Comparative evaluation of bio-based films made of commercial PHB(V) and laboratory PHB(V) polymers produced from sugar beet pulp hydrosol

• Tensile properties of lab and commercial PHB based melt blended films found comparable. • Lab PHBV showed higher ductility and lower strength compared to commercial PHBV. • Higher sensitivity to secondary crystallisation shown for commercial PHBV films. • Strong correlation of crystallinity index and degree of crystallinity with HV content. • Processing methodology, conditions, HV tuning analysed for industrial optimisation. Poly-(hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) fully biobased and biodegradable in various environments aliphatic polyesters, are produced by a wide range of microorganisms and renewable raw materials. The synthesis of PHB with co-polymers poly-(3-hydroxyvalerate) (HV) allows for a decrease of the glass transition and melting temperatures towards a broadened thermal processing window. Mechanical tensile properties monitoring natural ageing behaviour of either melt blending and compression moulding (MB) or solvent casting (SC) formed PHB and PHBV, with variable content of HV molar composition and molecular weight (Mw) films, of both commercial and laboratory grade (produced from sugar-beet pulp (SBP) and simulated SBP hydrosols), revealed some characteristic differences and their dependence on Mw. These macroscopic results were interpreted via Fourier transform infrared spectroscopy/attenuated total reflection (FTIR/ATR), differential scanning calorimetry (DSC) and polarised optical microscopy (POM). The variation of the ratio of absorbance in the crystalline and amorphous characteristic bands laid the basis for the quantitively determination of crystallinity index ratio ( CI ) dependence on the HV content and Mw, was consistent with the DSC crystallinity degree ( X c (%)). The crystallisation and melting behaviour of the laboratory and commercial PHB(V) grades, as expressed via POM, revealed the secondary crystallisation pattern predecessors. The goal was to associate the characteristics of polyhydroxyalkanoates (PHAs) with their response under industrial processing conditions.