Октаметилциклотетрасилоксан

Химические свойства

Octamethylcyclotetrasiloxane is also known as D4. It is an odorless, colorless non-oily silicone fluid which has C8H24O4Si4 as chemical formula. It is a cyclic organic silicon substance which can be used as monomer in the production of silicone polymers such as rubber, resins and greases.

Использование

Octamethylcyclotetrasiloxane is used as a monomer in the production of silicone polymers and as an intermediate in the production of other organosilicon substances.Further it finds its application in electronics, textiles, personal care products and household care products.
Polydimethylsiloxane by the Polymerization of Octamethylcyclotetrasiloxane: To a resin flask equipped with a thermometer, stirrer, and reflux eondenser is added 1000 gm of octamethylcyclotetrasiloxane. The siloxane is heated to 165°C, and then 0.14gm of a potassium hydroxide-isopropanol complex (neutral equivalent = 193.5) is added to give a Si : Κ ratio of 4470:1. In 25 min the stirrer begins to stall, and the polymer is now heated for 3(1/2) hr at 150°C to complete polymerization. The resulting polymer has an intrinsic viscosity of 1.5 dl/gm corresponding to a molecular weight of 804,600.

Подготовка

Commercially Octamethylcyclotetrasiloxane is produced from dimethyldichlorosilane. Dimethyldichlorosilane is added dropwise to water, the temperature is maintained at 30-40°C, stratified, the acid water is released, the oily material is hydrolyzed with sodium hydroxide solution, the hydrolysate and 0.5%-2% potassium hydroxide are added to the cracking kettle and cracked at 120-140°C and 99.8 kPa vacuum. The cracked material is fractionated and the fraction is collected at 173-176°C to obtain octamethylcyclotetraoxysilane.

Определение

ChEBI: Octamethylcyclotetrasiloxane is a cyclosiloxane that is the octamethyl derivative of cyclotetrasiloxane. It is an organosilicon compound and a cyclosiloxane. It derives from a hydride of a cyclotetrasiloxane.

Общее описание

Octamethylcyclotetrasiloxane (D4) is a volatile methylsiloxane (VMS) with a relatively low molecular weight. This silicone fluid has a silicon-oxygen bond in a cyclic arrangement and methyl groups are attached to the silicon atom. D4 can be used in the manufacture of silicone based polymers for use in medical devices and personal care products.

Профиль безопасности

A skin irritant. When heated todecomposition it emits acrid smoke and irritating vapors.

Методы очистки

The solid exists in two forms, m 16.30o and 17.65o. Dry it over CaH2 and distil it. Further fractionation can be effected by repeated partial freezing and discarding the liquid phase. [Osthoff & Grubb J Am Chem Soc 76 399 1954, Hoffman J Am Chem Soc 75 6313 1953, Beilstein 4 IV 4125.]