Crystallisation and mechanical properties of poly(3-hydroxybutyrate-co-hydroxyvalerate)/polypropylene blends

Poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) was melt blended with polypropylene (PP) with maleic anhydride grafted PP (MPP) used as the reactive compatibiliser. The PHBV/PP (97.5/2.5) blend exhibited optimum elongation at break. Scanning electron microscopy exhibited that the PP phase was dispersed evenly within the PHBV matrix; a reduction in the domain size of the PP phase and plastic deformation of PP were observed with the addition of MPP. Differential scanning calorimetry studies showed that PP enhanced the crystallisation of PHBV, while MPP weakened it. Polarised optical microscopy results demonstrated that small spherulites of PP were effective PHBV nucleation agents, whereas MPP restrained the nucleation of PHBV. The results of tensile tests revealed that the elongation of the blends improved after the addition of MPP and increased with increasing concentration of MPP. The blend containing 2.5 wt-% PP with MPP content of 3 wt-% exhibited the best toughness, increasing 295.7% compared with pure PHBV.