How does UV Degradation Occur in Paints?

Here are the three UV degradation factors:

1. Chromophores absorb UV-radiations: Paints contain polymers, additives, pigments, binders, and particles that absorb sunlight. These UV-sensitive components are called chromospheres. Chromospheres are present in all UV-sensitive paints. 
2. Structural changes and Free radicals: Chromospheres release energy after being exposed to sunlight and cause structural damage to paints. They break the chemical bonds of paint and release free radicals. 
3. Cleavage of polymer chains: Free radicals damage the bond between resin and pigments. These broken polymer chains affect the ability of paint to resist moisture, freeze-thaw cycles, and cracks. This paint separation also leads to color changes and poor paint adhesion. 

How Does UV-Resistant Paint Work?

UV-resistant paint contains specific pigments (titanium dioxide, zinc oxide), binders (acrylic, polyurethane, epoxy), and additives like microspheres to reflect the UV light. These components reflect the incident light at the same angle before it hits the substrate. Microspheres are composed of alkali aluminosilicate ceramic materials, which increase the density and strength of paint to resist weather changes. Heat-resistant paint contains UV stabilizers and absorbers to prevent polymer cleavage and dissipate UV radiation. Hindered Amine Light stabilizers (HALS) also neutralize the free radicals that form after paint’s structural damage. Heat-resistant paints have a strong protective resin system that prevents moisture and air from being trapped in. They protect paint film from bubbling and melting. Heat-resistant paints preserve the original colors and maintain the satin, matte, and glossy finishes. They are used in automotive, marine, and industrial locations due to their anti-oxidative properties. 

What are the Types of UV-Resistant Paints

Here are the seven types of UV-resistant paint:

1. Acrylic Exterior Paints: Acrylic paints contain acrylic resins, binders, UV stabilizers, reflectors, and tints to reflect light. These IR reflective tints scatter light and act as a protective barrier. Acrylic paints leave a durable paint film to reduce cracks and leaks. They do not allow color to fade or be prone to freeze-thaw cycles. Acrylic paints are resistant to UV radiation and changing weather conditions when applied correctly. 
2. Polyurethane and Urethane Coatings: Polyurethane coatings are created from urethane linkages with different pigments, catalysts, and polyols. Urethane is the structural component and single form of polyurethane. They contain isocyanate, which is an organic compound and provides strength against UV radiation. Polyurethane coatings prevent moisture and air from penetrating to reduce rust. They are flexible due to polyols (soft elements) in their formulations.  
3. Epoxy Paints with UV Additives: Epoxy paint with UV absorbers (benzotriazoles, benzophenones, and hydroxyphenyl-s-triazines) and stabilizers (hydroxybenzoates) resists paint from yellowing. It contains a hardener in its formulation to leave a durable finish. There are three types of epoxy paints that resist UV radiation. A 100% solid topcoat USI UV-resistant epoxy paint with two separate components (resin, hardener). UVPoxy and Liquid Art UV+ with water-clear and epoxy coatings dissipate sunlight. 
4. Fluoropolymer-Based Coatings: Fluoropolymer-Based coatings contain resins (PTFE, PVDF, FEP), pigment, and solvents in their formulations. They are known for their non-stick properties as they do not allow any dirt or mites to reside on the paint surface. Their carbon-fluorine bonds resist rust and corrosion. The most common type of fluoropolymer-based coating is fluorinated ethylene vinyl ether, which protects against UV radiation from the sun.
5. Silicone-Based Paints: Silicon-based paints are UV resistant due to strong silicon and oxygen (Si-O) bonds. They allow the water to evaporate and provide a durable paint layer. Silicon-based paints are used in roof coatings, masonry surfaces, and tire building industries. 
6. Alkyd-Based UV-Resistant Paints: Alkyd paints are used to achieve a hard and glossy finish. It contains alkyd resins, which are derived from fatty acids and diols to resist UV radiation. Unlike acrylic paints, which resist high temperature, color deterioration, and peeling, alkyd paints only resist ultraviolet radiation to a limited level. Their strength to resist UV light depends on the formulations, resins, and UV stabilizers. Acrylic and latex-based paints are the best alternatives to alkyd paints when used outdoors. 
7. Elastomeric Coatings: Elastomeric coatings are 10x thicker than standard water and oil-based paints. It is made of acrylic and silicon resins with pigments and binders to maintain viscosity. Elastomeric coatings provide a strong protective layer to the substrate for smooth freeze-thaw cycles. Its ability to withstand UV radiation, weather changes, and cracks makes it best for exteriors. Elastomeric coatings are used to paint stucco, concrete walls, and low-slope roofs. 

Where Is UV-Resistant Paint Commonly Used?

Here are the five common places where UV-resistant paints are used:

1. Building Exteriors and Rooftops: UV-resistant paint is used to paint concrete walls, metal cladding or siding, cement boards, window trims, frames, and stucco exteriors. These substrates have a high chance of corrosion due to direct UV light exposure. UV-resistant paints are not prone to contraction, so they protect them from cracking and chalking.
2. Boats, RVs, and Vehicles: UV-resistant paint is used to paint the hull, deck, fiberglass surfaces, bimini surface, railings, and metal trims of the boat. It is also applied to painting the doors, storage compartment cover, roof, bumper, and body panels of recreational vehicles. Apart from this, heat-resistant paints are used on gelcoats, vehicles, and hoods to prevent them from oxidation. 
3. Outdoor Furniture, Decks, and Fences: UV-resistant paint is a necessity for fences, decks, gates, benches, swings, and ottomans ( a part of the patio). It reduces our future expense and protects these surfaces from peeling and fading.
4. Signage, Murals, and Exposed Artwork: UV-resistant paint is used in decorative installations, painted art pieces, signage, and billboards. These artworks are prone to damage due to acid rainfall, heavy wind, and dirt. UV-resistant paints make them weather-resistant and increase durability.
5. Industrial and Commercial Coatings: UV-resistant paint is used on walls, roofs, generators, compressors, turbines, and pipelines. It is also applied on pumps, canopies, shipping containers, storage tanks, and silos to protect them from harsh environments.

How to Know If Your Paint Is UV-Resistant

Here are five ways to check if your paint is UV-resistant:

1. Check the Label or Datasheet: Check the material safety data sheet (MSDS) or safety data sheet (SDS) to inspect the details about the UV-resistant paint. Paint with labels “fade-resistant,” “weatherproof”, or “UV absorbers” has the strength to reflect harmful radiation. 
2. Ask the Manufacturer: Visit the official website of the manufacturer company for technical data sheets (TDS). TDS provides a complete set of information from product description to application instructions and performance of the paint. 
3. Review the Ingredients: Read the paint ingredients to check if it resists heat and UV radiation. Paint cans with titanium dioxide, zinc dioxide, UV stabilizers, and acrylic binder have light-reflecting properties. 
4. Look at Product Usage: Paint cans also provide usage instructions to guide where they can be used. Paints with automotive, marine, industrial, and outdoor usage bounce the UV radiation back. 
5. Field Performance: Apply paint on different substrates to check its durability and heat resistance. Field performance of paint highlights its ability to resist UV light, weather changes, and orange peels.

Accelerated weathering/UV test methods

Here are five UV test methods to examine the UV-resistance abilities of paint using artificial light sources:

1. ISO 16474: This test method measures the ability of paints and varnishes to withstand UV light. Xenon-arc lamps are used as an alternative to natural sunlight to fall on paint substrates. 
2. ISO 11507: In this standard method, a fluorescent UV lamp is used as a source of sunlight. ISO 11507 test measures the ability of paint coating to withstand moisture and cracks.
3. SAE J2527: This UV test method is used to examine the ability of car parts to resist weather changes. Xenon-arc lamps are used under controlled temperature and humid conditions.
4. ASTM G154: American Standard for Testing and Materials (ASTM) is a general test to observe the reaction of UV light on different materials. A fluorescent UV bulb with a wavelength of 300nm to 400nm is used in this procedure. 
5. ASTM D6695: Unlike ASTM G154, this standard test measures the UV-resistance of paints and coatings. Substrates are exposed to xenon light, high temperature, and humidity to observe the results.