木素对TEMPO氧化竹浆制备纳米纤维素的影响

Effect of Lignin on Nanocellulose Preparation by TEMPO-mediated Oxidation from Bamboo Pulp

中文关键词:  未漂竹浆  TEMPO氧化  纳米纤维素  薄膜  强度

Key Words:unbleached kraft bamboo pulp  TEMPO oxidation  nanocellulose  films  strength

中文摘要:

      以卡伯值不同的2种未漂硫酸盐竹浆(卡伯值为25.5和11.7的竹浆分别标记为SHK和SLK)为原料,通过TEMPO/NaBr/NaClO体系氧化及高压均质处理,制备了TEMPO氧化纳米纤维素(TOCN),并利用抽滤法制备TOCN膜。系统地研究了2种竹浆的TEMPO氧化过程、TEMPO氧化浆性能、TOCN性能及TOCN膜的力学性能等,探讨了木素对竹浆TEMPO氧化过程和TOCN制备的影响。结果表明,SHK的TEMPO氧化速率高于SLK,但SLK-TEMPO氧化浆的羧基含量达到1.01 mmol/g,高于SHK-TEMPO氧化浆的羧基含量(0.89 mmol/g)。2种TOCN形态结构差异不大,均呈纤丝状结构,直径约为5～8 nm,长径比>100,且均保持纤维素I的晶型结构；SLK-TOCN的结晶度和悬浮液的透光度均略高于SHK-TOCN。2种TOCN膜均具有优良的光学性能和力学性能,SLK-TOCN膜的杨氏模量、拉伸强度及裂断伸长率分别为2.6 GPa、92 MPa和10.9%,均高于SHK-TOCN膜的2.4 GPa、90 MPa和8.7%。

Abstract:

      TEMPO-oxidation cellulose nanofibers (TOCNs) were prepared from unbleached kraft bamboo pulps (SHK, Kappa No.=25.5; SLK, Kappa No.=11.7) by means of TEMPO/NaBr/NaClO oxidation and subsequent homogenization. The TOCN films were prepared by vacuum filtration. During the TEMPO-oxidation processes, the properties of TEMPO oxidized pulps, TOCNs and TOCN films of SHK and SLK were compared, the effect of lignin on TEMPO-oxidation process and TOCN production was studied. Results showed that the TEMPO-oxidation rate of SHK was faster than SLK, but the carboxyl content of SLK-TEMPO oxidized pulp was 1.01 mmol/g, much higher than SHK-TEMPO oxidized pulp (0.89 mmol/g). The obtained TOCNs exhibited a fibril-like structure, with a narrow width ranging from 5 nm to 8 nm and a high aspect ratio (>100), and the TOCNs were cellulose-I. The suspension transparency and crystalline index of SLK-TOCN were higher than SHK-TOCN. The two kinds of TOCN films displayed good optical and mechanical performance, and the Yong’s modules, tensile strength, and the elongation of SLK-TOCN film were 2.6 GPa, 92 MPa, and 10.9%, respectively, all of them were higher than the SHK-TOCN film which were 2.4 GPa, 90 MPa, and 8.7%, respectively.