Synthesis and mechanical properties of block copolymers of polyurethane (PU) with poly (4,4'-diphenylsulphone terephthalamide) (PSA)

Three poly(tetramethylene glycols) (PTMG) with molecular wights of 650, 1000, and 2000 were copolymerized with 4,4'-dephenyl-methane di-isocyanate (MDI) and poly (4,4'-diphenylsulphone terephthalamide) (PSA) prepolymer by polycondensation. Four different molar ratios of MDI, PSA prepolymer, and PTMG were synthesized to form 12 PU-PSA block copolymers. To evaluate the influence of the chemical structure and the amount of hard segment on the stress-relaxation properties of the copolymers, the 10s and 100s moduli, E(10s) and E(100s), were estimated, and the values of V sub r = (E(10s)--E(100s))/E(10s), which can be taken as a qualitative measure of the relaxation speed, were calculated for the copolymers at 80 deg C. The results indicated that the moduli E(10s) and E(100s) apparently increased with increasing the amount of hard segment, and the relative relaxation speed V sub r decreased. The drop of V sub r was supposedly caused by the influence of the amount of hard segment on the disapperance of viscoelastic properties. In particular, the PTMG of molecular weight 2000 exhibited more elastic behaviour. Graphs. 11 ref.--AA