MODELING OF UNSATURATED POLYESTER PREPOLYMER STRUCTURES .1. CHAIN BRANCHES AND OVERALL CHAIN-END NUMBERS

A review on the synthesis of unsaturated polyester (UP) prepolymers sh owed that Ordelt saturation (reaction of hydroxyl groups with double b onds) is the major effect that may cause formation of chain branches a nd then result in an uncertainty of chain end number or functionality. A model has been derived in this work to estimate the number of chain branches and the number of chain ends of UP prepolymers from several fundamental molecular parameters, including hydroxyl and carboxyl inde xes, Ordelt saturation extent, short- and long-chain branch distributi on, molecular polydispersity, and starting reactant composition and al so reasonable assumptions concerning the chain-branch lengths. Simulat ion results were compared with experimental ones. The influences of th e mentioned molecular parameters on the chain branches and on the over all molecular chain ends are discussed in this work. (C) 1997 John Wil ey & Sons, Inc.