Rubber compression molding process|Introduction to the molding process of rubber products

Jan 27, 2022

Rubber compression molding process

There are many kinds of rubber products, but the production process is basically the same. Products made of general solid rubber (raw rubber) as raw materials, its production process mainly includes: raw material preparation → plasticizing → mixing → molding → vulcanization → trimming → inspection
 (1) Plasticizing of raw rubber The process of transforming elastic raw rubber into a buried state is called plasticizing. The purpose of mastication is to reduce the elasticity of raw rubber, increase its plasticity, and obtain appropriate fluidity to meet the requirements of various processing processes such as mixing, calendering or extrusion molding, vulcanization, glue manufacturing, and sponge rubber manufacturing.
Plasticizing has mechanical plasticizing method and chemical plasticizing method. The former reduces the elasticity of the raw rubber and obtains a certain plasticity through the mechanical damage of the plasticizer. The latter achieves the purpose of plasticizing the raw rubber through the chemical action of chemicals. The essence of the plasticizing process is that the macromolecules of the rubber are broken into molecules with smaller relative molecular weights, thereby reducing the viscosity and increasing the plasticity.
 (2) Mixing of rubber compound The process of mixing various compounding agents into raw rubber to make a mixed rubber with uniform quality is called mixing. Its basic task is to produce a compounded rubber that meets the performance requirements, so that subsequent processes such as calendering or extrusion molding, rubber coating and vulcanization can be carried out normally. The mixing process is the process in which the compounding agent such as carbon black is uniformly dispersed in the raw rubber. The surface of each particle of the compounding agent must be completely surrounded and wetted by the rubber.
The equipment used to prepare plasticized rubber and mixed rubber includes open rubber mixing machine (referred to as open mixer) and closed rubber mixing machine (referred to as internal mixer).
The working principle of the open mill is that two hollow rollers rotating in opposite directions rotate relative to each other at different speeds, and the two rollers have the same size. The raw rubber or rubber material is drawn into the gap between the two rollers under the action of friction with the rotation of the roller. Due to the different rotation speeds of the two rollers, a velocity gradient is generated, and the raw rubber or rubber compound is subjected to strong frictional shearing, the molecular chain of the rubber is broken, and stable molecules with small relative molecular mass are generated under the action of surrounding oxygen or peptizer. , the plasticity of the rubber after mastication is improved, and the mixed rubber with uniform quality can be obtained after mixing.

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