Investigation of the physical and mechanical properties of Wood plastic composites based on high density polyethylene/ polypropylene/recycled poly (ethylene terephthalate): part Ⅱ, Constrained Optimization

The purpose of this study was to determine optimal process parameters such as recycled PET (RP), compatibilizer (COM), and wood flour (W) in HDPE/rPET/wood composites to maximize specified strength (the ratio of tensile strength to density) by consideration of water absorption (WA), tensile modulus (M), and impact energy (IE) as the constraints. In this regards, the wood composites samples were prepared with various contents of rPET (0, 15, 25, and 35 phr), MAPE as a compatibilizer (4, 8, and 12 phr), and wood flour (30 and 40 % wt.). The experimental tests were carried out to determine tensile strength (TS), tensile modulus, impact energy, density (ρ), and water absorption. Response surface methodology (RSM) was used to create the mathematical models between input parameters (RP, COM, W) and responses (TS, ρ, WA, M, and IE). The analysis of variance (ANOVA) was done to determine the significance of the model and each input parameter. Genetic algorithm (GA) code was performed to determine optimum condition. Specific strength formed the main function for GA, and water absorption, tensile modulus, and impact energy constituted the constraints of the function.