Siltech – Silsurf® Silicone Polyethers, For Coatings and Beyond
Silicone polyethers (SPEs), commonly referred to as silicone surfactants, are a workhorse of the speciality silicone toolkit. They contain a water-insoluble silicone backbone and a number of water-soluble polyether groups, normally ethylene oxide, or propylene oxide, or mixed.
There are two broad types, either multi-functional, or linear di-functional, and the structures are shown below.
The multi-functional types are most versatile, since they have five variables which can be changed, in a, b, c, d, and R. The chain length of the linear di-functional types can be extended from short (a = 10) to long (a = 400 units), and R can be varied again.
In terms of Coating applications for these silicones, the possibilities are almost endless. Properties such as solubility, cloud point, molecular weight, and viscosity can all be altered at will. These lead to lower surface tensions for wetting, levelling, flexibility, and gloss improvement. Such molecules also migrate to surfaces and provide slip, release, softness and stain resistance. Furthermore, they can be used to stabilise formulations such as emulsions, dispersions or other non-homogeneous media. One additional and widely-used benefit is that the non-end-capped variants are reactive, and can be chemically incorporated into isocyanates, epoxides and other resins.
More recently, Siltech has manufactured a silicone-terminated polyether, referred to as a Gemini surfactant, shown below. This molecule appears to be an excellent dispersant.
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