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High-strength cellulose nanofibers produced via swelling pretreatment based on a choline chloride–imidazole deep eutectic solvent
Green Chemistry ( IF 9.3 ) Pub Date : 2020/02/18 , DOI: 10.1039/c9gc04119b
Juho Antti Sirviö 1, 2, 3, 4 , Kalle Hyypiö 1, 2, 3, 4 , Shirin Asaadi 5, 6, 7 , Karoliina Junka 5, 6, 7 , Henrikki Liimatainen 1, 2, 3, 4
Affiliation  

A deep eutectic solvent (DES) based on choline chloride and imidazole (CCIMI) was investigated for swelling of cellulose fibers prior to mechanical disintegration into cellulose nanofibers (CNFs). The dimensions of the DES treated and washed fibers were investigated after various treatment conditions (time, temperature, and cellulose consistency) using DES based on choline chloride–urea (CCUrea) and pure imidazole as references. Even mild treatment conditions (15 minutes at 60 °C) with CCIMI increased the diameter of the fibers from 18.1 to 18.9 μm, and a maximum diameter of 19.9 μm was obtained after three hours at 100 °C. Overall, CCIMI resulted in a higher degree of swelling compared to both references. In addition, pure imidazole caused a decrease in the degree of polymerization of cellulose, whereas cellulose degradation in CCIMI was negligible. The mechanical disintegration of CCIMI-treated fibers resulted in the production of CNF films with very good mechanical properties—specific tensile strength and work capacity being over 200 kNm kg−1 and 10 kJ kg−1, respectively—whereas CNFs films produced using choline chloride–urea had notably lower values (182 kNM kg−1 and 7 kJ kg−1, respectively). In addition, CNF films exhibited good oxygen barrier properties, even at an elevated relative humidity level (80%). CCIMI could be recycled without any effect on the mechanical properties of CNF films. The results presented here indicate CCIMI is a highly efficient pretreatment media for swelling and further nanofibrillation of cellulose, even at mild treatment conditions.

中文翻译:

通过氯化胆碱-咪唑深共熔溶剂进行溶胀预处理制得的高强度纤维素纳米纤维

在机械崩解成纤维素纳米纤维(CNF)之前,研究了一种基于氯化胆碱和咪唑(C​​CIMI)的深共熔溶剂(DES)对纤维素纤维的溶胀。在各种处理条件(时间,温度和纤维素稠度)下,使用基于氯化胆碱-尿素(CCUrea)的DES和纯咪唑作为参考,研究了DES处理和洗涤后的纤维的尺寸。即使使用CCIMI进行温和的处理条件(在60°C下15分钟),纤维直径也从18.1μm增大到18.9μm,在100°C下放置3小时后,最大直径为19.9μm。总体而言,与两个参考文献相比,CCIMI导致更高程度的肿胀。此外,纯咪唑会降低纤维素的聚合度,而CCIMI中的纤维素降解可忽略不计。经过CCIMI处理的纤维的机械崩解导致生产出具有非常好的机械性能的CNF薄膜-比抗张强度和工作能力超过200 kNm kg分别为-1和10 kJ kg -1,而使用氯化胆碱-尿素生产的CNFs膜的值明显较低(分别为182 kNM kg -1和7 kJ kg -1)。另外,即使在较高的相对湿度水平(80%)下,CNF膜也表现出良好的阻氧性能。CCIMI可以回收利用,而不会影响CNF薄膜的机械性能。此处显示的结果表明,即使在温和的处理条件下,CCIMI还是一种用于纤维素溶胀和进一步纳米原纤化的高效预处理介质。
更新日期:2020-03-09
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