Rubber vulcanization press | What role does vulcanization pressure play in rubber molding process?

Apr 28, 2022

The principle of vulcanizer for measuring the vulcanization characteristics of unvulcanized rubber: put the unvulcanized rubber sample into a completely sealed or almost completely sealed mold cavity and keep it at the set test temperature. The mold cavity has two parts, one of which oscillates at a small swing angle. The vibration causes the sample to produce shear strain, and the reaction torque (force) of the sample to the mold cavity is measured. This torque (force) depends on the shear modulus produced by the compound during vulcanization and continuously varying with the length of vulcanization time. From the time the rubber is put into the mold, the vulcanizer will automatically record the torque value reflecting the shear strain of the rubber. Therefore, a curve between torque and time, i.e. vulcanization curve, is obtained. Its shape is related to the set test temperature and the characteristics of the compound.
(FL for some vulcanizers): Zui small torque or force (N.m or n);
(Fmax for some vulcanizers): flat, Zui large and Zui high torque or force (N.m or n) achieved within the specified time;
(T10 for some vulcanizers): also known as scorch time, that is, the time corresponding to the torque reaching ml + (mh-ml) * 10%; (some vulcanizers use T90): it is also called positive vulcanization time, that is, the time corresponding to the torque reaching ml + (mh-ml) * 90%, which is called process positive vulcanization time.
The vulcanization process is divided into four stages: vulcanization induction stage, thermal vulcanization stage, vulcanization flattening stage and over vulcanization stage.
The three technological parameters of vulcanization of rubber parts are: temperature, time and pressure. Among them, vulcanization temperature is a parameter that has Zui great influence on the properties of products, and the research on the influence of vulcanization temperature on rubber products can be found everywhere. However, the vulcanization pressure is less tested.
Vulcanization pressure refers to the pressure per unit area of rubber compound in the vulcanization process. Generally, except for some cloth clips and sponge rubber, other rubber products need to apply certain pressure during vulcanization.
Rubber vulcanization pressure is an important factor to ensure the geometric size, structural density and physical machinery of rubber parts. At the same time, it can also ensure that the surface of parts is smooth without defects and meet the sealing requirements of rubber products. The main functions are as follows:
Prevent bubbles in the vulcanization process of rubber mixture and improve the compactness of products;
The rubber filling cavity can provide the power to fill the mold within the specified time;
Improve the adhesion between rubber and clamps (cord fabric, etc.) and the bending resistance of rubber products;
Improve the physical and mechanical properties of rubber products.

rubber vulcanization press

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