HIGH-PERFORMANCE SEMIINTERPENETRATING POLYMER NETWORKS BASED ON ACETYLENE-TERMINATED SULFONE .2. PHASE-SEPARATION AND MORPHOLOGY

The dynamic mechanical behavior, phase separation, and morphology of h igh-performance semi-interpenetrating polymer network (semi-IPN) obtai ned from acetylene-terminated sulfone (ATS-C) and high-performance the rmoplastics have been studied by torsional braid analysis (TBA) and sc anning electron microscopy (SEM). All the ATS-C/thermoplastic blends s tudied are compatible before curing. The addition of ATS-C results in a dramatic reduction in the glass transition temperature (T-g) of the thermoplastic. As the reaction of cure proceeds, the initially compati ble blend passes through a stage of partial compatibility to achieve a fully incompatible semi-IPN. SEM observation of the fractured-etched surface reveals the formation of a co-continuous two-phase structure i n the semi-IPNs. The connected globule and network morphology of the c ured ATS-C phase are dispersed in a matrix of the thermoplastic phase. The size of dispersed particles decreases with increasing T-g of the thermoplastic. The mechanism of phase separation is discussed. (C) 199 4 John Wiley and Sons, Inc.