天然竹纤维的固态核磁共振谱表征

Characterization of Native Bamboo Fiber using Solid-State ^(13)C-CP/MAS NMR Spectroscopy

利用固态核磁共振碳谱分析研究了天然竹纤维的结晶结构,并与常规的天然纤维素纤维苎麻、亚麻和棉纤维进行了比较。研究表明竹纤维的结晶度、晶粒尺寸与苎麻相似,大于棉纤维和亚麻纤维。利用13C NMR分析计算出了竹纤维中纤维素的晶型含量,结果显示,竹纤维的晶型与棉纤维、苎麻和亚麻相似,纤维素Ⅰβ占优势。利用核磁共振谱计算的几种纤维素纤维的结晶度和晶粒尺寸小于利用X射线衍射计算的结果,只有对于高结晶度的纤维如竹纤维和苎麻偏差才比较小,主要原因在于NMR分析对小范围的有序更为敏感,只有晶区内的材料才能看作结晶区。

Crystalline structure of bamboo fiber was investigated by solid-state ^13C-CP/MAS NMR spectroscopy, and was compared to ramie, flax and cotton. The result showed that the crystallinity and crystallite sizes of bamboo fibers were similar to those of ramie fibers, but larger than those of cotton fiber and flax fiber. The allomorph contents in bamboo fibers were calculated by ^13C NMR and the result indicated that bamboo fibers were Ⅰβ-dominant type, which was similar to other native cellulose fibers. Crystallinity and crystalline size calculated by NMR method are less than the value by X-ray diffraction. Only to the fiber having high degree of crystallization, such as bamboo fiber and ramie fiber, the two methods was relatively small deviations. The reason is that the intensity of crystalline signal depends on the number of carbon atoms presented within crystallite in ^13C NMR spectra.