Introduction: Light stabilizer is a class of additives used to improve the light aging resistance of polymer materials. Among them, hindered amine stabilizers have attracted much attention and are widely used due to their excellent anti-photoaging properties. This article will introduce the commonly used light stabilizers on the market, the mechanism of action of light stabilizers, and give recommendations on the selection criteria.
Commonly used light stabilizers on the market:
Common light stabilizers on the market mainly include ultraviolet absorbers and hindered amine stabilizers. Ultraviolet absorbers reduce the impact of light energy on polymers by absorbing ultraviolet light energy and converting it into heat, thereby achieving the effect of anti-photoaging. Hindered amine stabilizers occupy an important position in photostable chemicals due to their unique mechanism.
Mechanism of action of light stabilizers:
Hindered amine stabilizers are able to inhibit the photoaging process of polymers in a variety of ways. First, it is able to break down hydroperoxide (RoOH) and convert it into a harmless substance. Secondly, the hindered amine stabilizer has a strong ability to trap free radicals, which can neutralize and stabilize free radicals and prevent the polymer chain breaking reaction caused by free radicals. In addition, hindered amine stabilizers have the ability to regenerate, i.e., they are able to regain their own stability after the free radical trapping reaction, so that they can continue to function.
Among them, the capture reaction of nitrogen oxide radicals generated by hindered amines on broken chain free radicals is considered to be the main role of hindered amines. This reaction can effectively block the chain breaking process of the polymer, thereby improving the photoaging resistance of the polymer.
Selection criteria: The following criteria should be considered when choosing to use a light stabilizer:
a.For thin products such as agricultural films, it is recommended to choose a light stabilizer with a large molecular weight, such as stabilizer 944. Large molecular weight light stabilizers can be better dispersed in the polymer matrix, provide a longer light stabilization effect, and effectively delay the aging rate of agricultural films.
b.For thick products such as coatings, it is recommended to choose a low molecular weight light stabilizer, such as stabilizer 292. Low-molecular-weight light stabilizers can penetrate more easily into the polymer, providing more comprehensive photostability and effectively preventing the aging reaction of coatings when exposed to UV light.
In addition, the pH of the system needs to be considered when selecting a light stabilizer. Different polymer materials have different sensitivities to pH, and light stabilizers should be selected according to the acid-base conditions of a specific system to ensure the maximum light stabilization effect. It is recommended that the stabilizer be adjusted and tested appropriately according to the specific polymer system and acid-base conditions to obtain the best light stabilization effect.