Analysis of unsaturated polyester‐polyurethane interpenetrating polymer networks II: Phase separation behavior

The phase separation behavior of unsaturated polyester (UPE)‐polyurethane (PU) interpenetrating polymer networks (IPNs) was investigated by light scattering measurements during simultaneous polymerization. The scattered light intensity change with time showed the formation of the dispersed domains, and the average domain correlation length could be calculated from the angle of maximum scattering intensify. It was noted that the dominant phase separation process was spinodal decomposition due to fast reaction. The morphology observed by the transmission electron micrographs for various process conditions showed similar results as obtained from the light scattering experiment.