HTV Silicone Rubber(high temperature vulcanized silicone), Nickname HCR (High Consistency Rubber)，also known as high - temperature vulcanized silicone, is an elastomer composed of long chains. These chains have vinyl groups attached to them. To endow it with special properties, it is filled with fumed or precipitated silica along with other additives. This type of silicone rubber is well - suited for several molding processes, namely compression molding, silicone rubber transfer molding, and rubber injection molding.
Liquid Silicone Rubber (LSR) is a two - component system. Long polysiloxane chains are reinforced by specially treated silica. Component A has a platinum catalyst; Component B contains methylhydrogensiloxane as a cross - linker and an alcohol inhibitor.
Due to its thermosetting nature, LSR injection molding requires special treatment like intensive distributive mixing. The material must be kept cold before being pushed into the heated cavity for vulcanization.
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Properties of Silicone Rubber
1. High Chemical Stability
2. Good Thermal Stability
3. Excellent Flexibility and Elasticity
4. Outstanding Electrical Insulation
5. Strong Adsorbability
6. Good Biocompatibility
7. High Weather Resistance
8. Easy to Process and Mold
9. Good Optical Properties
10. Low Surface Energy
11. Breathability
12. Color Adjustability
Silicone Rubber Manufacturing Process
Compression Molding
Weigh and take the pre - kneaded silicone rubber raw material, and then put it into the pre - heated mold cavity. After closing the mold, under the temperature of 150 - 200 °C and the pressure of 5 - 30 MPa, the silicone rubber cross - links and vulcanizes to form the product. It is suitable for manufacturing products with complex shapes, large sizes and high precision, such as automotive sealing gaskets. The advantages are high product precision, the ability to produce diverse products and relatively high efficiency. The disadvantages are high mold costs and strict requirements for operator skills.
Extrusion Molding
Put the kneaded silicone rubber raw material into the hopper of a screw extruder. Under the push of the screw, it is extruded through a die with a specific shape to form a continuous profile, and then it is cross - linked and solidified through a heating and vulcanization device. It is often used to produce continuous products with a fixed cross - section, such as sealing strips and rubber hoses. It features high production efficiency and low equipment investment, but the product cross - section is relatively fixed, and the raw material's fluidity is highly required.
Injection Molding
The silicone rubber raw material is heated and melted in the barrel of the injection molding machine. Driven by the screw, it is injected into the closed mold cavity at high pressure and speed. Under the temperature of the mold, it vulcanizes to form the product. After pressure - holding and cooling, the mold is opened to take out the product. It is suitable for small, precise, complex and high - volume products, like electronic buttons. Its advantages include a short production cycle, high precision and low material waste. The disadvantages are high mold and equipment costs, and precise control of process parameters is required.
Liquid Injection Molding (LIM)
The two - component liquid silicone rubber (A and B) is precisely mixed in a certain proportion in the mixing head of the injection machine and then injected into the mold cavity. Under the temperature of the mold, it quickly cross - links and vulcanizes. It is suitable for products with high precision, complexity and high appearance requirements, such as medical masks. The advantages are fast molding, high precision and high degree of automation. The disadvantages are high equipment and mold costs, and strict requirements for component ratio and production environment.
