Spin Trapping Analysis of the Thermal Degradation of Polypropylene
Spin Trapping Analysis of the Thermal Degradation of Polypropylene
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DOI：
10.1016/j.polymdegradstab.2022.109871
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发表时间：
2022-02
影响因子：
5.9
通讯作者：
Thu Anh Nguyen;Shota Ichise;K. Kinashi;W. Sakai;N. Tsutsumi;S. Okubayashi
中科院分区：
文献类型：
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作者：
Thu Anh Nguyen;Shota Ichise;K. Kinashi;W. Sakai;N. Tsutsumi;S. Okubayashi
采用电子自旋共振（ESR）自旋捕获技术研究了聚丙烯（PP）织物在室温至220 °C范围内的热降解机理。采用该方法延长热降解产生的短寿命自由基中间体的寿命，以检查其分子结构。采用超临界CO2（scCO 2）处理方法，在共溶剂存在下，将自旋捕获剂2，4，6-三叔丁基亚硝基苯（TTBNB）浸渍到PP织物中。使用质子核磁共振（1H NMR）光谱、傅里叶变换红外（FT-IR）光谱和扫描电子显微镜（SEM）评价浸渍效率和效果。ESR分析表明，PP的降解是从叔碳位开始的，通过均裂生成·CH 3和− CH 2 −·CH− 2 −自由基和夺氢生成− CH 2 −·C（CH 3）− CH 2 −自由基两条途径进行的。这些自由基也被氧攻击形成氢过氧化物，然后分解形成烷氧基自由基− CH 2 −CH（O·）− CH 2 −和− CH 2 −C（CH 3）（O·）− CH 2 −。这些自由基参与随后的β-断裂反应，产生伯碳自由基和仲碳自由基。烷氧自由基还参与涉及主链碳自由基（在β位具有羟基）的β-断裂反应，以及在高于熔点的温度下从五元环中夺取氢以产生α-羟基碳自由基·CH（OH）-。这些推断的过程中涉及的PP织物的热降解的支持由其他分析方法，包括差示扫描量热法（DSC），热重分析（TGA），和动态力学分析（DMA）。
The thermal degradation mechanism of poly(propylene) (PP) fabric from room temperature to 220 °C was analyzed using the electron spin resonance (ESR) spin-trapping technique. This method was adopted to prolong the lifetime of the short-lived radical intermediates generated by thermal degradation with the object of inspecting their molecular structure. A spin-trapping reagent, 2,4,6-tri‑tert-butylnitrosobenzene (TTBNB), was impregnated into the PP fabric using supercritical CO2(scCO2) treatment in the presence of a co-solvent. The impregnation efficiency and effect were evaluated using proton nuclear magnetic resonance (1H NMR) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM). ESR analysis showed that the degradation of PP is initiated from the tertiary carbon positions via two pathways: homolysis to generate ·CH3and −CH2−·CH−CH2− radicals, and hydrogen abstraction to generate −CH2−·C(CH3)−CH2− radicals. These radicals are also attacked by oxygen to form hydroperoxides, which then decompose to form the alkoxy radicals −CH2−CH(O·)−CH2− and −CH2−C(CH3)(O·)−CH2−. These radicals are involved in the subsequentβ-scission reactions that produce primary and secondary carbon radicals. Alkoxy radicals also take part in theβ-scission reactions involving the main chain carbon radicals, which have a hydroxyl group in theβ-position, and in hydrogen abstraction from a five-membered ring at temperatures higher than the melting-point to produce anα‑hydroxyl carbon radical, ·CH(OH)−. These inferred processes involved in the thermal degradation of PP fabric were supported by other methods of analysis, including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA).