When the term TPR is used in relation to shoes, it refers to thermoplastic rubber. Thermoplastic rubber for shoe sole and foxing strip usage was patented on April 15, 1975.
Thermoplastic rubber belongs to a group of copolymers called thermoplastic elastomers, or TPE. Kraton is a TPR that is commonly found in the construction of shoes. Kraton is also used as an ingredient in adhesives.
Advantages of thermoplastic rubbers include their ability to be recycled because of their ease of being molded and extruded. TPRs have been common in shoe production since the 1960s, and they are an inexpensive material.