Function of rubber internal mixer:
The purpose of rubber plasticization is to shorten the macromolecular chain of rubber under mechanical, thermal, chemical and other effects, so that the rubber temporarily loses its elasticity and increases its plasticity to meet the process requirements in the manufacturing process.
For example: to make the compounding agent easy to mix, easy to calender and press out, the molded pattern is clear, the shape is stable, increase the fluidity of the pressed and injected rubber, make the rubber easy to penetrate into the fiber, and improve the solubility and adhesion of the rubber.
Of course, some low-viscosity and constant-viscosity rubbers are sometimes not necessarily plasticized, domestic standard granular rubber, standard Malaysian rubber (SMR).
The plasticization of raw rubber by internal mixer belongs to high-temperature plasticization, with the lowest temperature above 120℃, generally between 155℃-165℃.
Raw rubber is subjected to high temperature and strong mechanical action in the internal mixer cavity, which causes severe oxidation and can obtain ideal plasticity in a short time. Therefore, the main factors affecting the internal mixer for raw rubber plasticization are:
1. Equipment technical performance, such as rotation speed, etc.,
2. Process conditions, such as time, temperature, wind pressure and capacity, etc.
The plasticization of rubber is closely related to its chemical composition, molecular structure, molecular weight and molecular weight distribution. Due to the different characteristics of natural rubber and synthetic rubber in structure and performance, it is generally easier to plasticize natural rubber, while it is more difficult to plasticize synthetic rubber. As for synthetic rubber, isoprene rubber and chloroprene rubber are close to natural rubber, followed by styrene-butadiene rubber and butyl rubber, and nitrile rubber is the most difficult.
The plasticity of raw rubber is related to the difficulty of the entire manufacturing process of the product, and directly affects the physical and mechanical properties of the vulcanized rubber and the performance of the product.
If the plasticity of raw rubber is too high, the physical and mechanical properties of the vulcanized rubber will be reduced. If the plasticity of the raw rubber is too low, it will cause difficulties in the subsequent processing, making it difficult to mix the rubber evenly, and the semi-finished product surface is not smooth when calendering and extruding, and the shrinkage rate is large. It is difficult to control the size of the semi-finished product. During calendering, the rubber is also difficult to rub into the fabric, causing the rubber curtain fabric to peel off, which greatly reduces the adhesion between the fabric layers.
Uneven plasticity will cause inconsistency in the process performance and physical and mechanical properties of the rubber, and even affect the inconsistent performance of the product. Therefore, correctly mastering the plasticity of raw rubber is an issue that cannot be ignored.
