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- May 25, 2018 -

Rubber: Highly elastic polymer material with reversible deformation. It is elastic at room temperature and can generate large deformation under a small external force. It can be restored after removing external force. Rubber is a completely amorphous polymer. Its glass transition temperature (Tg) is low, and its molecular weight is often very large, more than several hundred thousand. Rubber Stress Relaxation: When a rubber test piece is quickly stretched to a certain length and the length is kept constant, the stress is gradually reduced due to the prolonged time. We call it stress relaxation. In addition, the rubber vulcanized rubber belt is transported. The network structure, under the action of stress, if the time is very short, the viscosity of the rubber is very large, the effect of the force cannot be very uniform, so some segments are not pulled straight, the bond angle is twisted, Some large segments have not moved yet. At this time, the rubber is in a state of tension and its internal stress is large. However, after a certain period of time, the molecular chain of rubber gradually adapts to the action of external forces and moves, causing internal stress. Eliminated gradually to reach an equilibrium state where the stress is reduced to the ideal equilibrium value. Due to the differences in the chemical structure of the rubber, the relative molecular mass, and the vulcanization ingredients, the stress relaxation rate is constant even under the same relaxation conditions. , that is, the speed of stress reduction, the difference is also very large, nylon rubber belt stress relaxation process, from a few seconds or even days, that is, The time required for stress relaxation to equilibrium is very different. The stress relaxation of raw rubber is different from the stress relaxation of vulcanizates. Raw rubber does not have crosslinks, and plastic flow occurs during deformation. Therefore, it takes a long time. The stress can be reduced to zero. At this time, the stress is removed, and permanent deformation occurs and it is no longer restored.

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