Gilbert Ligner

Polymer bound HALS—expectations and possibilities

This study confronts the traditional opinion on the physical aspects of the HALS efficiency with the available experimental reality. The results indicate that the generally accepted importance of additive migration may need to be reconsidered. Based on the experimental evidence, three empirical requirements for an effective stabiliser are formulated: high solubility, minimal diffusion and high homogeneity of distribution of active species. Chemical grafting of a low molecular stabiliser is suggested to meet the defined empirical requirements. The results achieved with polymer bound HALS (PBH) prepared by reactive processing technology confirm the expectations. The stabilisation efficiency of PBH significantly outperforms the conventional low molecular and oligomeric stabilisers.

Hindered amine light stabilizers: introduction

The expansion of polyolefins into new areas of industrial and every-day use has achieved tremendous progress during the last three decades. This progress was in most cases allowed by the employment of various speciality chemicals, such as different catalysts, polymer additives etc. Parallel to the growth of polyolefins applications, a great advance was observed also in the field of additives. Perhaps the most exciting progress was reached in the area of light stabilization by the discovery and introduction of Hindered Amine Light Stabilizers (HALS).

Stabilization of Polyolefins by Photoreactive Light Stabilizers

Publisher Summary 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.