Abstract

The influence of the alkaline delignification of hemp on its moisture uptake has been studied under the project “Preparation and functionalization of hemp for textile substrates” focussed on the reduction of cotton imports for the manufacturing of clothing, household textiles and medical devices. The project looks for the partial replacement of cotton by hemp on the production of natural cellulosic textiles. Hemp fibres are alkaline delignified at different times to evaluate its effect on their moisture uptake behaviour to evaluate the ability of replacing cotton in the next-to-skin goods manufacturing. The paper gives three easy tools to analyse the moisture uptake behaviour by determining the sorption ratio, the hysteresis and the parameters of the isotherms fitted using three different models (GAB, Hailwood-Horrobin and Dent) to the absorption desorption isotherms. The samples of the original and delignified hemp have been subjected to moisture absorption/desorption trials from 5% to 95% RH at 25 °C. Sorption ratio and hysteresis reveal the greater influence of lignin on moisture uptake at low relative humidities, while at high, was cellulose which plays the most important role. The models fitted to the isotherms show that delignification decreases the size of the monolayer that, in desorption results always greater than in absorption. The energy constants of the monolayer for delignified fibres in absorption were higher than those for the original fibres, while the opposite occurred in desorption. Lignin caused great differences between absorption and desorption. The energy constants of the multilayer show a greater range of variation in delignified samples than in the original one, and results in absorption were higher than those in desorption. Delignification time of 3 h reached the highest cellulose content which best approached to the cellulose content of cotton causing that the moisture uptake behaviour drew near to it, especially at higher relative humidity.

摘要

在“用于纺织基材的大麻的制备和功能化”项目下，研究了大麻的碱性脱木质素对其吸湿性的影响，该项目的重点是减少用于制造服装、家用纺织品和医疗器械的棉花进口。该项目在天然纤维素纺织品的生产中寻找部分用大麻替代棉花。大麻纤维在不同时间进行碱性脱木质素，以评估其对其吸湿行为的影响，以评估在贴身商品制造中替代棉花的能力。本文提供了三种简单的工具，通过确定吸附比、滞后和使用三种不同模型（GAB、Hailwood-Horrobin 和 Dent) 到吸收解吸等温线。原始大麻和去木质大麻样品已在 25 °C 下进行了 5% 至 95% RH 的吸湿/解吸试验。吸附比和滞后表明木质素在低相对湿度下对水分吸收的影响更大，而在高相对湿度下，纤维素起着最重要的作用。拟合等温线的模型表明，脱木质作用减小了单层的尺寸，在解吸中的结果总是大于在吸收中的结果。脱木质素纤维的单层在吸收时的能量常数高于原始纤维的能量常数，而在解吸时则相反。木质素引起吸收和解吸之间的巨大差异。多层的能量常数在去木质样品中显示出比原始样品更大的变化范围，并且吸收的结果高于解吸的结果。脱木素时间 3 h达到最高的纤维素含量，最接近棉花的纤维素含量，导致吸湿行为接近它，特别是在较高的相对湿度下。