Effect of Rubber Accelerator on Shock Absorbing Rubber

Effect of Rubber Accelerator on Shock Absorbing Rubber

The vulcanization system has great influence on the stiffness, damping coefficient, heat resistance and fatigue resistance of the damping rubber. Generally, in the network structure of vulcanized rubber, the less sulfur atoms and free sulfur in the crosslinking bond, the stronger the crosslinking, the larger the elastic modulus of vulcanized rubber, the smaller the damping coefficient. Using traditional vulcanization system and improving the degree of crosslinking is beneficial to shock absorption and dynamic fatigue resistance, but not enough heat resistance. For example, when natural rubber uses effective vulcanization system and semi-effective vulcanization system, although the heat resistance is improved, the fatigue resistance and the adhesion of metal parts have a declining trend. Therefore, it is necessary to strike the right balance between these properties. After all, the heat resistance of sulfur sulfide system is limited, so the new sulfur sulfide system with higher heat resistance grade is studied.

Some good heat resistance rubber, such as fluorine rubber, acrylic rubber, ethylene propylene diene rubber, silicone rubber, hydrogenated nitrile rubber, chlorosulfonated polyethylene, copolychlorol rubber, due to their high deformation under the fatigue resistance and metal bonding reliability are relatively poor, so it is not suitable for shock absorption rubber. If you need to use these rubber must overcome the above defects, through high deformation (actual service conditions assessment) test identification before use.

Besides rubber, the filling agent is a significant factor affecting the dynamic damping characteristics of rubber, which is closely related to the damping coefficient and modulus of vulcanized rubber. In the case of vulcanized rubber deformation, when rubber molecules move, the internal friction between the rubber chain segment and the filler or between the filler and the filler will increase the damping of the vulcanized rubber. The increment is related to the interaction between filler and rubber and the interface size. The smaller the particle size of the filler is, the larger the specific surface area is, the larger the contact surface with the rubber molecule is, the more physical binding points are, the larger thixotropy is, the hysteresis loss is generated in the dynamic strain, and the friction between the particles will also increase due to the increase of the surface area, so the larger tanB and the larger dynamic and static moduli are shown. The greater the activity of the filler, the greater the role of rubber molecules, the damping and stiffness of vulcanized rubber will also increase. The shape of the filler particle also has an effect on the damping characteristics and modulus of the rubber. For example, sheet mica powder can make the vulcanized rubber obtain higher damping and modulus.

In the formula of damping rubber, natural rubber uses semi-reinforcing furnace black and fine particle hot crack carbon black is better. In synthetic rubber, quick - press carbon black and universal carbon black can be used. With the increase of the amount of carbon black, the damping and stiffness of vulcanized rubber are also improved. Under the condition of a certain amount of carbon black, the damping and stiffness of high wear-resisting carbon black with small particle size and high activity are higher than that of semi-reinforced carbon black. In addition, with the increase of the amount of carbon black, the dependence on the amplitude also increases. With the increase of vibration amplitude, the larger the amount of carbon black, the more significant the reduction of modulus and damping increase. When the amplitude is very small (approaching 0), the damping coefficient has little relation with the packing content.

In conclusion, with the decrease of carbon black particle size, the increase of activity and the increase of dosage, the damping coefficient and modulus of damping rubber also increase. However, from the point of view of fatigue resistance, carbon black has an adverse effect on shock absorbing rubber: the smaller the particle size of carbon black, the more significant the fatigue, the heavier the fatigue damage. For high damping vibration isolation rubber, after adding carbon black and other fillers in rubber, due to the adsorption of rubber molecules by the surface of carbon black particles and the existence of rubber continuous phase and some of the discontinuous phase of the complex between the carbon black particles, coupled with the friction of rubber molecular chain itself, the apparent viscosity coefficient of the system increases; And the higher the content of carbon black, the greater the viscosity. If the rubber and carbon black system is applied, when the stress is applied, the rubber molecular chain will slip away from the original carbon black-rubber surface, and then re-adsorb and destroy the carbon black condensed phase, and then re-condense, resulting in great friction energy.

In order to improve the damping characteristics of damping rubber as much as possible and reduce the dependence of creep and performance on temperature, some special fillers, such as vermiculite and graphite, are often combined with high-damping vibration isolation rubber to cause internal friction in the system composed of rubber and special fillers, and part of the mechanical energy applied to the system is converted into heat energy and dissipated, which is the reduction of high-damping vibration isolation rubber The principle of shock.

White carbon black has small particle size and its reinforcing effect is second only to that of carbon black, but its dynamic performance is far inferior to that of carbon black. Calcium carbonate, clay, magnesium carbonate and other inorganic filler, reinforcement performance is generally weak. In order to obtain the specified elastic modulus, its dosage is larger than carbon black, which will have adverse effects on other properties, so it is rarely used. Used as a plasticizer for damping rubber except for Tg which has a reduced glass transition temperature. In addition to improving the machining performance, the damping transition zone is also required to be widened, which mainly depends on the characteristics of the plasticizer and its interaction with rubber. If the plasticizer in rubber only a certain limit of solubility, or plasticizer is incompatible and purely mechanical mix, damping transition usually in the damping rubber, with the increase of the amount of plasticizer, vulcanized rubber elastic modulus decreases, damping coefficient tan increase area will become wider in the damping rubber added plasticizer, although can improve rubber low temperature performance and fatigue resistance, but also Will make the creep and stress relaxation rate increase, affect the damping characteristics of damping rubber and the reliability of use, so the amount of plasticizer should not be too much.

General plasticizer molecular structure and raw rubber molecular structure in polarity to match, that is, polar rubber selection of polar plasticizer, vice versa. For natural rubber, plasticizers such as pine tar and spindle oil are usually used. The p-butyl nitrile rubber was mainly composed of dimethyl dibutyl benzyl ester, dioctyl sebacate, dioctyl phthalate and diisooctyl adipate.