Influence of Biobased Polyurethane Structure on Thermal and Mechanical Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)- Polyurethane Blends

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a promising alternative to petroleum-based polymers, however its high brittleness limits its practical applicability. In this study, two polyurethane elastomers (PUa and PUb) containing poly (epsilon-caprolactone) or poly(epsilon-caprolactone)/poly(butylene adipate) as soft segment and different hard segments content (38.16% for PUa and 53.12% for PUb) were synthesized and melt blended with PHBV in various proportions. The addition of 5-15 wt% PU elastomers to PHBV did not significantly change its thermal stability; however, the presence of PUs decreased the crystallization temperature of PHBV by up to 9 ?, and the crystallinity of PHBV decreased from 48.2% to 42.2 or 43.6% in the blends with 15% PUa or PUb, indicating the development of some interactions between PHBV and PUa/PUb. The addition of PUa to PHBV increased its elongation at break by up to 70%, a weaker effect being observed with PUb. Remarkably, a slight variation in the tensile strength and modulus, which remained close to those of neat PHBV, was concomitant with the increased ductility. The fatigue resistance of the selected blends was estimated by a DMA cyclic test under controlled force from - 20 to 70 ?, this test clearly differentiating the blends.