KINETICS OF PHASE-SEPARATION IN POLYURETHANE POLYSTYRENE SEMI-1 INTERPENETRATING POLYMER NETWORKS .2. MICROSCOPY OBSERVATIONS AND THEORETICAL APPROACH

The phase separation process of in-situ polyurethane/polystyrene semi- 1 interpenetrating polymer networks has been followed by optical micro scopy completed by image analysis. The final morphology has been exami ned by scanning electron microscopy, and its relation to the phase sep aration process has been established. When phase separation occurs bef ore gelation of the medium, polystyrene is dispersed both as large and small noduli in the polyurethane network; a polyurethane-rich interph ase separates the noduli from the matrix. These observations explain t he previous results on the turbidity of such systems measured by light transmission. In the opposite cases, no visible phase separation is o bserved on the micrographs. The thermodynamics of the phase separation process has also been examined.