The property that an object can recover its original shape after being deformed by an external force is called elasticity;
Resilience is a quantity used to describe the size of elasticity. It is expressed by the time when the object returns to its original shape or the size of the rebound force after the force is applied to the object under the specified conditions.
Factors affecting the resilience of rubber
Rubber is a kind of high elastic polymer material with reversible deformation, which is elastic at room temperature, can produce large deformation under a small external force, and can recover to its original state after removing the external force.
The resilience of rubber is a characterization of the recoverable elastic deformation of rubber under stress. The interaction between rubber molecules will hinder the movement of molecular chain segments. Part of the forces acting on rubber molecules are used to overcome the intermolecular viscosity resistance, and the other part deforms the molecular chain, which constitute the viscoelasticity of rubber. So rubber has both high elasticity and viscosity.
Factors affecting rubber resilience
1. Rubber with large elongation and small permanent deformation has good elasticity.
2. Rubber with large molecular weight has good elasticity.
3. Rubber with narrow molecular weight distribution has good elasticity.
4. The rubber with good molecular chain flexibility has good elasticity.
5. The elasticity of rubber becomes poor after crystallization.
6. The large intermolecular force reduces the elasticity (such as styrene-butadiene rubber and nitrile rubber)
7. The order of resilience of each rubber (unfilled) is as follows: BR -- NR -- EPDM -- NBR-18
——SBR——NBR-26——CR——NBR-40——IIR——ACM
8. The elasticity reaches its maximum with the increase of crosslinking density. Polysulfide bonds have good elasticity.
9. The accelerator with high sulfur and low compatibility has good elasticity.
10. Thiazole and hyposulphonamide accelerants have good elasticity.
11. For NBR, the resilience of DCP sulfur-free curing system is higher than that of conventional curing system.
12. For NR, the vulcanizate with semi-effective curing system has the best elasticity. The second is common and effective curing system.
13. Improving the rubber content is the most effective way to improve the resilience.
14. The addition of fillers with small particle size, large surface activity and high structural degree reduces the resilience of rubber.
15. The elasticity of rubber compound decreases with the increase of filler content. However, when the dosage of calcium carbonate and clay is no more than 30 phr, it has little effect on elasticity.
16. Softener reduces the elasticity of rubber (except EPDM)
Relevant standards for rubber resilience test
GB/T 1681-1991 Vulcanized rubber Determination of resilience
ISO 4662:1986 Vulcanized rubber Determination of resilience
ASTM D1054-2002 Test Method for Rubber Elasticity by Bouncing Pendulum Method
JIS K6255:1996 Test method for resilience of vulcanized rubber and thermoplastic rubber
DIN 53512-2000 Vulcanized rubber Determination of resilience
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