Grafting of chloromethylstyrene to polypropylene fibers by the use of ionizing radiation

Abstract

Chloromethylstyrene monomer was grafted to 3 denier (preformed) polypropylene fibers by using ionizing radiation. At elevated temperatures, microscopical investigations of changes in diameter and in birefringence demonstrated that this monomer swells the fibers without dissolving them. Thus, it is comparatively simple to achieve grafting all the way to the center. Such grafted fibers can be dyed by direct or acid dyes in non-aqueous baths (e.g., dimethylformamide at 210°C.) using levels of graft of ∼25% by weight. This leads to covalent bonding arising from reaction between the dye and the benzyl chloride group of the graft. Dyeing in standard aqueous baths can also be achieved at even lower levels of graft (less than 10% by weight) if the grafted material is treated with a nucleophilic reagent such as pyridine. Using thin cross sections of treated fibers, photomicrographs were taken with monochromatic UV radiation, and with visible light on color film. These, combined with electron micrographs of much thinner cross sections provide pictorial proof of the complete penetration of the graft and of the dyes as well as showing the opening up of the structure effected by grafting. By the means employed, it was possible to achieve marked improvements in dyeability, sticking temperature, moisture regain, and antistatic behavior without diminishing the excellent mechanical properties of the polypropylene fibers.