RADIATION-INDUCED GRAFTING OF ACRYLONITRILE ONTO POLY (VINYLIDENE CHLORIDE) FIBER

Abstract

Experiments have been undertaken to graft acrylonitrile onto poly(vinylidene chloride) fiber for the purpose of modifying properties without serious loss of flame-retardance of the original fiber.
The grafting took place smoothly when a suitable swelling agent such as dimethylformamide was used as a medium for the immersion grafting of acrylonitrile by a simultaneous irradiation technique. In most cases, 1:1 mixture of acrylonitrile and dimethylformamide was employed for the reaction and degree of grafting higher than 100% was achieved without difficulty.
Some properties of the graft fibers were measured. The density of poly(vinylidene chloride) fiber is about 1.70, which is the highest among common organic fibers; the value becomes lower by the grafting and the fiber of 100% graft shows a value of 1.40, which is similar to that of polyester. The initial Young's modulus of th fibers increases with grafting. Fiber with 33% graft shows a value of 239 kg/mm², which is 2.5 times greater than that of the original fiber.
With increasing degree of grafting, the extent of heat shrinkage becomes less and at about 100% graft, the fiber form is retained even at 300°C. Graft fibers are self-extinguishing so long as the graft percentage is less than 74% (Cl content is greater than 43.3%). In the case of poly (vinyl chloride) fabrics grafted with acrylonitrile, the threshold graft percentage is much lower than the poly(vinylidene chloride) grafts and has a value of about 36% which corresponds to a Cl content of about 42%. It seems that 42-43% Cl content is the common threshold for the self-extinguishing of poly(vinylidene chloride) and poly(vinyl chloride) fibers grafted with acrylonitrile.