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The Curing and Degradation Kinetics of Sulfur Cured EPDM Rubber A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science By ROBERT J. WEHRLE B.S., Northern Kentucky University, 2012 Wright State University 2014 WRIGHT STATE UNIVERSITY GRADUATE SCHOOL August 29, 2014 I HEREBY RECOMMEND THAT THE THESIS PREPARED UNDER MY SUPERVISION BY Robert Joseph Wehrle ENTITLED The Curing and Degradation Kinetics of Sulfur Cured EPDM Rubber BE ACCEPTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE. Eric Fossum Ph.D. Thesis Director David A. Grossie, Ph.D. Chair, Department of Chemistry Committee on Final Examination Eric Fossum, Ph.D. William A. Feld, Ph.D. Steven B. Glancy, Ph.D. Kenneth Turnbull, Ph.D. Robert E. W. Fyffe, Ph.D. Vice President for Research and Dean of the Graduate School Abstract Wehrle, Robert J. M.S, Department of Chemistry, Wright State University, 2014. The Curing and Degradation Kinetics of Sulfur Cured EPDM Rubber. Ethylene‐propylene‐diene (EPDM) rubbers containing varying amounts of diene were cured with sulfur using either a moving die rheometer (MDR) or a rubber process analyzer (RPA). The effect of removing curatives and how the curing reaction changed was explored. Kinetic data was extracted from the rheology plots and reaction rate constants were determined by two separate ways: manually choosing points of interest or by a computer model. iii TABLE OF CONTENTS Page 1. Introduction 1 1.1 EPDM Overview 1 1.2 Preparation of EPDM 2 1.2.1 Ziegler‐Natta Catalysts 2 1.2.2 Metallocene Catalysts 4 1.3 Cross‐link Chemistry 5 1.3.1 Peroxide Cure 5 1.3.2 Sulfur Cure 6 1.3.3 Cross‐link Sites 8 1.3.3.1 Polymer Branching 9 1.3.4 Rubber Ingredients 10 1.3.4.1 Non‐curative Ingredients 10 1.3.4.2 Curative Ingredients 11 1.4 Kinetics 12 1.5 Instrumentation 13 2. Experimental 15 2.1 Materials 15 2.2 Instrumentation 16 2.3 Rubber Mixing 16 iv Table of Contents (continued) Page 2.4 Rheology Testing 17 2.5 Curve Fitting 17 3. Results and Discussion 18 3.1 Ziegler‐Natta vs. Metallocene Catalysts 18 3.2 ENB Incorporation 20 3.3 Filler‐less Formulations 21 3.4 Curative Effects 23 3.5 Degradation Effects and Factors 32 3.6 Curve Fitting to Predict Reaction Rates 42 4. Conclusion 48 5. References 48 v LIST OF FIGURES Page Figure 1: A typical EPDM polymer………………………………………………………………………………….2 Figure 2: A typical metallocene catalyst…………………………………………………………………………4 Figure 3: An example of four entangled polymer chains………………………………………………..5 Figure 4: A peroxide cross‐link……………………………………………………………………………………….6 Figure 5: A mature sulfur cross‐link ……………………………………………………………………………….6 Figure 6: Three main dienes used in EPDM. A: DCPD B: VNB C: ENB…………………………..8 Figure 7: The ways the dienes can be incorporated into the polymer. A: Through the norbornene ring B: Outside the norbornene ring………………………………………………………….8 Figure 8: An example of LCB…………………………………………………………………………………………..9 Figure 9: Di(p‐octylphenyl)amine …………………………………………………………………………………10 Figure 10: A: MBT B:TMTD………………………………………………………………………………………….11 Figure 11: A: ZDBDC B: TDEDC…………………………………………………………………………………….12 Figure 12: A diagram of how the moving die rheometer and rubber process analyzer works…...………………………………………………………………………………………………………………………13 Figure 13: A torque vs. Time plot. Area A: induction zone Area B: cure zone Area C: overcure zone Line 1: marching Line 2: plateau Line 3: reversion/degradation……….15 Figure 14: Comparison of the metallocene and Ziegler‐Natta rubbers using MH‐ML vs. ENB content.........…………………………………………………………………………………………………………19 vi LIST OF FIGURES (continued) Page Figure 15: Alkene region of the 300 MHz 1H NMR spectra of A: EPDM‐5, B: EPDM‐1, C: EPDM‐3. The peaks at 5.44 ppm and 5.18 ppm correspond to the external and internal pathways, respectively……...…………………………………………………………………………………………21 Figure 16: Comparison of MDR (or RPA) data for identical formulations with and without carbon black...………………………………………………………………………………………………………………23 Figure 17: The curing of VL1710Z1 (1.8% ENB) at different temperatures…………………….25 Figure 18: RPA traces of VL1710Z1 and VL1710ZA1 (no MBT) at 170°C......…………………..26 Figure 19: RPA traces of VL1710Z1 and VL1710ZB1 (no TMTD) at 170°C...……………………27 Figure 20: RPA traces of VL1710Z1 and VL1710ZC1 (no ZDBDC) at 170°C …………………….28 Figure 21: RPA traces of VL1710Z1 and VL1710ZD1 (no TDEDC) at 170°C......……………….29 Figure 22: Derivative plots of VL1710ZA1‐VL1710ZD1 at 170°C. VL1710ZA1 (no MBT), VL1710ZB1 (no TMTD), VL1710ZC1 (no ZDBDC), and VL1710ZD1 (no TDEDC)………………30 Figure 23: RPA traces of VL1710Z1 and VL1710ZE1 (no sulfur) at 170°C……………………….31 Figure 24: VL1710ZE1 (no sulfur) at different temperatures...………………………………………31 Figure 25: Curing of VL1710ZI2 at 200°C for 20 minutes……………………………………………….34 Figure 26: TGA traces of (blue) raw polymer (EPDM‐5), (green) cured and (red) uncured samples of VL1710Z6. Samples were run under an air atmosphere …………………………….35 Figure 27: DCS traces of raw polymer (EPDM‐5) (blue), cured (green) and uncured (red) samples of VL1710Z6......………………………………………………………………………………………………36 vii LIST OF FIGURES (continued) Page Figure 28: An example of how the intersect points were made. The slope of the curing process was taken around the highest rate and the slope of the degradation was taken from where the MH was reached until the end…………………………………………………………….37 Figure 29: Torque vs. temperature of the intersect points of the various formulations at different temperatures…………………………………………………………………………………………………38 Figure 30: The Arrhenius plots for the curing process of VL1710Z1, VL1710Z3, VL1710Z5 and VL1710Z6 ………………………………………………………………………………………………………………39 Figure 31: Arrhenius plots for the degradation process of VL1710Z1, VL1710Z3, VL1710Z5 and VL1710Z6.……………………………………………………………………………………………..39 Figure 32: Arrhenius plots for the ratio of curing vs. degradation of VL1710Z1, VL1710Z3, VL1710Z5, and VL1710Z6……………………………………………………………………………………………..40 Figure 33: Activation energy required for both processes for varying ENB content………41 Figure 34: Fitted curve data for VL1710Z1 at various temperatures. Blue: RPA traces Red: Theoretical data obtained from curve fitting software Green: The absolute difference between the theoretical and experimental curves………………………………………42 Figure 35: Fitted curve data for VL1710Z3 at various temperatures. Blue: RPA traces Red: Theoretical data obtained from curve fitting software Green: The absolute difference between the theoretical and experimental curves………………………………………43 viii LIST OF FIGURES (continued) Page Figure 36: Fitted curve data for VL1710Z5 at various temperatures. Blue: RPA traces Red: Theoretical data obtained from curve fitting software Green: The absolute difference between the theoretical and experimental curves......…………………………………44 Figure 37: Fitted curve data for VL1710Z6 at various temperatures. Blue: RPA traces Red: Theoretical data obtained from curve fitting software Green: The absolute difference between the theoretical and experimental curves………………………………………45 Figure 38: Arrhenius plot of curing for all four formulations………………………………………..46 Figure 39: Arrhenius plot of degradation for all four formulations......…...……………………46 Figure 40: Activations energy required for both process......………………………………………..47 ix LIST OF TABLES Page Table 1: The standard minimal EPDM formulation……………………………………………………….17 Table 2: All the formulations in this set include the same ingredients except for the polymer used ………………………………………………………………………………………………………………18 Table 3: Polymers used in each formulation and their ENB content...………………………….19 Table 4: The filler‐less formulation…..…......……...…………………………………………………………22 Table 5: Basic formulations for curative studies…………………………………………………………..24 Table 6: Basic formulations for degradation studies…………………………………………………….32 x LIST OF EQUATIONS Page Equation 1: General kinetic model A: initial polymer B: cross‐linked rubber C: degradation product…………………………………………………………………………………………………….12 Equation 2: The rate equation for B…………………………………………………………………………….13 Equation 3: Kinetic equation used to describe curing behavior……...……………...…………..13 xi LIST OF SCHEMES Page Scheme 1: The catalytic process of α‐olefin polymization via a Ziegler‐Natta catalyst system……………………………………………………………………………………………………………………………3 Scheme 2: General peroxide curing mechanism ……………………………………………………………6 Scheme 3: General sulfur curing mechanisms………………………………………………………………..7 xii 1 Introduction One of the most widely used elastomers is ethylene propylene diene monomer rubber or EPDM rubber 1. In order to decrease the cure time for EPDM rubber the cure temperature can be increased, however, an increase in temperature can also lead to degradation. This work will focus on studying a kinetic relationship between the sulfur curing of EPDM rubber as well as a degradation process that occurs simultaneously. In addition, experiments will be designed that will allow for the development of a basic understanding of how the different curatives affect the two processes. 1.1 EPDM Overview Rubber has been an important material in consumer and industrial settings ever since Charles Goodyear first vulcanized natural rubber in 1844 2. Since that time many different rubber types were created for different purposes: styrene‐butadiene, isobutylene‐isoprene, acrylonitrile butadiene, fluoroelastomer, etc. Ethylene propylene diene monomer (EPDM) rubber was first introduced in the United States in 1962 and since has been widely used 1, having an extensive repertoire of applications.
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  • Study of UV Curing in the Wood Industry

    Study of UV Curing in the Wood Industry

    Study of UV Curing in the Wood Industry HAIDER OSAMA AL-MAHDI MY0001415 Dept. of Wood, Paper and Coating Technology School of Industrial Technology University Science Malaysia Abstract: Although mass production is the primary demand, the wood finishing must nevertheless conform to certain minimal standards. The surface should be protected and sealed against heat, dirt and abrasion, and insulated from the ingress and evaporation of moisture which would cause dimensional changes in the timber. The finish should be clear (unclouded) and smooth to enhance the natural beauty of the figure and the grain. The finish should also maintain its appearance, and adhesion, as well as protection given to the wood. The film should not seriously be degrading during the lifetime of the article. All the standards mentioned above are available in the 100% solid acrylic UV finishing system. A thorough study of the timber wood anatomy and of the physical and chemical properties of polymerized film is essential in order to match these properties with the wood substrate. Introduction: This paper is not meant to uncover any secrets that have not been known before nor establish new facts that have not been recognized, but to affirm these facts in an elaborate and analytical approach required by those who have interest in the subject, and Its scientific data are based on approved experiments and observations as a guideline for further study and further research. The UV curable wood coating technique offers obvious advantages over conventional wood finishing systems, and increasingly adopted for a wide range of applications. These advantages in short, as determined by the end- users are: 1- High curing speed Increased production: example flooring panels coated by UV with an average line running at 12 M/min can produce about 72,000 square meter per month per shift 2- Lower energy cost (compared to the heat generated by gas fir or electric ovens in some conventional coatings).