Cellulose Hydrate Research Articles

On the influence of additions of phthalocyanine metal complexes on the low temperature pyrolysis of cellulose hydrate

A study was made of the initial stage of pyrolysis of the cellulose hydrate fibre in the presence of cobalt and copper phthalocyanine additives. The temperature of the onset of degradation is lower in the presence of an additive, and the process of degradation of the cellulose elementary unit is initiated. It proceeds with the formation of intermediate furan rings. At T ∼ 300° C the modifier inhibits the depolymerization process. In the same temperature interval the modifier interacts with degradation products, and is incorporated in the carbon structure that is formed.

Structure and permeability of composite carboxyl membranes based on cellulose hydrate

Gas adsorption and mercury porometry have been used to study the porosity of composite ion-exchange membranes represented by porous cellulose hydrate with a microdispersion of a crosslinked carboxyl cation-exchanger incorporated into the structure. The permeability of these membranes at different degrees of ionization of the carboxyl in relation to the hydrogen ions has been studied for a fixed difference in the pH values on the two sides of the membrane. The rate constants of the forward and back reactions of interaction of hydrogen ions with the carboxyl groups of the membrane have been evaluated.

Experience of polymeric film application for abdominal cavity drainage

In the Emergency Surgery Clinic of Kazan Emergency Medical Care Hospital since July 1986, for drainage of abdominal cavity after operations for various purulent processes, drains prepared from 10-50 microns thick elastic hydratecellulose film are used. A sheet of film is folded in the form of an accordion into a package with a rib width of 0.5-1 cm and a length of 10-30 cm; such a package usually has 10-15 planes. The draining effect of the hydrate cellulose film drainage is maintained throughout its stay in the abdominal cavity. However, such drainage also has certain disadvantages.

Structure and Transport Properties of the Ultracell Membrane for Hemodialysis

Particular features of structure and transport properties of a new Soviet-made hydrate cellulose membrane Ultracell have been studied. The membrane has a structure of a swollen gel with well defined macropores that ensures high effectiveness in convectional transport of substances across the membrane. In view of the above the Ultracell membrane may be used both for conventional hemodialysis and also for hemodialysis with simultaneous or consecutive ultrafiltration aimed at removing the excessive water and metabolites with middle molecular weight.

Effect of the reaction between cellulose hydrate and water vapour on the properties of its hydrogels

The problem of the interaction between cellulose hydrate and water in the vapour and in the liquid phase is considered with cellulose-hydrate membranes with an open structure being taken as an example. Under conditions of enhanced humidity, it has been shown that a tendency is observed towards the postcrystallization of the hydrocellulose which leads to densification of the structure because of the formation of new physical nodes and the ratio between the free and the combined water in the gel is displaced towards a reduction in the amount of the former. This results in a change in the membranes' permeability with respect to water and with respect to substance dissolved in water.

Detection of a Metalloproteinase in Patients with Acute and Chronic Renal Failure

The effect of different dialyzer membrane materials (cuprophan, cellulose hydrate, polyacrylonitrile, polymethylmethacrylate, ethylene-vinyl alcohol copolymer) on the ultrafiltrate proteinase activity was investigated in 26 patients with acute renal failure (ARF) and 40 patients undergoing regular hemodialysis treatment (RDT). Furthermore, the proteinase activity was characterized in vitro using azocasein and phosphorylase kinase as substrates in the absence and presence of different proteinase inhibitors. Proteinase activity of ultrafiltrates obtained from ARF patients was significantly enhanced with the dialyzer KF 101 (ethylene-vinyl alcohol copolymer). The digestion pattern of phosphorylase kinase revealed an identical type of proteinases in ultrafiltrates of ARF and RDT patients. The pH optimum of this proteinase was at alkaline pH. The proteinase activity could be inhibited in the presence of EDTA, whereas serine proteinase inhibitors were ineffective. Furthermore, the inactivated proteinase after Sephadex G-10 chromatography (in order to separate ultrafiltrate electrolytes and trace elements from protein) could be reactivated after the addition of Mg++ and/or Ca++. We conclude that a metalloproteinase can be found in ARF and RDT patients, and that KF 101 is more effectively eliminating the proteinase activity in ARF patients than other dialyzer membranes.

Plasma levels of granulocyte elastase during hemodialysis: Effects of different dialyzer membranes

Plasma levels of granulocyte elastase in complex with alpha 1-proteinase inhibitor during hemodialysis were investigated in 15 patients (37.4 +/- 3.2 years) undergoing maintenance hemodialysis (47.0 +/- 12.9 months) with dialyzers made from cellulose hydrate, cuprophan, polymethylmethacrylate, ethylene-vinyl alcohol copolymer, and polyacrylonitrile. Cellulose hydrate membrane caused a maximal increase of the plasma levels of granulocyte elastase in complex with alpha 1-proteinase inhibitor (E-alpha 1PI: 1,659.0 +/- 256.8 ng/ml). Patients dialyzed with polyacrylonitrile dialyzers failed to exhibit comparable plasma levels of granulocyte elastase (E-alpha 1PI: 237.8 +/- 22.9 ng/ml). During hemodialysis plasma E-alpha 1PI values rose to a peak 643.0 +/- 174.7 ng/ml in patients on polymethylmethacrylate dialyzers, to 557.5 +/- 120.0 ng/ml on cuprophan dialyzers, but to only 381.9 +/- 54.0 ng/ml on ethylene-vinyl alcohol copolymer dialyzers. Plasma lysozyme levels decreased significantly in the presence of polyacrylonitrile and polymethylmethacrylate membranes. We conclude that the degree of PMNs stimulation depends on the nature of the dialyzer membrane material. The following membranes induce a reaction of increasing intensity: polyacrylonitrile, ethylene-vinyl alcohol copolymer, cuprophan, polymethylmethacrylate, and cellulose hydrate.

Molecular mobility and relaxation transitions in cellulose hydrate fibres in the range 20–560 K

A study has been made of temperature dependences of the dynamic shear modulus G′, the loss tangent tan δ and the low frequency rate of shear waves c t for individual cellulose hydrate fibres. The investigation was carried out with the aid of a microminiature torsion pendulum (frequency ∼ 1 Hz) and covered the range 20–560 K. Measurements were performed under vacuum on fibre samples of length ∼ 1 mm. Some relaxational transitions were observed on curves of temperature dependences of these parameters and some propositions regarding their nature have been advanced. The variety of temperature transitions in the cellulose hydrate fibres is attributed to the existence of several levels of supermolecular organization not only for crystalline, but also for amorphous parts of this polymer.

Chain propagation and breaking reactions in photooxidation of cellulose

1. Photooxidation of hydrated cellulose (HC) is a chain process with short chains. The kinetic parameters of this process were determined. 2. The radicals responsible for the reaction of chain propagation in oxidation of HC were identified. 3. Photostable acceptors of alkyl radicals could be the most effective photostabilizers of HC.

Sodium kinetics across dialysis membranes.

The kinetics of sodium across dialysis membranes were studied during diffusion and during convection utilizing cuprophan and cellulose hydrate membranes. During diffusion the changes in plasma water sodium concentration are correlated to the sodium concentration gradient between plasma water and dialysate but an increase also occurs when the gradient is annulled, due to the Donnan effect. During convection the plasma water sodium concentration increases during the passage through the dialyzer and the ultrafiltrate sodium concentration is significantly lower than the plasma water sodium concentration; this is due to the fact that the plasma proteins, as anions unable to cross the membrane, affect the kinetics of the sodium cations. Therefore, during diffusion the kinetics of sodium are mainly affected by the sodium concentration gradient and by the plasma protein concentration, while during convection the plasma protein concentration is the main factor affecting the kinetics of sodium.

Hemodialysis leukopenia and complement function with different dialyzers

AbstractHemodialysis leukopenia and complement function with different dialyzers. The relationship between leukopenia and the complement system during hemodialysis was re-examined by studying not only the in vivo effects of four different dialyzer membranes (cellulose hydrate, cuprophan, cellulose acetate, and polyacrilonitrile) on leukocyte counts and complement levels, but especially by investigating the effects of these membranes on complement function in vitro. Whereas from in vivo studies no definite conclusions could be drawn, in vitro investigations provided clear-cut information. When more sophisticated technical approaches were undertaken, it became evident that hemodialysis leukopenia has to be thought of in terms of chemotactic factor generation. In fact, a strict correlation was demonstrated between the degree of leukopenia induced by the dialyzers tested and the ability of the relative membrane to generate chemotactic activity in vitro. Moreover, the previously observed ability of polyacrilonitrile membrane to induce a decrement in complement function was due to the ability of polyacrilonitrile to adsorb complement activity and did not correspond to effective complement consumption. This finding explained why polyacrilonitrile dialysis is not accompanied by a decrease in circulating granulocytes. Taken together, our data strongly point to a pivotal role of complement system in the pathogenesis of hemodialysis leukopenia.Leucopénie de l'hémodialyse et fonction du complément avec différents dialyseurs. La relation entre la leucopénie et le système complémentaire pendant l'hémodialyse a été réexaminée en étudiant non seulement les effets in vivo de quatre membranes de dialyse différentes (hydrate de cellulose, cuprophan, acétate de cellulose, et polyacrilonitrile) sur les numérations leucocytaires et les niveaux du complément, mais surtout en étudiant les effets de ces membranes sur la fonction complémentaire in vitro. Alors que des études in vivo aucune conclusion définitive ne pouvait être tirée, les études in vitro ont apporté des informations précises. Quand des approches techniques plus sophistiquées ont été utilisées, il est apparu évident que la leucopénie de l'hémodialyse doit être pensée en termes de génération de facteurs chimiotactiques. De fait, une corrélation stricte a été démontrée entre le degré de leucopénie induite par le dialyseur testé et la capacité de la membrane à générer une activité chimiotactique in vitro. En outre, la capacité préalablement observée de la membrane en polyacrilonitrile d'induire une diminution de la fonction complémentaire était dûe à la capacité du polyacrilonitrile d'absorber l'activité complémentaire, et ne correspondait pas à une consommation effective du complément. Ce résultat a expliqué pourquoi la dialyse au polyacrilonitrile n'était pas accompagnée par une diminution des granulocytes circulants. Prises dans leur ensemble, nos données mettent fortement l'accent sur un rôle-clé du système complémentaire dans la pathogénie de leucopénie de l'hémodialyse.

Biological decomposition efficiency in different woodland soils.

The decomposition (meaning disappearance) of different leaf types and artificial leaves made from cellulose hydrate foil was studied in three forests - an alluvial forest (Ulmetum), a beech forest on limestone soil (Melico-Fagetum), and a spruce forest in soil overlying limestone bedrock.Fine, medium, and coarse mesh litter bags of special design were used to investigate the roles of abiotic factors, microorganisms, and meso- and macrofauna in effecting decomposition in the three habitats. Additionally, the experimental design was carefully arranged so as to provide information about the effects on decomposition processes of the duration of exposure and the date or moment of exposure. 1. Exposure of litter samples oor 12 months showed: a) Litter enclosed in fine mesh bags decomposed to some 40-44% of the initial amount placed in each of the three forests. Most of this decomposition can be attributed to abiotic factors and microoganisms. b) Litter placed in medium mesh litter bags reduced by ca. 60% in alluvial forest, ca. 50% in beech forest and ca. 44% in spruce forest. c) Litter enclosed in coarse mesh litter bags was reduced by 71% of the initial weights exposed in alluvial and beech forests; in the spruce forest decomposition was no greater than observed with fine and medium mesh litter bags. Clearly, in spruce forest the macrofauna has little or no part to play in effecting decomposition. 2. Sequential month by month exposure of hazel leaves and cellulose hydrate foil in coarse mesh litter bags in all three forests showed that one month of exposure led to only slight material losses, they did occur smallest between March and May, and largest between June and October/November. 3. Coarse mesh litter bags containing either hazel or artificial leaves of cellulose hydrate foil were exposed to natural decomposition processes in December 1977 and subsampled monthly over a period of one year, this series constituted the From-sequence of experiments. Each of the From-sequence samples removed was immediately replaced by a fresh litter bag which was left in place until December 1978, this series constituted the To-sequence of experiments. The results arising from the designated From- and To-sequences showed: a) During the course of one year hazel leaves decomposed completely in alluvial forest, almost completely in beech forest but to only 50% of the initial value in spruce forest. b) Duration of exposure and not the date of exposure is the major controlling influence on decomposition in alluvial forest, a characteristic reflected in the mirror-image courses of the From- and To-sequences curves with respect to the abscissa or time axis. Conversely the date of exposure and not the duration of exposure is the major controlling influence on decomposition in the spruce forest, a characteristic reflected in the mirror-image courses of the From-and To-sequences with respect to the ordinate or axis of percentage decomposition. c) Leaf powder amendment increased the decomposition rate of the hazel and cellulose hydrate leaves in the spruce forest but had no significant effect on their decomposition rate in alluvial and beech forests. It is concluded from this, and other evidence, that litter amendment by leaf fragments of phytophage frass in sites of low biological decomposition activity (eg. spruce) enhances decomposition processes. d) The time course of hazel leaf decomposition in both alluvial and beech forest is sigmoidal. Three s-phases are distinguished and correspond to the activity of microflora/microfauna, mesofauna/macrofauna, and then microflora/microfauna again. In general, the sigmoidal pattern of the curve can be considered valid for all decomposition processes occurring in terrestrial situations. It is contended that no decomposition (=disappearance) curve actually follows an e-type exponential function. A logarithmic linear regression can be constructed from the sigmoid curve data and although this facilitates inter-system comparisons it does not clearly express the dynamics of decomposition. 4. The course of the curve constructed from information about the standard deviations of means derived from the From- and To-sequence data does reflect the dynamics of litter decomposition. The three s-phases can be recognised and by comparing the actual From-sequence deviation curve with a mirror inversion representation of the To-sequence curve it is possible to determine whether decomposition is primarily controlled by the duration of exposure or the date of exposure. As is the case for hazel leaf decomposition in beech forest intermediate conditions can be readily recognised.

Pervaporation of alcohol—water mixtures on cellulose hydrate membranes

The permeation rate and selectivity of pretreated cellulose hydrate membranes for binary mixtures of alcohols and water, as well as their pure components, were studied at 333 K. The membranes were modified by solvent pretreatment with isopropanol, water, or their binary mixtures, and by heat treatment in air. The permeation rate of membranes towards the pure components and their mixtures depends very strongly on the preswelling of the membrane. The data obtained with solvent mixtures differ significantly from those expected on the basis of the pure component permeation rate. With increasing pressure at the permeate side, the composition of permeate approaches the thermodynamic equilibrium vapour composition of the feed mixtures.

Supermolecular structure of graft copolymers of cotton and cellulose hydrate fibres with certain fluorine-containing polymers

The results of a study of the supermolecular structure of graft copolymers of cotton and viscose cellulose hydrate fibres with certain fluorine-containing polymers are presented in the present paper. It has been observed by a study of IR spectroscopic data that, in all the fluorine-containing copolymers from the cellulose fibres, a reduction occurs in the absorption band regions related to bonded hydroxyl groups and deformation vibrations of water (adsorbed on the cellulose) and new characteristic absorption bands for the fluorine-containing polymers appear. Optical and electron-microscopic observations have revealed a number of features of the supermolecular structure of graft fluorine-containing copolymers formed by cellulose fibres.

Structural transformations of cellulose hydrate during heat treatment in the presence of aluminum chloride

Structural transformations of cellulose hydrate during heat treatment in the presence of aluminum chloride

Phase transitions in amorphized rigid and semirigid polymers under heating

Features of phase transitions in amorphized rigid polymers have been investigated for polyphenylenebenzimidazoleterephthalamide and cellulose hydrate as examples. It is shown that successive phase transitions of amorphous polymer to the liquid-crystalline and crystalline states are possible ways of structural regrouping in these polymers.

A critical examination of the electron‐microscopical evidence for swollen hydrated cellulose fibrils in green plants

SUMMARYThe electron‐microscopical evidence for the existence of ‘nascent cellulose fibrils in green plants’ (Leppard, G.G. & Colvin, J.R., J. Microsc. 113 (1978), 181) is examined critically. It is concluded that images of pre‐shadowed carbon replicas which appear to show cell wall microfibrils having a sheath enclosing a core are unavoidable technical artefacts in which the sheath consists of the replicating carbon. This interpretation is supported by the finding of similar apparent sheaths around air‐dried microfibrils which were suspended above the main plane of the substrate surface at the time of replica‐making. It is shown that the impressions of microfibrils in fractured plasma membranes have greater cross‐sectional dimensions than the microfibrils themselves as a result of the relationship between the microfibrils and the plasma membrane, and that such impressions are not evidence of ‘nascent fibrils’. Furthermore, it is argued that there is no evidence at present which supports the hypothesis that a swollen, sheathed ‘nascent fibril’ of cellulose is produced by prokaryotic Acetobacter xylinum. A light core is demonstrated in images of unshadowed replicas of microfibrils and it is proposed that radiation damage may play a rôle in the formation of this image. It is demonstrated that the coincidence of Fresnel fringes around unshadowed defocused replicas of microfibrils can also lead to the formation of an apparent core. Problems associated with obtaining measurements from replicas of cell wall microfibrils are discussed and some recommendations are made.

Spectroscopic investigation of the orientational heterogeneity of cellulose hydrate

The spectroscopic method of attenuated total internal reflection in the IR region has been used to study the anisotropy in the absorption of commercial cellulose hydrate films. The relative change in molecular orientation in layers adjacent to the surface and in layers within the polymeric films have been assessed from the dichroism of the band at 1162 cm −1. It has been shown that the presence of a highly oriented sheath, whose degree of orientation and dimensions depend on the specimen thickness, is characteristic of the films. The lower orientation of the internal layers has been confirmed and it has been shown that there is a gradient in the molecular orientation, its distribution in the section being along the normal to the surface. The change in orientation on going from the surface to the internal layers is not monotonic in character. The existence of a maximum orientational heterogeneity across the section is peculiar to thin films of cellulose hydrate.

On the activation energy of the pyrolysis of intercrystallite amorphous portions of cellulose hydrate fibres

A method is suggested for kinetic investigation of the pyrolysis of intercrystallite amorphous portions of cellulose hydrate fibres, using low and wide angle X-ray scattering data. The activation energy E 2 obtained by this method for the pyrolysis of intercrystallite amorphous portions of cellulose hydrate fibres is 52±2 kcal/mole, which is equal to the value of E a for the initial stage of pyrolysis of the fibre as a whole, based on isotherms of weight loss for T ⪕ 290°. The initial stages of pyrolysis of the fibre at higher temperatures are characterized by E a = 30 kcal/mole. The reduction in E a at T ⪖ 290° is associated with a larger role played by processes of surface degradation, which is corroborated by a change in the fibre diameter as a result of pyrolysis.

Hydrodynamic and optical characteristics of cellulose macromolecules in cadoxene

The sedimentation S, translational diffusion D, intrinsic viscosity [η] and flow birefringence of solutions of cellulose linters in cadoxene have been studied over the range of molecular weights M = 2 × 103−7 × 105. The relationships obtained are [η] = 4·5 × 104M0.74, D = 7·2 × 10−5M−0.58 and S = 1.8 sx 10−15M0.42. The length of the Kuhn segment in a 1 : 1 mixture of cadoxene and water is A = 100 Å, which indicates the high rigidity of the cellulose molecule. In cadoxene cellulose has positive anistropy, (α1−α2) = 180 × 10−25 cm3, due mainly to the contribution of anisotropy of molecular shape. Replacement of cadoxene by a cadoxene-water mixture (1 : 1·9) brings about an increase in [η] and (α1−α2) as a result of increase in the rigidity of the polymer molecule. It is shown that the optical anisotropy of the cellulose molecule is the same, regardless of the nature of the cellulose (bacterial, cellulose hydrate, mercerized or linters).