Tensile and longitudinal shrinkage behaviors of polylactide/wood‐fiber composites via direct injection molding

Abstract Polylactide (PLA), derived from bioresources, is an environmentally friendly plastic which has attracted tremendous interests in both academia and industry. This study investigates the feasibility of direct injection molding of PLA/wood‐fiber composites and their mechanical and longitudinal shrinkage behaviors under different molding conditions. To understand the processing–property relationship of the thermally sensitive composites, response surface methodology was applied to study the effects of molding parameters, as well as their interacting effects, on the tensile strength and the longitudinal shrinkage of the composites. Melt temperature, packing pressure, and injection speed were chosen as the molding parameters studied. The statistical models were validated through confirmation experiments. The predicted values are in agreement with experimental data, and the average prediction accuracy is more than 95% for both tensile strength and longitudinal shrinkage. The models would not only improve our understanding of the tensile strength and shrinkage behaviors, but also can be used to help tooling design and select a proper processing window to maximize the tensile strength while achieving the desired longitudinal shrinkage.