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The objective of this work was to find a rapid, high-yield process to obtain an aqueous stable colloid suspension of cellulose nanocrystals/whiskers. Large quantities are required since these whiskers are designed to be extruded into polymers in the production of nano-biocomposites. Microcrystalline cellulose (MCC), derived from Norway spruce (Picea abies), was used as the starting material. The processing...
Suspensions of negatively charged cellulose nanocrystal are obtained by sulfuric acid hydrolysis of cotton cellulose. Within a specific concentration range, the suspensions spontaneously phase separate to give isotropic and chiral nematic phases. Added anionic dyes of varying charge cause separation of an isotropic phase from the highly concentrated, completely anisotropic suspensions; these dyes...
In an attempt to prepare stable dispersions of cellulose nanocrystals in dipolar aprotic solvents, dilute aqueous suspensions of cellulose nanocrystals were prepared by sulfuric acid hydrolysis of cotton. The aqueous suspensions were freeze-dried, and then sonicated in the solvent of interest. Dispersions of 1 and 3% w/v concentration were prepared in polar organic solvents DMSO and DMF. The dispersions...
There is a resurgence of interest in composite materials incorporating cellulose as fibrous reinforcement in semicrystalline melt-processed polymers. Potential natural cellulose sources range from flax and ramie fibres down to whiskers and nanocrystals isolated from bacteria. It has long been known that the crystallization of matrix polymers such as polypropylene may be preferentially nucleated by...
Synthesis of Ag nanopaticles was carried out with carboxylated cellulose nanocrystals as the scaffolds by reducing metallic cations using NaBH4. Ag particles with a size less than 10 nm were readily prepared and dispersed well. The carboxyl and hydroxyl groups of carboxylated cellulose nanocrystals supplied a coordination effect to adsorb metallic cations and Ag nanoparticles, which prevent the aggregation...
Cellulose nanocrystals (CNC) were first isolated from kenaf bast fibers and then characterized. The raw fibers were subjected to alkali treatment and bleaching treatment and subsequent hydrolysis with sulfuric acid. The influence of the reaction time on the morphology, crystallinity, and thermal stability of CNC was investigated. Fourier transform infrared spectroscopy showed that lignin and hemicellulose...
Aqueous suspensions of cellulose nanocrystals (NCC) produced by sulfuric acid hydrolysis of natural cellulose fibres display a number of unique properties. In addition to forming equilibrium chiral nematic phases above some critical concentration, cellulose nanocrystal suspensions tend to gel or aggregate if the stability of the suspension decreases, for example because of a decrease in the surface...
Cellulose nanocrystals (NCC) are produced through acidic hydrolysis and mechanical disintegration of cellulose. Plans to produce NCC on an industrial scale point to the need for an efficient method to characterize its suspensions. Viscosity is a bulk property that could be used for this characterization since it accurately describes the suspension and the inherent properties of the nanocrystals. Our...
Bamboo cellulose nanocrystals (CNCs) were successfully prepared from the sulfuric acid hydrolysis of bamboo bleached fibers. Reaction parameters such as temperature, acid-to-pulp ratio and hydrolysis time were varied over a limited range and conditions for the preparation of individual bamboo nanorods with a yield of 30 % were identified. The characteristics of bamboo CNCs were compared with those...
The chiral nematic self-assembly of aqueous suspensions of cellulose nanocrystals is partially preserved on evaporation of water, but the ordering of the rod-like nanoparticles may become distorted by changes in volume, ionic strength and surface and convective forces during evaporation, thus affecting the morphology and optical properties of the dried film. Proposed applications for these solids...
An in-depth analysis was performed of the molecular deformation mechanisms in cellulose during axial stretching. For the first time, it was demonstrated that entropy affects the stiffness of cellulose nanocrystals significantly. This was achieved through Molecular Dynamics simulations of model nanocrystals subject to constant stress in the axial direction, for nanocrystals of varying lateral dimensions...
The conditions required for the accurate measurement of the sulfur content of cellulose nanocrystals (CNCs) by conductometric titration are discussed. CNCs from sulfuric acid hydrolysis are electrostatically stabilized in aqueous suspension due to the introduction of charged sulfate ester groups onto the surface of the crystallites during reaction. The sulfur content thus largely reflects the surface...
Cellulose nanocrystals (CNC) prepared from eucalyptus cellulose CNCs were modified by the reaction with methyl adipoyl chloride, CNCm, or with a mixture of acetic and sulfuric acid, CNCa. The CNC were either dispersed at 0.1 wt% in the pure solvents ethyl acetate (EA), tetrahydrofuran (THF) and dimethylformamide (DMF) or in cellulose acetate butyrate (CAB) solutions prepared in these solvents at 0...
A method to produce predefined patterns in solid iridescent films of cellulose nanocrystals (CNCs) by differential heating of aqueous CNC suspensions during film casting has been discovered. Placing materials of different temperatures beneath an evaporating CNC suspension results in watermark-like patterns of different reflection wavelength incorporated within the final film structure. The patterned...
Polyurethane/Cellulose nanocrystal (CNC) nanocomposites have been prepared by means of in situ polymerization using CNCs as precursors of polyurethane chains. Thermal, mechanical and morphological characterization has been analyzed to study the effect of CNC on the micro/nanostructure, which consisted of individualized nanocellulose crystallites covalently bonded to hard and soft segments of polyurethane...
Self-organized multilayer films were formed by sequential addition of oppositely charged cellulose I nanoparticles. The all-cellulosic multilayers were prepared via adsorption of cationicially modified cellulose nanofibrils (cat NFC) and anionic short crystalline cellulose (CNC) at pH 4.5 and pH 8.3. The properties and build-up behavior of layer-by-layer-constructed films were studied with microgravimetry...
Cellulose nanocrystals (CNCs) have drawn tremendous attention because of their extraordinary physical and chemical properties as well as renewability and sustainability. In this work, after a range of pretreatments, such as freeze-drying, ball-milling, mercerization, N-methylmorpholine-N-oxide dissolution and ionic liquid dissolution, various CNCs with different crystalline properties and morphologies...
A new class of liquid crystalline thermosets (LCTs) was successfully produced containing lyotropic cellulose nanocrystals (CNCs) as the primary mesogenic component (up to 72 wt%) by the addition of non-mesogenic epoxy monomers. Cellulose-based LCTs were produced by totally aqueous processing methods and ultimately cured at elevated temperatures to produce ordered networks of ‘frozen’ liquid crystalline...
Cellulose nanocrystals (CNC), extracted from cellulose fibers by the mean of acid hydrolysis, were subjected to ring opening polymerization of d-Lactide initiated from the hydroxyl groups available at their surface. The resulting CNC-g-PDLA nanohybrids were incorporated in poly(l-lactide) (PLLA) matrix through melt-blending and the obtained nanocomposites were characterized in terms of their thermo-mechanical...
The study explores the potential of cellulose nanocrystals (CNC), cellulose nanofibers (CNF) and chitin nanocrystals (ChNC) isolated from bioresidues to remove silver ions from contaminated water. Zeta sizer studies showed negatively charged surfaces for CNC and CNF isolated from cellulose sludge in the acidic and alkaline pHs, whereas ChNC isolated from crab shell residue showed either positive or...
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