Cellulose

A multicenter, 2-visit, open-label, 4-week study was conducted to determine the acceptability of hydroxypropyl cellulose ophthalmic inserts in adult patients with a history of dry eye syndrome (DES). At visit 1, patients (N = 520) were evaluated, screened by slit-lamp biomicroscopy, and completed the Ocular Surface Disease Index (OSDI), a validated measure of quality of life. Patients were trained in the proper placement and use of hydroxypropyl cellulose ophthalmic inserts and were contacted by telephone on day 3 of the study. At week 4, patients were given a clinical evaluation and completed a second questionnaire. Answers determined changes in symptoms and quality of life. Adverse events were monitored throughout the study. Four hundred eighteen patients completed the study and reported significant improvements in discomfort, burning, dryness, grittiness, stinging, and light sensitivity (P = .05) after 4 weeks use of hydroxypropyl cellulose ophthalmic inserts. Significant improve...

Because of their mechanical properties and low density, flax fibers seem to be competitive with glass fibers. However, these fibers present a non-uniformity in many of their characteristics (non-constant diameter along the fiber, variable length, presence of defects). This leads to a dispersion of their mechanical properties. This study focuses on the development of fully biodegradable green composites based on poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) matrix reinforced by flax fibers to determine their elastic characteristics and to analyze their tensile and flexural failure in order to evaluate the influence of the processes on the mechanical properties. The main task is to incorporate flax fibers of several millimeters into the polymer matrix and study of the influence of the twin-screw extrusion and single-screw extrusion which are used for the elaboration of the compound and after the injection of the materials. The first objective is to identify the optimal parameters of the manufacturing processes which permit to elaborate satisfactory products presenting acceptable mechanical properties. The study aims to understand the effect of the introduction of flax reinforcements from a thermal and mechanical point of view. From the main results, the thermal analyses show that the introduction of 20% PBS into the PLA matrix improves the thermal stability of PLA and increases the onset temperature of decomposition. The mechanical characterizations have shown that the stiffness of the resulted composites has been improved after the incorporation of the flax fibers from 1457MPa to 4353MPa compared to the matrix. On the contrary, a decrease in deformation rate was observed owing the addition of flax fibers from 4.4% to 1.9%. These preliminary results show the possibility to develop new bio-composites which are thermoplastic, recyclable, with configurable mechanical properties depending on the selected matrix.

In order to further understand the role of the cation when dissolving cellulose in aqueous solutions of hydroxide bases, different bases were combined in solution. Up to 5 wt.% of microcrystalline cellulose was dissolved using a combination of NaOH and the organic base tetramethylammonium hydroxide (TMAH) in water at low temperatures. Thermoscans of solutions containing both NaOH(aq) and TMAH(aq) indicated that cellulose interaction with TMAH seems to be favoured over NaOH. Dynamic rheology measurements of the solutions revealed that combining the two bases delayed gelation significantly when compared to cellulose dissolved in NaOH(aq) or TMAH(aq) alone. Intrinsic viscosity of cellulose in the combined NaOH- and TMAH(aq) solutions was slightly higher than that of the single-base solutions, indicating a slight increase in solvent quality. This shows that combining bases may lead to synergies that improve solvent stability without requiring the use of other additives. Graphic abstract

Cellulose nanofibers with a size range of 5–100 nm have the potential to be a low cost renewable material that has application in a range of products. However, current chemical methods to produce crystalline nanofibers suffer from low yields and high chemical costs, while mechanical methods require high energy costs. Methods to lower the energy costs of the mechanical methods have not been well documented in the literature. A bleached softwood kraft pulp was processed using a mechanical dispersion mill and a homogenizer to produce cellulose nanofibers. Two different commercial enzymes were used to pretreat the wood fibers before the mechanical treatments. The resulting nanofibers were characterized by light microscopy, atomic force microscopy, and inverse gas chromatography. Results indicate that the dispersion mill does not affect the overall pulp fiber fibrillation, but does help prepare the sample for the homogenizer. Most fibrillation occurs after three passes through the homogenizer. The enzyme pretreatment has little effect on the size of the fibers, but does allow for higher solids to pass through the homogenizer without clogging. The dispersion component of surface energy of the resulting nanofibrils is impacted by the type of enzyme used. The measurement of acid–base properties proved to be challenging using current IGC experimental protocols.

Environmental issues such as the depletion of non-renewable energy resources, pollution, and saturation of landfills need more scientific attention in order to be addressed in a way beneficial to life. The extent of solid waste production is a global concern and the recovery of cellulosic components can solve this problem. This paper describes how cellulosic biomass and wastepaper materials, major components of solid wastes, can be treated to produce biofuel and recycled raw materials.

Use of pyrolytic carbon from cellulose has been limited in practice to activated adsorbent carbon, but cellulose-derived carbon retaining the nanoscale microfibrillar morphology offers rich possibilities as an advanced material. Here we developed novel methods to prepare such materials by an improved drying of wet cellulose prior to pyrolysis. This procedure is an adaptation from electron microscopy techniques, i.e. rapid freeze drying of suspension and solvent exchange drying, both being effective in preventing coagulation of cellulose microfibrils/microcrystals. Pyrolytic carbon from such material has a large external surface area, with the graphitic carbon crystallites roughly aligned along the fiber axis. These features are potentially useful in developing novel carbon nanomaterials for electrodes, catalyst supports, or composite material elements.

In this study, we propose a convenient method for testing the fibrillation tendency of man-made cellulosic fibres (MMCFs) and investigate the possibility to apply a commercial crosslinker for Tencel fibres on the ionic liquid-based regenerated cellulosic fibre (Ioncell fibre). The fibrillation tendency of various MMCFs including viscose, Modal, Tencel and Ioncell fibres were examined through wet abrasion by using ball bearing and blending methods. The fibrillation tests using a laboratory blender was found to be a superior method over the ball bearing method in terms of time and energy saving. The fibrillation tendency of the fibres highly depended on their cellulose molecular orientation and the treatment intensity (time, temperature and alkalinity) in the blender. This fibrillation method was also applied to discover the effect of the crosslinking on the fibrillation tendency of the fibres. The Ioncell fibre proved to be suitable for crosslinking treatment to reduce fibrillation u...

Cellulose  TiO 2 nanoparticles  dielec-tric properties  electrical conductivity  epichlorohydrin  glutardialdehyde This work deals with preparation, characterization and dielectric evaluation of cellulose/titanium dioxide nanopartic-les. These nanocomposites were successful prepared via emulsion technique in the presence of two different crosslin-kers such as epichlorohydrin and glutar-dialdehyde. The nanocomposites were characterized using infrared spectrosco-py, thermogravimetric analysis, scanning and transmitting electron microscopes and the dielectric measurements were investigated. The results indicated that TiO 2 was physically adsorbed and distributed between the cellulosic fibers. Du to the polarization effect, the dielectric parameters were increased in the case of using epichlorohydrin, while they had low values in the case of using glutardialdehyde. The presence of TiO 2 enhanced the AC conductivity. Rationelles Design von Cellulose/ Titandioxid-Nanokompositen Cellulose  TiO 2-Nanopartikel  dielekt-rische Eigenschaften  elektrische Leit-fähigkeit  Epichlorhydrin  Glutardial-dehyd Diese Arbeit befasst sich mit der Vorbe-reitung, Charakterisierung und dielektri-schen Bewertung von Cellulose/Titan-dioxid-Nanopartikeln. Diese Nanokom-posite wurden erfolgreich in Emulsions-technik in Gegenwart von den zwei verschiedenen Vernetzern Epichlorhyd-rin und Glutardialdehyd hergestellt. Die Nanokomposite wurden mittels Inf-rarotspektroskopie, Thermogravimetrie, Raster-und Transmissionselektronen mikroskopie charakterisiert und hin-sichtlich den dielektrischen Eigenschaf-ten untersucht. Die Ergebnisse zeigten, dass TiO 2 zwischen den Zellulosefasern physikalisch adsorbiert und verteilt war. Im Vergleich zum Polarisationseffekt waren die dielektrischen Eigenschaften im Fall der Verwendung von Epichlorhy-drin erhöht, während sie bei der Ver-wendung von Glutardialdehyd ernied-rigt sind. Figures and Tables: By a kind approval of the authors.

The rate of interaction between the CS2 and the alkali solution was studied in presence as well as in absence of cellulose.The sulphide and trithiocarbonate were considerably higher in presence of cellulose, even in the earliest period of the reaction where it was still far away from the equilibrium state; this is most probably due to catalytic, respectively autocatalytic effect of the cellulose. Increasing the agitation velocity resulted into higher rates of sulphide and thiocarbonate formation, either in presence or in absence of cellulose proving that the reaction is mainly a diffusion one. Emulsion xanthation is chiefly governed by the diffusion of the CS2 into the alkali solution and to a lesser extent by the diffusion of the dissolved CS2 into the cellulose fibres. Hence, reactivity or rate curves measurements, by applying light agitation, are considerably governed by the rate of diffusion of CS2 into the alkali solution, rather than the rate of diffusion of CS2 into the pulp supermolecular structure. Therefore, no accurate differentiation between the pulps according to their supermolecular resistance to diffusion could be obtained. On the other hand, intensifying the agitation velocity accelerates both diffusion processes and thus diminishes as well the diffusion resistance due to pulp supermolecular structure leading to slight differences between pulps. The diffusion of CS2 into the alkali solution was considerably eliminated by including or occluding the fibres with CS2 before adding the alkali solution. Xanthation was then carried out by applying the lightest possible agitation velocity. In this way, the rate of the reaction is mainly governed by diffusion resistance due to the pulp supermolecular structure and good differentiation between pulps was obtained.
By this method, CS2 less than 50% based on cellulose and 10% NaOH were sufficient to dissolve cellulose, especially of low DP, till 12 % conc. Inclusion respectively occlusion before or after partial alkalization in one or more step was favorable in technical fibrous xanthation.

The development of solid materials which are able to upconvert optical radiation into photons of higher energy is attractive for many applications such as photocatalytic cells and photovoltaic devices. However, to fully exploit triplet-triplet annihilation photon energy upconversion (TTA-UC), oxygen protection is imperative because molecular oxygen is an ultimate quencher of the photon upconversion process. So far, reported solid TTA-UC materials have focused mainly on elastomeric matrices with low barrier properties because the TTA-UC efficiency generally drops significantly in glassy and semicrystalline matrices. To overcome this limit, for example, combine effective and sustainable annihilation upconversion with exhaustive oxygen protection of dyes, we prepare a sustainable solid-state-like material based on nanocellulose. Inspired by the structural buildup of leaves in Nature, we compartmentalize the dyes in the liquid core of nanocellulose-based capsules which are then further ...

Disintegration performance was measured by analysing both water ingress and tablet swelling of pure microcrystalline cellulose (MCC) and in mixture with croscarmellose sodium using terahertz pulsed imaging (TPI). Tablets made from pure MCC with porosities of 10% and 15% showed similar swelling and transport kinetics: within the first 15 s, tablets had swollen by up to 33% of their original thickness and water had fully penetrated the tablet following Darcy flow kinetics. In contrast, MCC tablets with a porosity of 5% exhibited much slower transport kinetics, with swelling to only 17% of their original thickness and full water penetration reached after 100 s, dominated by case II transport kinetics. The effect of adding superdisintegrant to the formulation and varying the temperature of the dissolution medium between 20°C and 37°C on the swelling and transport process was quantified. We have demonstrated that TPI can be used to non-invasively analyse the complex disintegration kineti...