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Lyocell: Properties and applications
Abstract
This is a comprehensive article covering a wide range of characteristics of this widely used material. The definition of lyocell, a cellulose fibre obtained using an organic solvent spinning process is given together with explanations of the terms used. Physical properties noted include tensile strength, microscopic appearance, average diameter, and density. It is noted that is the strongest known cellulose fibre even when wet when it is stronger than cotton fibre. Table 2 lists the physical properties of lyocell fibres that are compared with three other fibres. Table 1 shows the manufacturer, country of manufacture and trade names for a variety of commercial fibres. Selected physical properties such as thermal, chemical and physiological properties are briefly noted. The penultimate paragraph discusses relatively new material, tencel denim, an indigo dyed material with better softness than traditional denim made from cotton. Table 3 lists the large variety of personal, home and industrial uses for lyocell.
... The calculated stability constants for the complexations between PZQ and a-, b-and g- CDs were 56.18, 396.91 and 15.17 M − 1 , respectively . The higher stability constant for the b-CD complex (396.91 M − 1 ) may reflect spatial compatibility of the guest PZQ molecule and the strength of the interaction by partial fit into the CD cavity (Szejtli, 1984 ). The lower stability constants given by the a-and g-complexes suggest weaker more labile interactions which would result in premature release of the drug. ...
... The lower stability constants given by the a-and g-complexes suggest weaker more labile interactions which would result in premature release of the drug. Only the b-CD complex had a stability constant within the limits reported to be suitable for pharmaceutical utilisation (Szejtli, 1984 ). Computer-aided modelling and 1 H NMR data indicated the formation of 1:1 complexes. ...
... M − 1 ), resulting in the fastest dissolution. Inclusion complexes with small stability constants have also been observed by other investigators (Uekama et al., 1983; Szejtli, 1984; Duchêne and Wouessidjewe, 1990), who have reported faster dissolution rates and extensive dissociation upon dissolution. The low stability constant for the a-CD complex suggests both a high solubility and a fast dissolution rate. ...
Although praziquantel (PZQ) is the primary drug of choice in the treatment of schistosomiasis, its poor solubility has restricted its delivery via the oral route. In spite of its poor solubility, PZQ is well absorbed across the gastrointestinal tract, but large doses are required to achieve adequate concentrations at the target sites. Improving the solubility would enable the parenteral route to be used, thereby avoiding significant first pass metabolism. The aqueous solubility of PZQ was improved by forming inclusion complexes with α-, β- and γ-cyclodextrins (CDs). These complexes were assessed and confirmed by solubility analysis, Fourier transform infrared analysis, elemental analysis, differential scanning calorimetry and mass spectrometry. Dissolution of PZQ from the α-, β- and γ-CD complexes was 2.6-, 5- and 8-fold greater, respectively, than that of the pure drug. However, only the β-complex had a stability constant in the optimum range for pharmaceutical use, suggesting that the preferred complex for further development would be a water-soluble β-CD derivative.
The basic aim is to study the resistance of corrosion and hardness of heat treatment of coatings with electro-less NiP -CNT. Various concentration of CNTs ranging, 0, 0.1, 0.2 and 0.4g/L in NiP -CNT composite was deposited on low alloy steel in electro-less immersion. The NiP -CNT electro-less coatings were prepared by using nickel chloride as a source for nickel in the alkaline bath and used CNT. The formulas were characterized with means of EDS, SEM, micro hardness, surface roughness and corrosion measurements. Results of the micro hardness show that hardness higher (560 HV) was achieved for sample (Ni-B-0.1g/l CNT) heat treated. Results enhance that the concentration of CNTs caused the structure of as-coated NiP conversion from amorphous to crystalline. Compared to the NiP coating, the resistance of corrosion of composite coating (Ni-P-CNT) are better, and they become much better with the increase of the CNT concentration. The addition of CNT makes the coating denser, and the presence of CNT decreases the size of grain to the heat treated formulas but too much CNT deposited on the substrate leads to a high region of the CNT wrapped together and the resulting agglomeration that occur is very unfavorable to coating, resulting in the lead resistance of the corrosion of the composite coating which becomes worse
Alkali treatment can change the structures and properties of cellulosic fibers. The paper was to study the mechanism of structure changes of Tencel fibers treated with different alkali concentration and two treatment methods. Raman spectrum showed that the molecular conformation of Tencel fibers remained unchanged. XRD (X-ray diffraction) indicated that the crystallinty of Tencel fibers in original length increased while that of fibers in relaxation condition remained unchanged. The average crystallite size increased and the orientation index decreased. The quasi-crystallite disassociation and recrystallization in the quasi-crystalline phase during the process of alkali treatment lead to the changes of the crystallinity and the orientation index of Tencel fibers.
A high sensitive NO2 gas sensor with rapid response and recovery at low temperature was fabricated with zinc phthalocyanine (1) that was found to have the room-temperature crystallization and higher-temperature liquid crystalline properties. A good response and reliable concentration dependence signal towards NO2 at the concentration range of 0.1–5 ppm were observed at the optimum temperature of 60 °C. As a result, this sensor is a high sensitive, low-temperature-operated and easy-fabricated all-organic NO2 sensing candidate to be used in the practical environment.
An amorphous mechanically alloyed Co67B33 powder has been compacted by hot forging at 200, 300, 400, 500, 700°C applying a load up to 2 GPa in 2 seconds. The density approaches the theoretical value operating under inert gas at 700°C. The alloy structure changes from amorphous to crystalline. Hardness and wear resistance of the material forged at 700°C are superior to those of the starting amorphous alloy as well as to those of an alloy of identical composition obtained by conventional slow cooling of the melt.
Traces the development of Tencel by courtaulds and compares the fibre properties of Tencel to those of cotton, viscose and polyester. The advantages of the fibre include strength, biodegradability, low shrinkage and launderability. The cellulose fibre industry, based on woodpulp, is claimed to have a lower environmental impact compared to synthetics.
Research efforts in the field of cellulose solvents are reviewed. Current solvent systems for the commercial processing of cellulose are summarized. Among the systems described, only amine oxides appeared to offer a viable alternative to existing methods for the production of cellulose fibres. Staple fibre production based on amide oxide processing is a promising technology.
Lyocell is a man-made but ecofriendly cellulosic fibre with a number of interesting properties, notably high wet strength and fibrillation. The authors provide a background sketch of this new fibre, looking at: history and trade names; spinning of lyocell; fibre properties; yarn manufacture; warping, sizing and weaving; and applications.
THE development of new methods for nucleating and growing
microporous crystals has made available new framework structures and
morphologies for these technologically important materials1.
These approaches have included solution-based synthesis2 and the
use of simple organic structure-directing agents3 and complex
organic assemblies such as liquid-crystal phases4,5. Here we
show that the growth of microporous zincophosphate6–8 with
the sodalite structure can be controlled by preparing the crystals from
reactants included within the interior aqueous phase of reverse micelles
dispersed in an organic solvent. The growth of inorganic phases in reverse
micelles has been exploited previously for the preparation of monodisperse
oxide9, semiconductor10 and metal
particles11. In this study, we introduce the two inorganic
components—zinc and phosphate ions—in separate micelles, so that
crystallization is controlled by the collision and exchange kinetics of the
surfactant structures. Moreover, the surfactant–water interface provides
the site for crystal nucleation, favouring initial nucleation at the
(111) and/or (110) crystal faces and subsequent growth of
the zinco-phosphate crystals by deposition along the {100} faces. The
growth process is ultimately interrupted by sedimentation when the crystals
grow large enough, producing a precipitate of micro-crystals several hundred
nanometres in size. Our results indicate that this approach can provide a means
of controlling the morphology as well as the size of growing crystals.