Fully biodegradable blends of poly(l-lactide) and poly(ethylene succinate): Miscibility, crystallization, and mechanical properties

Both poly(l-lactide) (PLLA) and poly(ethylene succinate) (PES) are biodegradable semicrystalline polyesters. The disadvantages of poor mechanical properties and slow crystallization rate of PLLA limit its wide application. Fully biodegradable polymer blends were prepared by blending PLLA with PES. Miscibility, crystallization behavior, and mechanical properties of PLLA/PES blends were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), and tensile tests in this work. Experimental results indicated that PLLA was immiscible with PES. Crystallization of PLLA/PES blends was studied by DSC using two-step crystallization condition and analyzed by the Avrami equation. The crystallization rate of PLLA at 100 °C was accelerated with the increase of PES in the blends while the crystallization mechanism did not change. In the case of the isothermal crystallization of PES at 67.5 °C, the crystallization mechanism did not change, and the crystallization rate decreased with the increase of PLLA. The mechanical properties of PLLA/PES blends were examined by tensile testing. The elongation at break of PLLA was improved significantly in the blends, while its considerably high Young's modulus was still kept. SEM images of fracture surfaces indicated that the fracture behavior of PLLA/PES blends changed from brittle fracture to ductile fracture behavior in the blends.