STUDIES ON THE FUNCTIONALITY DISTRIBUTION OF HYDROXYL-TERMINATED POLYBUTADIENE AND CORRELATION WITH MECHANICAL-PROPERTIES

The functionality distribution of hydroxyl-terminated polybutadiene (HTPB) prepolymer was studied by a combination of preparative and analytical gel permeation chromatography (g.p.c.) and the results correlated with mechanical properties and sol content of the resins cured with diisocyanate. The prepolymers were converted to their ultra-voilet-absorbing ester derivatives and fractionated according to their molecular weights. The functionalities of the fractions were determined using dual-detector analytical g.p.c. The functionality distribution was found to depend on the method of polymerization; increasing with molecular weight for free-radically polymerized HTPBs and remaining constant at around two for anionically polymerized HTPB. The different batches of free-radical HTPB were found to contain varying amounts of non- and monofunctional, chain-extending difunctional and crosslinking tri- and polyfunctional species, and their relative amounts have for the first time been quantitatively correlated with the stress-strain properties of the cured resin.