RECOVERY OF THERMAL AND MECHANICAL-PROPERTIES AFTER THERMAL-TREATMENT IN A POLYESTER-BASED POLYURETHANE

Solution casted films of segmented polyurethanes based on poly (ethylene adipate) glycol, 4,4'diphenylmethanediisocyanate, and 1,4 butanediol were studied by thermal-mechanical methods including differential scanning calorimetry and mechanical hysteresis. Data demonstrate that, following thermal treatment at 70-degrees-C for 15 min, these polymers show time-dependent thermal and mechanical properties. In fact, because 70-degrees-C is a temperature greater than the melting point of soft segments (about 42-degrees-C), the soft-segment crystals are melted and their crystallization is time dependent. The results are explained in terms of phase separation. In particular, the sample with better phase separation has a faster and larger recovery.