KINETICS OF SIMULTANEOUS INTERPENETRATING POLYMER NETWORKS OF POLY(DIMETHYLSILOXANE-URETHANE) POLY(METHYL METHACRYLATE) FORMATION AND STUDIES OF THEIR PHASE MORPHOLOGY

Kinetics studies of simultaneous interpenetrating polymer networks (SIPNs) of poly-(dimethylsiloxane-urethane)(PDMSU)/poly(methyl methacrylate)(PMMA) have been carried out by means of differential scanning calorimetry (DSC) with computer-aided DSC data analysis programs. The kinetic parameters such as conversion versus time and temperature, heat of reaction DELTAH, activation energy DELTAE, and reaction order n have been investigated by DSC isothermal and scanning modes. The experimental evidence clearly showed that the phase morphology of the SIPN of PDMSU/PMMA was changed by changing rates of their cross-linking reactions. A miscible IPN with 80 wt % PDMSU made with well-matched rates of cross-linking reactions in the network formation exhibited one glass transition temperature (T(g)) and no SEM observable phase domains. However, an immiscible IPN with the same composition of PDMSU could be prepared with a much slower cross-linking reaction producing a phase-separated IPN with two T(g)s from DSC measurements and a heterogeneous phase morphology observed by SEM.