Morphology, dynamic mechanical properties and swelling behaivor of polyurethane-polystyrene IPN's

Abstract

Hydrophilic-hydrophobic interpenetrating polymer networks (IPN’s) of polyurethane (PU) and polystyrene (PS) were prepared by a simultaneous polymerization method under high pressure up to 10000kg/cm2. The hydrophilic polyurethane networks were prepared by reacting hexamethylene diisocyanate(HDI) with a mixture of poly(tetramethylene ether glycol) (PTMEG) and polyethylene glycol (PEG) (50%/50% by weight) and with trimethylol propane(TMP) as the cross-linking agent. The morphology, dynamic mechanical properties, and swelling behavior of the IPN’s prepared were analyzed to evaluate the effect of the synthesis pressure on the degree of intermixing of the component polymers. The morphology and the dynamic mechanical behavior showed that the degree of intermixing increased with increasing synthesis pressure. The domain size decreased from about 2000 Å at atmospheric pressure to 100 Å at 10000kg/cm2, and the dynamic mechanical behavior also showed an inward shift in Tg’s with increasing synthesis pressure. The swelling behavior showed that the welling properties of the simultaneous interpenetrating polymer networks (SIN’s) were influenced strongly by the morphology. The swelling ratios in water and ethanol, which were good solvents for the PU network, decreased with increasing degree of intermixing. The swelling ratios in toluene, a good solvent for both PU and PS networks, showed that the swelling behavior of the SIN’s was not influenced by the morphology.