STUDIES ON THE GRAFT COPOLYMERIZATION OF VINYL MONMERS IN WOOL FIBERS

(4) CONVERTING TO ELASTOMERIC FIBER OF WOOL BY GRAFATING WITH ETHYL ACRYLATE

Abstract

EA-grafting for unreduced and reduced wool fibers was performed in aqueous Br^--S₂O₈^2- redox system at 0-15°C. The rate of garfting increases very rapidly as soon as the grafting are starts and it proceeds until almost all the monomers converted to the graft polymers and homopolymers. Thus, EA-grafting was reached to about 3000% graft-on. Judging from the aspects of the grafting, this graft reaction seems to be a popcorn polymerization.
It was found that the breaking elongation of high grafted fibers iecreases to 400-900% and the elastic recovery was excellent. The tensile strength, initial modulus of elasticity and average toughness decreased to about 1/40, 1/3000 and 1/2 of original wool fibers respectively. These grafted fibers revealed the typical rubber elastic behaviors in the range of over 1200% graft-on for reduced fibers and 1500% for unreduced fibers.
A considerable stress softening (Mullins effect) occurs in grafted fibers for both unreduced and reduced wool fibers. The grafted fibers for unreduced wool fibers were treated with thioglycollic acid and recrosslinked by H₂O₂. The modulus of elasticity and energy-loss decreased by the reduction and recovered nearly to that of the grafted fibers before reduction by the oxidation.
It seems that the -S-S- crosslinks in wool parts are responsible for the formation of a network strutucre and for the reinforcement of PEA as fillers.