Mechanical properties of microcellular and nanocellular silicone rubber foams obtained by supercritical carbon dioxide

Abstract

In this work, nanocellular silicone rubber foams were first prepared by supercritical carbon dioxide. The cellular morphologies and mechanical properties of the microcellular and nanocellular silicone rubber foams are presented. The cell size and cell density of the microcellular silicone rubber foams can reach 1–4 μm and 1011 cells/cm3, respectively. The nanocellular silicone rubber foams have an upper limit diameter of 59 nm, and the density of the nanocellular silicone rubber foams is on the order of 1014 cells/cm3, which is several orders of magnitude greater than that of the typical microcellular silicone rubber foams. The stretching-induced cavitation can play an important role in the formation of the nanocellular structure on cell walls. The effect of the cellular structure on the mechanical properties is investigated. As a result, the nanocellular structure causes an early breakdown, resulting in a decrease in the tensile strength. Furthermore, when the open-cell content (OCC) increases, the compressive curves change from having three regions to two regions, indicating that the compression plateau disappears when the OCC is greater than 0.45. Microcellular and nanocellular silicone rubber foam are prepared by supercritical carbon dioxide in this work. The tpre and Ps are important factors which affect the open-cell content (OCC). When the tpre and Ps increases, the OCC sharply improves and could reach to more than 96%. The OCC has a significant effect on the mechanical properties of the nano/micro silicone rubber foam.