Mechanical properties of foams comprising virgin and waste polyethylene

Abstract

This paper addresses the use of waste polyethylene (p-PE) in low-density polyethylene (LDPE) foams with azodicarbonamide as the blowing agent. The amount of blowing agent was fixed at 5% for all mixtures, with 0.5% cross-linking agent, 1.7% zinc oxide and 1.7% stearic acid, by weight. Proportions of LDPE/p-PE (% wt) tested in foams were: 100/0, 85/15, 70/30, 60/40, 50/50 and 30/70. The components used to obtain the foams were processed in a Banbury mixer at 120 °C. The pre-form (non expanded material) was placed in a mold and the foaming was carried out in a hot press at 190 °C. The apparent densities of the foams obtained were 60–65 kg.m-3. The mechanical properties (compression set under constant deflection, compressive strength and tear resistance) of LDPE foams containing different proportions of p-PE were compared with the LDPE foam obtained from virgin material only. The mechanical properties of foams with p-PE in their formulation were superior in relation to foams made from LDPE, because p-PE contains high-density polyethylene (HDPE), which is more rigid than LDPE.