Abstract Conventional thermogravimetry (TG) is a common method for studying thermal degradation and/or thermal oxidation of polymers. However, the temperature range for isothermal TG studies is limited to regions close to the melting temperature, where thermal degradation and/or thermal oxidation proceed slowly. Higher temperatures cannot be reached because thermal degradation and/or thermal oxidation start upon heating, even using the highest possible heating rate of the conventional TG. The method of fast scanning calorimetry (FSC) to obtain a quasi-real-time isothermal TG curve via a nanogram-weight sample (nano-TG method) was reported. During the 50 cycles of FSC measurements of polypropylene (PP) between room temperature and 300 °C, regardless of air flow, all FSC traces were consistent with each other (i.e., thermal oxidation of PP was fully suppressed during the fast scanning). On the other hand, when the sample was annealed for a few seconds at 300 °C during the cyclic FSC runs, the apparent heat capacity (which can be converted into relative weight) decreased with increasing total annealing time. The decrease in apparent heat capacity is explained by the progression of thermal oxidation. The nano-TG method was applied to determine the thermal oxidation kinetics of PP using the Avrami-Erofeev model. The non-isothermal TG curve calculated from the kinetic parameters of the nano-TG analysis was in good agreement with the experimental data obtained from the conventional TG measurements for the early stage of weight loss. The present method is applicable for the thermal degradation/oxidation analysis of microplastics in the environment or small impurity analysis of polymers.

中文翻译：

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快速扫描量热仪等温热重法及其在纳克级聚丙烯等温氧化中的应用

摘要 常规热重法 (TG) 是研究聚合物热降解和/或热氧化的常用方法。然而，等温 TG 研究的温度范围仅限于接近熔化温度的区域，在那里热降解和/或热氧化进行得很慢。无法达到更高的温度，因为热降解和/或热氧化在加热时开始，即使使用常规 TG 的最高可能加热速率。报道了快速扫描量热法（FSC）通过纳克级样品获得准实时等温热重曲线的方法（纳米热重法）。在室温和 300 °C 之间聚丙烯 (PP) 的 50 次 FSC 测量循环期间，无论气流如何，所有 FSC 迹线都彼此一致（即，PP 的热氧化在快速扫描过程中被完全抑制）。另一方面，当样品在循环 FSC 运行期间在 300 °C 下退火几秒钟时，表观热容（可以转换为相对重量）随着总退火时间的增加而降低。表观热容的降低是由热氧化的进展来解释的。使用 Avrami-Erofeev 模型，应用纳米 TG 方法来确定 PP 的热氧化动力学。从纳米TG分析的动力学参数计算的非等温TG曲线与从常规TG测量获得的失重早期的实验数据非常吻合。