Polyethylene-Based Polyurethane Copolymers and Block Copolymers

摘要

Low molecular weight hydroxy terminated polyethylene (HTPE) containing on averagean ethyl group every 16-18 carbon atoms, and a hydroxy functionality of 2.6, has been used to prepare polyurethane copolymers and block copolymers which have good solvent resistance. The polymers show somewhat complicated thermal behavior, including T sub g at around -40 deg C due to the HTPE and diffuse endotherms between 40 and 60 deg C. The simple copolymers, containing only the polyol and a diisocyanate,show infrared evidence for two phases in the case where CHDI (trans-1,4-diisocya natocyclohexane), was used, and poorer phase separation where other diisocyanates were used. Dynamic mechanical spectra show very broad tan delta transitions for the copolymers in the range of -9 to -23 deg C. All the polymers exhibit another transition inthe G curve above room temperature. For the simple copolymers at 30 deg C, SAXS reveals a microphase separated structure which increases in spacing, then disappears in the 60-70 deg C range. With cooling, the microphase separated structure reappears readily for the CHDI-based copolymer, while its reappearance shows a hysteresis resulting from rateeffects for the other copolymers. (jg).