Hardness is an indicator of the ability of a material to resist deformation, nicks and scratches. TPU hardness is usually measured by Shore A and Shore D hardness testers. Shore A is used for softer TPU and Shore D is used for harder TPU. Due to the nature of the block copolymer TPU determines its wide range, between Shore A60 and Shore D80, spanning the hardness of rubber and plastics. The hardness of TPU is related to many properties. As the hardness increases, the following properties of TPU change. Tensile modulus and tear strength increase, rigidity and compressive stress (load capacity) increase, elongation at break decreases, density and dynamic heat generation increase, and environmental resistance increases.

  The relationship between TPU hardness and temperature changes from room temperature cooling down to sudden temperature (-4～-12℃), there is no obvious change in hardness; at sudden temperature, TPU hardness suddenly increases and becomes very hard and loses elasticity. This is As a result of the crystallization of the soft segment. The hardness of TPU does not change much at 6～93℃, especially PPDI-TPU, indicating that there is no obvious change in the morphology in this temperature range; the hardness of all TPU formulations is basically the same at -18℃, which is due to soft segment crystallization; The hardness of TPU decreases sharply at 149℃, especially for MDI-TPU. This is due to the destruction of the ordered structure of the hard segment; the hardness of PPDI-TPU does not change from a wide span temperature of -18～149℃. Large, indicating that it has good heat resistance and low temperature resistance