Polyurethane–Polystyrene Simultaneous Interpenetrating Networks from Modified Castor Oil

A series of simultaneous interpenetrating polymer networks (SINs) based on pentaerythritol modified castor oil polyurethane and polystyrene were studied. Miscibility, phase continuity and phase separation are studied by dynamic mechanical thermal analysis (DMTA). The patterns of extent of the phase separation and the characteristics of the interpenetration reached as a function of the components were deduced. The modulus-composition relationship has been analyzed for the synthesized SINs using theoretical equations based on mechanical models. Most of these models assume perfect adhesion between the homogeneous isotropic phases and the inclusions in the matrix are spherical. The IPNs follow the Budiansky model, which predicts a phase inversion at intermediate compositions.