Tetraethyl orthosilicate and hexamethyldisilazane

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EFSA Panel on Food ingredients and packaging

This scientific opinion of the EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF) deals with the risk assessment of tetraethyl orthosilicate (TEOS), Chemical Abstract Service (CAS) No 78-10-4, Food Contact Material (FCM) substance No 01013, and hexamethyldisilazane (HMDS), CAS No 999-97-3, Ref. No 18455 and FCM substance No 01014. According to the applicant, the two substances are used together as a chain extender for polyethylene terephthalate (PET) to increase the molecular weight of the polymer after recycling. Final articles are intended for contact with all types of foodstuffs for long-term storage at room temperature, with- or without prior pasteurisation at up to 70°C. Specific migration tests for TEOS and HMDS were not performed. Instead, the residual content of the substances in a recycled PET polymer manufactured with the modifier mixture was determined. The substances were not detected at detection levels up to 4 µg/6 dm², supporting that the substances react completely with the PET chains. In a migration study, a recycled PET modified using the mixture was compared with virgin PET. All detected migrating substances corresponded to oligomers identical to those from the virgin PET, at a detection level estimated to be 3 μg/kg. Based on the toxicological data provided, the CEF Panel concluded that there is no indication of a genotoxic potential for TEOS. HMDS was evaluated in 2007 by the EFSA Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food (AFC). As HMDS is rapidly converted into hexamethyldisiloxane (HMDSO) in humid air or aqueous media, the genotoxic potential of HMDS is covered by the genotoxicity data for HMDSO. The AFC Panel concluded that HMDSO was non-genotoxic. The CEF Panel concluded therefore that the mixture composed of TEOS and HMDS in a ratio of 97:3 does not raise a safety concern for the consumer if it is used at up to 0.12% (w/w) for the production of recycled PET.