Structure‐property relationships in thermoplastic elastomers III. Segmented polyacetal‐polyurethanes

Abstract

AbstractDihydroxy‐terminated polyacetals had been synthesized from aldehydes and glycols and used as soft segments to obtain segmented polyurethane block copolymers. For soft segment ≥ 1700Mn, the Tg ranges from–48 to −58°C and is insensitive to the structures of diisocyanate and chain extender. The Tg of PacPU with 1350 Mn polyacetals is raised to −38°C, and none was observed for shorter polyacetal chains. The copolymers can be synthesized to have a broad range of mechanical properties, such as modulus from 0.5 to 130 MPa, stress at break from 0.7 to 21 MPa, and elongation at break from 66 to 1300% through the variation of the constituents and composition. The rheologic properties are only slightly dependent on temperature for symmetrical diisocyanates but quite temperature sensitive with asymmetric diisocyanate copolymers. The polyacetals are selected to build in acid‐catalyzed thermal decomposition of the thermoplastic elastomers. The extreme acid sensitivity of the polyacetal block is buffered in the coplymers.