The Effect of Cell Size on the Tensile Behavior of Microcellular Polycarbonate

Abstract

Previously, processing conditions were presented that produce polycarbonate (PC) foams with the same density and significantly different average cell size (Kumar and Weller, 1994a). It was shown that the average cell size could be varied by an order of magnitude in different foams while maintaining the same foam density. The ability to produce foams with controlled density and cell size opened the possibility for a systematic evaluation of the effect of cell size on the mechanical properties of cellular materials. A set of experiments was performed to determine if cell size (or equivalently processing conditions) had an affects the tensile behavior of microcellular polycarbonate. A series of tensile tests was performed on polycarbonate foams where the cell size was varied from approximately 2 μm to 37 μm, while the relative density was held nearly constant at 0.56. It was determined that the tensile behavior of microcellular PC is not affected by the average cell size for the range of microstructures produced in this study. The stiffness, strength and toughness showed no definitive trends with cell size. Consequently, the only microstructural variable that determines the tensile properties is the bulk foam density.