Acrylic Coatings
Acrylics are the most versatile resins in coatings, found in waterborne latex paints, solvent-borne sealers, elastomeric roof coatings, urethane topcoats and fast-curing MMA floors.
Key takeaways
- Acrylic polymers are built from acrylic and methacrylic ester monomers and are inherently resistant to UV, giving good color and gloss retention.
- The term covers very different products: waterborne latex, solvent-borne lacquers and sealers, elastomeric roof coatings, acrylic urethanes and reactive MMA systems.
- Waterborne acrylics are low-odor and low-VOC but need adequate temperature and drying conditions to form a film.
- Most acrylics are not suited to immersion or strong chemical exposure; reactive and cross-linked variants extend their range.
Acrylic chemistry appears across almost every segment of the coatings industry. Architectural house paints, direct-to-metal (DTM) maintenance coatings, concrete sealers, elastomeric roof coatings and many high-performance topcoats all rely on acrylic polymers. Their popularity rests on clarity, light stability, versatility and, for waterborne products, low VOC content.
Because the word “acrylic” covers such different products, it is important to know which kind is being specified. A waterborne acrylic DTM and a methyl methacrylate floor system share a chemical family but behave very differently.
Acrylic chemistry
Acrylic resins are polymers of esters of acrylic acid and methacrylic acid, such as methyl methacrylate, butyl acrylate and ethyl acrylate. Formulators blend “hard” monomers like methyl methacrylate with “soft” monomers like butyl acrylate to tune hardness, flexibility and the temperature at which the film forms. Styrene is often copolymerized to make styrene-acrylics, which cost less but have somewhat lower exterior durability.
The acrylic backbone absorbs little UV light, so it resists the photodegradation that causes yellowing and chalking in many other resins. This is why acrylic polyols are the preferred building blocks for exterior polyurethane topcoats.
Types of acrylic coatings
| Type | How it forms a film | Typical uses |
|---|---|---|
| Waterborne acrylic latex (emulsion) | Water evaporates and polymer particles coalesce | Architectural paints, DTM coatings, concrete walls |
| Solvent-borne thermoplastic acrylic | Solvent evaporation only | Concrete and masonry sealers, lacquers |
| Elastomeric acrylic | Coalescence of a soft, high-elongation polymer | Roof coatings, masonry wall coatings |
| Acrylic urethane | Acrylic polyol cross-linked with isocyanate | High-performance exterior topcoats |
| Thermoset baking acrylic | Heat-cured with amino resins or other cross-linkers | Factory finishes on appliances and equipment |
| Methyl methacrylate (MMA) reactive resin | Free-radical polymerization with a peroxide initiator | Rapid-cure floors, cold-storage areas, line marking |
Acrylic urethanes are discussed in more detail under polyurethane coatings; the remainder of this article focuses mainly on waterborne, solvent-borne and reactive acrylics.
How acrylics cure
Coalescence
Waterborne acrylic latex consists of tiny polymer particles dispersed in water. As water evaporates, the particles pack together, deform and fuse into a continuous film. This only works above the minimum film formation temperature (MFFT) of the formulation, which is why data sheets specify minimum air and surface temperatures, commonly around 50 °F (10 °C) for standard products and lower for specially formulated grades. See how coatings cure for a comparison of mechanisms.
High humidity and low airflow slow evaporation. Rain, dew or condensation on a film that has not yet coalesced can wash it out or leave surfactant streaks.
Solvent evaporation
Thermoplastic solvent-borne acrylics dry as the solvent leaves. The film remains soluble in its original solvent, which allows easy recoating and touch-up but limits solvent resistance.
Reactive cure
MMA systems cure by chain-growth polymerization started by a peroxide initiator. They can cure in about an hour even at temperatures near or below freezing, making them useful where downtime must be minimal. They have a strong odor during application, and their monomer vapor is flammable, so ventilation and ignition control are required.
Common applications
- Light-duty steel: waterborne DTM acrylics on handrails, structural steel in mild environments and equipment, typically in low to moderate corrosivity categories.
- Roofs: elastomeric acrylic coatings over metal, single-ply and spray foam roofs. ASTM D6083 is a commonly cited specification for liquid-applied acrylic roof coatings. See roof coatings.
- Concrete and masonry: breathable wall coatings and solvent-borne or waterborne sealers.
- Floors: MMA systems for food plants, freezers and commercial spaces needing rapid return to service.
- Architectural: interior and exterior wall paints and trim enamels.
Waterborne DTM coatings applied to bare blast-cleaned steel in humid conditions can cause flash rusting, a light orange bloom as the film dries. Choose products formulated with flash-rust inhibitors, apply in good drying conditions, and follow the data sheet’s guidance on first-coat thickness.
Surface preparation still matters with these forgiving products. On steel, waterborne DTM acrylics are commonly applied over hand- or power-tool-cleaned surfaces in light-duty work, but adhesion and service life improve markedly over abrasive-blasted steel with a suitable profile. On concrete and masonry, the surface should be clean, sound and free of laitance, efflorescence and release agents, and the moisture and alkalinity of new concrete should be within the product’s limits. Previously painted surfaces should be cleaned, deglossed where necessary and tested for compatibility with a small trial patch before full application.
Limitations and precautions
Thermoplastic acrylics can soften at elevated temperatures and may show blocking (sticking) when freshly painted surfaces are stacked or pressed together. Their resistance to solvents, fuels and strong chemicals is generally lower than that of epoxies and polyurethanes. Waterborne acrylics are generally not recommended for immersion, and they may show early water sensitivity until fully coalesced.
Compared with oil-based alkyds, waterborne acrylics usually offer better UV resistance and flexibility over time, with less yellowing and embrittlement, but they may wet oily or poorly cleaned surfaces less effectively.
Do not apply waterborne acrylics when temperatures will drop below the data-sheet minimum before the film has dried, or when rain or dew is expected. A film that freezes or gets wet before coalescing may crack, wash off or have poor adhesion.
Advantages and limitations
Advantages
- Very good UV, color and gloss retention
- Low VOC and low odor (waterborne)
- Easy application and water cleanup
- Very wide range of formulations
Limitations
- Limited chemical, solvent and immersion resistance
- Waterborne types sensitive to cold and humidity during drying
- Thermoplastic films soften with heat
- Lower barrier performance than epoxy systems
Frequently asked questions
Is acrylic paint the same as latex paint?
In common usage, “latex” refers to waterborne emulsion paints, many of which use acrylic or styrene-acrylic polymers. Not all latex paints are 100% acrylic, and not all acrylic coatings are latex.
Can acrylic coatings be used on steel?
Yes, waterborne DTM acrylics are used on steel in mild to moderate environments. For severe or immersion exposures, epoxy-based systems are usually specified.
How thick should an acrylic roof coating be?
Elastomeric roof coatings are applied much thicker than paints, often in multiple coats. The required dry film thickness depends on the product, substrate and warranty, so follow the manufacturer’s specification.
Do acrylic coatings contain VOCs?
Waterborne acrylics typically contain far less volatile organic content than solvent-borne coatings, but most still include small amounts of coalescing solvents. Solvent-borne acrylic sealers can be considerably higher. Check the VOC content on the data sheet against local regulations.
Educational reference. Coating performance varies by formulation. Always follow the manufacturer’s product data sheet, safety data sheet and your project specification.
