The synthesis and characterization of chlorinated polyethylene-g-styrene and its application as a blend modifier.

Abstract

The graft products were purified by solvent extraction followed by selective precipitation to remove the styrene homopolymer and unreacted chlorinated polyethylene. Solubility behavior of CPE and polystyrene in various solvents was studied and the solubility parameter was estimated from the solubility result. The compositions of the separated fractions were determined by infrared spectroscopy (IR) so that the degree of grafting and graft efficiency could be evaluated.

The graft copolymers were melt blended with incompatible polyblends such as polyvinyl chloride-polystyrene blend and low density polyethylene-polyvinyl chloride-polystyrene blend in an attempt to improve the interface adhesion between incompatible phases. Evidences of interaction between the graft copolymer and the homopolymers were obtained from photomicrographs and dynamic mechanical results of the graft modified polyblends. Impact strength of the polyvinyl chloride-polystyrene blend increased by 48 to 75%, with the addition of CPE-g-styrene copolymers. The fact the addition of the graft copolymer reduced the domain size substantially indicates the modification effect due to graft copolymer.

The graft copolymers and CPE were characterized by IR and laser-Raman spectroscopy, differential scanning calorimetry and dilute solution viscosity measurement.

Chlorinated polyethylene-g-styrene copolymers have been synthesized by chemical and radiation initiation methods. With the use of a pre-initiation technique, graft efficiency as high as 0.84 has been achieved from the chemical-initiated graft copolymerization. The chemical-initiated grafting was found to be significantly affected by the degree of swelling, initiation time and temperature and concentration of initiator and monomer. High initiation temperatures or long initiation times may result in crosslinking in the CPE films. The radiation-induced grafting was carried out using a mutual-irradiation method and graft efficiency was found to be around 0.40. No crosslinking was observed with the dose level used in this study.