Modification of polymeric materials to improve their performance for specific use has been a fascinating field for research. A great amount of research work has been published in this a r e a [ 1, 21.

SynopsisThe gamma radiation-induced graft copolymerization of methacrylic acid onto polypropylene fibers was investigated by simultaneous-irradiation technique. The effect of various synthesis conditions on the graft content was studied. At a constant dose, the percent grafting was found to be higher at low dose rate. For all the dose rates, a linear increase in the grafting was observed up to 0.25 Mrad, beyond which the grafting levelled off. Percent grafting also increased continuously with increasing monomer concentration up to 4.0 mol/L, but a linear increase in grafting was observed only up to 2.0 mol/L. The initial rate of grafting increased with the increase in dose rate and monomer concentration. The dependence of rate of grafting on dose rate and monomer concentration was found to be 0.70 and 1.71, respectively. The effect of liquor ratio upon grafting was also studied.

No abstract

SynopsisGraft copolymerization of methacrylic acid onto polypropylene fibers by simultaneous-gamma ray irradiation technique was carried out. The effect of various solvents on grafting was studied. The results have been presented in terms of swelling behavior of polypropylene fiber and the extent of homopolymerization. An accelerative effect upon the rate of grafting was observed when benzene was partly replaced by methanol. At the dose rate of 24 rad/s and monomer concentration of 3 mol/L, a maximum in the rate of grafting was observed with 40% methanol fraction in the benzene-methanol mixture. However, a further increase in the methanol fraction in the solvent mixture resulted in a sharp decrease in the rate of grafting. No grafting was observed in pure methanol. This behavior has been explained in terms of the inhibitory action of methanol for polymerization of methacrylic acid and the extent of swelling of polypropylene fiber in various compositions of benzenemethanol mixture.

SynopsisPolypropylene-g-polymethacrylic acid graft copolymer, prepared by simultaneous-irradiation technique, was characterized to determine the structural changes, occurring in the copolymer. The presence of polymethacrylic acid graft in the copolymer was ascertained by infrared spectroscopy. Crystallinity of the grafted fibers, as deduced from X-ray diffraction pattern, showed a decrease with the increase in graft level in the fiber. Such a behavior has been attributed to the dilution of crystalline fraction of polypropylene by the incorporation of amorphous polymethacrylic acid chains in the fiber matrix, without disrupting the original crystallites of the backbone polymer. The density of the grafted samples showed a continuous increase with the increase in percent graft. However, the diameter did not change up to 16% graft content, beyond which an increase in the diameter was observed. This increase in diameter has been related with the sharp increase in disperse dye uptake of the grafted fiber at higher levels of grafting. INTRODUCTIONA graft copolymer results from the chemical linkage of a growing macromolecular chain with the preformed polymer, thereby producing a branched structure.' The interaction of grafted moiety with the polymer backbone, nature of bonding, and the distribution of the graft chains strongly influence the properties of a graft copolymer. It, therefore, is of interest to determine the composition and structural changes in a copolymer, induced by graft copolymerization and to correlate them with the polymer properties.Terada2 carried out the grafting of l-phthalimido-1,3-butadiene onto polypropylene by thermal mastication. It has been shown that the percentage of grafted monomer against feed can be determined by ultraviolet spectroscopy. Mi~rointerferometry~ has been successfully used for the determination of transversal distribution of the graft concentration, thus providing a qualitative tool to characterize a graft copolymer. Ohshika4 studied the graft copolymerization of vinyl monomers onto chlorinated polypropylene, using benzoyl peroxide and UV rays as initiator and used infrared spectroscopy to prove that various monomers, such as acrylic acid, methyl methacrylate, acrylonitrile, and vinyl acetate can be grafted onto polypropylene. Similar technique has been used by Ikeda et al.5 to characterize polypropylene fabric grafted with acrylic acid.The present investigation aims to evaluate structural changes induced EXPERIMENTAL Materials. Various polypropylene-g-polymethacrylic acid (PP-g-PMAA)samples with different graft content were prepared by simultaneous irradiation-induced graft copolymerization of methacrylic acid onto polypropylene fibers, under different reaction conditions, as reported previo~sly.~,'Infrared Spectroscopy. The infrared spectra (IR) were measured on a Perkin-Elmer Model 580 B Infrared Spectrophotometer in the range of 400"-400 cm-'. X-Ray Diffraction. X-ray diffraction pattern (intensity vs. diffraction angle plot) was recorded in the range of diffraction angl...