Kinetics of phase separation in polyurethane/polystyrene semi-1 interpenetrating polymer networks. 1. Light transmission studies

The phase separation of different in‐situ semi‐1 interpenetrating polymer networks (IPNs) based on polyurethane and polystyrene has been followed by light transmission. The effect of the presence ab initio of small amounts of homopolystyrene in the initial reaction mixture on the phase separation process has also been examined. If gelation of the polyurethane occurs before the onset of phase separation, the latter is impeded or strongly limited, and transparent semi‐1 IPNs are obtained. In the opposite case, phase separation is macroscopic and the material is turbid.