Search for Unified Action Mechanism of Hindered Amine Light Stabilizers

Abstract

Hindered amine light stabilizers (HALS) possess many functions unlike other additives and are frequently used to extend the service life of polymeric materials, but show particular compatibility with certain other additives. However, combination does not always show synergistic actions, but sometimes has antagonistic effects. Most previous research into the interaction of HALS with other additives has focused on qualitative high synergism to high antagonism, and no common understanding has been reached. HALS and homologs have many derivatives which are classified here as "good" HALS and "bad" HALS, including a new HALS derivative, HALS nitrosonium. The investigation of the antagonism of HALS with other additives has been based on only "good" HALS. The present study discusses the chaotic interactions of HALS with other additives kinetically and thermodynamically by separately considering the synergism of "good" HALS and the antagonism of "bad" HALS. This approach has lead to a new technique for unified evaluation of the interaction semi-quantitatively. The results summarized here clarify the complex and diverse characteristics of HALS and present the possibility that the action mechanism of HALS alone and together with other additives can be discussed based on a unified mechanism. Such united ideas can determine additive formulation much more easily and facilitate the development of new additives, resulting in more stable and functional polymeric materials.

Global and Local Aging in Differently Stabilized Polypropylenes Exposed to Hot Chlorinated Water with and without Superimposed Mechanical-Environmental Loads

“…According to other investigations, this is due to the primary phenolic antioxidant becoming increasingly acidic, which interacts with the alkaline environment of the hindered amine stabilizer. The resulting antagonistic acid/base mechanism, which involves the consumption of phenol by the activated hindered amine stabilizer, is also discussed in literature [48,49,50]. Moreover, this may be related to the insufficient compatibility of the stabilizer with the base polymer, which leads to the stabilizer aggregates at inter-spherulitic boundaries acting as inherent defects.…”

Analytical evaluation of the performance of stabilization systems for polyolefinic materials. Part I: Interactions between hindered amine light stabilizers and phenolic antioxidants

“…This acid/ base mechanism leads to the quinoid structures observed. The antagonistic mechanism involving this useless consumption of the phenol by the NO•e compound is frequently discussed in the literature [6,12]. In these investigations either ESR-spectroscopy or GC was used for monitoring the transformation of the individual species.…”

Preparation of a novel stabilizer and its thermal‐oxidative stabilization effect on polyamide 6

“…Hindered amine light stabilizers (HALS) have been used widely as antioxidants . They were originally developed as light stabilizers, but now they are also used as multifunctional additives, since they have been found to work as a radical‐trapping agent, a heavy metal deactivator, a hydroperoxide decomposer, and so on . The HALS and phenolic antioxidants are frequently used together practically , but previous studies have shown either antagonism or synergism .…”