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Graft Copolymerization of Methyl Acrylamide Onto Jute Fibers Initiated by Peroxydisulfate Catalyzed by Fe(L11)

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Graft Copolymerization of Methyl Acrylamide Onto Jute Fibers Initiated by Peroxydisulfate Catalyzed by Fe(L11) Polymer Journal, Vol. 21, No. 10, pp 821-828 (1989) Graft Copolymerization of Methyl Acrylamide onto Jute Fibers Initiated by Peroxydisulfate Catalyzed by Fe(l11) Rajani K. SAMAL,* Sabyasachi DASH, and Atish K. SWAIN Makromolecu/ar Research Laboratory, Department of Chemistry, Ravenshaw College, Cuttack-753003. Orissa. India (Received August 31, 1988) ABSTRACT: Graft copolymerization of methyl acrylamide [MAM] onto jute fiber has been studied in an aqueous medium using potassium persulfate as an initiator, under the catalytic influence of FeC13 in nitrogen atmosphere. Grafting is influenced by reaction time, temperature, concentration of monomer, initiator, catalyst, and base polymer. For comparative catalytic influence the reaction has also been carried out in presence of various salts and organic solvents. The maximum graft percent of 70.6 is obtained at 50°C for the following concentrations; monomer (0.8 M), K 2 S2O8 (0.03 M), catalyst Fe(III) (1.5 x 10- 3 M) and composition of acetic and formic acid of 2.5% (v/v). From the experimental results a mechanism for graft initiation and termination has been suggested. The extent of absorption of water and water vapors, the tensile properties and thermal behavior of the grafts have also been tested. KEY WORDS Graft Copolymerization / Methyl Acrylamide / Jute Fiber / Potassium Persulfate / FeCl 3 / Tensile Modulus / Primary Thermogram / Graft copolymerization of vinyl monomers mm1m1ze the import of synthetic fibers. Al­ onto cellulose, lignocellulose and their de­ though jute fiber possesses high dimensional rivatives has been the subject of extensive stability, certain unfavorable textile properties studies since 1946. 1 Graft copolymerization of like high stiffness, very low elasticity, suscepti­ preformed polymers both natural and syn­ bility towards sun light, etc. they have tremen­ thetic provides a potential route for signif­ dously limited for their use. 2 Therefore, to icantly altering their physical and mechanical minimize the undesirableness for intensified properties. The grafting possesses great poten­ textile uses, graft copolymerization of some tial for tailoring material properties to specific vinyl monomers onto jute fibers has been end use. Jute, a lignocellulosic polymer, is the attempted during the recent years using chemi­ most abundant renewable agricultural raw ma­ cal, photo chemical, and radiation induced terial. It is transformed into multiferious prod­ methods of initiation. 3 - 14 Among all these ucts due to its wide application for making reports encouraging results have been ob­ coarse woven fabrics such as gunny sacks and tained by Mehta et al. 4 •5 where the grafted bagging where the cheapness is the essential fibers showed improved tenacity, dyability and factor. Recently efforts are being made in tensile properties while rest of the reports are India and Bangladesh for commercial utili­ not so much convincing. Further among the zation of jute fibers to meet the total fabric methods of initiation, chemical methods of requirements of the country as well as to initiation of grafting involving oxidizers like • To whom all correspondence are to be addressed. 821 R. K. SAMAL, S. DASH, and A. K. SWAIN Ce(IV), V(V), Mn(VII), K 2S2 O8 , KHSO5 etc. nitrogen gas for one hour and were then sealed are promising from the economic and in­ airtight by rubber capping. The vessels were dustrial point of view and are quite selective in than kept in a continuous shaking thermo­ nature. Among the chemical initiators per­ sttated bath, till the mixtures attained ther­ sulfate ion (S 20~-) has a separate identity of mal equilibrium after which required amount its own. Persulfate ion is known to act as a of the initiator was injected through the rub­ strong oxidizing agent in an aqueous solution, ber capping. The reaction was carried out for and either alone or in the presence of an the desired time. The homopolymers were ex­ activator has been used as an initiator of vinyl tracted by repeated boiling of the grafts in dis­ polymerization. 15 - 22 However the use of per­ tilled water till washings did not yield any sulfate redox system for initiation of graft precipitate with methanol. copolymerization of vinyl monomers onto cel­ From the weight of the grafts and parent lulosic substrates was recognised in 1963. Since fiber, the percent grafting was calculated as then persulfate ion alone or with suitable follows: catalyst has been used for initiating graft co­ X-Y polymerization onto various cellulosic sub­ Percent grafting=-y- x 100 strates.13·23 -33 The present report describes graft copolymerization of methyl acrylamide where X and Y was weight of the graft co­ [MAM] onto jute fibers initiated by K2 S2O8 / polymer, and that of the original base poly­ Fe(III) couple and the effect of percent graft­ mer, respectively. ing on the properties of the grafts. MECHANISM EXPERIMENTAL The mechanism of graft copolymerization Materials may be pictured as involving generation of Jute fibers (Corchoru capsularis) were pu­ macro-jute radicals resulting from the attack rified by repeated Soxhelation with a mixture of the primary radicals so.;:-. and er produced of ethanol and benzene (1 : 2 by v/v) followed from the initiator either alone or under the by washing with cold ethanol and air dried. catalytic influence of Feel3 at the jute back­ Methyl acrylamide (MAM) was purified by bone. Further the macro-jute radical for­ recrystallization from acetone. A stock so­ mation may be caused by Ho· radicals pro­ lution (4 M) of the monomer was used for the duced from the oxidation of H2O by SO4'. 34 grafting reaction. A stock solution of the Attack of the resulting jute radicals on the initiator "K2 S2O8 " (0.1 M) was prepared by monomer molecules at the immediate vicinity dissolving 10.81 g of the salt (E. Merck) in results in graft initiation. Homopolymeriza­ triple distilled water. The activity of stock tion of methyl acrylamide and oxidation of solution was determined by cerimetry. All jute radicals through primary radical initiation other reagents were used after purification by may also take place as side reactions. standard methods. 1. Primary Radical Production Graft copolymerization was carried out in a reaction vessel carrying out­ (i) s2O~- kd 2so.;:-· specially designed Thermal let and inlet systems, for deaeration. The de­ fatted jute fibers (0.2-1.0 g) were immersed in (ii) S2O~ - + FeC1 3 a mixture containing water, required amount so.;:-· +soi- +er+ Fec12 of MAM and ferric chloride. The reaction vessels were deaerated by passing oxygen-free (iii) so.;:-·+ H2O ~SOi- +HO'+ H+ 822 Polymer J., Vol. 21, No. 10. 1989 Graft Copolymerization of MAM onto Jute Fibers Step (ii) of primary radical production seems Table I. Graft percent in K2 S2 O8 initiated graft to be true, as has been verified from the copolymerization of MAM onto jute fiber under the influence of various salts liberation of Cl2 which may result from the coupling of two er radicals er + er~ Cl 2 Salts Grafting% 2. Formation of Macrojute Radical No salt 1.1 J-H+R· ~J" +R-H FeCl3 11. 7 Fe,(SO4 h 7.2 0 (R =SO4 °, HO", and Cl") CuSO4 4.8 NaBr 2.3 Initiation 3. Graft ZnSO4 3.3 K2 SO4 2.2 J"+M~J-M" CdC12 5.8 4.8 4. Non-Graft Initiation CoSO4 Cr,(SO4 h 8.2 MgSO 4.4 R- M" 4 R" + M MnSO4 1.3 5. Propagation NiSO4 4.9 AgNO 1.1 (a) Grafting: 3 FeSO4 10.3 Na S O 0 J-M"+M~J-M; 2 2 3 Jute=0.2g; [MAM]=0.2M; [K2S2O8]=0.0l M; [Salt]= 1.5 X 10-3 Mat 45°C for 6h. J-M~- 1 +M~J-M~ (b) Homopolymerization: and Na S20 enhance the percent grafting. R-M"+M~R-M" 2 3 . 2 The enhancement of percent grafting in the presence of these salts and increasing trend as R-M~- 1 +M~R-M~ cited above may be attributed to the pro­ 6. Termination of Grafting gressive increase in the rate of decomposition of (i) J - M: + J - M: K2 S2O8 to massive free radicals (SO~-)- They ~cross-linked polymer attack the jute backbone resulting in the for­ (ii) J - M: + Fe(III) mation of a number of free radical sites, then ~Graft copolymer+Fe(II)+H+ the monomer addition takes place on it. The (iii) J-M~+R· ~J-M"-R complete inhibition of grafting in the presence 7. Oxidation ~f Na2 S2O3 may be due to the deactivation of the initiator through oxidative disproportion­ r +so;· ~oxidation products ation of the latter. RESULTS AND DISCUSSION (i) Effect of Monomer Concentration Graft copolymerization of MAM onto jute Methyl acrylamide [MAM] was graft co­ fibers has been studied with different monomer polymerized onto defatted jute fibers using concentration. The percent grafting increases K 2S20 8 as an initiator either alone or in the with increase of monomer concentration upto presence of a number of salts as catalyst. The 0.9 M, beyond which it decreases (Figure 1). results of percent grafting for the individual The enhancement of percent grafting in this systems are presented in Table I. case may be interpreted in terms of increase in From the results in Table I, it is observed the concentration of MAM at the reaction site that the presence of all the salts except AgNO3 and complexation of jute with MAM enhanc- Polymer J .. Vol. 21, No. 10, 1989 823 R. K. SAMAL, S. DASH, and A. K. SWAIN Temperature/°C [Fecl,]X 104 mol-' 30 O 50 60 70 . 80 90 1 0 110 120 0 20 16 12 8 10 20 5 30 40 60 10 cf i!: '-.. cf .::: ::: 50 c'.5 cf ft> e 30v '-.
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