Characterization of the network structure of hydroxyl terminated poly(butadiene) elastomers prepared by different reactive systems

Abstract

Three types of hydroxyl terminated poly(butadiene) (HTPB) networks having different NCO/OH reactive group ratios were prepared using three different reactive systems (i.e., Desmodur N-100 pluriisocyanate, isophorone diisocyanate (IPDI)/trimethylol propane (TMP), and hexamethylene diisocyanate (HMDI)/TMP). Desmodur N-100 and TMP were used as polyfunctional reactants. The polymer–solvent interaction parameters (χ1) for HTPB–tetrahydrofuran (THF) and HTPB–chloroform systems at 45°C were determined, using a vapor pressure osmometer (VPO), as 0.31 and 0.24, respectively. Equilibrium swelling values of the networks in THF and chloroform and the data obtained by osmometry were further used for the calculation of the mean number-average molecular weight between junction points (Mc) of HTPB networks through the Flory-Rehner equation. The Mc values of each network, which were calculated from the swelling data obtained in THF and chloroform using the corresponding χ1 parameters for polymer–solvent systems, were found to be nearly the same. The changes in the mechanical, swelling, and the solubility properties of the networks prepared by three different reactive systems were followed. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1129–1135, 1998