Polyurethane is a copolymer composed of polyurea/modified polyurethane, with micropores and polyurethane resin wall channels. It is always called polyurethane foam or cellular polyurethane. Featuring cellularity, low density and high specific strength, polyurethane has high resilience and air permeability, low hysteresis loss and high compression load ratio, and is resistant to flame, thermal aging, humidity-based aging and dynamic fatigue.