Investigations of morphology of moisture-cured silicone-urethanes

Results of studies on synthesis and properties of siloxane-urethane prepoly mers as well as on selected properties of moisture-cured silicone-urethanes have already been published. In Mis paper, some results of investigations of the effect of chemical structure of such silicone-urethane polymers on t heir phase seggregation investigated using mainly (TEM) transmission electr on microscopy and small-angle x-ray scattering (SAXS) techniques are presen ted. It was found in TEM studies that in silicone-urethanes obtained by moi sture-curing of NCO-terminated prepolymers prepared from siloxane oligomer diets (SOD) and isophoronediisocyanate (IPDI), two factors determine the mo rphology of samples: length of siloxane chain and NCO/OH ratio. SAXS invest igations showed that these silicone-urethanes had a lamellar structure. It was found that the long period of this structure changed from 4 to 9 nanome ters as the siloxane chain length increased nine times. The increase of the long period correlated with the decrease of Young's modulus of Me correspo nding samples. TEM investigations of silicone-urethanes obtained by moistur e-curing of NCO-terminated prepolymers prepared from the blends of SOD and polyoxypropylenediol (PPG) revealed complex morphology which depended on th e SOD/PPG ratio. Copyright (C) 2000 John Wiley & Sons, Ltd.