Synthesis of chemically crosslinked poly(vinyl chloride) by vinyl chloride/divinyls suspension copolymerization

Vinyl chloride (VC)/divinyl derivative copolymerization was carried out in the suspension process for preparing chemically crosslinked poly(vinyl chloride) (PVC). Effects of the reactivity ratios and concentration of divinyl, polymerization temperature and conversion on the structure of crosslinked PVC (such as the gel fraction, polymerization degree of sol and crosslinking density of gel) were investigated. It showed that the crosslinking behavior of various divinyls was different. The crosslinking efficiency of diallyl maleate (DAM) was higher than that of diallyl phthalate (DAP) and ethyl glycol dimethyl acrylate (EGDMA). The crosslinking efficiency of EGDMA was very law due to its high probability of homopolymerization. The gel fraction and crosslinking density of gel increased as the concentration of DAP increased, and decreased with the increase of polymerization temperature for VC/DAP copolymer. Polymerization degree of sol of VC/DAP copolymer decreased with the increase of concentration of DAP and varied with polymerization temperature. The crosslinking density of gel increased gradually with the increase of the gel fraction at lower gel fraction stage, and increased rapidly at higher gel fraction stage. The concentration of double bonds of VC/DAP copolymerization system increased as polymerization proceeded, which resulted in the increase of gel fraction of VC/DAP copolymer as conversion increased. (C) 2000 Elsevier Science Ltd. All rights reserved.