Siltech – Silicone Waxes for Coating Applications
The potential for silicone waxes in a wide variety of Coating applications is largely under-explored.
Generally speaking, silicone waxes consist of a silicone backbone plus alkyl or aryl groups. The trademark for such products at Siltech is Silwax®.
Most of the Silwax silicones are based on alkyl groups ranging from C2 to C32, with the structure shown below:
The ratio of silicone to alkyl (“a” to “b”) and the chain length of the alkyl group (“c”) determine the melting point and liquidity of the final product. Hence the products can range from liquids to gels to soft waxes to hard waxes at room temperature, with melting points of up to 70 degrees C and % alkyl character of up to 90%, making these (mostly, but not exclusively) water-insoluble materials. It is also possible to incorporate different types of alkyl groups on the same backbone, for example, C2 and C21, to create multi-domain structures with different glass transition temperatures.
For Coatings applications, these products can be used to:
- Provide surface slip
- Impart water and solvent repellency
- Provide flow, levelling and mar resistance
- Add shine and improve organo-compatibility
Some products can also be loosely cross-linked in order to enhance substantivity and reduce surface migration.
Another structural type of Silwax is the alkyl aryl variation, shown here:
The incorporation of aryl groups provides better heat stability and improved over-paintability, meaning that these types can be used as paintable release agents in higher temperature applications.
Silicone waxes can also be used in Coating defoamers, since their solubility-insolubility profiles can be perfect when it comes to destroying foam.
Other silicone waxes have been certified as GRAS (generally regarded as safe), meaning that they can be used in pulp manufacturing and potentially in greaseproof Coatings.
One further silicone wax, called Silwax D02, is becoming more widely recognised in the silicone industry as a potential replacement for D5.
Silicone waxes can also be blended with silicone polyethers in order to make them self-emulsifiable.
Alternatively, alkyl and polyether functionalities can be grafted onto a single backbone, which essentially converts these molecules into reactive silicone waxes which can be incorporated into Coatings via their polyether carbinol functionalities, such as shown below:
Trimethoxysilane- and epoxy-functional silicone waxes have also been manufactured.
Ready to use alkyl aryl silicone emulsions are also available, providing excellent mold release for plastics, rubber and die cast metal parts where paintability is important.
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