In most polymer applications, degradation is an undesirable process. It often leads to changes in the chemical and physical structure of the polymer, leading to the loss of many useful properties. UV degradation of polymers can negatively affect molecular weight, impact resistance, elongation at break, gloss and color. Such damage can be greatly slowed down by adding weather stabilizers. Discuss in detail the basics of light stabilizers/UV absorbers and the mechanisms of degradation in different polymers. Plus, get tips for selecting the most appropriate light stabilizer/UV absorber for your polymer application and formulation examples.
Light stabilizers and UV absorbers are required in polymers
The useful life of polymers is limited by their degradation. Degradation can be caused by many environmental factors such as temperature, humidity, impurities, mechanical loads, radiation, microorganisms, chemicals and air.
Light stabilizers and UV absorbers counteract possible degradation of polymers under the influence of:
Sunlight
ultraviolet rays
hot
react with oxygen
For example, several engineering thermoplastics such as polyamides, which are primarily used in outdoor applications, require long-term UV stability. Polybutylene terephthalate (PBT) can be used in pigmented automotive exterior applications. Polyurethane-based end products such as automotive door trims, dashboards, steering wheels, window sealants, headrests and armrests, and shoe soles degrade when exposed to heat and light. This degradation leads to discoloration and the formation of cracks.
The addition of light stabilizers and UV absorbers to polymer blends can improve the appearance/aesthetics and overall longevity of the product. The choice of light stabilizer/UV absorber depends largely on the substrate to be protected, its expected functional lifetime and its susceptibility to photodegradation.
The most commonly used light stabilizers in plastics are hindered amine light stabilizers (HALS).
The most common UV absorbers are benzotriazoles, benzophenones, and organonickel compounds.
UV Degradation Effects in Polymers
The effect of UV degradation on polymers can be evaluated from the factors discussed below.
