In 1844, Charles Goodyear invented heating rubber mixed with sulfur to create shoe rubber, called vulcanization. This is still how shoe brands make rubber shoe bottoms today. The recipes and processes are all about the same for brands. Natural rubber processing focuses on the mold release for polyurethane integral skin molding for shoe soles.
Soles Molded from Different Materials
Soles from TPU are obtained by injection molding at high temperature under pressure. The bottom of thermoplastic elastomer is molded by injection molding, and then glued. PVC soles are most often fixed by injection molding in shoes for outdoor activities and everyday wear. EVA soles are attached to shoes only by injection molding. Tunit and leather soles are only glued.
The process includes: pressing rubber outsoles using molds with colors added. Close the mold and heat to create the outsole. Model finishing is done on molds. Silicone or plaster molds are prepared. Molten aluminium alloy is used for casting. CAD/CAM/CNC reverse engineering of the casting is done.