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The use of thermal analysis to assess oxidative damage in polyolefins

机译:使用热分析评估聚烯烃的氧化损伤

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摘要

During the thermal oxidation oxidation of polyolefins, exemplified by isotactic polypropylene, few observable physical and chemical changes occur until embrittlement or similar failure. The increasing oxidative and auto-oxidative behavior that accompanies oxidation can be measured as a reducing oxidation induction time using isothermal thermal analysis. Alternatively, dynamic thermal analysis (DSC or TGA) may be used more conveniently to record the shift to lower temperatures of the post-fusion, oxidative exotherm quantified as an onset (T_(on)) temperature. This paper collates data from a number of previous and current studies on the oxidative behavior of oriented polypropylene tapes and filaments exposed at elevated (130 deg C) temperature in air. During expousre, T_(on) values decrease according to a power law dependence with time and these shifts may be used to assess degress of oxidation pressent in aged specimens. The implications of these shifts are discussed in terms of monitoring in-service behavior of exposed polyolefins and their relationship to oxidative and auto-oxidative mechanisms are discussed.
机译:在聚烯烃的热氧化氧化过程中,以全同立构聚丙烯为例,几乎没有可观察到的物理和化学变化发生,直到变脆或类似的破坏为止。使用等温热分析,可以测量伴随氧化而增加的氧化和自氧化行为,作为减少的氧化诱导时间。备选地,可以更方便地使用动态热分析(DSC或TGA)来记录向熔融后温度的转变,该温度被量化为起始(T(on))温度。本文整理了来自先前和当前大量研究的数据,这些研究涉及在升高的温度(130摄氏度)下暴露在空气中的定向聚丙烯带和单丝的氧化行为。在暴露期间,T_(on)值根据幂律随时间的变化而降低,这些位移可用于评估老化样品中氧化压力的降低。从监测裸露的聚烯烃在役状态方面讨论了这些转变的含义,并讨论了它们与氧化和自氧化机理的关系。

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