Fabrication of Silicone Rubber Foam with Tailored Porous Structures by Supercritical CO₂

Abstract

In spite of great concern on the wide application of silicone rubber foams, few works have been reported about easy‐operating foaming method. In this study, the effects of silica content and foaming process on the porous structure of high‐temperature‐vulcanized silicon rubber foams are evaluated, which are prepared by supercritical CO2 at different conditions, with fumed silica used for reinforcement. Silicone rubber foams with cell size in 8–120 μm, cell density in 105–108 cm−3, and density between 0.45 and 0.9 g cm−3 are prepared under different saturation conditions. The results show that increasing silica content can decrease cell size. It is also found that cell density improves exponentially with increasing saturation pressure and decreasing saturation temperature. Besides, it demands less than 1 h for specimens to reach equilibrium on thickness around 3 mm. All the results indicate that the porous structures of silicone foams can be tailored by foaming process parameters facilely and are predictable with fitted equation.

Chemistry, Processing, Properties, and Applications of Rubber Foams

“…On the other hand, the cell size and cell density are mainly determined by the diffusivity and solubility of PFA. Yan and coworkers reported that when the saturation pressure increases (fixed temperature), the cell size decreases resulting in narrower cell size distributions [ 51 ]. Hence, increasing the CO 2 saturation pressure in their case led to more molecules being absorbed by the silicone rubber matrix leading to a more important homogeneous nucleation effect producing a higher number of larger cells.…”

Electric Heating Behavior of Reduced Oxide Graphene/Carbon Nanotube/Natural Rubber Composites with Macro-Porous Structure and Segregated Filler Network

“…Moreover, lightweight porous CPCs characterized by low density, high specific mechanical properties, and high capability to adsorb impact-energy have great potential in several application sectors [ 27 , 28 ]. The electrical conductivity of CPCs in which the conductive fillers were randomly dispersed improved significantly after a foaming procedure because of the redistribution of conductive fillers and their constraint in a reduced volume (struts and walls of the porous material) with consequent reduction of a distance between adjacent conductive fillers [ 29 , 30 ].…”

New trends in cellular silicone: Innovations and applications

“…silica. Yan et al 139 also used high amount of silica up to 60 phr but without precrosslinking. They achieved foam with cell size in the range between 8 and 120 mm, cell density between 10 5 and 10 8 cells/cm 3 and density between 0.45 and 0.9.…”