POLYETHYLENE-BASED POLYURETHANE COPOLYMERS AND BLOCK-COPOLYMERS

Low molecular weight hydroxy terminated polyethylene (HTPE) containing on average an ethyl group every 16-18 carbon atoms, and a hydroxy fun ctionality of 2.6, has been used to prepare polyurethane copolymers an d block copolymers which have good solvent resistance. The polymers sh ow somewhat complicated thermal behavior, including T-g's at around -4 0 degrees C due to the HTPE and diffuse endotherms between 40 and 60 d egrees C. The simple copolymers, containing only the polyol and a diis ocyanate, show infrared evidence for two phases in the case where CHDI (trans-1,4-diisocyanatocyclohexane) was used, and poorer phase separa tion where other diisocyanates were used. Dynamic mechanical spectra s how very broad tan delta transitions for the copolymers in the range o f -9 to -23 degrees C. All the polymers exhibit another transition in the G'' curve above room temperature. SAXS reveals a microphase separa ted structure at 30 degrees C for the simple copolymers which increase s in spacing, then disappears in the 60-70 degrees C range. With cooli ng, the microphase separated structure reappears readily for the CHDI- based copolymer, while its reappearance shows a hysteresis resulting f rom rate effects for the other copolymers.