1. Formation of raw rubber:

 

Raw rubber can be divided into natural rubber and synthetic rubber.

 

1. Natural rubber: raw rubber material formed by cutting the trunk of a rubber tree and collecting the effluent of the rubber paste through the process of removing impurities, solidifying, smoking and drying.

 

2. Rubber: By-products produced by petrochemical industry, raw rubber materials with different physical properties are synthesized according to different requirements. Commonly used such as: SBR, NBR, EPDM, BR, IIR, CR, Q, FKM and so on. However, due to the different synthetic methods, the same kind of rubber can be divided into several different kinds of raw rubber, and through the formulation setting, any type of rubber can be changed into hundreds of raw rubber to meet the product requirements.

 

2. Preparation of rubber raw materials:

 

The preparation of rubber raw materials can be divided into three basic processes:

 

1. Plasticizing: Plasticizing is to cut the raw rubber, plasticize and homogenize the raw rubber, and help the mixing operation of the mixing agent. The effect is to improve the dispersion of drugs, prevent friction heat from occurring during operation, and cause rubber scorch, thereby changing the processability of rubber.

 

2. Blending: Blending is to blend medicines evenly into the finished raw rubber, and the quality of blending directly affects the quality of products. Drugs are unevenly dispersed, molecular structure can not be fully cross-linked, rubber can not achieve the desired physical properties.

 

3. Extrusion: Raw rubber mixed, after extrusion operation, the excess air contained in the rubber is extruded, and the required thickness is completed to facilitate the molding operation in the die.

 

Forming of rubber:

 

The molecular structure of raw rubber is an elastomer with unsaturated long bonds. Therefore, proper drug additives and external environmental factors (such as time, temperature and pressure) are needed in the forming process. The unsaturated bonds are destroyed and then re-combined to form a saturated bond. With vacuum assistance, the inner air is completely forced out. Only in this way can the moulded rubber display its proper characteristics. If there are any deficiencies in the forming process (such as incorrect formulation, insufficient time, inappropriate temperature, etc.), the physical properties will be lost, the surplus drugs will be released, the deformation will be accelerated, and a variety of serious adverse phenomena will occur.

 

4. Aging of rubber:

 

According to the environmental conditions of rubber products, over time, cracking or hardening, rubber physical property degradation and other phenomena are called aging phenomenon. The causes of aging include external factors and internal factors.

 

1. External factors: external factors include oxygen, oxides, ozone, heat, light, radiation, mechanical fatigue, lack of processing and so on.

 

2. Internal factors: Internal factors include types of rubber, moulding methods, bonding degree, types of matching drugs, factors in processing engineering, etc.

 

The prevention of aging phenomenon focuses on the correct selection of rubber species and formulation design, plus rigorous production concept. Only in this way can the life of rubber products be prolonged and special functions be given full play.

 

V. Basic characteristics of rubber products:

 

1. The cohesion of the elastomer can not be eliminated when rubber products are pressed under high pressure. When the elastomer is separated from the mould, it often produces very unstable shrinkage (the shrinkage rate of rubber varies according to the type of rubber). Only after a period of time can it be stabilized gently. Therefore, at the beginning of rubber product design, no matter the formulation or the mould, it is necessary to carefully calculate the coordination. If not, the size of the product will be unstable and the quality of the product will be low.

 

2. Rubber is an elastomer of thermosolubility, while plastics are thermosolubility and cold solidity. The temperature range of rubber forming and curing differs considerably due to the main sulfide species, and may even be affected by climate change and indoor temperature and humidity. Therefore, the production conditions of rubber products need to be adjusted appropriately at any time. If not, there may be differences in product quality.

 

6. Rubber bonding shall be distinguished by double-sided adhesive:

 

Generally, double-sided adhesives for industrial use can be divided into two categories: acrylic adhesives and rubber adhesives. These two types can be divided into two types: base material and non-base material (base material: adding a layer of cotton to the adhesive, strengthening the glue volume and strength of the double-sided adhesive itself, no base material: pure gum, ensuring the transparency of the double-sided adhesive). Because the main body of rubber system is CR, which is used in rubber products, it is easy to react with the vulcanization system of rubber and turn yellow. Therefore, the lighter color rubber products are all made of the base double-sided adhesives in the acrylic system (the same kind of double-sided adhesives, whether with or without base materials, are distinguished by their own colloid thickness.

 

VII. Styrene Butadiene Rubber

 

Styrene-butadiene rubber (SBR) is a rubber prepared by copolymerization of butadiene and styrene. The English abbreviation is SBR. It is the most productive general rubber, including emulsion styrene-butadiene rubber and soluble styrene-butadiene rubber.

 

About 87% of the styrene butadiene rubber production capacity in the world uses emulsion polymerization. Generally speaking, styrene butadiene rubber mainly refers to emulsion polymerized styrene butadiene rubber. Emulsion polymerized styrene butadiene rubber also includes high temperature emulsion polymerization of butadiene styrene and low temperature emulsion polymerization of cold butadiene. The former was industrialized in 1942 and still has a small amount of production. It is mainly used for cement, adhesives, chewing gum, and some fabric coating and moulding products and mechanical products. Generally speaking, styrene butadiene rubber mainly refers to styrene butadiene rubber produced by low temperature emulsion polymerization. In 1947, it has high wear resistance and high tensile strength, good processability and other comprehensive properties. It is the largest and most widely used synthetic rubber compound at present.