Silicones come from a unique chemical compound, one of the most common on earth: silicone dioxide or silica noted SiO2 en chemistry. Silica or silicone dioxide is currently related to quartz or glass sand.
In order to obtain a workable raw material, few steps are necessary. After isolating silicon chemical element noted Si in chemistry, various chemical reactions such as synthesis and distillation generate more or less long chains of polysiloxane, more commonly called polymers, the basic component of silicones.
The groups R and R ', that constitute the length of the chains, may be functional groups, that are reactive or not. These functional groups will give rise to different technical properties. The most common functional groups being:
• reactive groups: vinyl, hydrogen silane and silanol;
• non-reactive groups: methyl, phenyl and fluoro.
Catalyst: a substance that triggers a reaction
Vulcanization or Curing: Change of state; Passage from raw material to a processed product.
The changes of state, or curing, of silicone mixtures, may be done in two ways :
by heat input, or High Temperature Vulcanisation (HTV) or Hot Vulcanizable Elastomer
or with the relative humidity of the ambient air, or Room Temperature Vulcanisation (RTV) or Cold Vulcanizable Rubber. RTV silicones are used for sticking and assembly (single-component) or for mold creation (two-component).
Two principal catalysts are used in operating mode :
The so-called rubbery property of silicones makes it possible to present standardized hardness indices of 0 to 100 Shore A, and the most effective breakage elongations associated with tear-off behaviors. Silicones also have natural adhesion capabilities and are hydrophobic.
The open cells of silicones allow active and passive charge integration, increasing thermal properties, vapor and flame resistance, a decreasing adhesion coefficient, economic charges, and so on.
Based on the intended use and characteristics needed, we can use our experience to help you choose the best silicone, taking both hardness and functional group into account, and perform the necessary tests.
VMQ Silicones (siloxane composed with vinyl groups) are widely used. They can be used from -50 to +200°C with hardness from 7 to 90 +/- 5 shA, catalyzed with platinum or peroxide.
PVMQ Silicones (siloxane composed with phenyl and vinyl functional groups) allow product use at low temperatures to -110°C.
Fluoronated FVMQ Silicones (siloxane composed by fluoronated and vinyl functional groups) have the same characteristics as VMQ, but they react better with oil, solvents and hydrocarbons.
Silicones can meet various standards, varying in color and degree of hardness.