(24f) Reactive Compatibilization of Biodegradable Blends from Phbv and Pbsa: Study on Effect of Chain Extender on the Mechanical, Thermal and Morphological Properties

Being aware of the global problem of plastic pollution, our society is claiming for new biodegradable materials to replace conventional polymers in short-life and single-use products like packaging, bags or cutlery. However, balancing their mechanical performance is required to increase their presence in the market. Brittleness of biodegradable poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) was attempted to be decreased by melt blending with the flexible biopolyester poly(butylene succinate-co-butylene adipate) (PBSA). A epoxy-functionalized chain extender was used as a compatibilizing agent to enhance interaction between both immiscible polymers. The mechanical performance (tensile, flexural, impact) of three injection-moulded PHBV-PBSA compositions (70-30, 50-50 and 30-70 wt.%) in presence and absence of the chain extender was assessed. Morphology, rheology and crystallization behaviour were studied by scanning electron microscopy (SEM), frequency-sweep tests and dynamic scanning calorimetry (DSC). Crystallization of PHBV was hindered by the addition of the chain extender, which was reflected in the improvement of the mechanical performance of blends. In case of 50% and 70%-PBSA blends, homogeneity of results was increased while for 30%-PBSA blend elongation at break was 45% higher and flexural behaviour changed from brittle fracture to non-breakable. The addition of the epoxy-functionalized chain extender did not change the type of morphology developed by each blend nor the toughening mechanisms, so impact strength was barely affected in any blend composition. However, it reduced the size of dispersed phase domains due to a viscosity change. As higher the content of PHBV in the blend, the higher the effect of the chain extender in storage modulus and complex viscosity. Higher interaction between polymers led to increased mobility of PHBV chains and thus, improved processability.

Acknowledgements: The authors would like to thank the following for their financial support: i) Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)/University of Guelph-Bioeconomy for Industrial Uses Research Program (Project Nos. 030486, 030578; and ii) the Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Research Chair (CRC) program Project No. 460788.