Step 1: Raw material preparation - Good foam, the core raw materials are the key
Silicone material: This serves as the "base" of foam (shown in liquid silicone form), maintaining fluidity at room temperature to seamlessly integrate with other components. The purity level directly determines the foam's thermal stability (-60℃ to 200℃ temperature tolerance) and elasticity. Premium liquid silicone ensures rapid rebound after repeated compression, preventing long-term use from aging or hardening.
Fume silica (fume-bonded silica): The "structural reinforcement agent" for foam. This fine white powder, when blended with liquid silicone, acts as a "microscopic framework" that supports the structure, significantly enhancing foam's tear resistance and strength--. Without it, the foamed silicone would become soft and fragile, unable to withstand real-world compression and friction during use.
Of course, depending on the application scenario, a small number of auxiliary components (such as foaming agent to provide expansion power and vulcanizing agent to promote curing) will be added, but liquid silicone and fumed silica are always the "core CP" that determines the performance of foam.
Step 2: Mix and stir -- Let the ingredients "get close"
Once the ingredients are ready, they go into a special mixing device to "team up". The fluidity of liquid silicone makes the mixing more efficient, but there are two key points:
Temperature control: must be kept below 50℃, otherwise the subsequent foaming will "lose control" in advance;
Mixing time: generally 20-30 minutes, until the gas phase silica is completely dispersed, and the rubber compound presents a uniform and delicate state -- like well-blended cream, without granular sense, to ensure uniform air holes after foaming.
What happens if the mixing is not uniform? In some places, the gas phase silica clusters and the foam will become hard; in other places, the content is insufficient and the foam will be too soft and easy to break. Therefore, this step is the basis of "uniform foaming".
Step 3: Foam molding -- The "transformation moment" of foam
This is the most amazing step! The mixed compound is sent to the "foaming workshop" and transformed through the process:
Continuous Foaming Process: Mass Production of "Rolls/Plates" First, pre-treated rubber compounds are precision-pressed into uniformly thick sheets using specialized equipment. This step establishes the foundation for ensuring final product flatness. The sheets are then smoothly transported onto conveyor belts and fed into a multi-meter-long high-temperature curing chamber---the core area for foaming and solidification. Within the chamber, as the rubber sheets progress along the conveyor belt, they undergo foaming reactions under intense heat: The material gradually forms fine, uniform cells with expanded volume, while simultaneously undergoing thermal curing to enhance elasticity and structural stability.
When the material comes out of the oven, it has become a foam roll with uniform texture and flat shape (or cut into sheets as required).
Key: How are pores controlled? You may wonder: Why do some foam bubbles have holes like sesame (0.1-0.5mm) and others like mung beans (1-3mm)?
• It is mainly determined by the amount of foaming agent and heating speed: the more foaming agent, the faster the heating, the larger the air hole (suitable for shock absorption and sound insulation); otherwise, the air hole is fine (suitable for waterproof sealing).
• The pores of high quality foam must be evenly distributed -- When viewed with a magnifying glass, the size is basically the same, and there will be no confusion of "large holes over small holes", which is the performance of the process.
Step 4: Post-processing -- "do a physical examination and repair details" for the foam
The foam just foamed cannot be used directly. It needs to undergo "fine grinding" : secondary vulcanization: Put it in an oven at about 200℃ for 2-4 hours to remove the remaining volatile substances and avoid "oiling" or shrinkage during subsequent use. Cutting/Trimming: Roll materials are cut into standard sheets, and the edges of irregular parts are ground to ensure accurate dimensions (for example, for waterproof foam, the error should not exceed 0.1mm, otherwise it may leak). Performance spot-check: Measure density (ranging from 0.3 to 0.8g/cm³, adjusted as needed) and compression rebound rate (to determine service life).
Then , silicone foam sheet is finished
