A dispersion is a liquid mixture in which very small solid or liquid particles (such as synthetic resin, pigments or cement) are evenly distributed in a continuous phase, usually water. In construction, the term mainly turns up in water-based paints, adhesives and polymer-modified mortars — collectively called *dispersion products*.
How a dispersion works
Unlike a true solution (such as salt in water) the constituents of a dispersion are not mixed at the molecular level but are mechanically finely divided. Surfactants keep the particles in suspension and prevent agglomeration. On application:
- Application — the dispersion is brushed, rolled or sprayed onto the surface
- Water evaporates — the space between particles shrinks
- Film formation — the particles touch, deform and merge into a continuous film
- Drying and curing — residual water leaves and the film becomes hard and tough
Application
In construction, dispersions appear in many products:
- Dispersion paint (emulsion paint) — acrylic or vinyl-acetate dispersion as binder, with pigments and fillers
- Latex paint — common synonym for water-based resin dispersion
- Dispersion adhesives — for tiles, flooring, wood and plastic
- Primers — thin dispersion that binds the substrate and regulates suction
- Polymer-modified mortars (PCC and PC mortars) — cement plus polymer dispersion for added bond and flexibility
- Bitumen dispersion — for cold-applied roof membranes and waterproofing
Advantages
- Water-based — little or no solvents, low VOC emission
- Easy clean-up — wash tools in water
- Fast drying — touch-dry within hours
- Good adhesion — bonds well to many substrates without a primer
- Non-flammable — safe to store and apply
Considerations
- Minimum film-formation temperature — usually at least 5 °C; in frost the product fails
- Not water-resistant before full cure — avoid direct moisture and high humidity
- Limited chemical resistance — less suitable in aggressive environments
- Shelf life — frost-sensitive in storage; otherwise good for 1–2 years
Related terms
- Acrylic
- Binder
- Latex cement
- PCC mortar
- Primer
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