What are silicones emulsions?
Silicone emulsions are silicone oils dispersed in an aqueous system. Emulsions are ideal for surface treatments, being easy to apply, and are simple to prepare.
The high viscosity of certain silicone oils can be effectively reduced by their emulsification. The aim of silicone emulsion formulation is to improve & facilitate the product's presentation, processing and efficiency. The various components in emulsions (the carrier, typically water, the silicone, and its emulsifiers) do not react with one another, nor do they react with the surfaces that they are applied to. Emulsions are therefore ideal for surface treatment applications since they are less viscous than the oils they are delivering. Their other advantage is that preparation is simple: Polydimethylsiloxane (PDMS) oils are dispersed (emulsified) in an aqueous system (and they are particularly practical since they are easy and safe for the end user to handle, apply and dilute.
Silicone emulsions properties
Silicone emulsions are insoluble silicones evenly dispersed in water with the aid of an emulsifying surfactant. They can be divided into three groups, depending on the type of emulsifier system used, i.e. they can be anionic, cationic and non-ionic. Most emulsions are non-ionic, making them compatible with either of the other two systems but, depending on the application, cationic or anionic emulsions may be preferable.
The physical characteristics of these emulsions can be altered by using different polymers to modify their viscosity if needed. High percentage solid versions supplied as concentrates, for dilution with water prior to use, reduce transport costs and the space required for their storage.
Silicone fluids are commonly used in the form of aqueous emulsions, which may be further diluted with water. A distinction is made between opaque (i.e. milky) macro-emulsions with particle sizes from 100 nm to several µm and clear or opalescent micro-emulsions, with particle sizes below 100 nm.
|Technology ||Emulsion |
|Definition ||Emulsion is a category of product form. Emulsion is a formulation of silicones in aqueous form.|
|General Information ||Emulsions are dispersions of one liquid in another liquid, generally stabilized by an emulsifier, both liquids being non-miscible. In the specific case of silicone emulsions, silicones are dispersed as droplets in a water continuous medium.|
|Typical properties ||Water-based, water-dilutable, stable, easy to use, environmentally-friendly, safe in storage, transportation and application. Enable small and uniform quantity of coating on the substrate. Sensitive to chemical, thermal & mechanical environment, cannot be applied in a system which is not compatible with water.|
|Structural units ||Silicone, Emulsifier / surfactant, Water + other additives (rheological agents, preservatives, …)|
|Processability ||Dispersion of the silicone phase into the aqueous phase under shear, either by direct process or by phase-inversion process|
|Application/final products ||Release coating, textile & tissue softener, antifoams, water repellents & paints, lubrication & demoulding, personal care|
Silicone emulsions are easy to use and apply, are more environmentally friendly than solvent-based systems and, being water-based do not generate additional health hazards in the workplace. For
example, baking and cooking paper manufacturers use emulsion silicones for
coatings to replace other coating types including solvent containing
formulations. The uniform distribution of a thin layer of silicone onto
substrates gives efficient non-stick performance improving hygiene, reducing
food waste and aiding efficiency in both industrial and home cooking
applications. Silicone emulsion-based food papers can be used in all types of
cooking, including baking, pan-frying and steaming
Emulsion silicone release coating also contribute to lower processing costs and higher production efficiency, since they can be coated in-line directly in paper-making machines, which avoids offline coating, reducing floor space requirements in manufacturing facilities and manpower costs, as well as simplifying logistical requirements.
Emulsion silicones are used in:
- Rubber and plastics as release agents and lubricants
- Food trays and plastic serving dishes as release agents
- Car polishes and household cleaners to improve protection, resistance, gloss and spreadability
- Textile finishing to enhance feel, water repellency and reduce the need for ironing
- Perlite, vermiculite and clay and other building materials to improve water repellency and protect against dampness
- Printing and papermaking for lubrication and as an antistatic agent.
Beyond the use of silicone emulsions as process facilitators in the industries cited in our summary table above, they are also used as formulation ingredients in cosmetics and body care products, in particular in shampoos, where silicone emulsions give hair a silky softness, making it easier to comb and untangle after washing.