to the PTFE free radical matrix. (a) Early in the reaction the cnains can terminate easily since there are few steric hindrances and enough near neighbors with which termination can occur. (b) As the conversion increases, the chains become longer. More entanglements result and there are fewer neighbors available for termination. The chains must grow far away from the PTFE matrix to avoid entanglements and find a reactive end with which termination can occur.

PMHA GRA"

\ I .1 I/- "I , , "

ACTIVE SITES \<, PTP! SUIFACI

Fi gure 26a

"\ ~~.oOIllL_------~~~l~iNS ,I , / , , \ , I I " E~LEH!NTS I , '/ I i TF.RHItiAIEP ?a. ,. .. / .- - "' .1~/_ . CHAINS \ , I ,I ." , ' " --- ..... JI: .~ .... " \I " , ..... " , \ \ ',---!...... /" ' '\ \ \0 -- , .. I I \

Fi gure 26b 110

Fi gure 27: ~ Hmelting (JIg) of the graft polymer vs. grams graft/ gram PTFE. Data were obtalned from DSC scans in Figures 11 - 13.

n 78 75 74 7J 72

~ 71 .,1:11 "..., 70 1: 89 88 67 6& 85 D' 64 83 0 0.1 0.2 0.3 0.4 9 GRAFf/ Q PTFE

Linear Regression Line: y = -31.98x +76~27 r = 0.95 111

Figure 28: ~Hcrystallization (J/g) of the graft polymer vs, gram graft/ gram PTFE. Data were obtained fro DSC scans in Figures 11 - 13.

78 75 74 73 72 71 70 89 88 "G 87 -, ....,., S8 J: 6S 64 63 62 81 D 80 59 D 58 57 58 0 0.1 0.2 0.3 0.4 9 GPNT/ 9 PTFE

Linear Regression Line: y = -44.99x + 74.16 r = 0.96 Donato, Karen Ann. M.S. Nov., lq85 Cherni ca1 Engi neeri ng

Graft polymerization of methyl methacrylate onto polytetrafluoroethylene free radlcals.(III pp.)

Director of Thesis: C. A. Sperati

The purpose of this research is to use polytetrafluoroethylene (PTFE) free radicals, as formed by irradiation, to initiate a methyl methacrylate (MMA) polymerization. This results in the formation of a block copolymer of PTFE and PMMA. The kinetics of this system are of special interest, since the steady state assumption in the theory of free radical polymerization does not apply. To carry out this reaction, samples of irradiated PTFE were weighed in test tubes and methyl methacrylate was added volumetrically. The mixture was placed in a constant temperature bath and the reaction was carried out for a specified amount of time. At the end of the time limit, hydroquinone at approximately one weight per cent of the total reacting mixture was added to the test tube to quench the reaction. All reactions were performed in air at atmospheric pressure. Various temperatures and ratios of PTFE to MMA were used. The contents of the test tubes were removed to dried preweighed extraction thimbles. Extractions in acetone were carried out in a Soxleht extraction column until the thimbles and their contents reached a constant weight. The amount of poly(methyl methacrylate) grafted onto the polytetrafluoroethylene free radicals was found by sUbtracting the mass of the thimble and amount of PTFE used from the total mass of the thimble and its contents. Conversion was defined as the amount of graft formed divided by the initial mass of MMA used. DSC, ESR, and FTIR were used to substantiate the gravimetric analysis. The amount of conversion of MMA to a graft onto the PTFE free radicals is a function of concentration, time, and temperature. Given a set amount of MMA, more conversion to PMMA graft occurs if more PTFE free radicals are available to initiate the polymerization. Various grades of PTFE formed by different radiation doses result in different conversions because they do not contain the same amount of free radicals. Higher reaction temperature and longer times result in more conversion. Initiation in this system is very fast, and the PTFE free radicals are used up almost immediately. Steady state assumptions do not apply to this system since no more PTFE free radical initiators can be produced. Propagation is assumed to follow the same scheme as for a methyl methacrylate homopolymerization in a solvent. Termination is more difficult in this case than in a solvent system since the MMA chains are restricted by being attached to the PTFE matrix and must grow far enough away from this matrix to find another chain with which to terminate. In order to satisfy the kinetics of this system, an equation is derived that relates the natural logarithm of the ratio of the initial to the final quantity of MMA to the natural logarithm of time. This straight line has a slope of kp/kt, the ratio of the rate