Silanes and siloxanes from abcr – information and application areas
The designation silane, which actually stands for silicon-hydrogen compounds, is often used for organofunctional silanes of the structure RxSi−(OR`)(4-x).
Siloxanes have the general structure R3Si−[O−SiR2]n−O−SiR3 (R = hydrogen, alkyl or an arbitrarily selectable organic rest). The designation silicones is also used if no hydrogen atoms are present and the chains are longer.
Organofunctional silanes can be optimally applied to inorganic surfaces such as glass, metal, metal oxides, minerals, pigments, etc. and thereby allow for modification and functionalisation of these surfaces. There are many procedures for chemically binding silanes to a surface such as the gas phase technologies CVD, ALD or from the liquid phase as in the SOL GEL process. Metal acid esters from abcr are also used. For smooth surfaces, silanes are often applied from alcoholic-aqueous solutions by dipping or brushing or also by spraying for rough surfaces such as powders or inorganic pigments.
Organofunctional silanes are often bifunctional. Alkoxy or other leaving groups bound to silicon such as amino, amido or chloro substituents hydrolyse in the presence of moisture, creating the reactive intermediate phase – “silanol”. Silanol then chemically binds to inorganic surfaces, ideally as a monomolecular layer. The surface can be arbitrarily changed with the free selection of the ligand for the silicon, the “organofunctional group”. The modification provides adhesion to organic substrates or a change of polarity at the surface. Typical representatives for adhesion are amino, epoxy, methacryl or vinylsilanes as these combine with the polymer side as for example in glass-fibre reinforced plastics. Non-functional alkylsilanes are also used for pure hydrophobisation. Concrete hydrophobisation is a classic example of this. Fluorosilanes have a highly water and dirt-repellent effect, which can be seen in extremely high contact angles.
For gas phase processes such as CVD or ALD, silanes are most often degraded and then separate on surfaces, which can then also be of an organic nature, as SiOx or SiNx. The silanes are so-called precursors in these procedures like the metal complexes from the abcr programme.
Various abcr product classes are used in the sol gel procedure. In addition to the main component tetraethoxysilane TEOS, other components such as organofunctional silanes, metal acid ester or di(meth)acrylate are also available. abcr offers more than just the common silanes. Our production facility in Spain focuses on specialities. A few thousand silane types are available for special requirements.