Modulated differential scanning calorimetry: XVI. Degree of mixing in interpenetrating polymer networks

Quantitative analysis using the differential of heat capacity with temperature, dC(p)/dT, signal from modulated-temperature differential scanning calorimetry (M-TDSC) allows the extent of phase mixing to be calculated for interpenetrating polymer networks (IPNs). As an example, the extents of phase mixing of polyurethane-polystyrene (PUR/PS) (60/40, wt/wt) IPNs with different levels of grafting agent, benzene-1-(1-isocyanato-1-methyl ethyl)-3-(1-methylethenyl) (TMI) have been analysed. At lower TMI contents, the dC(p)/dT with temperature signal shows two significant glass-transition temperatures. With increasing TMT contents, a broad transition peak appears in the dC(p)/dT with temperature signal. This indicates that with increasing TMI contents, the degree of phase mixing increases. It is believed that the dC(p)/dT vs. temperature signal will become a useful tool and a powerful complement to solid-state NMR, scattering and direct non-radiative energy-transfer methods in analysing the morphology of IPNs. (C) 1998 Elsevier Science B.V.