This study evaluated the effects of lightweight waste plastic (LWP) content on the foaming characteristics, crosslinking properties, and mechanical performance of EVA (ethylene-vinyl acetate) composite foams. The analysis of foaming characteristics revealed that as LWP content increased, the foaming ratio decreased and the specific gravity increased, indicating limitations in the lightweight properties of the foams. Crosslinking property measurements showed that an increase in LWP content led to higher crosslink density, which contributed to improvements in mechanical properties such as tensile strength. However, elongation at break and tear strength decreased due to phase separation, reflecting the complex interactions within the material. Mechanical property analysis indicated that hardness and rebound resilience increased with higher LWP content, while recovery performance after compression decreased. The increase in compression set was attributed to reduced network flexibility caused by increased crosslink density and limitations in recovery performance due to phase separation. Furthermore, microscopic analysis demonstrated that higher LWP content resulted in smaller cell sizes, denser cell structures, and increased non-uniformity. These structural changes directly influenced the material properties of the foams, suggesting that phase separation was a major factor in the deterioration of cell structure and mechanical performance. This study highlights the recyclability of EVA/LWP composite foams and confirms the potential of using waste plastics for developing sustainable foam materials. As the LWP blend ratio increases, hardness, resilience, and tensile strength increase, but tear strength, elongation and compression set decrease. The LWP blend ratio of 20-30 wt% is considered optimal, as mechanical strength improves while the reduction in compression set is not significant.

Keywords: EVA, Foaming behavior, EVA recycling, Lightweight waste plastic