Modified melamine-formaldehyde resins improve tensile strength along with antifouling and flame retardancy in impregnation of cellulose paper

Solvents that produce cellulose nanocrystals (CNCs) and promote cellulose fibrillation are of current interest. In this work, CNCs were fabricated from cotton at 80 and 100 degrees C using deep eutectic solvents (DESs) having choline chloride/oxalic acid dihydrate (OA) ratios of 1:1, 1:2 and 1:3. To investigate the side effects of the fabrication, the crystal structure and morphology of micro-sized treated cellulose together with nano-sized CNCs were analyzed by X-ray diffraction, field emission scanning electron microscopy and atomic force microscopy. OA promoted the formation of carboxyl groups on the C6 positions of molecules on the hydrophilic (1-10) lattice planes, causing extensive fibrillation of cellulose and disruption of surface layers on (110) and (200) planes.

可制备纤维素纳米晶体（cellulose nanocrystals, CNCs）并促进纤维素原纤化的溶剂，是当前广受关注的研究对象。本研究以氯化胆碱/二水合草酸（choline chloride/oxalic acid dihydrate, OA）摩尔比分别为1:1、1:2及1:3的低共熔溶剂（deep eutectic solvents, DESs）为反应介质，在80℃与100℃条件下从棉花中制备得到CNCs。为探究该制备过程的副效应，研究人员通过X射线衍射（X-ray diffraction）、场发射扫描电子显微镜（field emission scanning electron microscopy）与原子力显微镜（atomic force microscopy），对经处理的微米级纤维素以及纳米级CNCs的晶体结构与形貌进行了表征分析。OA可促进纤维素分子C6位羧基的形成，且该反应主要发生在亲水的(1-10)晶面，进而引发纤维素大规模原纤化，并破坏(110)与(200)晶面的表层结构。