Coatings and nonwovens work hard to protect the buildings from the elements. They provide vital UV and water resistance properties, helping to extend the building’s lifespan and reduce required maintenance cycles.
Using high-quality binders is important for these products, as it allows them to optimize performance through added strength and resistance, which prevents failures from occurring and compromising the building’s protective envelope.
With over 150 years of experience and a diverse product portfolio, BASF develops dispersions to match your exact formulation needs, whether that’s extreme UV blocking capabilities, enhanced water resistance, advanced adhesion, or all of the above.
The UV challenge
Ultraviolet radiation (UV rays) can damage nonwovens and coatings over time. When these materials are exposed to radiation, they absorb it, which weakens chemical bonds and leads to discoloration, cracking, fading, and an eventual loss of structural integrity.
This loss of structural integrity is caused by photodegradation. This chemical reaction occurs in the polymer backbone, which produces radicals and changes the chemical composition and molecular weight of the polymer in a process called polymer degradation.
Photodegradation is a leading contributor to polymer degradation, which starts at the outer surface and penetrates gradually into the bulk of the material. Other sources of polymer degradation include heat or thermal degradation, mechanical degradation, and biodegradation from yeast, fungi, bacteria, enzymes, and other sources.
Furthermore, the depleting ozone layer has real implications in how UV resistant resins are chosen. Although we’ve made strides towards partially restoring it, a thinning ozone layer lets in more UV rays, demanding more protection.
Protection and defense
The damage from photodegradation can be minimized with photostabilization of the polymers through stabilizers such as UV absorbers, light screeners, free radical scavengers and other solutions.
Styrene-acrylic, styrene-butadiene and acrylic polymers in resins can all contribute to UV and other resistance properties, but some are more effective than others, so it’s important to know which type to choose based on the end application.
“If you were using a styrene-butadiene polymer, the UV rays can quickly damage those polymers and, in essence, make the butadiene unzip from the polymer,” says John Norton, Technical Specialist at BASF. “First the polymer becomes very brittle, and then it starts to completely lose strength over time.”
Styrene-acrylic polymers provide more UV resistance to adhesives or coatings than styrene-butadiene polymers, but straight acrylic polymers are the go-to choice for exterior applications as they provide the most UV resistance.
“Straight acrylics could be made up of any type of acrylic monomer, but typically they're based on methyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate or ethyl acrylate -- one of those families of monomers,” says Norton.
These polymers derive their resistance abilities from their chemical properties, which help diffuse or screen out UV rays or, in some cases, absorb them.
BASF offers several resins that help nonwovens and coatings stand against photodegradation.
ACRONAL NX 4612 X is a hydrophobic, APEO-free acrylic binder that offers exceptional UV and water resistance and is ideal as a hydrophobic binder in applications where water permeation is a concern.
ACRONAL EDGE 4750 is an all-acrylic latex binder that’s designed for interior or exterior premium grade flat through semi-gloss paints and can be used as a paint-and-primer-in-one. It delivers great early block resistance, superior stain and tannin blocking, and it is low-VOC.
With so many different options, choosing the right resin can feel challenging. Formulators will often have to balance cost and performance, but with the right chemistry, an effective and economical solution can be reached. BASF is there to help.
Additionally, light stabilizers and UV absorbers can be added to polymers or coatings to improve UV resistance. This allows customers to manipulate a particular polymer and adjust performance as needed without having to add another SKU to their portfolio.
ACRONAL NX 4787, for example, doesn’t offer UV resistance as strong as ACRONAL NX 4612 X, but light stabilizers and absorbers can be added to enhance its performance.
In an ever-changing world where climate concerns are top-of-mind, it will always be important to defend against UV rays. Regardless of what your adhesives, composites, coatings and nonwovens require or where they’ll be used, BASF has the tools and chemistry to meet your precise needs.
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