Лако-красочные материалы — производство

In the preceding discussion we dealt with BTZs and HALSs as classes of light stabilizer without much attention to structure variations within each class. As demonstrated by the numerous chapters of this book, many polymers are used for adhesive applications. Each of these materials may have unique photostability concerns. It is beyond the scope of this chapter to address the stabilization of specific adhesives. Similarly, it is beyond our scope to discuss the many structural variations of UVA and HALS chemistry. Many derivatives of these compounds are commercially available, and some adhesive and sealant formula­tions and/or applications may dictate the use of one stabilizer over another.

In the case of BTZs, the UV absorption properties of the compounds are relatively similar, with some variations in absorptivity and absorption maxima (1max). Since suffi­cient BTZ is typically used to remove essentially all the light in the surface layer of the polymer, the performance characteristics of BTZs are usually comparable. Selection of the BTZ is therefore based on physical properties, not photochemical properties. Properties such as volatility (molecular weight) and physical form are usually considered, as well as economic concerns.

In the case of HALSs, the activity is dependent on the amine functionality concen­tration. Therefore, the highest-activity HALSs are generally those with a high portion of the molecular weight contributed by an amine such as HALS-1 and HALS-2. Additional structure built into the molecules may dilute and decrease the activity, but in some appli­cations may increase polymer compatibility or decrease volatility. Oligomeric HALS have found extensive utility in high-surface-area applications such as films and fibers, due to their reduced volatility. Almost by definition, adhesives have high surface areas, but they also are between two substrates, which will limit volatility. As in the case of BTZs, physical properties are also important. Additionally, due to the basicity of the amine functionality, the use of conventional HALSs is intolerable in some applications, and structural mod­ifications of the HALS functionality are used to reduce interactions.