Question

What are silicones how are they prepared explain it's properties and uses

Answer 1

Answer:

Silicones are polymers, which are large molecules composed of many repeated sub-units. These polymers are made up of siloxane – a chain of alternating silicon atoms and oxygen atoms frequently combined with carbon and/or hydrogen. Silicon is an element found in sand, where it is extracted from and passed through hydrocarbons.

Preparation of Silicones: The preparation of silicones is generally carried out by the hydrolysis of dialkyldichlorosilanes (R2SiCl2) or diaryldichlorosilanes Ar2SiCl2, which are prepared by passing vapors of RCl or ArCl over silicon at 570 K with copper as a catalyst.

Silicones may be obtained in the form of oils, rubber on resins depending upon the extent of polymerization which depends upon reaction conditions and nature of alkyl groups.

Uses:

(a) Silicones have been used for making water-proof papers, wools, textiles, wood etc., after coating these articles with silicones.

(b) The viscosities of silicones do not change with changes in temperature; therefore, these are used as all weather lubricants.

(c) As antifoaming agent in industrial processes.

(d) As a mould releasing agent in rubber industry and foundry. It avoids the sticking of the castings to the mould.

(e) For making body implants in cosmetic surgery due to its inert nature.

(f) Silicones are now incorporated in paints for resisting dampness and for water proofing.

(g) Due to their water repellent nature and high dielectric constant, silicones are used in electrical condensers.

Answer 2

Answer:

Preparation

Silicones are prepared by the hydrolysis of alkyl or aryl substituted silicon halides. Alkyl or aryl substituted silicon halides are prepared by passing gaseous alkyl or aryl. halide over an alloy of copper and silicon at 300°C. The hydrolysis of dimethyldichlorosilane gives dimethyl silanol.

properties and uses:They are typically heat-resistant and either liquid or 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.