CHARACTERIZATION OF THE NETWORK STRUCTURE OF HYDROXYL TERMINATED POLY(BUTADIENE) ELASTOMERS PREPARED BY DIFFERENT REACTIVE SYSTEMS

Three types of hydroxyl terminated poly(butadiene) (HTPB) networks hav ing different NCO/OH reactive group ratios were prepared using three d ifferent reactive systems (i.e., Desmodur N-100 pluriisocyanate, isoph orone diisocyanate (IPDI)/trimethylol propane (TMP), and hexamethylene diisocyanate (HMDI)/TMP). Desmodur N-100 and TMP were used as polyfun ctional reactants. The polymer-solvent interaction parameters (chi(1)) for HTPB-tetrahydrofuran (THF) and HTPB-chloroform systems at 45 degr ees C were determined, using a vapor pressure osmometer (VPO), as 0.31 and 0.24, respectively. Equilibrium swelling values of the networks i n THF and chloroform and the data obtained by osmometry were further u sed for the calculation of the mean number-average molecular weight be tween junction points ((M) over bar(c)) of HTPB networks through the F lory-Rehner equation. The (M) over bar(c) values of each network, whic h were calculated from the swelling data obtained in THF and chlorofor m using the corresponding chi(1) parameters for polymer-solvent system s, were found to be nearly the same. The changes in the mechanical, sw elling, and the solubility properties of the networks prepared by thre e different reactive systems were followed. (C) 1998 John Wiley & Sons , Inc.