Optimization of the Effects of Thermoplastic Starch and Glycerol Concentration on Physicomechanical Properties of Polylactic acid/Thermoplastic Starch Blend by Response Surface Methodology

Polylactic acid (PLA)/Thermoplastic starch (TPS) blends as fully biodegradable materials have the potential of substituting petroleum-derived synthetic polymers for packaging applications and, especially producing disposable containers. In the present research the mentioned blends with compatibilizer were prepared by melt mixing method and the simultaneous effect of the factors of TPS weight percentage (CTPS) on the blend in the range of 10-50% and the glycerol weight percentage in its mixture with sorbitol (CGLY) in the range of 0-100% on tensile strength, impact strength and equilibrium moisture content of the blends was investigated by the response surface methodology. According to the obtained results, the blend with the optimum amounts of CTPS and CGLY of 34.9% and 28.7% respectively had the tensile strength, impact strength and equilibrium moisture content of 28 MPa, 25.5 J/m, and 14.3% respectively. The compatibilized PLA/TPS blend with the optimum amounts of CTPS and CGLY of 34.9% and 28.7% respectively, and the TPS phase containing 35 wt% of mixed plasticizer was prepared by a co-rotating twin screw extruder and its tensile strength, impact strength and equilibrium moisture content were measured. The relative deviation of the experimental data and the data predicted by the regression model for tensile strength, impact strength and equilibrium moisture content were 4.4%, 2.4% and 10.6% respectively.