Low hardness plastic is called soft plastic. The hardness ranges from 30-90. It is relatively soft at room temperature. Soft plastic has excellent elasticity, slip resistance, and vibration damping performance. It is necessary during the development of most products. The common soft plastic includes TPE、SBS、TPU、TPV、rubber（SBR）and silica gel, and they are widely used during the process of soft plastic rapid prototype. TPR is softer than rubber, but in terms of tensile strength, fatigue resistance and mechanical performance, it is inferior to perduren.
