Nanocellulose
This naming distinction might arise from the very peculiar morphology of these materials compared to the more traditional ones made of wood or cotton cellulose.
A. Battista showed that in milder hydrolysis conditions, the crystalline nanorods stay aggregated as micron size objects.
[14][15] This material was later referred to as microcrystalline cellulose (MCC) and commercialised under the name Avicel by FMC Corporation.
[16] Microfibrillated cellulose (MFC) was discovered later, in the 1980s, by Turbak, Snyder and Sandberg at the ITT Rayonier labs in Shelton, Washington.
[citation needed] Rather, Turbak et al. pursued 1) finding new uses for the MFC, including using as a thickener and binder in foods, cosmetics, paper formation, textiles, nonwovens, etc.
[22] Nanocellulose materials can be prepared from any natural cellulose source including wood, cotton, agricultural[23] or household wastes,[24] algae,[25] bacteria or tunicate.
[citation needed] To address this problem, sometimes enzymatic/mechanical pre-treatments and introduction of charged groups for example through carboxymethylation or TEMPO-mediated oxidation are used.
[27][28] Functionalized nanofibers obtained using nitro-oxidation have been found to be an excellent substrate to remove heavy metal ion impurities such as lead,[29] cadmium,[30] and uranium.
[34][35] Spherical shaped carboxycellulose nanoparticles prepared by nitric acid-phosphoric acid treatment are stable in dispersion in its non-ionic form.
[41] Aggregate widths can be determined by CP/MAS NMR developed by Innventia AB, Sweden, which also has been demonstrated to work for nanocellulose (enzymatic pre-treatment).
[55] Multi-parametric surface plasmon resonance is one of the methods to study barrier properties of natural, modified or coated nanocellulose.
Chemical vapour deposition of a fluorinated silane was used to uniformly coat the aerogel to tune their wetting properties towards non-polar liquids/oils.
The authors demonstrated that it is possible to switch the wettability behaviour of the cellulose surfaces between super-wetting and super-repellent, using different scales of roughness and porosity created by the freeze-drying technique and change of concentration of the nanocellulose dispersion.
Olsson et al.[69] demonstrated that these networks can be further impregnated with metalhydroxide/oxide precursors, which can readily be transformed into grafted magnetic nanoparticles along the cellulose nanofibers.
Notably, these highly porous foams (>98% air) can be compressed into strong magnetic nanopapers, which may find use as functional membranes in various applications.
Nanocelluloses can stabilize emulsions and foams by a Pickering mechanism, i.e. they adsorb at the oil-water or air-water interface and prevent their energetic unfavorable contact.
Nanocelluloses form oil-in-water emulsions with a droplet size in the range of 4-10 μm that are stable for months and can resist high temperatures and changes in pH.
[70][71] Nanocelluloses decrease the oil-water interface tension[72] and their surface charge induces electrostatic repulsion within emulsion droplets.
[73] The emulsion droplets even remain stable in the human stomach and resist gastric lipolysis, thereby delaying lipid absorption and satiation.
[74][75] In contrast to emulsions, native nanocelluloses are generally not suitable for the Pickering stabilization of foams, which is attributed to their primarily hydrophilic surface properties that results in an unfavorable contact angle below 90° (they are preferably wetted by the aqueous phase).
[80] A bottom up approach can be used to create a high-performance bulk material with low density, high strength and toughness, and great thermal dimensional stability: cellulose nanofiber plate (CNFP).
[81] This structure gives CNFP its high strength by distributing stress and adding barriers to crack formation and propagation.
To reduce delamination, the hydrogel can be treated with silicic acid, which creates strong covalent cross-links between layers during hot pressing.
Nanocelluloses were demonstrated to exhibit limited toxicity and oxidative stress in in vitro intestinal epithelium[85][86][87] or animal models.
[101] Wet-end surface application of mineral pigments and MFC mixture to improve barrier, mechanical and printing properties of paperboard are also being explored.
[48][107] Nanocellulose has been reported to improve the mechanical properties of thermosetting resins, starch-based matrixes, soy protein, rubber latex, poly(lactide).
Hybrid cellulose nanofibrils-clay minerals composites present interesting mechanical, gas barrier and fire retardancy properties.
Nanocellulose can be used as a low calorie replacement for carbohydrate additives used as thickeners, flavour carriers, and suspension stabilizers in a wide variety of food products.
In April 2013 breakthroughs in nanocellulose production, by algae, were announced at an American Chemical Society conference, by speaker R. Malcolm Brown, Jr., Ph.D, who has pioneered research in the field for more than 40 years, spoke at the First International Symposium on Nanocellulose, part of the American Chemical Society meeting.
It is thus possible to manufacture totally bio-based pigments and glitters, films including sequins having a metallic glare and a small footprint compared to fossil-based alternatives.
