Compatibilization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)– poly(lactic acid) blends with diisocyanates

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was blended with poly(lactic acid) (PLA) with various reactive processing agents to decrease its brittleness and enhance its processability. Three diisocyanates, namely, hexamethylene diisocyanate, poly(hexamethylene diisocyanate), and 1,4-phenylene diisocyanate, were used as compatibilizing agents. The morphology, thermomechanical properties, and rheological behavior were investigated with scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, tensile testing, dynamomechanical thermal analysis in torsion mode (dynamic mechanical analysis), and oscillatory rheometry with a parallel-plate setup. The presence of the diisocyanates resulted in an enhanced polymer blend compatibility; this led to an improvement in the overall mechanical performance but did not affect the thermal stability of the system. A slight reduction in the PHBV crystallinity was observed with the incorporation of the diisocyanates. The addition of diisocyanates to the PHBV–PLA blend resulted in a notable increase in the final complex viscosity at low frequencies when compared with the same system without compatibilizersFinancial support for this research from the Ministerio de Economía y Competitividad (project AGL2015-63855-C2-2-R), the Generalitat Valenciana (contract grant GV/2014/123), and the Pla de Promoció de la Investigació de la Universitat Jaume I (contract grant numbers PREDOC/2012/32 and E-2015-22) is gratefully acknowledged. The authors are also grateful to Raquel Oliver and José Ortega for their support with the experiments