Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati 781 039, India.
Waste Manag. 2010 May;30(5):814-20. doi: 10.1016/j.wasman.2009.12.013. Epub 2010 Feb 8.
In this work, a product distribution study from thermal degradation of low-density polyethylene (LDPE) is presented. Thermal degradation of the polymer was investigated under dynamic condition in an inert environment using a thermo-gravimetric analyzer (TGA) coupled with evolved products' analysis using a gas chromatograph (GC). Fractions evolved at nine different temperatures from 200 to 600 degrees C were injected into GC for a detailed product analysis. The main objective of the present investigation is to highlight the species-specific evolution profiles of LDPE pyrolyzates (C5-C44) at different stages of its degradation under an inert environment. Pyrograms have been analyzed in terms of amount of different products evolved at various pyrolysis temperatures. Volatile pyrolyzates essentially remain low at low decomposition temperature (200-300 degrees C) of the polymer, which gradually increase to attain a maximum at maximum decomposition temperature (470 degrees C) and finally level off at 600 degrees C. In the mechanistic approach adopted to understand the decomposition mechanism of LDPE, the following reaction types were considered: (a) main chain cleavage to form chain-terminus radicals; (b) intramolecular hydrogen transfer to generate internal radicals; (c) intermolecular hydrogen transfer to form both volatile products and radicals; and (d) beta-scission to form both volatiles and terminally unsaturated polymer.
本工作介绍了低密度聚乙烯（LDPE）热降解产物分布研究。采用热重分析仪（TGA）在惰性环境下对聚合物进行动态热降解研究，并结合气相色谱仪（GC）分析逸出产物。在 200 至 600°C 的九个不同温度下，将逸出的馏分注入 GC 进行详细的产物分析。本研究的主要目的是在惰性环境下，突出 LDPE 热解物（C5-C44）在其降解的不同阶段的特征特定演化曲线。通过分析不同热解温度下不同产物的生成量对热谱图进行分析。在聚合物的低分解温度（200-300°C）下，挥发性热解物的含量基本保持较低水平，然后逐渐增加，在最大分解温度（470°C）下达到最大值，最后在 600°C 时趋于稳定。在采用的理解 LDPE 分解机制的机械方法中，考虑了以下反应类型：（a）主链断裂形成链端自由基；（b）分子内氢转移生成内部自由基；（c）分子间氢转移形成挥发性产物和自由基；和（d）β-断裂形成挥发性产物和端不饱和聚合物。
