1. Raw material preparation: laying the foundation for quality
The main raw material for silicone products is silicone rubber, which is a high molecular weight elastomer with silicon oxygen bonds as the main chain. There are many types of silicone rubber, which can be divided into high-temperature vulcanized silicone rubber (HTV) and room temperature vulcanized silicone rubber (RTV) based on their vulcanization characteristics and performance. Different types of silicone rubber are suitable for different product manufacturing. For example, high-temperature vulcanized silicone rubber has high strength and heat resistance, and is commonly used to manufacture industrial products with high performance requirements; Room temperature vulcanized silicone rubber has the advantages of easy operation and adjustable curing speed, and is commonly used in sealing, potting, and other scenarios.
In addition to the silicone rubber matrix, various additives need to be added to improve the performance of silicone products. Common additives include vulcanizing agents, reinforcing agents, plasticizers, pigments, etc. Vulcanizing agent is a key substance that causes cross-linking reaction and forms a three-dimensional network structure in silicone rubber. It determines the vulcanization speed and degree of silicone products. Reinforcing agents can improve the strength and hardness of silicone rubber, and commonly used reinforcing agents include white carbon black. Plasticizers are used to increase the flexibility and processability of silicone rubber, making the product easier to shape. Pigments endow silicone products with rich and colorful colors, meeting the aesthetic needs of different consumers.
In the raw material preparation stage, it is necessary to accurately weigh the silicone rubber and various additives according to the formula ratio and mix them thoroughly and evenly. This process is usually carried out in professional mixing equipment, such as open mixers or internal mixers. Through mechanical stirring and shearing, various raw materials are fully dispersed to form a uniform adhesive material, preparing for subsequent molding processes.
2. Forming processing: endowing the product with a shape
The uniform adhesive obtained through the raw material preparation stage is then processed into semi-finished products with specific shapes in the molding process. There are various molding methods for silicone products, including compression molding, injection molding, extrusion molding, and liquid silicone injection molding.
molding
Compression molding is one of the most commonly used methods for molding silicone products. It is suitable for manufacturing products with complex shapes and high dimensional accuracy requirements. During the molding process, the rubber material is first placed into the preheated mold cavity, and then a certain pressure is applied through a hydraulic press to fill the cavity with the rubber material under high temperature and pressure, and undergo vulcanization reaction. After a period of pressure holding and vulcanization, open the mold and take out the product. The advantages of compression molding are high dimensional accuracy and good surface quality of the product, but the production efficiency is relatively low, making it suitable for small batch and multi variety production.
injection molding
Injection molding is an efficient and automated molding method. It heats and plasticizes the rubber material through the screw of the injection machine, and injects it into the closed mold cavity for rapid vulcanization and molding under high temperature and pressure. Injection molding has the advantages of high production efficiency, stable product quality, and the ability to achieve automated production. It is suitable for mass production of silicone products with relatively simple shapes, such as silicone buttons and sealing rings.
Extrusion
Extrusion molding is mainly used to manufacture silicone products with fixed cross-sectional shape and continuous length, such as silicone tubes, silicone strips, etc. During the extrusion molding process, the rubber material is extruded into the desired shape through the die of the extruder under the action of the screw, and then undergoes vulcanization treatment to shape it. Extrusion molding has the advantages of high production efficiency and continuous production, which can meet the needs of large-scale production.
Liquid silicone injection molding
Liquid silicone injection molding is a new molding technology developed in recent years. It uses liquid silicone rubber as raw material, and precisely injects the liquid silicone rubber into the mold cavity through a dedicated liquid silicone injection machine, rapidly vulcanizing and forming at low temperatures. Liquid silicone injection molding has the advantages of fast molding speed, high product accuracy, and the ability to achieve complex structural molding, especially suitable for manufacturing silicone products in medical, food, and other fields that require high hygiene.
3. Sulfurization treatment: key to improving performance
Sulfurization is a key step in the production process of silicone products, which determines the physical and chemical properties of silicone products. During the vulcanization process, the molecular chains of silicone rubber undergo cross-linking reactions under the action of vulcanizing agents, forming a three-dimensional network structure, thereby endowing silicone products with properties such as elasticity, strength, and heat resistance.
The vulcanization method used in different molding methods also varies. Compression molding and injection molding usually use hot vulcanization method, which heats the mold to a certain temperature, causing the rubber material to undergo vulcanization reaction at high temperature. Liquid silicone injection molding often adopts low-temperature rapid vulcanization technology, which achieves rapid vulcanization at lower temperatures by adding special vulcanizing agents and catalysts, thereby shortening the production cycle and improving production efficiency.
The vulcanization time and temperature are important factors affecting the vulcanization effect. Short vulcanization time and incomplete vulcanization reaction can affect the physical and chemical properties of the product; If the vulcanization time is too long, it will lead to over vulcanization of the product, resulting in problems such as decreased elasticity and brittleness. Excessive sulfurization temperature can cause defects such as bubbles and burning on the surface of the product; If the vulcanization temperature is too low, the vulcanization speed will be slow and the production efficiency will be low. Therefore, in the production process, it is necessary to accurately control the vulcanization time and temperature based on factors such as the type of silicone rubber, the shape and size of the product, etc., to ensure the quality of the product.
4. Post processing steps: Improve product details
The semi-finished silicone products obtained after molding and vulcanization treatment require a series of post-processing steps to become the final product. Common post-processing procedures include trimming, cleaning, inspection, and packaging.
Trimming
During the molding process, due to factors such as the mold clamping line, there may be some excess adhesive residue at the edges of the product. The trimming process is to remove these excess adhesive edges, making the edges of the product smooth and neat. There are two methods for edge trimming: manual trimming and mechanical trimming. Artificial edge trimming is suitable for products with complex shapes and high precision requirements, but the production efficiency is low; Mechanical trimming is suitable for products with regular shapes and large batches, and has the advantages of high production efficiency and stable trimming quality.
clean
Silicone products may be contaminated with impurities such as oil and dust during the production process, and require cleaning treatment. The cleaning methods include water washing, solvent cleaning, etc. Water washing is a commonly used cleaning method with advantages such as low cost and environmental friendliness. However, for some products with heavy oil stains, solvent cleaning may be required. The cleaned products need to be dried to ensure their quality.
test
Inspection is an important step in ensuring the quality of silicone products. During the inspection process, it is necessary to conduct comprehensive testing on the appearance, size, physical properties, and chemical properties of the product. Appearance inspection mainly checks whether there are defects such as bubbles, cracks, and missing materials on the surface of the product; Dimensional inspection uses measuring tools to check whether the dimensions of the product meet the design requirements; Physical performance testing includes testing of indicators such as hardness, tensile strength, tear strength, etc; Chemical performance testing mainly tests whether the product meets relevant environmental standards and hygiene requirements. Only products that have passed strict inspection and are qualified can proceed to the next process.
package
Packaging is the final process in the production of silicone products. Appropriate packaging not only protects products from damage during transportation and storage, but also enhances the product's image and market competitiveness. The selection of packaging materials should be determined based on the characteristics and usage requirements of the product. Common packaging materials include plastic bags, paper boxes, wooden boxes, etc. During the packaging process, it is also necessary to label the product name, specifications, model, production date, and other information on the packaging for consumers to identify and use.
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