Abstract Pyrolysis of a phenolic polymer is a well-known heat removal mechanism in charring ablators, but the process has not been well-quantified. Here, we perform scale-bridging molecular dynamics (MD) simulations based on a reactive-force-field (ReaxFF) potential to elucidate the pyrolysis kinetics of a highly crosslinked phenolic formaldehyde resin. We show that bulk pyrolysis starts at temperatures of ∼500 K, and exhibits a temperature dependence that follows the Arrhenius law. The pyrolysis process initiates with the removal of –OH functional groups and –H atoms from aromatic C rings within the bulk phenolic resin to release H2O, followed by breaking of these C rings to release C-based fragments. Using the pyrolysis rates from MD simulations, we develop a thermal material response model applied to predict the heat transfer within a charring syntactic foam ablator. Our model predictions of the char thickness and temperature distributions, under a variety of heat loads, are in good agreement with prior experiments.

中文翻译：

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烧蚀热保护系统：通过尺度桥接分子动力学进行热解建模

摘要 酚类聚合物的热解是炭化烧蚀器中众所周知的散热机制，但该过程尚未得到很好的量化。在这里，我们基于反应力场 (ReaxFF) 潜力进行了尺度桥接分子动力学 (MD) 模拟，以阐明高度交联的酚醛树脂的热解动力学。我们表明，本体热解在约 500 K 的温度下开始，并表现出遵循阿伦尼乌斯定律的温度依赖性。热解过程开始于从本体酚醛树脂内的芳族 C 环中去除 –OH 官能团和 –H 原子以释放 H2O，然后破坏这些 C 环以释放基于 C 的片段。使用来自 MD 模拟的热解速率，我们开发了一种热材料响应模型，用于预测炭化复合泡沫消融器内的热传递。我们在各种热负荷下对炭厚度和温度分布的模型预测与先前的实验非常一致。