Stabilization of Polyolefins by Photoreactive Light Stabilizers

Abstract

This chapter describes stabilization of polyolefins by photoreactive light stabilizer. The chapter illustrates that most of the works dealing with HALS performance emphasize the importance of compatibility and solubility of the additive. Terms such as “reduced migration” or “limited compatibility” are used very often to explain differences in the stabilization performance, especially in connection with oligomeric and polymeric additives. The available physical measurements, as well as their relation to the stabilization efficiency, imply three empirical requirements for an effective stabilizer: high solubility, minimal diffusion, and high homogeneity in the distribution of active species. This chapter presents the data that show that under optimal conditions, the use of photografting HALS-4/4 could satisfy all three empirical requirements. As a low molecular weight HALS, this stabilizer is readily homogeneously distributed in the polymer during the processing step. The chemical structure of HALS-4/4 leads to expectation that its behavior in a polymer matrix would be similar to other low molecular weight stabilizers. Subsequent light exposure initiates a photochemical reaction by which the additive can be grafted to polymer chains. This chapter concludes that the reported results obtained so far with this product confirm the expectations and show a better stabilization performance that of conventional low molecular weight and oligomeric additives.