Silanization

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Silanization is a chemical bonding of a silane compound to a surface. The connection takes place through condensation reactions between hydrolyzable groups of the silanes used and chemical groups on the surface.

mechanism

Mechanism of Silanization. The example shows a substrate on which a fresh silicon dioxide layer was applied as a primer by flame coating . In this example, the silane only reacts through hydrolysis reactions with water to form the silanol, which is then anchored to the substrate surface through condensation reactions with the OH groups.

The silanes used for the silanization have the general form R m SiX n , where R stands for organically functionalized radicals and X for hydrolyzable groups (mostly alkoxy groups , more rarely - Cl ), ie they can be silanols of the form R m by hydrolysis reactions with water Form Si (OH) n . Similarly, they (or the silanols they form) can react with OH or COOH groups on surfaces and form a composite, as shown in the figure.

Goals of silanization

The properties of the coated surface depend on the silane compound used. The most important applications relate to the promotion of adhesion for subsequently applied coatings and the implementation of non-stick coatings . The silanes can either be applied directly to the surfaces (e.g. 1,7-dichloro-1,1,3,3,5,5,7,7-octamethyltetrasiloxane is often used in biochemistry as a 5% solution in heptane applied directly to glass to create a temporary non-stick coating) or a primer can be created first, e.g. B. by flame coating or physical vapor deposition , on which the silanes can then be firmly anchored. In chemical laboratories, silanization prevents polar compounds from sticking to the glass surface and thus prevents analyte loss.

An important example of silanization in the two-stage process is its use in dental technology to join different materials with one another or to coat metal surfaces with ceramic components. Since mechanical connections would loosen again after a certain time under oral conditions, a primer is first created by " silicating " and then anchoring the bonding agent , which firmly connects the two dental materials, by "silanizing" . The adhesive strength achieved in this way is far superior to that which can be achieved by "direct" silanization, that is to say without prior creation of a primer.

Web links

www.zahnlabor.de: with a demo photo and a slightly better explanation

See also

Individual evidence

  1. ↑ R. Musil, H.-J. Tiller: The plastic-metal composite - the silicoater process . Dr. Alfred Hüthig Verlag Heidelberg, 1988, ISBN 3-7785-1682-5 .