Light stabilizers Detailed introduction

light stabilizers can be added to plastics to protect them from the degradative effects of exposure to sun and weather. Polyolefins are susceptible to attack by ultraviolet light, oxygen, moisture, and heat resulting in polymer brittleness, surface crazing, color change and product failure. There are three major classes of light stabilizers for polyolefins.

1. UV AbsorberS .....

Typical examples are benzophenones and benzotriazoles. These are low cost, effective stabilizers that function by the absorption of UV light. They are effective for short-term exposures.

2. NICKEL QUENCHERS .....

are Energy Transfer Agents that function by “quenching” the excited state of carbonyl groups formed during photo-oxidation and also through the decomposition of hydroperoxides. These types of stabilizers are not in wide use since they contain heavy metal, impart color to the final product, and are not as effective as the HALS discussed in the next paragraph.

3 . HINDERED AMINE LIGHT STABILIZERS (HALS) ...

are the most effective of the light stabilizers for polyolefins. Available in a wide range of molecular weights and structures suitable for almost any application. They can also perform as long-term thermal stabilizers (HATS). They function by “trapping” free radicals formed during the photo-oxidation process.

Since all three stabilizer types function by different mechanisms, they are often used in combinations which can be synergistic. For example, HALS are commonly used with benzotriazoles to minimize color changes in pigmented systems.

All of the above stabilizers will function most effectively in the presence of an appropriate base stabilization package containing both primary and secondary antioxidants along with a residual catalyst neutralizer. It is necessary to note that the gauge of the product, the geographic location of exposure, and the chemical environment are among the crucial factors in determining the amount of stabilizer needed for a particular application. Please consult with Ampacet for recommended usage levels of the following products.

Our most cost effective HALS, suitable for a wide range of polyolefin applications (“NR\/NH” type blend). High molecular weight HALS with low volatility and high migration resistance. Preferred for color critical applications such as polypropylene fiber\/carpet applications. (“NR” type)

TIANGANG UVA PRODUCTS A benzotriazole UV absorber. Designed for the protection of contents of packaging materials from harmful UV radiation. FDA approved for indirect food contact. 100645 is 100977 with AO (2500 ppm). -