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

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 mu m and 10(11) cells/cm(3), 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 10(14) cells/cm(3), 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.