Thermoplastic apparent interpenetrating polymer networks of polyurethane and styrene/acrylic acid copolymer obtained by melt mixing. Structure-property relationships

Thermoplastic apparent interpenetrating polymer networks (thermoplastic-AIP Ns) were prepared at several compositions by melting and pressing of crysta llizable polyurethane (CPU), based on butylene adipate glycol (BAG), and st yrene/acrylic acid random copolymer (S/AA). Structure-property relationship s in the thermoplastic-AIPNs were investigated by means of wide-angle and s mall-angle X-ray scattering (WAXS, SAXS), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), thermally stimulated de polarization currents (TSDC) techniques, dielectric relaxation spectroscopy (DRS) and several physico-mechanical characterization techniques. The resu lts obtained by the various techniques were critically compared to each oth er. They suggest that the two components show weak affinity to each other a nd that the thermoplastic-AIPNs can be classified into two groups with high and low contents of CPU, showing essentially the behavior of CPU and S/AA, respectively. However, deviations from additivity and significant changes for several properties on addition of small amounts of either of the compon ents suggest partial miscibility. Most of the results are explained by phys ical interactions of COOH- groups of AA in S/AA with the ester groups of th e flexible CPU blocks, which promote microphase separation in both the CPU and the S/AA components.