What is the process of liquid silicone rubber coating?

The injection bonding of liquid silicone rubber coating generally adopts the secondary injection molding process. Fix the hard plastic parts to be processed (injection molding) on the plastic wrapping mold, and then inject and glue the liquid silicone rubber to the hard plastic parts at a suitable temperature, and obtain the products by heating the mold. The injection temperature of adhesive coating injection varies according to the hard rubber material of adhesive coating. Because the temperature should consider the applicability of hard glue and liquid silicone rubber. Generally, PC or PA is selected as the base material of rubber coated plastic. Hardware made of aluminum alloy and other materials can also be treated by liquid silicone rubber coating.

Liquid silicone rubber is widely used because it does not release toxic substances, feels soft and comfortable, and can withstand high and low temperatures (- 60 ℃~+300 ℃). Few other polymers can compete. Strong and powerful elastomer, with better sealing performance than rubber, excellent electrical insulation and resistance to chemicals, fuels, oil and water, is a good material that can cope with harsh environments.

Although the equipment investment and raw material cost of liquid silicone rubber are very high, its production speed is fast, the processing degree is low, and the waste is small. Through the injection molding of liquid silicone rubber, accurate, efficient and automatic injection molding can be realized. This must be the future development trend of silicone rubber industry. The compound injection molding process of liquid silicone rubber and other materials is required for the production of liquid silicone rubber coated products.

In polymer materials, silicone rubber and polytetrafluoroethylene have inert surfaces, so they are also special materials that are particularly difficult to bond. Therefore, how to use the rubber coating (composite injection molding) process when preparing soft and hard products is really a problem, involving UV treatment of liquid silicone rubber/hard resin substrate and other methods to treat the substrate surface, but these methods are cumbersome. In fact, good adhesion of silicone rubber hard resin coating can be achieved mainly by strictly controlling the process:

1. Keep the substrate surface clean and dry before liquid silicone rubber coating

As we usually use glue to bond objects, surface cleaning is also very important for bonding the adhesive package. Of course, it is also necessary to keep the substrate completely dry, otherwise dust and water will seriously affect the bonding. These two aspects are the basic conditions;

2. Maintain high molding process temperature

The reaction curing temperature of liquid silicone rubber coating is mainly considered as the molding temperature. The typical molding temperature of liquid silicone rubber is 150-205 ℃. Liquid silicone rubber usually needs to be fully cured at relatively high temperatures to have good adhesion. Therefore, it is very important to maintain the high molding temperature of the substrate products;

3. No lubricating or demoulding additives

Silicone rubber itself is inert and close to the product used as release agent. If these products are added again, the situation will become worse, which is not conducive to product adhesion. Therefore, additives such as internal release agent, external release machine or self-lubricating agent should not be used in the base material, even though these additives may not affect the bonding effect; Liquid silicone rubber coating

4. Carefully demould

The curing process of liquid silicone rubber is relatively slow, so even though the liquid silicone rubber seems to have good bonding strength after just demoulding, it may not have a complete curing time when the mold is opened. Therefore, do not pull the liquid silicone rubber forcibly during demoulding, so that it will maintain a good bonding effect after slow cooling.

In a word, good self-adhesive liquid silicone rubber products can be obtained by strictly using the above methods. In fact, this is not because liquid silicone rubber has good adhesion, but because it is a liquid with better impregnation and permeability.

None post curing liquid silicone rubber MY LSR66A/B