N-取代烷氧基受阻胺类阻燃剂及其在聚烯烃中的应用

Flame Retardant Based on N-Alkoxyoxy Hindered Amines and Their Application in Polyolefins

近年来,长期作为光稳定剂的受阻胺在性能改善过程中发现其中的N-取代烷氧基受阻胺具有优异的阻燃性能。本文对N-取代烷氧基受阻胺类阻燃剂(NORs)的结构、性能、合成、阻燃机理及其在聚烯烃中的应用进行了系统的评述。NORs主要是以22,,6,6-四甲基哌啶衍生物在催化剂作用下与烷基自由基经过数步反应制得,其在聚烯烃中的阻燃功效主要是通过燃烧分解产生的高效可循环再生的自由基捕捉剂干扰和抑制燃烧过程中产生的自由基,并使之转化为相对稳定的醇、酮等化合物来实现的。此外,通过凝聚相的自由基反应,NORs还可提升含溴或磷系等传统阻燃剂的阻燃效率。研究表明,NORs应用于聚烯烃薄制品如纤维和薄膜等体现出优异的阻燃效率,且低浓高效,添加0.5%左右即能达到满意的阻燃性能。同时,其良好的阻燃协效作用可显著减少传统阻燃剂的用量。此外,NORs本身作为一种受阻胺稳定剂,能为聚烯烃材料提供优良的光稳定性和长效的热稳定性。

Hindered amines have been used as UV stabilizers for a long period.The recent attempt to improve the properties of hindered amines revealed that the N-alkoxyoxy hindered amines（NORs） poss excellent flame retardancy.In this article,the chemical structure,properties,synthesis methods,flame-retardant mechanism of NORs and their application in polyolefins are systematically reviewed.NORs are synthesized through the reaction of 2,2,6,6-tetramethylpiperidine derivatives with alkyl radicals in several steps with the presence of catalysts.The mechanism of NORs as flame retardant（FR） in polyolefins is generally based on the thermolysis of NORs that leads to the formation of efficient and regenerable free radical scavengers.NORs are involved in the free radical chemical reactions during the combustion process and reduce the free radicals concentration by converting them into alcohols and ketones that are relatively stable.Furthermore,NORs can interact with conventional brominated or phosphorus-based FR through radical reactions in the condensed phase,resulting in improved FR efficiency.Researches indicate that NORs provide excellent FR performance for thin polyolefin section such as fibers and films at unexpected low concentration.The loading as low as 0.5wt% can result in satisfied flame retardancy.Moreover,they have a good synergistic effect in combination with conventional FR to improve their efficiency,so the loading of conventional FR can be significantly decreased.Additionally,NORs also provide polyolefin with excellent UV stability and long-term thermal stability.