Influence of Phase Ratio Upon Cellular Structure and Compressive Stress-Strain Behavior of Crosslinked LDPE/EVA Foams

In the present work, the influence of phase ratio upon cellular strucutre and compression behavior of crosslinked foams based on blend of low-density polyethylene (LDPE) and ethylene-vinyl acetate copolymer (EVA) have been studied. For this purpose, blend compounds with phase ratios (90/10, 70/30 and 50/50) from LD-rich and EVA-rich containing dicumyl peroxide (DCP) and azodicarbonamide (ADC) as crosslinking and foaming agent respectively prepared via melt mixing, and thereafter foaming was conducted in one-step compression molding. EVA-rich foams revealed higher gel content and cell density in compared to LD-rich counterparts due to the higher crosslinking effeciency of EVA than LDPE. As per scanning-electron-microscopy (SEM) analysis, EVA-rich foams (phase ratio 90/10) demonstrated much higher cell density and lower cell diameter compared with similar LD-rich foam. Compressive stress-strain test exhibited lower mechanical hysteresis for LD-rich foams increasing EVA level, as a result of more rubbery-effect of EVA on the cell walls and also decrease in LDPE crystallinity. This led to the increase of strain recovery behavior of LD-rich foams with EVA content.