Biodegradable poly(lactic acid)/poly(propylene carbonate) blend with enhanced mechanical properties and heat resistance by uniaxial pre‐stretching

Abstract

Biodegradable poly(lactic acid)/poly(propylene carbonate) (PLA/PPC) blends with balanced strength, ductility, and heat resistance were prepared by combining the modification of 30 wt% PPC and uniaxial pre‐stretching at 60°C. The undrawn PLA/PPC blend fractured in a brittle way due to the network structure composed of cohesional entanglements. After pre‐stretching, the elongation at break was increased to 229.4% at pre‐stretching ratio (PSR) of only 0.5, which should be attributed to the destruction of the network structure of cohesional entanglements and the orientation of PPC component in PLA matrix. With the increase of PSR, the modulus, strength at yielding, and break were improved obviously (2433.4, 76.1, and 98.3 MPa at PSR = 2.5) whereas the elongation at break (51.7% at PSR = 2.5) reduced gradually because of the formation of orientation, mesophase, and crystal phase. However, the elongation at break was still larger than that of neat PLA (6.8%) and undrawn PLA/PPC blend (12.3%), indicating that the uniaxial pre‐stretching was an effect way to strengthen and toughen PLA blends. Significantly, the heat resistance of ps‐PLA/PPC blend was increased obviously with increasing the PSR, which will promote the widespread application of the blends.