The formula design of silicone rubber is an art of walking a tightrope between minimalism and perfection. Unlike the complex formula of ordinary rubber, which often involves more than ten different compounding agents, high-temperature vulcanized silicone rubber usually only requires five to six components to form a practical formula. However, the ratio and selection of these few raw materials determine whether the final product is as tough as steel or as fragile as paper, whether it can withstand temperatures of up to 300 degrees Celsius or soften and deform within 200 degrees Celsius.

The core of the formula is raw rubber. Methyl vinyl silicone rubber (VMQ) occupies the C position with its absolute advantage of the largest amount and the most grades. The introduction of vinyl greatly improves the efficiency of peroxide crosslinking - almost all commercial silicone rubber contains a certain amount of vinyl, which is like a "grip point" on the molecular chain, making the crosslinking reaction fast and dense. When the temperature requirement is higher, reaching the extreme range of -90 ° C to 300 ° C, low phenyl silicone rubber comes into play. The introduction of phenyl groups is like embedding a rigid "scaffold" in the molecular chain, significantly improving the resistance to high and low temperatures. When products need to withstand both extreme temperatures and the erosion of fuel and solvents, fluorosilicone rubber or nitrile silicone rubber becomes the best choice - the introduction of trifluoropropyl or cyano groups allows silicone rubber to remain calm in harsh chemical environments.

The selection of reinforcing agents is the soul of the formula. The unreinforced silicone rubber vulcanized rubber has a strength of only about 0.3MPa, and has almost no practical value; After adding appropriate reinforcing agents, the strength can jump to 3.9 to 9.8 MPa, an increase of more than ten times. Gas phase white carbon black is the most commonly used reinforcing agent for silicone rubber, with a particle size of only 10 to 50 nanometers and a specific surface area of up to 70 to 400 square meters per gram. The reinforced rubber material has high mechanical strength and excellent electrical properties; Although the reinforcement effect of precipitated white carbon black is slightly inferior, it has better heat aging resistance and lower cost, making it very useful in situations where mechanical strength is not required. In actual production, two types of white carbon black are often used in combination to complement each other's strengths and weaknesses. The amount of white carbon black used in a typical formula is about 25%, which may seem simple, but behind it is the golden ratio polished by countless experiments.

Structural control agents play a crucial but often overlooked role in formulations. The adhesive material reinforced with gas-phase white carbon black will gradually become harder and the plasticity value will decrease during storage, and this "structured" effect will cause the adhesive material to lose its processing performance. To counter this trend, it is necessary to add low molecular weight organosilicon compounds containing hydroxyl or boron atoms, such as diphenylsilanediol, low molecular weight hydroxyl silicone oil, silazane, etc. They act as molecular level "lubricants", forming a protective layer on the surface of white carbon black particles to prevent excessive aggregation between particles. The typical dosage is about 2%, with an excess of one part affecting vulcanization and a deficiency of one part causing structural loss of control.

Regarding liquid silicone rubber, please refer to our website for details: IOTA Liquid Silicone Rubber