Effects of moisture content and extrusion parameters on tensile strength of starch and poly(lactic acid) blends

The objective of this work was to study the effects of moisture content (MC) and extrusion parameters on tensile strength of starch and poly(lactic acid) (PLA) blends. Starch and PLA were blended (50150 wt) in a twin-screw lab-scale extruder and then injection molded into tensile bars for testing. Temperatures at the first heating zone (T1), and the second-third heating zone (T2-3), screw speed (RMP), and MC injected into the first heating zone during extrusion were the variables. Central composite design and response surface methodology were used to minimize the number of experiments. MC and screw speed had a significant effect on the tensile strength of starch/PLA blends. Appropriate MC in the starch or in the blending system with appropriate extrusion intensity enhanced starch granule melting, which would enhance the formation of the interpenetrating polymer network between starch and PLA. TI was important in controlling the tensile strength of the blends. Blends with higher tensile strength had lower water absorption, less than 15% after a 10-day soaking test.