Effects of Cell Destruction on Compression Moduli of Closed-Celled Polyethylene Foams

Abstract

Effects of cell destruction on compression moduli of four closed-cell polyethylene were studied by the dynamic viscoelastic measurements in compression mode and the static compression test. In the dynamic viscoelastic measurements, dynamic modulus after cell destruction was smaller than that before cell destruction, and in foams after cell destruction the relations with the dynamic modulus and the initial shrinkage for foams of small elastic modulus was different from those for foams of large elastic modulus. In the static compression test, stress-strain curves of virgin foams gave a bend in the small strain region as observed for expanded polystyrene foams, whereas after cell destruction the stress monotonically increased with strain for foams having low elastic modulus. On the other hand for foams of high elastic modulus, stress-strain curves gave a bend in the small strain region as observed for virgin foams after cell destruction. It is considered that the ratio of the resistance against the pressure inside the cells to the total resistance varies with the elastic modulus of foams.