Viscoelastic properties of a modified bio-polymers prepared by blending poly(3-hydrobutyrate-co-4-hydrobutyrate) with chain extenders

A modified bio-polymers was prepared by melt reactive blending Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] with commercial chain extenders (ADR-4367). Steady shear and oscillatory measurements were employed to characterize viscoelastic properties of the chain extended bio-polymres. The results show that after P(3HB-co-4HB) is blended with ADR-4367, the co-polymer chains are branched or coupled. Steady shear viscosity of the modified bio-polymers increase by about one order of magnitude, and melts of such polymers behave more viscoelasticity and thermal stability by storage modulus and loss modulus correlated with oscillatory shear frequency and elapsed time. Owing to possessing branches, modified P(3HB-co-4HB) samples have enhanced complex viscosity magnitude and the first normal stress difference values compared with neat P(3HB-co-4HB). Addition of ADR-4367 with contents of 2~6 wt% brings remarkable effect on improving viscoelastic properties of the modified bio-polymers.