(b) what are silicones ? write its one use.
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Silicone is a tough artificial substance made from silicon, which is used to make polishes, and also used in cosmetic surgery and plastic surgery.
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Silicones, also known as polysiloxanes, arepolymers that include any inert, synthetic compound made up of repeating units ofsiloxane, which is a chain of alternatingsilicon atoms and oxygen atoms, frequently combined with carbon or hydrogen or both. They are typically heat-resistant and rubber-like, and are used in sealants, adhesives, lubricants, medicine, cooking utensils, and thermal and electrical insulation. Some common forms include silicone oil, silicone grease, silicone rubber, silicone resin, and silicone caulk.[1] Silicones are of three types: 1. straight chain silicones; 2. cyclic silicones; 3. crosslinked silicones.
UsesEdit
Silicones are used in many products.Ullmann's Encyclopedia of Industrial Chemistry lists the following major categories of application: Electrical (e.g., insulation), electronics (e.g., coatings), household (e.g., sealants for cooking apparatus), automobile (e.g., gaskets), aeroplane (e.g., seals), office machines (e.g., keyboard pads), medicine and dentistry (e.g., tooth impression molds), textiles and paper (e.g., coatings). For these applications, an estimated 400,000 tons of silicones were produced in 1991. Specific examples, both large and small are presented below.[1]
AutomotiveEdit
In the automotive field, silicone grease is typically used as a lubricant for brakecomponents since it is stable at high temperatures, is not water-soluble, and is far less likely than other lubricants to foul. It is also used as DOT 5 brake fluid.
Automotive spark plug wires are insulated by multiple layers of silicone to prevent sparks from jumping to adjacent wires, causing misfires. Silicone tubing is sometimes used in automotive intake systems (especially for engines with forced induction).
Sheet silicone is used to manufacture gasketsused in automotive engines, transmissions, and other applications.
Automotive body manufacturing plants and paint shops avoid silicones, as they may cause "fish eyes", small, circular craters in the finish.
Additionally, silicone compounds such as silicone rubber are used as coatings and sealants for airbags; the high strength of silicone rubber makes it an optimal adhesive and sealant for high impact airbags. Recent technological advancements allow convenient use of silicone in combination with thermoplastics to provide improvements in scratch and mar resistance and lowered coefficient of friction.
CoatingsEdit
Silicone films can be applied to such silica-based substrates as glass to form acovalently bonded hydrophobic coating.
Many fabrics can be coated or impregnated with silicone to form a strong, waterproof composite such as silnylon.
UsesEdit
Silicones are used in many products.Ullmann's Encyclopedia of Industrial Chemistry lists the following major categories of application: Electrical (e.g., insulation), electronics (e.g., coatings), household (e.g., sealants for cooking apparatus), automobile (e.g., gaskets), aeroplane (e.g., seals), office machines (e.g., keyboard pads), medicine and dentistry (e.g., tooth impression molds), textiles and paper (e.g., coatings). For these applications, an estimated 400,000 tons of silicones were produced in 1991. Specific examples, both large and small are presented below.[1]
AutomotiveEdit
In the automotive field, silicone grease is typically used as a lubricant for brakecomponents since it is stable at high temperatures, is not water-soluble, and is far less likely than other lubricants to foul. It is also used as DOT 5 brake fluid.
Automotive spark plug wires are insulated by multiple layers of silicone to prevent sparks from jumping to adjacent wires, causing misfires. Silicone tubing is sometimes used in automotive intake systems (especially for engines with forced induction).
Sheet silicone is used to manufacture gasketsused in automotive engines, transmissions, and other applications.
Automotive body manufacturing plants and paint shops avoid silicones, as they may cause "fish eyes", small, circular craters in the finish.
Additionally, silicone compounds such as silicone rubber are used as coatings and sealants for airbags; the high strength of silicone rubber makes it an optimal adhesive and sealant for high impact airbags. Recent technological advancements allow convenient use of silicone in combination with thermoplastics to provide improvements in scratch and mar resistance and lowered coefficient of friction.
CoatingsEdit
Silicone films can be applied to such silica-based substrates as glass to form acovalently bonded hydrophobic coating.
Many fabrics can be coated or impregnated with silicone to form a strong, waterproof composite such as silnylon.
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