Modeling of Mechanical Properties for Plasticized Poly(vinyl chloride) (PVC)/Poly(methyl methacrylate) (PMMA)/Poly(lactic acid) (PLA) Ternary Blends: An Optimal Custom Mixture Design Approach

Abstract

Ternary blends of plasticized PVC (P-PVC)/PMMA/poly(lactic acid) (PLA) were prepared in a twin-screw extruder and characterized by mechanical properties. Eleven compositions were designed by a mixture design approach. Weight percentage of P-PVC, PMMA, and PLA were assigned as independent variables, while flexural strength and modulus and impact strength were the dependent variables. Measured response variables were fitted by the special quartic model with a p < 0.05. An ascending trend was observed for flexural strength and modulus by increasing PMMA and PLA concentrations. Flexural properties were decreased by enhancing the P-PVC content due to the plasticization effect of dioctyl phthalate (DOP). The impact strength was decreased by PMMA and PLA contents in the blend, except at PMMA concentrations lower than 25%, where highly toughened blends with over 50 kJ/m² impact strength were achieved. Flory–Huggins interaction parameters revealed a high tendency of plasticizer to PMMA, which facilitates the compatibilizing role of PMMA in the blends. The efficiency of the model was verified by two optimization criteria leading to over 0.76 desirability and less than 15% relative deviation between experimental and predicted values. A more brittle morphology with lower toughness was observed in PMMA-rich blends. Highly toughened ternary blends were achieved at simultaneous high plasticizer and low PMMA concentrations.