Thermo-oxidative degradation of isotactic polypropylene at high temperatures: phenolic antioxidants versus HAS

被引:121
作者
Gensler, R
Plummer, CJG [1 ]
Kausch, HH
Kramer, E
Pauquet, JR
Zweifel, H
机构
[1] Swiss Fed Inst Technol, Dept Mat Sci, Polymer Lab, CH-1015 Lausanne, Switzerland
[2] Ciba Specialty Chem Inc, Addit Div, CH-4002 Basel, Switzerland
[3] Swiss Fed Inst Technol, Inst Polymers, Dept Mat Sci, CH-8000 Zurich, Switzerland
关键词
polypropylene; thermo-oxidative degradation; hindered amine stabilizers; phenolic antioxidants; ESR spectroscopy;
D O I
10.1016/S0141-3910(99)00113-5
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
The influence of a phenolic antioxidant and two hindered amine stabilizers (HAS) on the degradation behaviour of isotactic polypropylene was investigated for temperatures in the range 120-149 degrees C. Consistent with earlier reports, phenolic-stabilized specimens were found to decompose in a catastrophic manner at the end of an induction period, whereas the mechanical properties of HAS-stabilized samples deteriorated more gradually. These differences are due to fundamental differences in the mode of action of the stabilizers. Phenolic antioxidants act as inhibitors, hindering the formation of hydroperoxide sequences and the scission of primary bonds, provided that their concentration in the polymer remains above a critical value. On the other hand, gel permeation chromatography and viscosity measurements show that HAS do not inhibit the steady cleavage of polymer chains. This has been ascribed primarily to the observation that nitroxyl radicals and hydroxylamine ethers, considered to be the most important stabilizing species associated with HAS, are formed during aging. HAS are thought, therefore, only to retard the degradation of the polymer. (C) 2000 Elsevier Science Ltd. All rights reserved.
引用
收藏
页码:195 / 208
页数:14
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