Full definition
The bulk elastomeric material forming the main body of a power transmission belt, surrounding the tension cords and providing structural integrity, flexibility, and environmental resistance. Two dominant compounds: Neoprene (CR) offers resistance to mineral oils, moderate heat (up to 90°C continuous), and flame retardancy; it was the industry standard from the 1950s through the 1990s. EPDM provides superior ozone, UV, and weathering resistance with a wider temperature range (-40 to +130°C) and 20-40% longer life in clean environments. Body hardness typically 55-75 Shore A. The compound also determines minimum flex radius and heat generation under cyclic bending. Specialty compounds include HNBR (oil + heat) and polyurethane (timing belts).