1、Plasticity of raw rubber
The rubber processing process has certain requirements on the plasticity of raw rubber. In order to meet the process performance, raw rubber must be plasticized. However, most synthetic rubbers control the initial plasticity of raw rubber in the synthesis process. It can be blended directly without plasticizing. In addition, natural rubber, hard butadiene rubber, isoprene rubber, butadiene rubber, etc. need to be moderately plasticized.
Plastic refining can reduce the drilling degree of rubber, so that the matching agent is easy to mix; plastic refining can improve the rheological properties of rubber, reduce mouth expansion and calendering shrinkage; plastic refining can also improve the solubility of rubber and molding drill adhesion. Plasticizing must be moderate, excessive plasticizing will reduce the strength, elasticity, wear resistance and aging resistance of the vulcanized rubber properties. The degree of plasticity is mainly determined by the process performance of the compound and the performance requirements of the product. The plasticity of raw rubber is generally carried out in open refining machine, but closed refining machine is also available for plasticizing.
The amount of raw rubber and various compounding agents are accurately weighed according to the practical rubber formula.
The process of pressing various compounding agents and raw rubber together on the rubber making machine is called mixing. Mixing is not only a simple mechanical mixing process of raw rubber and compounding agent, but also a physical and chemical process of each component to infiltrate and disperse, adsorb and combine and form a gum dispersion with complex network structure, which is actually a rubber modification process.
In the whole process of rubber processing, the quality of rubber compounding has a decisive influence on the further processing of the rubber and the performance of the final product, and mixing is one of the processes most prone to quality fluctuations. If the mixing is not good, the rubber will have uneven dispersal of compounding agent, plasticity fluctuation, even scorching, spraying frost and other phenomena, resulting in the degradation of vulcanized rubber and finished product performance.
Mixing can be carried out on the open refiner or in the dense refiner. For the small scale, small batch, frequent change of varieties of rubber, more open machine mixing. In addition, the open refiner is also particularly suitable for some special rubber materials, such as sponge rubber, hard rubber and butyl rubber, atmosphere rubber and other rubber materials preparation mouth close refining than open refining operation security, dust flying phenomenon improved significantly, mixing process mechanization, reduce the labor intensity, mixing time shortened, production efficiency improved. The rubber material mixed by the dense refining machine must be parked for 4-8h before additional processing on the open refining machine, adding accelerator and vulcanizing agent.
4. Preparation of semi-finished products
The production of O-shaped rubber seals is still generally based on the production of the molding method. In order to improve production efficiency and product quality, reduce waste, pre-manufactured semi-finished products are necessary. The traditional manufacturing process of flat vulcanized semi-finished products is. Qualified compounding rubber is pressed into film after full refining and cut into rubber strips and blocks. For the large amount or specification of large products, can be extruded in the extruder L according to the required specifications into the rubber rope, cut into a certain length, the joint according to 45, lap, made of O-ring semi-finished products. In recent years . Many domestic manufacturers have used precision preforming machine to produce O-rings and other products of semi-finished products. This not only improves the production efficiency. And to ensure the accuracy of the volume and weight of semi-finished products, improve the level of rubber products production process. With injection molding machine production, semi-finished products without special preparation, just pressed rubber strips can be fed directly.
5、The last step is the vulcanization of the rubber seal