Superior Toughened Biodegradable Poly(L-lactic acid)-based Blends with Enhanced Melt Strength and Excellent Low-temperature Toughness via In situ Reaction Compatibilization

The toughened poly(L-lactic acid)/poly(butylene succinate-butylene terephthalate) (PLLA/PBST) blend with enhanced melt strength and excellent low temperature toughness and strength was prepared by melt compounding through in situ compatibilization reaction in presence of multifunctional epoxy compound (ADR). The PLLA/PBST blend was an immiscible system, and the compatibility of the PLLA/PBST blend was improved after adding ADR. FTIR and GPC curves confirmed the formation of the PLLA-g-PBST copolymer, which improved the interfacial bonding of the blend and therefore the PLLA/PBST/ADR blend showed excellent melt strength and mechanical properties. For the PLLA/PBST/ADR blend with 70/30 PLLA/PBST content, the complex viscosity increased significantly with increasing ADR content. Moreover, the tensile strength, elongation at break and impact strength all increased obviously with increasing the ADR content. The elongation at break of the blend reached the maximum value of 392.7%, which was 93.2 times that of neat PLLA. And the impact strength of the blend reached the maximum value of 74.7 kJ/m(2), which was 21.3 times that of neat PLLA. Interestingly, the PLLA/PBST/ADR blend exhibited excellent low-temperature toughness and strength. At -20 degrees C, the elongation at break of the PLLA/PBST/ADR blend was as high as 93.2%, and the impact strength reached 18.8 kJ/m(2). Meanwhile, the tensile strength of the blend at low temperature was also high (64.7 MPa), which was beneficial to the application of PLA in the low temperature field. In addition, the PLLA/PBST/ADR blend maintaind good biodegradability, which was of great significance to the wide application of PLLA.