The Universal Selection Source:
Adhesives Ingredients

Techno Brief: UV/Light Stabilizers for Adhesives

The action of light can lead to irreversible damages in adhesives and sealants properties, at the edges of the adhesive bond or if the substrates are permeable to light. This UV/Light Stabilizers guide is designed to help you understand more about the use of UV/Light Stabilizers in the adhesives & sealant industry, focusing on how to reduce the damage done by light, oxygen and heat to adhesives.

Reactive Hot-melts

Polyurethane (PUR) reactive hot melt adhesives are based on a combination of PUR and hot-melt technology.

The hot melt is a 100 percent solid, one-component urethane prepolymer. It is fast setting, like a standard hot melt, but then reacts with atmospheric or substrate moisture to cross-link or chain extend, forming a new polyurethane polymer. 

This combination results in a hot melt with enhanced performance. Unlike conventional thermoplastic adhesives, which remelt when heated, PUR hot melts cure to a thermoset material, retaining their structural integrity once cured. In addition, the cured adhesive has excellent temperature and environmental resistance, generally withstanding exposure to temperatures from -30°C to +150°C, while maintaining strong bonds between similar and dissimilar substrates.

0.5% UVA
0.5% UVA
Figure 1 : PUR Hot Melt Adhesive – 12 hours Weatherometer 65°C

As with other PUR adhesives, PUR hot melt adhesives rapidly discolor and lose some of its mechanical properties if not protected from UV-induced degradation. A light stabilizer or antioxidant/light stabilizer systems are able to protect and considerably reduce the amount of discoloration of PUR hot melt adhesive.

Figure 2 : Light Stability of PUR HMA 
Weathering WOM CI 35 (bp 65°C)

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