How Does Chemicals Used in Paint Work?

What’s in paint?

In our summer educational series on paint and color technology, we begin with a review of one of the basics: what ingredients are in paint? The variety of paint products offered can be overwhelming. And with each variety of paint offering different properties that affect the outcome of a design project, understanding what's in a can of paint is key to success.

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All paints generally have four main ingredients -- pigments, binders, solvents (liquids) and additives. Pigments provide color and hide, while binders work to "bind" the pigment together and create the paint film. Solvents are the liquids that suspend the ingredients and allow you to place the paint on the surfaces, and additives are ingredients that provide specific paint properties such as mildew resistance. All four ingredients combine to provide paint that meets your specific design needs. To begin...

Pigments - Provide Color, Hide and Bulk

Pigments are finely ground particles that are dispensed into paint and provide color and hiding properties. There are two primary types of pigment - prime pigments and extender pigments.

Prime pigments are those that contribute to both wet and dry hide in paint. Titanium dioxide (TiO2 ) is the most costly pigment and it contributes directly to a paint's wet hide, while providing whiteness Colorants are prime pigments that provide the actual color within the can. There are two main types - organic and inorganic.

• Organic colorants provide the brighter colors, and examples of these pigments include hansa yellow and phthalo blue. These are not very durable for exterior paint application.

• Inorganic colorants are the duller, earthy colors and are more durable for exterior paint application. Examples of these kinds of pigments include red oxide, yellow ochre and umber.

Extender pigments are lower cost pigments that give extra weight or bulk to the paint. These types of pigments contribute only to a paints dry hide, but are necessary in order to control gloss. Some extender pigments also provide additional film performance in the areas of scrub or abrasion resistance. Commonly used extenders include clay, silica, diatomaceous silica, calcium carbonate, talc and zinc oxide.

• Clay: Used mainly in interior paints, clay provides hiding power.
• Silica: Provides enhanced durability in exterior paints as well as scrub and abrasion resistance.
• Diatomaceous silica: Consisting of fossilized organisms, this form of silica is used to control sheen levels.
• Calcium Carbonate: Used in both interior and exterior paints, calcium carbonate, also called chalk, is a general purpose, low cost, low hide pigment.
• Talc: Also called magnesium silicate, talc is a soft, general purpose extender pigment.
• Zinc oxide: Used primarily in primers and exterior paints, zinc oxide provides mildew resistance, corrosion inhibition and stain blocking support.

 
Binders - Provide Performance and Support for Dry Paint Film

Binders are ingredients that provide a binding effect that holds the pigments together to create a dry film on the surface. A paints binder is the key ingredient that directly relates to a paints performance, including adhesion,, washability, scrub resistance, fade resistance or gloss retention.

Alkyd (oil) based binders are made from various oil derivatives such as linseed oil, tung oil, and soya oil. Traditional alkyd paints dry to a very hard finish and provide superior adhesion and flow and leveling; however, they will yellow in light colors and are prone to oxidation and chalking when used on exterior surfaces. As technology and VOC restrictions have changed over the years, fewer paints today are made with traditional alkyd binders. A newer technology based on modified oil binders is available; alkyd emulsion.. This type of hybrid binder gives you oil-like performance with the ease of soap and water clean-up. Alkyd-emulsion paints dry harder, flow more smoothly than typical latex paints; however, they may still yellow in lighter colors. If used on exterior surfaces subjected to UV exposure, alkyd-emulsion paints may eventually oxidize, and chalk over time.

Latex Paint and Ingredients:

Latex binders are used in water-based paints. There are various types of latex binders available, such as 100% acrylic, styrene acrylic or vinyl acrylic, each providing specific performance characteristics.

Acrylic Paint and Ingredients:

• 100% Acrylic binders: often used in exterior paints as the benefits include adhesion (both wet and dry), fade resistance, alkali and efflorescence resistance. 100% acrylic binders are typically regarded as the best overall performing.
  • Adhesion under wet conditions allow for greater performance in blister, cracking and peeling resistance.
  • UV fade resistance allows the painted surface to retain its color and sheen longer.
  • Alkali resistance means the paint is less likely to “burn" over fresh concrete or masonry.
• Vinyl acrylic, also called PVA, binders: often used in interior paints as the benefits include scrub resistance and washability.
• Styrenated acrylic binders: often used in masonry primer/sealers and top coats due to its resistance to alkali burn and efflorescence,

 
Solvents (liquids) --- Provides a vehicle for the pigment and binder to get from the can onto the surface

Solvents, or liquids, are the vehicle for allowing paint to get from the can to the surfaces and these types of liquids differ depending on the type of paint. Combining the pigments and binders, considered solids, with the liquids, creates the paint coating you see in the paint can.

• Oil-based and alkyd paints: the liquid is typically paint thinner or other type of solvent.
• Latex paints: the liquid is primarily water.

Higher-quality paints allow for more solids, typically 35-40%, depending on gloss level. Solids by volume indicate how much paint will remain on the surface after the liquids have evaporated. The overall paint performance is directly attributable to the make-up of the solids. Just because a paint has high solids by volume does not always translate to a high quality product..
 
Additives - Provides additional property enhancements

Additives are used in paints to create additional performance properties and the most commonly used are:

• Thickening agents: provides “viscosity" or additional thickness so the paint can be applied properly; also allows for better “flow and leveling" and resists a splatter effect when rolling out the paint
• Surfactants or soaps: provides paint stability so the paint won't separate; also keeps the pigments dispersed in the liquid to allow for better hiding power and additional assurance for color accuracy
• Biocides: in latex paints, there are two types of biocides used – a preservative to keep bacteria from growing; and a mildewcide to discourage mildew growth
• Defoamers: provides a way to break bubbles as they are formed during the paint manufacturing process, when paint is shaken at the tint center and when paint is applied onto a surface
• Co-solvents: provides additional liquids to the water and can assist the binders in forming a good film when applied in cold temperatures and assists brushing properties so paint has time to be applied before drying

All four ingredients are key to creating the foundation for a top-quality paint. Happy painting!

Paint is a ubiquitous part of our lives, adorning everything from doors and walls to architecture and automobiles. It enables artistic expression, creates the perfect finish to a product and provides an almost endless list of possibilities when it comes to colour.

Its significance spans across cultures and eras, from the cave paintings of our ancient ancestors to the modern buildings and artworks that captivate us today. In this blog, we look at the hugely diverse world of paint, tracing its origins, understanding its chemical composition, exploring various finishes, and highlighting advancements in modern paint technology.

The Origins and Significance of Paint

The history of paint dates back thousands of years when early humans utilised naturally occurring pigments like charcoal. clay and minerals to adorn cave walls with primitive art. These early forms of paint offered both aesthetic and symbolic value and there are reported finds of primitive paint making which date back to more than 100,000 years ago!

As civilisations developed, paint found its place in architecture and decoration. From ancient Egyptian tombs to Renaissance masterpieces, paint has been a key tool throughout the centuries to enhance our surroundings, but it isn't just about aesthetics anymore; it also serves as a protective barrier. Whether it's shielding a ship from the corrosive effects of seawater, protecting outdoor metals from rust, or preserving materials used in construction, paint plays a crucial role in extending the lifespan of a huge variety of end products.

Essential Components of Paint

At its core, paint consists of four key components:

• Pigments: These provide colour and opacity.
• Binders: Binders hold pigments together and adhere them to surfaces.
• Solvents: Solvents keep the paint in a workable consistency, facilitating application.
• Additives: Additives enhance paint properties, like durability and drying time.
• Working Together: These components all work in harmony. Pigments give colour, binders provide adhesion, solvents maintain fluidity, and additives offer special characteristics.

Paint Chemistry: The Basics

Pigments

Pigments are responsible for providing the desired hue and opacity to paint. They are finely ground, insoluble particles that are dispersed throughout the paint. Pigments can be organic or inorganic and are chosen based on the specific colour and performance requirements of the paint being produced.

Inorganic Pigments: These are often minerals or metallic compounds. For example, titanium dioxide is a widely used white pigment known for its excellent opacity and brightness. Iron oxide pigments produce various shades of red, brown, and yellow, while chromium oxide green creates green colours.

Organic Pigments: These are synthetic compounds with complex molecular structures. Organic pigments offer a broad spectrum of vibrant colours. For instance, phthalocyanine pigments produce brilliant blues and greens, while azo pigments create reds, oranges, and yellows.

Natural Pigments: Some paints incorporate pigments derived from natural sources, like minerals, plants, or animals. Examples include ochre, a natural earth pigment, and carmine, a red pigment obtained from crushed cochineal insects.

The chemical composition of pigments dictates their colour and lightfastness (resistance to fading over time). Pigments are typically mixed with binders to create a uniform paste, which is then dispersed evenly throughout the paint.

Binders

Binders, also known as resins or polymers, serve as the glue that holds pigments together and adheres them to the surface. Binders are responsible for the film-forming properties of paint, determining characteristics such as adhesion, durability, and flexibility.

Common types of binders include:

Acrylic Binders: These binders are commonly found in both water-based and solvent-based coatings, enamels, and emulsions. They form a durable and flexible film that resists cracking and peeling. Acrylic binders can also be used in artist's acrylic paints. They offer excellent colour and gloss retention whilst also preventing colour fading from weather extremes.

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Alkyd Binders: These oil-based binders are frequently used in oil-based paints, gloss, and enamels. They provide a smooth, hard finish and are known for their durability. Used in both architectural applications as well as automotive and decorative, they offer great adhesion, corrosion resistance and gloss retention.

Polyurethane Binders: Polyurethane binders are used in high-performance coatings, such as automotive paints and industrial finishes. They offer exceptional resistance to abrasion, chemicals, and UV deterioration.

Epoxy Binders: Epoxy resins are highly adhesive and resistant to moisture, making them suitable for applications like industrial floor coatings and marine paints such as offshore oil, gas and turbine applications.

Overall the choice of binder is hugely important as it affects the various paint properties, such as drying time, gloss, and compatibility with other materials. Additionally, binders can influence the environmental impact of the paint, with water-based binders being more environmentally friendly due to their lower VOC (volatile organic compound) content.

Solvents

Solvents are essential components of paint that control its viscosity, allowing for proper application. They dissolve or disperse the binder and pigments to form a homogeneous mixture. As the paint is applied, solvents evaporate, leaving behind a solid, painted surface.

Common solvents include:

Water:  Water is the primary solvent in water-based paints, such as acrylic paints. It is environmentally favourable and emits fewer VOCs compared to organic solvents.

Mineral Spirits: Mineral spirits are commonly used in oil-based paints and provide a slower drying time, allowing for smoother application and blending. They are classified as organic solvents.

Turpentine: Turpentine is an organic solvent used primarily in oil-based paints. It has a strong odour and can contribute to VOC emissions.

Methyl Ethyl Ketone (MEK): MEK is a fast-evaporating solvent used in specialty coatings, particularly those requiring rapid drying times.

The choice of solvent impacts the paint's workability, drying time, and environmental considerations. Water-based paints are preferred for their lower environmental impact, while solvent-based paints may have higher VOC emissions and require proper ventilation during application.

Additives

Additives are a diverse group of chemicals added to paint formulations to enhance specific properties or address particular challenges. They play a crucial role in fine-tuning the paint's performance.

Common additives and their functions include:

Thickeners: Thickeners adjust the paint's viscosity, making it easier to apply evenly. They are especially important in paint formulations designed for specific application methods, like roller or spray.

Antifoam: These antifoam additives prevent the formation of bubbles or foam during paint production, application, and drying.

Antioxidants: Antioxidants help protect the paint from oxidation and degradation, increasing its shelf life and resistance to colour discolouration due to aging.

Anti-settling Agents: These additives prevent pigments from settling at the bottom of the paint can over time, ensuring consistent colour and performance.

Mildewcides and Biocides: These additives inhibit the growth of mould, mildew, and other microorganisms on painted surfaces, particularly important in humid environments.

Rheology Modifiers: These additives influence the flow and levelling of the paint, improving its application characteristics.

The choice of additives depends on the specific requirements of the paint formulation and the desired end-use properties.

The Spectrum of Paint Finishes



Paints come in various formulations, including water-based, oil-based, and specialty types like enamel and acrylic, each with distinct chemical compositions.

Gloss Paints: High gloss paints are known for their reflective surfaces. This effect is achieved through specific binders that create a smooth, reflective layer. Gloss paints are commonly used in areas requiring easy cleaning, like kitchens and bathrooms.

Matte Paints: Matte finishes have a non-reflective, flat appearance. They are prized for their ability to hide imperfections and provide a velvety look. Matte paints are often used in bedrooms and living rooms.

Satin and Eggshell Finishes: Sitting between gloss and matte, satin and eggshell finishes offer a subtle sheen. They strike a balance between aesthetics and practicality, making them suitable for many applications.

Other Specialty Finishes: There's a wide array of specialty finishes, including metallic paints for a shimmering effect, textured finishes for added depth, and chalkboard/whiteboard paints that turn walls into interactive surfaces.

Advancements in Colour Technology: Nanotechnology has enabled the development of colorants with enhanced properties, offering greater vibrancy, durability, and environmental friendliness.

Advancements in Paint Technology

Innovations in Formulations: Low-VOC (volatile organic compound) and eco-friendly paints, along with solar paint (yes, you read that right) have gained popularity as consumers seek more sustainable options. These formulations reduce harmful emissions and help towards cleaner energy.

Smart Paints and Coatings: Emerging technologies have led to the creation of smart paints with self-cleaning properties, thermochromic coatings that change colour with temperature, and photochromic coatings that react to light.

Antimicrobial Coatings: Paints, particularly those used in public spaces, are also being manufactured to offer protection against bacteria and viruses. Adding silver nanoparticles to paint can kill microbes on contact to keep surfaces sterile without the need for disinfecting or regular cleaning. These coatings are ideal for educational facilities, healthcare settings, food prep areas and other surfaces that can be a potential transmitter of germs.

In conclusion, paint is much more than a simple coating; it's a complex blend of chemistry and artistry that has shaped our world for millennia. From its humble origins to cutting-edge innovations, paint continues to evolve, offering new possibilities and environmentally friendly solutions.

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