STRUCTURE-PROPERTY RELATIONSHIPS IN POLYCAPROLACTONE-POLYURETHANES.

Abstract

In the reported experiments, the structure-property relationships of polycaprolactone-based segmented polyurethanes were studied using differential scanning calorimetry (DSC), small-angle x-ray scattering (SAXS), wide-angle x-ray diffraction (WAXD), dynamic mechanical, and stress-strain testing. The materials studied varied in hard-segment type left bracket 4,4 prime -diphenylmethane diisocyanate/butanediol (MDI/BD) or 4,4 prime -dicyclohexyl methane diisocyanate/butanediol (H//1//2MDI/BD) right bracket , soft-segment molecular weight (830 or 2000 MW polycaprolactone), hard-segment content (23-77% by weight), and thermal history. The materials with aromatic (MDI/BD) hard segments had semicrystalline hard-segment domains, while the materials with aliphatic (H//1//2MDI/BD) hard segments had mostly amorphous domains. Materials with the shorter polycaprolactone soft segment (830 MW) exhibited thermal and mechanical behavior which indicated a considerable degree of hard- and soft-segment compatibility. Changing the hard segment from aromatic to aliphatic gave materials with larger interfacial area and slightly higher tensile strength. A range of morphologies between isolated hard domains in a rubbery matrix and isolated rubbery domains in a hard matrix was observed.