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Thermal stabilization of TEMPO-oxidized cellulose

机译：TEMPO氧化纤维素的热稳定性

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摘要

A partially C6-carboxylated cellulose with carboxylate content of 1.68 mmol/g was prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation of a softwood bleached kraft pulp. Thermogravimetric analyses of the TEMPO-oxidized cellulose (TOC) and its related materials were studied to improve thermal stability of the TOC. Thermal decomposition (T_d) points of the TOC with sodium carboxylate groups, alkali-treated TOC with free carboxyl groups of 0.23 mmol/g and the original cellulose were 222 ℃, 264 ℃ and 275 ℃, respectively. Thus, the anhydroglucuronic acid units formed by TEMPO-mediated oxidation of the native wood cellulose and present in the TOC cause the decrease in Td point by decarbonation during heating process. When carboxyl groups in the TOC were methylated with trimethylsilyl diazomethane (TMSCHN_2), the T_d point increased from 222 ℃ to 249 ℃, and the peak temperature in its derivative thermogravimetric (DTG) curve increased from 273 ℃ to 313 ℃, which was almost equal to that of the original cellulose. Thus, the methyl esterification of carboxyl groups in the TOC is effective in improving thermal stability. When sodium ions present in the TOC as counter ions of carboxylate groups were exchanged to some other metal ions, thermal stability was improved to some extent. Especially, when CaCl_2, Ca(OAc)_2, Ca(NO_3)_2 and CaI_2 solutions were used in the ion-exchange treatments, the peak temperatures in the DTG curves increased to approximately 300 ℃. MgCl_2, NiCl_2, SrCl_2 and Sr(OAc)_2 solutions were also effective to some extent in increasing the peak temperatures of DTG curves. Thus, thermal stability of the fibrous TOC can be improved to some extent by methyl esterification of the sodium carboxylate groups present in the original TOC with TMSCHN_2 or ion-exchange treatments with some metal salt solutions.
机译：通过2,2,6,6-四甲基哌啶-1-氧基（TEMPO）介导的软木漂白牛皮纸浆的氧化反应，制备了羧酸含量为1.68 mmol / g的部分C6-羧化纤维素。研究了TEMPO氧化纤维素（TOC）及其相关材料的热重分析，以提高TOC的热稳定性。带有羧酸钠基团的TOC，具有0.23 mmol / g游离碱的碱处理过的TOC和原始纤维素的热分解（T_d）点分别为222℃，264℃和275℃。因此，由TEMPO介导的天然木材纤维素的氧化形成并存在于TOC中的脱水葡萄糖醛酸单元会在加热过程中因脱碳而导致Td点降低。当三甲基甲硅烷基重氮甲烷（TMSCHN_2）甲基化TOC中的羧基时，T_d点从222℃增加到249℃，其导数热重（DTG）曲线的峰值温度从273℃增加到313℃，几乎相等到原始纤维素的因此，TOC中羧基的甲基酯化对于改善热稳定性是有效的。当存在于TOC中的作为羧酸根抗衡离子的钠离子交换为其他一些金属离子时，热稳定性在一定程度上得到了改善。特别是，当离子交换处理中使用CaCl_2，Ca（OAc）_2，Ca（NO_3）_2和CaI_2溶液时，DTG曲线中的峰值温度升高到大约300℃。 MgCl_2，NiCl_2，SrCl_2和Sr（OAc）_2溶液在提高DTG曲线的峰值温度方面也有一定程度的效果。因此，可以通过用TMSCHN_2对原始TOC中存在的羧酸钠基进行甲基酯化或对某些金属盐溶液进行离子交换处理，从而在一定程度上改善纤维状TOC的热稳定性。

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  • 来源
    《Polymer Degradation and Stability》 |2010年第9期|p.1502-1508|共7页
  • 作者

    Hayaka Fukuzumi; rnTsuguyuki Saito; rnYusuke Okita; rnAkira Isogai;

  • 作者单位

    Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi Bunkyo-ku, Tokyo 113-8657, Japan;

    rnDepartment of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi Bunkyo-ku, Tokyo 113-8657, Japan;

    rnDepartment of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi Bunkyo-ku, Tokyo 113-8657, Japan;

    rnDepartment of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi Bunkyo-ku, Tokyo 113-8657, Japan;

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  • 原文格式 PDF
  • 正文语种 eng
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  • 关键词

    TEMPO-oxidized cellulose; thermal stability; thermal decomposition; methyl ester; ion-exchange; decarbonation;

    机译：TEMPO氧化纤维素;热稳定性;热分解;甲酯离子交换;脱碳;

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