Grafting to Fibers to Impact High Elasticity

Abstract

Details of a preirradiation grafting technique to render cellulosic fibers highly elastic have heen examined. Special emphasis has been given to the grafting of ethylacrylate to continuous filament rayon from an aqueous emulsion. In addition comparative studies using selected chemically initiated systems have been carried out. Preirradiation grafting rates were found to increase substantially with temperature, reducing the grafting times necessary to achieve highly elastic rayon to the order of minutes at 50°C compared to 20 hr at ambient temperatures. The onset of high "rubber like" elasticity occurs around 1000%, accompanied by a large drop in tenacity. By adding a small quantity of a bi functional monomer to the grafting solution, this strength loss can be reduced without any loss in elongation. Elastomeric properties have been attained even at grafting levels below 100% by subjecting the grafted fihers to a treatment capable of decrystallizing the cellulose. The morphology and structural modifications observed by electron microscopy and x-ray diffraction are discussed for rayon fibers grafted to various levels by both preirradiation and chemical initiation, with and without sulsequent postdecrystallization. These studies indicate that in order to achieve elastomeric properties, grafting must take place throughout the fiber, expanding the fiber and disrupting its crystalline regions.