Preparation and properties of low density polyethylene-activated carbon composite foams

Abstract

Low density polyethylene (LDPE) containing activated carbon (AC) was foamed with azodicarbonamide (ADC), an exothermic chemical foaming agent, through an extrusion process. The effects of ADC and AC contents on the cellular structure, density, void fraction, and mechanical properties of LDPE-AC composite foams were investigated. The density of composite foams decreased but the void fraction increased as the content of ADC increased due to higher gas liberation. Moreover, the large cell size was also observed in composite foams with high amount of ADC. At low AC dosages (5-10 wt%), the density of composite foams decreased with increasing the void fraction compared to the composite foam without AC because more foaming nucleation centers was induced by adding AC in the composite foam leading to more gas bubble generation. However, the addition of AC up to 15-20 wt% decreased the cell formation and the average cell size tended to decrease with increasing AC content. This attributed to AC particles that assisted to generate more foaming nucleation sites in the polymer matrix, resulting in high viscosity, which enhanced the resistance against cell growth and produced cells with smaller dimensions. Maximum reduction of density by 30% with the void fraction of 30% was achieved when ADC and AC were applied at 7 wt% and 10 wt%, respectively. Larger content of ADC and AC led to composite foams with lower tensile properties as well as impact strength, because of the formation of thinner cell walls, AC agglomeration, and the reduction of polymer matrix.