Poly[(R)3-hydroxybutyrate] (PHB)/poly(l-lactic acid) (PLLA) blends with poly(PHB/PLLA urethane) as a compatibilizer

Poly(PHB/PLLA urethane) (poly(ester urethane), PEU) was synthesized with telechelic poly[(R)3-hydroxybutyrate]-diol (PHB-diol) and poly(l-lactic acid)-diol (PLLA-diol). The miscibility of cast PHB/PLLA blends was enhanced by adding PEU as a compatibilizer, as observed by DSC, WAXS, SAXS, alkaline solution etching test and mechanical properties measurement. It is shown that the crystalline unit cells of PHB and PLLA didn't interfere with each other and the biphasic separation was kept in the blends with PEU. However, the miscibility of PHB/PLLA in the amorphous phase of the blends was improved due to the presence of PEU. The changes of their thermal properties and morphology of the phase boundaries indicated the enhanced miscibility of PHB/PLLA blends by adding PEU. The mechanical properties of PHB/PLLA blends with PEU were amended due to the better entangled amorphous polymer chains. The results demonstrated that PEU was a good compatibilizer for PHB/PLLA blends.

Enhanced miscibility between PHB and PLLA with PEU was observed after alkaline hydrolytic degradation of the samples.