The elasticity of the raw rubber and the light vulcanized rubber is high, and the resilience is 50% to 85% in the range of 0 to 100 ° C, and the elastic modulus is only 1/3000 of the steel. When the elongation is 350%, the removal is performed. After the external force, it will quickly retract, leaving only 15% permanent deformation. The elasticity of the universal rubber NR is only lower than BR. The medium elasticity of NR is derived from the good flexibility of its macromolecules. Flexibility is derived from: the inner rotation barrier of the 1 bond is low, such as the double bond can not be rotated, and the a bond rotation position connected to the double bond is only 2.07 (kJ / mol), which can be considered as free rotation; every 4 chains on the 2 molecular chain The carbon atoms of the main chain have a side methyl group, the side groups are not dense and not large; the interaction between the three molecules is not large, and the cohesive energy density is only 266. 2MJ/m3, and the macromolecular motions are tightly bound to each other. BR has no pendant groups, NR has pendant groups, and IIR has dense side methyl groups.