Characterization of PHBV-PVP blend

Poly (vinyl pyrrolidone) (PVP) resins of varying molecular weight and poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) of varying 3- hydroxyvalerate (HV) comonomer content were used to produce solution cast films, which may be expected to be biodegradable, yet biocompatible. The blends were characterized by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Mechanical Analysis (DMA), and tensile testing as well as a preliminary examination of biodegradation, in vitro, in a M-MEM solution.

The glass transition temperatures (T_g) of PHBV obtained from dynamic mechanical analysis (DMA) show that at low PVP concentration, the experimentally determined T_g of the blends are similar to the results obtained empirically. No change in T_g with composition of PVP was observed for concentrations higher than 10%. This result predicts the immiscibility of the polymer pair at high concentrations of the PVP. The change in T_g correlates well with shifts in the carbonyl band of PHBV copolymer to lower wavenumber position in FTIR spectra. The shift of the carbonyl absorption band implies interaction between PHBV and PVP molecules.

A change in PVP molecular weight or HV content in PHBV copolymers affects both the thermal and mechanical properties. Comparison of a series of blends indicates that, in this study, PHBV(19.1%HV)/PVP(K-90) represents the best mixture status and vi mechanical properties. The mechanical properties were found to be extremely sensitive to the water content in blends and results obtained from tensile tests imply that moisture acts like a plasticizer in this blend system.