Inorganic Polymers - 23- Silanes скачать в хорошем качестве

Inorganic Polymers - 23- Silanes

The silicones are different from many industrial polymers where the chain of atoms that build the backbones of their molecules does not include carbon, being the characteristic member of organic compounds. The absence of carbon makes silicone a unique polymer, though maximum members of class II organic groups such as methyl(CH3), vinyl(CH2) are linked to every silicon atom. The general formula of silicone is (R2SiO)x, where R belongs to any one of the organic groups. Poly-dimethylsiloxane is the most silicone compound can which illustrates the primary characteristics of the organic class. The first substance is the metallic silicon, obtained from the silica sand. The silicon reacts with methyl chloride (Ch3Cl) and forms dimethyldichlorosilane ([CH3]2Si[Cl]2), over a copper catalyst. When this compound is made to react with water, the atoms of chlorine gets replaced by hydroxyl groups(OH). The resulting compound, silanol ([CH3]2Si[OH]2) polymerizes in a condensation reaction. Every individual unit of molecules Silicones exhibit many useful characteristics, including: Low thermal conductivity Low chemical reactivity Low toxicity Thermal stability (constancy of properties over a wide temperature range of −100 to 250 °C). The ability to repel water and form watertight seals. Does not stick to many substrates, but adheres very well to others, e.g. glass. Does not support microbiological growth. Resistance to oxygen, ozone, and ultraviolet (UV) light. This property has led to the widespread use of silicones in the construction industry (e.g. coatings, fire protection, glazing seals) and the automotive industry (external gaskets, external trim). Electrical insulation properties. Because silicone can be formulated to be electrically insulative or conductive, it is suitable for a wide range of electrical applications. High gas permeability: at room temperature (25 °C), the permeability of silicone rubber for such gases as oxygen is approximately 400 times[citation needed] that of butyl rubber, making silicone useful for medical applications in which increased aeration is desired. Conversely, silicone rubbers cannot be used where gas-tight seals are necessary such as seals for high-pressure gasses or high vacuum. Silicone can be developed into rubber sheeting, where it has other properties, such as being FDA compliant. This extends the uses of silicone sheeting to industries that demand hygiene, for example, food and beverage and pharmaceutical. links together to form poly-dimethylsiloxane with associated loss of water.