Studies on thermoplastic polyurethanes based on new diphenylethane-derivative diols. III. The effect of molecular weight and structure of soft segment on some properties of segmented polyurethanes

摘要

Two series of poly(ether urethane)s and one series of poly(ester urethane)s were synthesized, containing, respectively, poly(oxytetramethylene) diol (PTMO) of (M-n) over bar = 1000 and 2000 and poly(c-caprolactone) diol of (M-n) over bar = 2000 as soft segments. In each series the same hard segment, i.e., 4,4'-(ethane-1,2-diyl)bis(benzenethiohexanol)/hexane-1,6-diyl diisocyanate, with different content (similar to 14-72 wt %) was used. The polymers were prepared by a one-step melt polymerization in the presence of dibutyltin dilaurate as a catalyst, at the molar ratio of NCO/OH = 1 (in the case of the polymers from PTMO of (M-n) over bar = 1000 also at 1.05). For all polymers structures (by FTIR and X-ray diffraction analysis) and physicochemical, thermal (by differential scanning calorimetry and thermogravimetric analysis), and tensile properties as well as Shore A/D hardness were determined. The resulting polymers were thermoplastic materials with partially crystalline structures (except the polymer with the highest content of PTMO of (M-n) over bar = 2000). It was found that the poly(ether urethane)s showed lower crystallinity, glass-transition temperature (T-g), and hardness as well as better thermal stability than the poly(ester urethane)s. Poly(ether urethane)s also exhibited higher tensile strength (up to 23.5 MPa vs. 20.3 MPa) and elongation at break (up to similar to 1950% vs. 1200%) in comparison with the corresponding poly(ester urethane)s. Among the poly(ether urethane)s an increase in soft-segment length was accompanied by an increase in thermal stability, tensile strength, and elongation at break, as well as a decrease in T-g, crystallinity, and hardness. (C) 2008 Wiley Periodicals, Inc.