Guiles Celeste H, Benitez Yanice, Morales Gavin N, Engerer Jeffrey D, Hernandez-Sanchez Bernadette A, Minton Timothy K
Smead Department of Aerospace Engineering Sciences, University of Colorado Boulder, 3775 Discovery Drive, Boulder, Colorado 80303, United States.
Fire Science and Technology, Sandia National Laboratories, Albuquerque, New Mexico 87123, United States.
ACS Appl Mater Interfaces. 2025 Jul 9;17(27):39526-39541. doi: 10.1021/acsami.5c06849. Epub 2025 Jun 24.
Most pyrolyzing ablative heat shields contain phenolic resin; therefore, an understanding of the thermal decomposition mechanisms of this material can provide a foundation upon which to develop improved materials response models, which can, in turn, lead to better heat shield design and performance prediction. With the goal of obtaining high-fidelity data on the thermal decomposition mechanisms of phenolic materials, a baseline study of the gaseous pyrolysis products from the phenolic resin derived by curing Durite SC-1008 has been conducted. Product yields were detected by a mass spectrometer as a function of sample temperature, over the range of 25-1200 °C, at five linear temperature gradients with respect to time (0.83, 3.03, 5.83, 11.54, and 23.11 °C s) with the use of a molecular beam mass spectrometry sampling method similar to the method used in earlier work by [Bessire, B. K.; Minton, T. K. 2017, 9, 21422-21437]. Quantitative molar and mass yields of 15 gaseous products have been determined as a function of temperature, and thermogravimetric analysis curves have been synthesized from the temperature-dependent mass yield data and measurements of total mass loss. Both the molar and mass yields exhibit temperature-gradient dependencies, as decomposition mechanisms compete and the residence time at each temperature may be comparable to or shorter than mass diffusion and heat conduction time scales. The total mass loss increases with an increase in the rate of temperature change, as a result of the competition between condensation and methylene bridge scission reactions, which was proposed previously, and this competition combined with the direct breakdown of backbone phenolic groups contributes to the changing molar yields. The new high-fidelity pyrolysis data provide mechanistic insight into the thermal decomposition of phenolic resin that can be used as a benchmark for understanding and modeling the pyrolysis of carbon phenolic composites that are used in thermal protection systems on space vehicles.
大多数热解烧蚀隔热罩都含有酚醛树脂；因此，了解这种材料的热分解机制可以为开发改进的材料响应模型提供基础，进而有助于更好地进行隔热罩设计和性能预测。为了获得关于酚醛材料热分解机制的高保真数据，对固化杜里特SC - 1008得到的酚醛树脂的气态热解产物进行了基线研究。使用与[贝西雷，B.K.；明顿，T.K. 2017, 9, 21422 - 21437]早期工作中使用的方法类似的分子束质谱采样方法，在25 - 1200°C范围内，以相对于时间的五个线性温度梯度（0.83、3.03、5.83、11.54和23.11°C/s），通过质谱仪检测产物产率随样品温度的变化。已确定了15种气态产物的定量摩尔产率和质量产率随温度的变化情况，并根据与温度相关的质量产率数据和总质量损失测量结果合成了热重分析曲线。由于分解机制相互竞争，且每个温度下的停留时间可能与质量扩散和热传导时间尺度相当或更短，摩尔产率和质量产率均表现出对温度梯度的依赖性。由于之前提出的缩合反应和亚甲基桥断裂反应之间的竞争，总质量损失随温度变化速率的增加而增加，这种竞争与主链酚基的直接分解共同导致了摩尔产率的变化。新的高保真热解数据为酚醛树脂的热分解提供了机理见解，可作为理解和模拟用于航天器热防护系统的碳酚醛复合材料热解的基准。
