Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador São Carlense, 400, 13566-590 São Carlos, SP, Brazil.
Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador São Carlense, 400, 13566-590 São Carlos, SP, Brazil.
Carbohydr Polym. 2019 Dec 1;225:115232. doi: 10.1016/j.carbpol.2019.115232. Epub 2019 Aug 24.
Chitins and Chitosans with different degrees of deacetylation (DD¯) were analyzed for the first time by thermogravimetry coupled to infrared spectroscopy TG-FTIR in order to evaluate the effect of DD¯ on the thermal decomposition process. DD¯ values of chitins and chitosans were determined by H-NMR and structural difference were investigated by FTIR, SEM and XRD. Thermal stability of chitosan with 98, 87, 71% DD¯, chitins with 47 and 27% DD¯ and commercial α-chitin were evaluated. Thermal decomposition of chitosans occurs in two steps, while for chitins occurs predominantly in first stage under air atmosphere. Commercial chitin thermally decomposed at lower temperatures than highly deacetylated chitosan. A faster thermal degradation process was found for chitins, except for commercial sample. TG-FTIR of evolved gas evidenced a complex gaseous mixture mainly composed by ammonia, acetic acid, acetamide, water, monoxide and carbon dioxide in proportions that are deeply dependent on the DD¯.
首次通过热重分析-傅里叶变换红外光谱联用（TG-FTIR）对不同脱乙酰度（DD¯）的壳聚糖和几丁聚糖进行了分析，以评估 DD¯对热分解过程的影响。通过 1H-NMR 确定了壳聚糖和几丁聚糖的 DD¯值，并通过 FTIR、SEM 和 XRD 研究了结构差异。评估了 DD¯值分别为 98、87、71%的壳聚糖、DD¯值分别为 47 和 27%的几丁聚糖和商业 α-几丁质的热稳定性。在空气气氛下，壳聚糖的热分解分为两步进行，而几丁聚糖的热分解主要发生在第一阶段。与高度脱乙酰化的壳聚糖相比，商业几丁质在较低温度下热分解。发现几丁质的热降解过程较快，商业样品除外。气体逸出物的 TG-FTIR 表明，气体混合物主要由氨、乙酸、乙酰胺、水、一氧化碳和二氧化碳组成，其比例与 DD¯密切相关。
