Synthesis and Properties of Poly(butylene terephthalate)—Poly(dimethylsiloxane) Block Copolymers

Abstract

Silanol-terminated poly(dimethyl siloxanes) were demonstrated to copolymerize into PBT under normal polyester polymerization conditions. The resultant polymers exhibited enhanced chemical resistance, and only modest loss of molded mechanical properties up to 15% PDMS content in the copolymer. At higher PDMS levels, the polymer exhibited no cohesive properties in molded parts. Model studies suggest that the actual mode of chemical reactivity is for the silanol end groups to form silanol ethers with the excess diol present in the reaction system, or more likely, with hydroxyl end groups of growing polyester chains. These silanol-diol ethers can serve effectively as chain extenders, and reduce the overall polymerization times.