Aspects of the impact of stabilizer mass on performance in polymers 1. Performance of low and high molecular mass HALS in PP

摘要

There is little specific work on the influence of stabilizer mass on performance. In addition, the published work in this respect concerns essentially the effect of increasing mass of polymeric stabilizers. However, there are much more data available on the efficiency of commercial stabilizers with significantly different mass. Nevertheless, all these data have been generated with various objectives, mainly to improve the stabilizer systems for practical stabilization. They were never used for examination of the direct influence of molecular mass. This led to considerable confusion concerning the effect of mass on stabilizer efficiency. For this rea- son, some of the data available have been collected and examined more specifically with respect to this effect. The results presented in the first part of this series concern the effect of mass observed mainly with commercial HALS in PP. They show that the mole- cular mass of the stabilizers has considerable impact on their performance in polypropylene. This impact depends strongly on sample form and exposure conditions. In thick PP samples for which surface protection is especially important, there is consider- able decrease of performance if the stabilizer molecular mass increases from approximately 500 to approximately 800. In thin PP samples such as PP tapes these effects are not so pronounced but nevertheless highly significant. The results are important from a practical as well as from a fundamental point of view. They confirm that optimum stabilization requests the right stabilizer or stabilizer system for a given applic