Design for enhanced mechanical and barrier properties of poly (butylene-adipate-co-terephtalate)/poly (glycolicacid) composite films using biobased poly (lacticacid) as intermediates through gradient reactive extrusion.

Blending PGA is expected to enhance the mechanical and barrier properties of PBAT. However, the temperature of the melt blend usually needs to reach more than 220 °C, which may cause the mechanical properties of PBAT to decrease due to chain breakage and thermal degradation. In this paper, the strategy of gradient melt blending using PLA as intermediates is proposed to solve this processing problem. Briefly, PGA was firstly blended within PLA using ADR as compatibilizer at up to no more than 230 °C. Then the PGA@PLA pellets were further blended with PBAT and blow molded into films at PBAT processing temperature to prevent thermal degradation of PBAT. When the PGA and PLA contents were 15 wt%, respectively, the yield strength of the composite film was 24.7 MPa, and Young's modulus was 125.5 MPa, and the composite film had a transmission rate of 592 cc/mꞏdayꞏ0.1 MPa for oxygen and 401 g/mꞏday for water vapor. The gradient blending strategy effectively avoid the chain breakage and thermal degradation of PBAT at high temperature, and PLA intermediate can also improve the barrier properties and tensile strength of the PBAT without affecting the biodegradation performance. This work provides a promising strategy for blending PGA into PBAT films for high barrier properties and a new application of biobased PLA.