Among polymer materials, silicone rubber and polytetrafluoroethylene are a special type of material with the most surface inertness, making them particularly difficult to bond. Therefore, it is indeed a challenge to use encapsulation (composite injection molding) technology in the preparation of soft and hard products involving liquid silicone rubber/hard resin substrates. Although there are also some surface treatment methods such as applying primer and using ultraviolet treatment to treat the substrate surface, these methods are relatively cumbersome. In fact, it is still possible to achieve good adhesion between silicone rubber and hard resin encapsulation mainly through strict process control.

1. Keep the surface of the substrate clean and dry before gluing
Just like how we usually use glue to bond objects, surface cleanliness is also very important for the bonding of the adhesive. Of course, it is also necessary to keep the substrate fully dry, otherwise dirt and water will seriously affect the bonding. These two aspects are basic conditions;

2. Maintain a high molding process temperature
The molding temperature mainly considers the reaction curing temperature of liquid silicone rubber. The typical molding temperature of liquid silicone rubber is 150-205 ℃. Liquid silicone rubber often needs to be fully cured at a relatively high temperature in order to have good bonding performance. Therefore, maintaining a high molding temperature for the substrate product is crucial;

3. No additives with lubrication or demolding properties added
Silicone rubber itself is already close to being used as a mold release agent due to its inertness. If these products are added, it will make things worse and not be conducive to the bonding of the products. Therefore, it is advisable not to use internal mold release agents, external mold release machines, or self-lubricating additives in the substrate, even if these additives may not affect the bonding effect;

4. Be careful with demolding
The curing process of liquid silicone rubber is relatively slow, so even if liquid silicone rubber appears to have good bonding strength just after demolding, it may not be fully cured at the time of mold opening. Therefore, try not to pull the liquid silicone rubber hard during demolding, as it will maintain good bonding effect after slow cooling.

About injection liquid silicone rubber,please check the details: High Strengh Liquid Silicone Rubber IOTA 28-Series