Abstract One of the major limiting factors in fire modelling involving solid pyrolysis of polymer materials is the fundamental understanding of thermal degradation process from solid fuel to gas volatiles. This also brings along other challenges such as the characterisation of the parent combustion fuel in the gas-phase chemical reaction process. To bridge the knowledge gap, this article proposes a methodology applying molecular dynamics (MD) simulation as a tool to characterise the thermal degradation process of polymer composites, especially the emission of volatile and toxic gas species. The method was applied to three common engineering polymers: i) high-density polyethene (HDPE), ii) polymethyl methacrylate (PMMA), and iii) high-impact polystyrene (HIPS). Based on the modelling results, the chemical distribution of the fully-decomposed chemical compounds was realised for the selected polymers. The chemical composition and charring kinetics were validated against thermogravimetry data via experimental measurement. Numerical simulations demonstrated good agreement with the thermogravimetric analysis experiments. It was found that all HDPE, PMMA, and HIPS formed fuel gas with alkane group (i.e. mainly C1-C3) that acted as the combustible source. Furthermore, the composition of char formations for the selective polymers can be predicted by the MD simulation through analysing the accumulation of pure carbon chain compounds. In this study, MD simulation identified the detailed decomposition process from solid to gas phases, which could further act as the precursors of combustible fuel gases in combustion models, and significantly enhance the reliability of toxic gas, charring, and smoke particulate predictions.

中文翻译：

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通过反应分子动力学 (ReaxFF) 表征工程聚合物的热解动力学和详细的气体种类形成

摘要 涉及聚合物材料固体热解的火灾建模的主要限制因素之一是对从固体燃料到气体挥发物的热降解过程的基本理解。这也带来了其他挑战，例如气相化学反应过程中母体燃烧燃料的表征。为了弥补知识差距，本文提出了一种方法，将分子动力学 (MD) 模拟作为表征聚合物复合材料热降解过程的工具，尤其是挥发性和有毒气体种类的排放。该方法应用于三种常见的工程聚合物：i) 高密度聚乙烯 (HDPE)，ii) 聚甲基丙烯酸甲酯 (PMMA)，和 iii) 高抗冲聚苯乙烯 (HIPS)。根据建模结果，对于选定的聚合物，实现了完全分解的化合物的化学分布。通过实验测量，根据热重分析数据验证了化学成分和炭化动力学。数值模拟证明与热重分析实验非常吻合。发现所有HDPE、PMMA和HIPS都形成了作为可燃源的具有烷烃基团（即主要是C1-C3）的燃料气。此外，通过分析纯碳链化合物的积累，可以通过 MD 模拟预测选择性聚合物的炭形成组成。在这项研究中，MD 模拟确定了从固相到气相的详细分解过程，这可以进一步作为燃烧模型中可燃气体的前体，