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1. Molecular structure of rubber: Rubber is also a polymer compound with a relative molecular mass of several hundred thousand. The molecular size of the polymer compound is not fixed, and the so-called relative molecular mass refers to its average relative molecular mass. The relative molecular mass has a great influence on the rubber strength. Generally, the molecular strength is only a certain degree to a certain extent, and the aging resistance of the polymer decreases with the increase of the polymerization degree (the index for measuring the molecular size of the polymer). However, the rubber will break the rubber molecules during the mastication process, and the relative molecular mass will become smaller, which can increase the plasticity and improve the processing conditions.
From the geometrical shape of the rubber molecular chain, it can be divided into three types: linear type, branched type and crosslinked type (also called body type). Different geometries with completely different physical properties. Rubber is very flexible because the carbon atoms in the C-C chain of the rubber molecule can rotate around the chemical bond.
2. Aggregation Properties of Rubber The state in which the rubber molecules are brought together is called the aggregation state. Aggregation states can be divided into three states: solid, liquid, and gas. Rubber has liquid properties because the molecular segments of rubber can move relatively freely like low molecular liquids. Rubber has the property of being solid, because the molecular chain cannot be relatively displaced from the viewpoint of the entire macromolecular chain, and can maintain a certain shape and a large strength. Rubber also has the property of gas, such as the modulus of elasticity increases with the increase of temperature, and heat is generated when stretching, as if the gas is compressed, the heat is converted by energy.
3, rubber viscoelastic rubber has a very good elasticity, in addition, it also has some characteristics of the viscous liquid, mainly in the rubber after the force, like the viscous liquid, its deformation linearly develops with time . Therefore, rubber is considered to be a viscoelastic material, resulting in a series of viscoelastic phenomena such as creep, stress relaxation, and internal friction.
4. Although the rheological rubber of rubber has high elasticity, it needs to be deformed under flowing state during molding processing, such as mastication, kneading, pressing or calendering. Therefore, the molding process necessarily involves the fluidity of rubber. Viscosity is an important parameter to characterize liquid fluidity. The viscosity of rubber is different from that of plastic. Plastic can greatly reduce the viscosity of the melt by increasing the temperature. The viscosity of rubber is little affected by temperature, which depends mainly on the relative molecular mass. Reducing the relative molecular mass can reduce the viscosity and elasticity, which will be beneficial to the molding process of rubber.look more about rubber aging
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