This study has examined the foaming process of a silicone rubber which is a type of crosslinked polymer that uses an environment-friendly physical blowing agent. Since crosslinking progresses in a silicone rubber over time and as temperature increases, it is extremely difficult to mold foams that have the required cell size. Here, the degree of vulcanization of a silicone rubber was controlled by the plasticity, and it groped for the foaming process based on this plasticity. And the microstructure and mechanical properties of a silicone rubber that has been foamed by using this process have been evaluated. As a result of this, the following has been found. 1) The degree of crosslinking that varies with time and temperature has been evaluated by using plasticity, and a physical foaming process based on this plasticity has been proposed. 2) The plasticity of a silicone rubber can be adjusted by means of temperature and time, the time-temperature equivalent law holding between these, and the shift factors take on an Arrhenius's type behavior. 3) It has been found that there exists an optimum range of plasticity for obtaining a foamed silicone rubber of the desired cell size, and foaming control can be achieved by using the process proposed in 1) above. 4) By changing the plasticity before foaming by employing the proposed foaming process, a foamed silicone rubber has successfully been obtained which has a cell size of several micrometers and a hardness that represents tactile impressions as human body.
