Investigation of injection molding process parameters on the properties of EVA-based foams using response surface methodology

Abstract

Polymers exhibit diverse applications and properties depending on their shapes, morphologies, and structures. Among them, polymer foams—especially those based on ethylene-vinyl acetate (EVA)—are widely used across various industries. This study investigates the structural and mechanical properties of EVA foams produced via plastic injection molding. Key processing parameters—screw temperature, mold temperature, and curing time—were optimized using Design Expert software with a Box–Behnken experimental design. Each parameter was tested at three levels: mold temperature (185, 200, and 215°C), screw temperature (90, 100, and 110°C), and curing time (5, 10, and 15 min), selected based on the characteristics of the curing and foaming agents. Mechanical performance was evaluated through tensile and compression tests, while structural features were characterized by optical microscopy, density, and Shore A hardness measurements. The results showed that a higher foam density (∼0.14 g/cm³) was achieved at lower mold and screw temperatures, or with a combination of reduced screw temperature and curing time. Additionally, the highest elongation at break—exceeding 150%—was observed under a mold temperature of 185°C, curing time of 15 min, and screw temperature of 110°C.