Unveiling the Rubber Product Manufacturing Process

I. Basic Process Flow
Rubber products are diverse, but their production processes are basically the same. The basic process of rubber products using general solid rubber-raw rubber as raw materials includes: plasticizing, mixing, calendering, extrusion, molding, and vulcanization, six basic processes. Of course, basic processes such as raw material preparation, finished product finishing, inspection, and packaging are also indispensable. The rubber processing process mainly solves the contradiction between plasticity and elasticity. Through various technological means, the elastic rubber is made into plasticized plasticized rubber, then various compounding agents are added to make semi-finished products, and then vulcanization is used to make the semi-finished products with plasticity into rubber products with high elasticity and good physical and mechanical properties.
II. Raw Material Preparation
1. The main raw material of rubber products is raw rubber as the basic material, and raw rubber is collected by artificially cutting the bark of rubber trees grown in tropical and subtropical regions.
2. Various compounding agents are auxiliary materials added to improve certain properties of rubber products.
3. Fiber materials include (cotton, linen, various artificial fibers, synthetic fibers, and metal materials, steel wire) as the skeleton material of rubber products to enhance mechanical strength and limit product deformation. In the raw material preparation process, the materials must be weighed accurately according to the formula. In order to make the raw rubber and compounding agents mix evenly, the materials need to be processed. The raw rubber should be softened in a 60-70°C drying room before being cut and broken into small pieces. The compounding agents are blocky. For example, paraffin wax, stearic acid, rosin, etc., need to be crushed. Powdery ones need to be screened to remove mechanical impurities or coarse particles if they contain them. Liquid ones, such as pine tar and coumarone, need to be heated, melted, evaporated, and filtered to remove impurities. Compounding agents should be dried to prevent agglomeration. If they cannot be evenly dispersed during mixing, bubbles will be generated during vulcanization, which will affect product quality.
III. Plasticizing
Raw rubber is elastic and lacks the plasticity required for processing, making it inconvenient to process. In order to improve its plasticity, the raw rubber must be plasticized, so that the compounding agents are easily and evenly dispersed in the raw rubber during mixing, and it also helps to improve the permeability of the rubber in the calendering and molding processes, entering the fiber fabric and molding fluidity. The process of degrading the long-chain molecules of raw rubber to form a plasticized state is called plasticizing. There are two methods for plasticizing raw rubber: mechanical plasticizing and thermal plasticizing. Mechanical plasticizing is to degrade and shorten the long-chain rubber molecules under the action of mechanical extrusion and friction of the plasticizing machine at a not too high temperature, changing from a highly elastic state to a plastic state. Thermal plasticizing is to introduce hot compressed air into the raw rubber, and under the action of heat and oxygen, the long-chain molecules are degraded and shortened to obtain plasticity.
IV. Mixing
In order to adapt to various different usage conditions and obtain various different properties, and also to improve the performance of rubber products and reduce costs, different compounding agents must be added to the raw rubber. Mixing is a process in which the plasticized raw rubber and compounding agents are mixed and placed in a rubber mill, and the compounding agents are completely and evenly dispersed in the raw rubber through mechanical mixing. Mixing is an important process in the production of rubber products. If the mixing is not uniform, the functions of rubber and compounding agents cannot be fully utilized, affecting the use performance of the product. The rubber material obtained after mixing is called mixed rubber, which is a semi-finished material for manufacturing various rubber products, commonly known as rubber material, and is usually sold as a commodity. Purchasers can use the rubber material to directly process and mold, vulcanize to make the required rubber products. According to different formulas, mixed rubber has a series of different grades and varieties with different properties, providing choices.
V. Molding
In the production process of rubber products, the process of using a calender or extruder to pre-make various shapes and sizes is called molding. Molding methods include:
1. Calendering
Suitable for manufacturing simple sheet-like and plate-like products. It is a method of pressing mixed rubber into a sheet of a certain shape and size through a calender, called calendering. Some rubber products, such as tires, rubber cloth, and rubber tubes, require textile fiber materials to be coated with a thin layer of rubber. Coating rubber on fibers is also called sticking rubber or wiping rubber. The coating process is generally completed on a calender. The fiber materials need to be dried and rubber-dipped before calendering. The purpose of drying is to reduce the water content of the fiber materials to prevent water vapor from bubbling and to increase the temperature of the fiber materials to ensure the quality of the calendering process. Rubber dipping is a necessary process before rubber coating, aiming to improve the bonding performance between the fiber materials and the rubber material.
2. Extrusion Molding
Used for more complex rubber products. For example, tire treads, rubber tubes, and metal wire surface rubber coating need to be manufactured using extrusion molding. It is a method of continuously shaping a plastic mixed rubber into a hopper of an extruder, and extruding it through various dies, also called templates, under the extrusion of a screw. Before extrusion, the rubber material must be preheated to make the rubber material soft and easy to extrude, so as to obtain rubber products with a smooth surface and accurate dimensions.
3. Compression Molding
It can also be used to manufacture rubber products with complex shapes, such as leather washers and sealing rings, using a mold method. The rubber material is placed in a mold and heated to form using the positive and negative molds.