Fine porous structure with the size of several ten nm to several μm can be obtained by foaming of polymers using supercritical fluids such as supercritical carbon dioxide. Owing to the characteristic properties originated from the fine porous structure, porous materials obtained by supercritical foaming are expected to be applied to structural materials, medical materials, insulation materials, and electronic materials. Control of porous structure of rubbers using supercritical fluids is also briefly described.
This paper introduces practical examples of foaming technology for automotive rubber parts for the purpose of deepening the foaming technology of elastomer materials.
In particular, we explain the foaming technology for weather strip which is our main product.
Weather strips are parts that are attached around the doors of automobiles and around the glass of the body. It is a seal part that prevents wind, rain, dust, and noise from entering through the gap of other parts.
Weather strips are made of flexible foamed EPDM or foamed TPE in order to give them the properties as automotive body seal parts, and it is manufactured by extrusion foam molding.
It is important to control foaming process for satisfying required performance and manufacturing stable of the weather strips, and they are realized by mean of foaming agent optimization and material management.
Expandable microcapsule is used as the foaming agent for rubber. It does not generate gas and not affect vulcanization. It must expand before the rubber is fully vulcanized. This foaming technique will contribute to a fine closed cell structure and a nice surface texture of rubber.