纳米纤维制备过程中酶处理对分散性能的影响

Effect of enzymatic treatment on fiber dispersion characteristics during nanofiber preparation

植物纤维原料中少量的纤维素、半纤维素及木质素之间存在着醚键、酯键和苯基糖苷键等化学键联结,形成木质素碳水化合物复合体(LCCs),而这种共价键联接可能使微纤丝难以彻底解离成纳米纤维,由此影响到纳米纤维的分散及稳定性能.试验以漂白硫酸盐云杉木浆为原料,经打浆、磨浆及高压均质处理的常规制备纳米纤维流程,在高压均质前增加木聚糖酶/漆酶体系处理环节,研究探讨其对纳米纤维分散及稳定性能的影响.结果表明,经木聚糖酶和漆酶处理后,红外吸收光谱分析发现在811 cm-1处的半乳葡甘聚糖、896 cm-1处异头碳(C1)伸缩振动、1 056 cm-1处苯环伸展振动(木素)、1 161 cm-1处C-O-C不对称伸展振动、1 460 cm-1处-CH2变形振动(木质素苯环间侧链)等特征吸收峰强度均明显减弱或消失,表明存在于微纤丝之间的半纤维素和木质素发生降解,LC键发生断裂.同时,经过木聚糖酶和漆酶处理后,SEM显示纤维结构变得疏松、表面裂纹及孔隙变大;经高压均质处理后制得的纳米纤维,其水相分散及稳定性能得到明显提高.

Lignin-carbohydrate complexes （LCCs） , formed by ether, ester or phenyl glycoside bond among cellulose, hemicelluloseand lignin in lignocellulosic material, add difficulty on dissociating microfiber into nanofiber, thus adversively affecting dispersionand stability of fiber. To develop treatments that increase stability of nanofiber isolated from conventionally bleached spruce kraftpulp, xylanase/laccase treatment was added before high-pressure homogenization. Fourier transform infrared spectroscopy （FTIR）spectra demonstrated reduced or disappeared characteristic absorption peaks at 811, 896, 1 056, 1 161and 1 460 cm-1, whichcould be attributed to galactoglucommannan, anomeric carbon stretching vibration, benzene stretching vibration （lignin） , C-O-Casymmetric stretching vibration and -CH2 deformation vibration, respectively. Reduced characteristic absorption peaks indicated de-graded hemicellulose and lignin, which were products after the covalent linkages between lignin and carbohydrates （LC bonds） wereremoved. Moreover, scanning electron microscopic （SEM） images of fibers subjected to xylanase/laccase treatment confirmed thatxylanase/laccase treated fibers had looser structure, larger pores and cracks, resulting in improved stability and dispersibility ofnanofibers in aqueous solution.