Foamed silicone rubber is divided into open-cell foamed silicone rubber and closed-cell foamed silicone rubber.
Open-cell foamed silicone rubber refers to the type where the internal cells are interconnected with each other. Its characteristic is that the product feels soft and smooth to the touch. It is generally used for filling materials, reducing weight, and can also play a role in vibration reduction and shock resistance.
Closed-cell foamed silicone rubber refers to the type where the internal cells do not communicate with each other. It is characterized by good resilience and compressive properties. It is generally used for sealing and serves to prevent dust and water. How are open-cell foaming and closed-cell foaming achieved? The vulcanization process of silicone rubber foaming is divided into two processes: the vulcanization process of foaming silicone rubber and the decomposition process of the foaming agent.
Open-cell foaming requires adjusting the vulcanization system so that the decomposition process of the foaming agent occurs earlier than the vulcanization process. In simple terms, it involves first decomposing the foaming agent to produce bubbles. At this point, the cross-linking reaction has not yet begun, and the bubbles will break through the pore walls, forming a foam where the pores are interconnected. Then, the silicone gel undergoes a cross-linking reaction to fix the bubbles.
Conversely, for closed-cell foaming, the vulcanization system needs to be adjusted so that the decomposition process of the foaming agent is later than the vulcanization process. Extrusion foaming is generally open-cell foaming silicone rubber, while compression foaming can be either open-cell foaming silicone rubber or closed-cell foaming silicone rubber.