Polycarbonate‐polyurethane semi‐interpenetrating polymer networks: Tg behavior and morphology

The dynamic mechanical properties, transition behavior, and morphology of polycarbonate (PC)‐polyurethane (PU) semi‐interpenetrating polymer networks (semi‐IPNs) and linear blends were studied by means of Rheovibron, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Two glass transition temperatures corresponding to polycarbonate and polyurethane were observed and microphase separation was further evident with TEM. In PC/PU semi‐IPNs, two glass transition temperatures were shifted inwardly indicating that the interpenetrating network of polyurethane increases the mutual miscibility of PC and PU. The average phase domain was 500Å in semi‐IPNs and the phase domains were in the range 1000–6000 Å in linear blends of the corresponding polymers. The compatibilities of PC and PU were greatly influenced by the molecular weight of polyols in PU prepolymer and the ratio of NCO/OH; lower molecular weight polyols and higher NCO/OH ratio resulted in better compatibility, and finer phase domains in PC and PU linear blends and semi‐IPNs.