The use of isopropanol (IPA) as the reaction solvent for the preparation of high molecular weight segmented polyether-urea copolymers based on cycloaliphatic diisocyanates was investigated. Reactivity of IPA with bis(4-isocyanatohexyl)methane (HMDI) and isophorone diisocyanate (IPDI) was studied between 0 and 40°C using in-situ FTIR spectroscopy. HMDI, which has secondary isocyanate groups, shows a very slow reaction with a large excess of IPA at 0 and 23°C. Analysis of the kinetic data indicates an activation energy of 51 kJ/mol for the reaction between HMDI and IPA. As expected, IPDI, which has both a primary and a secondary isocyanate (NCO) group, reacts faster with IPA compared with HMDI, which only has secondary NCO groups. However, the rate of reaction of IPDI with IPA at 0°C is extremely slow (approximately 1% consumption of isocyanate in 60 min) thus allowing the use of IPA as the reaction solvent for polyether-urea synthesis. Preparation of high molecular weight, high-strength HMDI and IPDI based polyether-urea segmented copolymers in IPA has been demonstrated. Thermal analysis and stress-strain analyses were used to characterize the products.
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