UV rays can degrade coatings and compromise performance over time. Knock them out with BASF light stabilizers and UV absorbers

Many of us are familiar with “new car smell”, which is actually caused by a chemical process known as off-gassing. When it comes to a new car’s shine or gloss, the secret also lies in chemistry.

BASF Performance Additives are partially responsible. For more than 50 years, BASF has supplied Original Equipment Manufacturers (OEMs) with high-quality UV absorbers and light stabilizers to keep the paint looking glossy and colorful, even after years on the road.

These versatile additives keep our cars looking shiny by protecting them from strong ultraviolet (UV) rays that can damage the coating and the car over time. They’re also used in interior automotive, furniture, industrial, and even candle applications to add resistance and performance capabilities.

Breaking down UV

Photodegradation caused by light exposure, thermal degradation from heat, biodegradation from bacteria or fungi, and physical or mechanical action can all contribute to overall polymer degradation in coatings and materials.

Photodegradation occurs in coatings when photodegradable molecules absorb photons, particularly those wavelengths found in sunlight, such as infrared radiation, visible light, and ultraviolet light. This creates free radicals and reduces molecular weight, which causes mechanical properties to deteriorate over time.

When a coating is exposed to ultraviolet radiation it absorbs it, weakening chemical bonds and causing damage over time in the form of both chemical and physical changes, including fading, cracking, and discoloration.

Infrared radiation also causes a process known as oxidation, where oxygen intermingles with the coating's polymers, causing fading and a rougher surface. 

Suncare for polymers

In order to mitigate the effects of photodegradation and polymer degradation, coating manufacturers incorporate UV absorbers and light stabilizers into their formulations.

There are two main classes of light stabilizers: ultraviolet light absorbers (UVA) and hindered amine light stabilizers, or HALS.

Ultraviolet light stabilizers work by slowing down the degradation process by competitively absorbing harmful ultraviolet radiation and dissipating it as thermal energy. While HALS do not absorb UV radiation themselves, they inhibit degradation of the polymer by acting as radical scavengers, and significant levels of stabilization can be achieved at relatively low concentrations.

Many formulators will use a combination of the two to achieve the best protection and resistance properties in their formulations.

What’s new?

BASF offers a variety of UVA and HALS light stabilizers, as well as antioxidants and optical brighteners.

TINUVIN® 123 and TINUVIN 249 are both popular HALS in our portfolio and are commonly used in coatings, plastics, and adhesives,” says Mervin Wood Jr, Technical Expert at BASF. “TINUVIN 123 was launched about 25 years ago, and TINUVIN 249 is its improvement, as it’s a much lighter-colored product than TINUVIN 123 and is more broadly applicable, especially in color-sensitive areas such as clear automotive coatings or clear coats over white pigments.”

TINUVIN 249 is ideal for a wide variety of applications thanks to its versatility and is designed to meet the high performance and durability requirements of solvent-based automotive, industrial, and decorative coatings where other HALS fail either related to their basicity or for compatibility reasons.
A non-basic HALS, TINUVIN 249 offers low viscosity and does not interact with acidic paint ingredients such as catalysts, biocides, or pigments, giving it high thermal stability and broad compatibility in solvent-based systems of different polarity.

Although HALS typically need to be combined with a UV absorber for many applications, UVA/HALS blends can offer the benefits of both in a single product.

TINUVIN 5070 is a brand-new product designed to meet the high performance and durability requirements of applications where other products fail due to basicity, compatibility, or both.

“TINUVIN 5070 is a blend of a UV absorber and a hindered amine light stabilizer, and is designed to have high thermal stability, broad compatibility in a variety of formulations and good weathering performance,” says Wood. “In the automotive sector, TINUVIN 5070 allows the coating to last longer, which is good for automotive resale.”

UV protection is especially important in this area. Without UVAs and light stabilizers, automotive coatings can become compromised, leading to a snowball effect where water will penetrate the coating, leading to corrosion and cracks and eventually failure. It’s important for both OEMs and automotive refinishers to use these protective additives in their coatings to ensure consistency in color and gloss.

There’s another popular market where color protection and fading prevention are important: candles.

“When we entered into this market about 20 years ago, candles were gaining popularity and were starting to have their own stores,” says Wood. “Salesclerks in the store would have to rotate their candle merchandise once a week to make sure it was fading evenly, and if they didn’t do this, the side of the candle that saw the store light would fade. TINUVIN 5070 helps limit or stop UV light-induced candle dye degradation, essentially reducing fading."

Additives such as IRGANOX® 1010, a sterically hindered phenol antioxidant that acts as a radical scavenger in candles, plastics or in coatings, reduce radicals to limit the amount of breakdown of the candle wax, both natural- and paraffin-based waxes, coating resins,  plastics, or adhesives.

Warming up

The need for protection from heat and the sun is becoming more important for both humans and coatings as temperatures warm and the sun’s rays grow stronger. A 30-year study completed in 2010 by NASA found that the amount of ultraviolet (UV) radiation reaching Earth's surface has increased markedly over those past three decades.

While we have ingredients like zinc oxide and titanium dioxide in sunscreen to protect our skin, we can thank UVA and HALS additives for protecting our automotive, architectural, and industrial coatings that require a bit more protection.

“All of these Performance Additives help maintain the longevity of the overall coating while using fewer materials and having less of an environmental impact,” says Erin Moore, Marketing Manager at BASF. “These products are all about performance and maintaining performance and the longevity of the overall coating. They allow customers to invest in quality products that will last a long time.”

Learn more about BASF’s UVA and HALS additives

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