Quantitative analysis of crosslinking junctions of vulcanized natural rubber through rubber-state NMR spectroscopy
Quantitative analysis of crosslinking junctions of vulcanized natural rubber through rubber-state NMR spectroscopy
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通过橡胶态核磁共振光谱定量分析硫化天然橡胶的交联点
DOI：
10.1016/j.polymertesting.2021.107130
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发表时间：
2021
期刊：
影响因子：
5.1
通讯作者：
Kawahara Seiichi
中科院分区：
文献类型：
--
作者：
Saito Takayuki;Yamano Masaki;Nakayama Kazumi;Kawahara Seiichi
采用一种新的分析方法--橡胶态核磁共振波谱对天然橡胶(NR)硫化胶的交联结和未交联侧硫基进行了定量分析。采用硫黄、氧化锌、硬脂酸和N-叔丁基苯并噻唑-2-亚磺酰胺(TBBS)为促进剂和硫黄、氧化锌、硬脂酸为促进剂的两种配方对天然橡胶进行硫化。用溶胀法和橡胶态核磁共振波谱对所得硫化胶进行了表征，分别测定了交联度、交联点的硫原子数和交联点的结构。用二维核磁共振技术将天然橡胶硫化胶的~(13)C和~1H核磁共振谱中出现的小信号归属于交联点、未交联侧基硫化基团及其邻近基团。在指认的基础上，根据天然橡胶硫化胶的信号强度，估算了作为交联点的CH与硫磺的连接量与CH与硫磺的连接量的比例。
Rubber-state nuclear magnetic resonance (NMR) spectroscopy, a novel analytical method, was applied to quantitative analyses of crosslinking junctions and uncrosslinked pendant sulfidic groups for natural rubber (NR) vulcanizates. NR was vulcanized with two formulations:i.e., one including sulfur, ZnO, stearic acid andN-tert-butylbenzothiazole-2-sulfenamide (TBBS) as an accelerator and the other including sulfur, ZnO and stearic acid without the accelerator. The resulting NR vulcanizates were characterized by swelling methods and rubber-state NMR spectroscopy to determine crosslink density, number of sulfur atoms at crosslinking junctions and structure of crosslinking junctions, respectively. Small signals appearing in rubber-state13C and1H NMR spectra for the NR vulcanizates were assigned to crosslinking junctions, uncrosslinked pendant sulfidic groups and their neighboring groups by two-dimensional NMR spectroscopy. Based on the assignments, a proportion of the amount of CH linking to sulfur as the crosslinking junctions to total amount of CH linking to sulfur were estimated from intensities of the signals for the NR vulcanizates.