What conditions should be met for the encapsulation process of silicone rubber products?
Among the polymer materials, silicone rubber and PTFE are the most surface inert and are also a special kind of materials which are particularly difficult to bond. Therefore, how to use encapsulation (composite injection moulding) technology in the preparation of both soft and hard products involving liquid silicone rubber/hard resin substrates is really a difficult problem. Although there are some surface treatments, such as applying primer, using ultraviolet treatment and other methods to treat the substrate surface, but these methods are more cumbersome, in fact, mainly from the strict control of the process, it is possible to achieve good bonding of silicone rubber-hard resin coating.
In the silica gel forming process, the mixed rubber is used to wrap the hardware after high temperature forming and oil pressure, and the hardware is wrapped inside the silica gel, which is called silica gel wrapping process for short.
The silica gel coating process requires higher precision of the die, and the conditions to be satisfied are as follows:
1. Precision die making equipment
2. Die Testing Equipment
3. Process control
Secondly, keep the high temperature of forming process. The reaction curing temperature of liquid silicone rubber is the main consideration of forming temperature. The typical forming temperature of liquid silicone rubber is 150-205 C. The liquid silicone rubber usually needs to be fully cured at a relatively high temperature in order to have better bonding performance, so the base material products are better. High forming temperature is critical.
The inertia of silicone rubber is close to the product as a release agent without lubricant or release agent. If these products are added again, it will be worse, which is not conducive to the bonding of the product. Therefore, try not to use such additives as internal release agent, external release machine or self-lubrication in the base material, even if these additives are used. The agent may not affect the bonding effect.