STABILIZATION MECHANISM AND STRUCTURAL CHARACTERISTICS OF BENZOPHENONE-BASED LIGHT ABSORBER (UV ABSORBER)
Benzophenone stabilization mechanism
UV absorbers are composed of a functional group (-OH) that absorbs UV light and substituents attached to the basic structure.
The UV absorber added to plastic exposed to UV light reacts to UV light as follows.
Hydroxyl(-OH) group absorbs UV light and forms a hydrogen bond with the neighboring -CO group, continuously causing resonance, and the absorbed UV energy is released as heat. Afterwards, it is restored to its original stabilized structure and continues to function as a UV absorber.
Structure and properties of representative benzophenone UV absorbers
In benzophenone UV absorbers, 2, 4 -dihydroxy benzophenone is a representative basic structure with a functional group. By substituting the functional group at the 4th position in this structure, a UV absorber tailored to each application was developed.
Product 1 has a methoxy (-OCH3) group at the 4 position and product 3 has an octoxy (-OC8H17).
Product 3 (UV 531, Solvay product name) is the most widely used benzophenone product. Compared to product 1, it is designed to increase heat resistance by increasing the molecular weight and prevent volatilization during processing. It has a long chain structure of C8 and has a hydrocarbon structure. Compatibility with DOP of PE and soft PVC has been improved.
By introducing –OH (2′-hydroxy group) into product 1, product 2, which has two -OH groups, has a maximum UV absorption region that extends from 327 nm to 356 nm and a UV maximum absorption peak that increases from 41 to 54.
In the case of Product 1, due to its strong UV absorption properties, it is added to the coating liquid when developing a UV blocking film to provide UV blocking properties, thereby protecting the color and physical properties of the coated material and increasing durability.
