Highly toughening modification of Hyperbranched polyester with environment-friendly caprolactone as end group on poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Hyperbranched polymer with flexible long chains (Ɛ-CL) were synthesized based on hydroxyl terminated hyperbranched polyesters (HBPEs). The prepared HBP-CLs were used to toughen poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by melt-blending. Comparing with pure PHBV, the crystallinity (X c ) of the PHBV/3.0phr HBP-CLs blends decreased by 10.2% (from 67.8 to 60.9%), the impact strength increased by 533.3% (from 5.1 kJ·m − 2 to 32.3 kJ·m − 2 ), and the elongation at break increased by 160.5% (from 1.62 to 4.22%). With the increase of HBP-CLs, the fracture surface of the PHBV/HBP-CLs blends became rough and a significant decrease in crystallization area can be seen from POM images. Even filamentous structures and tiny holes was formed, which further demonstrated that HBP-CLs acted as an excellent toughening effect on PHBV.