The basic production process of rubber products

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1 Basic process flow: With the rapid development of modern industry, particularly the chemical industry, there is a wide variety of rubber products, yet their production processes are essentially the same. Products made from ordinary solid rubber (raw rubber) involve the following main production processes: raw material preparation → plasticization → mixing → molding → vulcanization → finishing → inspection. 2 Raw material preparation: The main materials for rubber products include raw rubber, additives, fiber materials, and metal materials. Among them, raw rubber is the basic material ； Adjuvants are auxiliary materials added to improve certain properties of rubber products ； Fiber materials (cotton, linen, wool, and various artificial and synthetic fibers) and metal materials (steel wire, copper wire) are used as the structural materials for rubber products to enhance mechanical strength and prevent deformation of the products. During the preparation of raw materials, the ingredients must be weighed accurately according to the recipe. To ensure that the raw rubber and additives can mix evenly with each other, certain materials need to be processed: the raw rubber must first be softened in an oven at 60–70°C, after which it is cut and broken into small pieces ； Bulk binders such as paraffin, stearic acid, rosin, etc. need to be crushed ； If the powdered additive contains mechanical impurities or coarse particles, it needs to be screened out ； Liquid binders (pine tar, guayule) require heating, melting, evaporating moisture, and filtering out impurities ； The compounding agents need to be dried; otherwise, they tend to clump together, fail to disperse evenly during mixing, and cause bubbles to form during vulcanization, thereby affecting product quality ； 3. The plasticized rubber is elastic but lacks the properties necessary for processing (plasticity), making it difficult to work with. To improve its plasticity, the raw rubber needs to be vulcanized ； In this way, the additives can be easily and evenly dispersed in the raw rubber during mixing ； At the same time, it also helps to improve the permeability of the rubber compound (penetration into fiber fabrics) and its flowability during calendering and molding processes. The process of breaking down the long-chain molecules of raw rubber to create plasticity is called vulcanization. The methods for vulcanizing raw rubber are mechanical vulcanization and thermal vulcanization. Mechanical vulcanization involves, at relatively low temperatures, using the mechanical compression and friction forces of a vulcanizing machine to break down long-chain rubber molecules and shorten them, thereby transforming them from a highly elastic state to a pliable state. Thermoplasticization involves introducing hot compressed air into the raw rubber; under the action of heat and oxygen, the long-chain molecules are degraded and shortened, thereby granting plasticity. 4. Mixing: In order to adapt to various operating conditions and achieve different properties, as well as to improve the performance of rubber products and reduce costs, it is necessary to add different additives to the raw rubber. Mixing is a process in which the vulcanized raw rubber is combined with additives, and then placed in a rubber mixing machine; through mechanical stirring, the additives are dispersed completely and evenly within the raw rubber. Mixing is an important step in the production of rubber products; if the mixing is uneven, the rubber and additives cannot function properly, which affects the performance of the final product. The compound obtained after mixing is known as mixed rubber; it is a semi-finished material used for manufacturing various rubber products. Commonly referred to as rubber compound, it is usually sold as a commodity, allowing buyers to use it to directly shape and vulcanize it into the desired rubber products. Depending on the formulation, compound rubber is available in a range of different grades and types with varying properties, offering choices. 5 Molding: In the production of rubber products, the process of giving them various shapes and sizes in advance using calenders or extruders is known as molding. The methods of shaping include: extrusion molding, which is suitable for manufacturing simple sheet-like and plate-like products. It is a method in which the compounded rubber is pressed into sheets of a certain shape and size using a calender; this process is called calendering. For some rubber products (such as tires, adhesive tape, hoses, etc.), the textile fiber materials used must be coated with a thin layer of glue (applying glue to the fibers is also known as gluing or coating them). This gluing process is generally carried out on a calendering machine. Fiber materials need to be dried and impregnated before calendering. Drying is intended to reduce the moisture content of the fiber materials (to prevent bubbling due to water vaporization) and to raise their temperature, thereby ensuring the quality of the calendering process. Impregnation is a necessary step before coating, aimed at improving the bonding strength between the fiber material and the adhesive. Extrusion molding is used for more complex rubber products; items such as tire treads, hoses, and rubber-coated metal wires require to be manufactured using the extrusion molding method. It is a method in which a rubber compound with certain plasticity is placed into the hopper of an extruder, and under the pressure of the screw, it is continuously shaped through various die shapes (also known as molds). . Before extrusion, the rubber compound must be preheated to make it soft and easier to extrude, thereby producing rubber products with a smooth surface and accurate dimensions. Molding: Rubber products with complex shapes, such as rubber cups and seals, can also be manufactured using the molding method. By utilizing male and female molds for shaping, the rubber material is placed in these molds and heated to undergo molding. 6 Vulcanization: The process of converting plastic rubber into elastic rubber is called vulcanization. It involves adding a certain amount of vulcanizing agents (such as sulfur, vulcanization accelerators, etc.) to the semi-finished product made from raw rubber (in a vulcanization tank), and then heating it at a specified temperature while maintaining that temperature. This causes the linear molecules of the raw rubber to cross-link with each other through the formation of “sulfur bridges,” thereby creating a three-dimensional network structure that transforms the plastic rubber into highly elastic vulcanized rubber. Since the cross-linking bonds are primarily composed of sulfur, it is called “vulcanization”. With the rapid development of synthetic rubber, there are now many types of vulcanizing agents; in addition to sulfur, these include organic polysulfides, peroxides, metal oxides, and others. Therefore, any process that transforms plastic rubber with a linear structure into elastic rubber with a three-dimensional network structure is called vulcanization, and any substance that can act as a \"bridge\" within the rubber material is referred to as a \"vulcanizing agent\". Elastic rubber after vulcanization is called vulcanized rubber, also known as soft rubber, and is commonly referred to as “rubber”. Vulcanization is one of the most important processing steps in rubber manufacturing; various rubber products must undergo vulcanization to achieve optimal performance. Unvulcanized rubber has little practical value for use, but both under-vulcanization (insufficient vulcanization degree, inadequate vulcanization time, failure to reach the optimal state) and over-vulcanization (excessive vulcanization time, significant decline in performance) reduce the properties of rubber. Therefore, the vulcanization time must be strictly controlled during the production process to ensure that the vulcanized rubber products possess the best performance and the longest service life. 7 Auxiliary measures To achieve the desired performance levels, additional auxiliary measures should be incorporated into the production process: 7.1 Increasing strength – using hard carbon black and incorporating phenolic resin ； 7.2 Improving wear resistance – using hard carbon black ； 7.3 High airtightness requirements – use fewer components with high volatility ； 4.7.4 Improving heat resistance – adopting a new vulcanization process ； 7.5 Improving cold resistance – by reducing the tendency to crystallize through the depolymerization of the raw rubber, and by using plasticizers that are resistant to low temperatures ； 7.6 Improving flame resistance – avoiding flammable additives, using fewer softening agents, and employing flame retardants (such as antimony trioxide). 7.7 Enhancing oxygen and ozone resistance – using diamine-based protective agents ； 7.8 Improving electrical insulation – by using high-structure fillers or metal powders, as well as antistatic agents ； 7.9 Improving magnetism – Using strontium ferrite powder, aluminum-nickel-iron powder, iron-barium powder, etc. as fillers ； 7.10 Improving water resistance – using lead oxide or resin vulcanization systems, along with fillers with low water absorption (such as barium sulfate, clay) ； 7.11 Improving oil resistance – thorough cross-linking, reduced use of plasticizers ； 7.12 Improving acid and alkali resistance – using more fillers ； 7.13 Improving high vacuum performance – using additives with low volatility ； 7.14 Reducing hardness – using large amounts of softening agents. 8. Classification of rubber products and their applications in automobiles. Rubber products are widely used and come in many different types. Based on their use, they are generally divided into two categories: industrial and domestic. Industrial rubber products mainly include: tires, tapes, hoses, printing plates, adhesive tapes and tape-based products, seals, vibration-damping components, latex products, rigid rubber products, rubber-insulated products, rubber rollers, and rubber linings