POLYDIMETHYLSILOXANE
Prepared at the 69th JECFA (2008), published in FAO JECFA Monographs 5 (2008), superseding specifications prepared at the 37th JECFA (1990), published in the Combined Compendium of Food Additive Specifications, FAO JECFA Monographs 1 (2005). An ADI of 0-1.5 mg/kg bw was established at the 74th JECFA (2011).
SYNONYMS Poly(dimethylsiloxane); dimethylpolysiloxane; dimethylsilicone fluid; dimethylsilicone oil; dimethicone; INS No. 900a
DEFINITION Polydimethylsiloxane consists of fully methylated linear siloxane polymers containing repeating units of the formula [(CH3)2SiO]with
trimethylsiloxy end-blocking units of the formula (CH3)3SiO-. The additive is produced by hydrolysis of a mixture of dimethyldichlorosilane and a small quantity of trimethylchlorosilane. The average molecular weights of the linear polymers range from approximately 6,800 to 30,000.
(NOTE: In commerce, polydimethylsiloxane is frequently used in preparations usually containing silica gel. The pure substance described in this monograph can be isolated from silica gel-containing liquids by centrifuging at about 20,000 rpm. Before testing the Polydimethylsiloxane for Identification, Refractive index, Specific gravity, and Viscosity, any silica gel present must be removed by centrifugation.)
(NOTE: This monograph does not apply to aqueous formulations of Polydimethylsiloxane containing emulsifying agents and preservatives, in addition to silica gel.)
Chemical names α-(Trimethylsilyl)-ω-methylpoly(oxy(dimethylsilylene))
C.A.S. number 9006-65-9
Assay Silicon content not less than 37.3% and not more than 38.5% of the total
DESCRIPTION Clear, colourless, viscous liquid.
FUNCTIONAL USES Antifoaming agent, anticaking agent
