Characterization of Volatile Nylon 6.6 Thermal-Oxidative Degradation Products by Selective Isotopic Labeling and Cryo-GC/MS
Characterization of Volatile Nylon 6.6 Thermal-Oxidative Degradation Products by Selective Isotopic Labeling and Cryo-GC/MS
复制标题
通过选择性同位素标记和冷冻 GC/MS 表征挥发性尼龙 6.6 热氧化降解产物
DOI：
10.1007/s13361-012-0415-x
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发表时间：
2012
影响因子：
3.2
通讯作者：
J. Hochrein
中科院分区：
文献类型：
--
作者：
J. N. Smith;G. White;M. White;R. Bernstein;J. Hochrein
老化的材料，如聚合物，可以表现出其化学结构和物理性质的变化，这可能使材料对其预期目的无效。同位素标记用于表征尼龙6.6的低分子量挥发性热氧化降解产物，以更好地理解和预测老化聚合物的变化。来自老化（在138 °C下长达243天）的尼龙6.6单体（己二酸和1，6-己二胺）和聚合物的顶空气体被预浓缩、分离并使用低温聚焦气相色谱质谱（cryo-GC/MS）检测。将各色谱峰相对于老化时间的相对浓度观察结果与环境空气下老化样品的质谱图结合使用，以确定18种降解产物的存在和鉴别。通过比较美国国家标准与技术研究院（NIST）文库、未标记和同位素标记质谱（C-13或N-15）以及各降解产物的预期裂解途径，确定产物化学结构中同位素标记原子的位置，随后可用于确定物质的确切来源。此外，使用在富含O-18的气氛中老化的未标记尼龙6.6的观察结果来确定适用降解产物中的氧来源是来自气态环境还是聚合物。适当时，报告未标记产品与标记产品的相对同位素比的近似值。
Aged materials, such as polymers, can exhibit modifications to their chemical structure and physical properties, which may render the material ineffective for its intended purpose. Isotopic labeling was used to characterize low-molecular weight volatile thermal-oxidative degradation products of nylon 6.6 in an effort to better understand and predict changes in the aged polymer. Headspace gas from aged (up to 243 d at 138 °C) nylon 6.6 monomers (adipic acid and 1,6-hexanediamine) and polymer were preconcentrated, separated, and detected using cryofocusing gas chromatography mass spectrometry (cryo-GC/MS). Observations regarding the relative concentrations observed in each chromatographic peak with respect to aging time were used in conjunction with mass spectra for samples aged under ambient air to determine the presence and identity of 18 degradation products. A comparison of the National Institute of Standards and Technology (NIST) library, unlabeled, and isotopically labeled mass spectra (C-13 or N-15) and expected fragmentation pathways of each degradation product were used to identify the location of isotopically labeled atoms within the product’s chemical structure, which can later be used to determine the exact origin of the species. In addition, observations for unlabeled nylon 6.6 aged in an O-18 enriched atmosphere were used to determine if the source of oxygen in the applicable degradation products was from the gaseous environment or the polymer. Approximations for relative isotopic ratios of unlabeled to labeled products are reported, where appropriate.