Solutions Of Cellulose Nitrate Research Articles

Fabrication of cellulose acetate/cellulose nitrate/carbon black nanofiber composite for oil spill treatment

AbstractThere are global challenges in addressing the oil spill treatment. Nanofiber has become a great potential in the oil spill cleaning process because of the environmental friendliness, high efficiency, low cost, and stability of the obtained nanofiber mats. This study presents a novel composite fabricated from cellulose acetate (CA) and cellulose nitrate (CN) nanofibers with the incorporation of carbon black (CA-CN/CB) for efficient oil removal. This nanofiber composite was fabricated in one-step electrospinning of 10% CA and CN solution with different concentrations of carbon black (CB). The morphology and fiber diameter of the CA-CN/CB nanofiber composite were analyzed using scanning electron microscopy (SEM), and they appeared to be smooth, uniform fibers without beads. The average fiber diameter was in nano-meter size and increased with the increasing CB amount in the composite, ranging from 327 to 755 nm. The FTIR results indicated the presence of CA and CN as characteristic peaks of C = O for CA and O-NO2 for CN. The nanofibers mats of the CA-CN, CA-CN/CB0.7, CA-CN/CB1.5, and CA-CN/CB2.2 composites had Brunauer–Emmett–Teller (BET) surface area of 15.29, 38.40, 4.08, and 6.17 m2 g−1, respectively. Under optimal conditions, CA-CN/CB nanofiber mats absorb more than their weight oil in just 30 min. The adsorption result showed that loading 1.5% of CB to CA-CN mats (CA-CN/CB1.5) was more favorable for oil adsorption. The CA-CN/CB1.5 nanofiber showed its reusability for oil adsorption. The Freundlich isotherm model was the most appropriate model among other isotherm models, including Langmuir and Temkin, with a value of correlation coefficient (R2) equal to or closer to unity, and this result was confirmed by the data obtained from studying different error function models. The adsorption kinetics showed that oil adsorption into CA-CN/CB1.5 nanofiber follows a pseudo-second-order kinetics model with R2 close to unity.

Features of the Structure and Rheology of Nitrocellulose Solutions

The latest methods – rotation viscometry, IR spectroscopy, NMR spectroscopy, gel permeation chromatography, and the turbidity spectrum method – were used to investigate the structural, rheological, and molecular properties of cellulose nitrate solutions. Results clarified the laws governing the structure formation in medium- and semidilute cellulose nitrate solutions.

Experimental study of the flow of solutions of cellulose nitrate in a tube rotating about its own axis

An experimental study is made of the flow of solutions of cellulose nitrates in a stationary tube and a tube rotating about its own axis. Comparison of the results obtained from experimental and theoretical studies shows that they agree well with one another.

Residual stress and mechanical properties of Al2O3/ZrO2 functionally graded material prepared by EPD from 2‐butanone based suspension

Electrophoretic deposition (EPD) is an attractive forming process to fabricate plate shaped binary functionally graded materials (FGMs) from suitable stable suspensions. In the present work, the capability to produce Al2O3 and ZrO2 functionally graded bulk material by means of EPD from a non‐aqueous stable suspension based on 2‐butanone, n‐butylamine and cellulose nitrate solution is presented. The EPD processing parameters and sintering are described, and the density of the FGM composite, hardness, toughness and residual stresses are measured using indentation methods on cross‐sections of the sample. Scanning electron microscopy confirmed that the sintered body is an FGM.

Electrospun Cellulose Nitrate Nanofibers

Cellulose nitrate nonwoven mats of submicron-sized fibers (100-1200 nm in diameter) were obtained by electrospinning cellulose nitrate solutions. Two solvent systems were evaluated. A 70:30 (wt) ratio of ethanol to acetone and a 60:40 (wt) ratio of tetrahydrofuran (THF) to N,N-dimethylformamide (DMF) were studied. The effects of the two solvent systems, and type two different collectors; void gap, and steel drum coated with polyvinylidene dichloride (PVDC), were investigated. The PVDC layer applied to the rotating drum aided in fiber harvesting. Electron microscopy (FESEM and ESEM) studies of as-spun fibers revealed that the morphology of cellulose nitrate fibers depended on the collector type and solution viscosity. When a rotating steel drum was employed a random morphology was observed, while the void gap collector produced aligned fiber mats. Increases in viscosity lead to larger diameter fibers.

Cellulose nitrate-based multilayer composite membranes for gas separation

Cellulose nitrate (CN)-based composite hollow fiber membranes are prepared for gas separation. The membrane performance is studied in terms of the concentration of CN coating solution, polysulfone (PS) substrate, pre-wetting treatment, solvent used in CN solution, and the various substrate materials. In order to fabricate a useful multilayer composite membrane, the surface porosity of composite hollow fiber has to be reduced to a certain degree, before silicone rubber coating, by adjusting the CN coated layer and the PS substrate structure. The effect of pre-wetting treatment on the membrane performance is found to be minor, which may be due to the coating technique and the relatively highly permeable substrate used in this study. The solvent used in dissolving CN also affects the gas permselective property of the multilayer composite membranes and this effect may be attributed to the formation of different membrane morphology of CN layer caused by the different physical properties of solvents. The selection of substrate materials is important and this work suggests that a permeable material is more suitable to serve as the substrate. Besides, the substructure resistance in the substrate should be kept as low as possible in order not to deteriorate membrane performance of the resultant multilayer composite hollow fiber membranes.

Hydrogen bonds and molecular complexes in solutions of cellulose nitrate

Intermolecular hydrogen bonds in the systems based on cellulose nitrate and a number of low-molecular solvents were studied by IR spectroscopy. The majority of the systems under study are characterized only by redistribution of intensities of the spectral bands corresponding to the pure polymer accompanied by their minor shift. In this case, acceptors of cellulose nitrate become sterically accessible for the redistribution of hydrogen bonds, and only an insignificant portion of them forms hydrogen bonds with a solvent. New spectral bands in the IR spectra were observed only for solutions containing diethyldiphenyl carbamide, suggesting the formation of a molecular complex.

Thin-layer chromatography-mass spectrometry with ionization by californium-252 fission products used for studying molecular mass distribution of oligomeric polystyrenes

The potential of a time-of-flight mass spectrometer with ionization by californium-252 fission products has been studied with regard to identification of oligomeric polystyrenes (PS) by means of their positive molecular ions M +. The optimized procedure for sample preparation prior to mass spectrometry consists of evaporation of PS on a substrate prepared by electrodispersion of a cellulose nitrate solution. The sensitivity of the method depends on the molecular mass of the oligomeric polymerhomologues and on the sample mass, but is in any case high enough for being used for investigating fractions obtained by thin-layer chromatography (TLC) and having molecular masses of up to 2 × 10 3, without the necessity of a prior sample concentration. The method enables one to identify oligomeric polymerhomologues extracted from the TLC plate and to determine the mass of the monomer unit and of the end groups from the difference in the molar mass of the ions M + of neighbouring oligomers. These results, along with those of quantitative thin-layer chromatography (and also chromatograms obtained by means of other chromatographic methods) contain all information necessary for establishing the molecular mass distribution (MMD) of the oligomers, i.e. comprise an absolute method for determining the MMD of oligomers.

Shear rate dependence of the viscosity of cellulose nitrate solutions in the dilute concentration regime revisited

AbstractA detailed rheological study of cellulose nitrate in ethylacetate had been carried out in the dilute concentration (c) regime, covering a degree of polymerization (DP) range between 300 < DPη < 7000 and shear rates (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}) between 100 s−1 < \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} < 2000 s−1. The results show a strong dependence of the transition Newtonian to non‐Newtonian behavior on the three variables \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}, DP, and c, similar to that found recently on solutions of synthetic polymers. Emphasis has been put on the critical concentrations corresponding to the standard shear rate 1000 s−1 to correspond to the standard conditions (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} ≅ 1000 s−1; 0.3 < [η] · c < 0.6; DS = 2.90 ± 0.02) proposed for the determination of the intrinsic viscosity [η] of cellulose nitrates. It is shown that solutions with concentrations adjusted according to the above given conditions still exhibit Newtonian behavior, up to the highest range of DP. It follows, therefore, that applying the standard conditions, an extrapolation to \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} = 0 as has been proposed often for the intrinsic viscosity determination of cellulose nitrate is not advisable and results in considerable error. Considering the relationship between [η] and DP, the present results indicate that the decrease of the exponent (a) from a = 1.0 to a = 0.76, taking place above a DP ≅ 1000, is not a consequence of the applied shear rate but rather of the molecular properties of the solutes themselves.

Rheologic properties of semi‐rigid polymers for the example of cellulose nitrate, 2. Influence of molecular weight distribution on the flow curves of semi‐dilute solutions

AbstractThe apparent viscosity η of semi‐dilute solutions of cellulose nitrate in ethyl acetate was measured as a function of shear rate at 20°C by rotational viscometry. The mass concentration c of the solutions was chosen such that the product between c and the intrinsic viscosity was 8 < c · [η] < 22, lying in the range of viscosity‐average degrees of polymerization covered by the employed samples 550 < DPη < 7600. The experimental flow curves were interpreted in terms of Graessley's theory for non‐Newtonian flow of polydisperse polymers. The polydispersities derived for five individual samples according to the theory of Graessley were used for calculating the resulting theoretical curves belonging to four binary mixtures each between two of them. The reasonable good agreement between calculated and experimental reduced flow curves of blends indicates consistency of the theory when applied to the present system of a semi‐rigid polymer. This and other results point to a flow behaviour of semi‐rigid cellulose nitrate being similar to that of linear flexible polymers.

Phase heterogeneity of acetone solutions of cellulose nitrate

NMR and turbidity points were used to study temperature transitions in concentrated solutions of CN with a nitrogen content of 13·5 and 14·01%. Turbidity curves show two regions where light scattering changes suddenly. The critical concentration, above which these transitions are observed, is close to that predicted by the Flory theory for a narrow two-phase region. The transitions observed are accompanied by unusual changes in the drop of free induction of CN and transverse relaxation time of solvent molecules. Based on these results a conclusion was drawn about the LC form of transitions taking place.

Studies on ceiilulose nitrate destruction in solution. Part II. The effect of some alkaline substances on the increase in acid number of cellulose nitrate solutions

Studies on ceiilulose nitrate destruction in solution. Part II. The effect of some alkaline substances on the increase in acid number of cellulose nitrate solutions

Studies on the processes of cellulose nitrate destruction in solution. Part I. The effect of some physical and chemical agents on the viscosity reduction of cellulose nitrate solutions

Studies on the processes of cellulose nitrate destruction in solution. Part I. The effect of some physical and chemical agents on the viscosity reduction of cellulose nitrate solutions

The Kerr effect in cellulose nitrate solutions

Electrical birefringence values have been measured in pulsed fields for cellulose nitrate solutions in cyclohexanone by a compensation method based on sinusoidal modulation of elliptical light polarization. The specific Kerr constants K have been determined for nitrocellulose (NC) samples with nitrogen contents of 11·0, 12·1, 13· and 13·4%. This was done by extrapolation of concentration dependences of K to zero concentration. For the fractionated samples with N contents of 12·1 and 13·4% it was found that the experimental plots of K vs. MW of fractions are described by the theory of Kerr's effect in solutions of vermicular chains. The magnitude and the angle slope of the dipole moments of units relative to contour lengths of the NC chains have been evaluated. Birefringence relaxation has been investigated for NC solutions when the electrical pulse has ended, and the orientational relaxation times τ have been determined. On comparing τ values (obtained by extrapolation to zero concentration) with the intrinsic viscosity and MW of the fractions it is deduced that the NC chains have now acquired kinetic flexibility.

Sedimentation velocity of dilute and moderately concentrated solutions of cellulose nitrate

The velocity sedimentation of solutions of rigid macromolecules of cellulose nitrate in ethyl acetate has been investigated over a wide range of MW (960−60) × 10 3 and concentration 0⩽ c[ η]⩽12. Over the entire range of concentration examined the concentration dependence of the sedimentation coefficient may be interpreted on the basis of Bürger's theory. Data obtained in the range: 0⩽c⩽c ∗=[η] −1 provide a basis for a reasonable evaluation of MW of the studied fractions. In addition, qualitative agreement with the de Genes-Brochard theory was observed in the region where c>c ∗ where S∼ c − α for all MWs, and α=0·43±0·01.

Nuclear magnetic relaxation and segmental motion of nitrocellulose in solution

The transverse and longitudinal magnetic relaxation of solutions of cellulose nitrate (CN) with nitrogen contents of 13·5 and 11·9% have been studied in deuterated acetone in the temperature range from −100 to +70°C al two concentrations (34 and 50 wt. %). The two-component nature of the decay of the transverse magnetization points to the structural non-uniformity of CN in solution. The observed minima on the temperature dependence of the spin-lattice relaxation time in the laboratory system of coordinates, T 1, and in a rotating system of coordinates are caused by segmental movement in open-packed regions of the solution. The contribution of slow movements to the spectrum of correlation times at the temperatures of the minimum T 1 has been assessed. The values obtained for the activation energy for segmental motion in the unordered regions show that a vibrational-rotational mechanism predominates in the segmental motion of CN.

The dydrodynamic, electron-optical and molecular characteristics of cellulose nitrate solutions

The flow and electrical birefringences, the diffusion, sedimentation and intrinsic viscosity have been studied on 7 cellulose nitrate (CN) fraction solutions where the CN contained is 10·7% N. There were clear correlations between the Maxwell and Kerr effects and the mol.wt. of the fractions. The nature of the experimental dependences indicates that the CN molecules have a lower kinetic rigidity in a mechanical than in an electrical field. The experimental results have been used to determine the equilibrial and kinetic rigidities, the optical anisotropy and the dipole moments of the monomer unit, and also its longitudinal component in axial direction.

Features of the NMR-relaxation of solvent molecules and the structure of cellulose nitrate solutions in acetone

The lateral NMR-relaxation of acetone has been studied on cellulose nitrate (CN) concentrates containing 11·9 and 13·13·5% nitrogen in the - 100 to 80°C range. Multi-impulse experiments have shown the proton relaxation of the solvent to depend on the non-averaged dipole-dipole interactions with the macromolecular protons present in the structural formation. The rapid relaxation of the acetone present in solutions of CN with a large nitrogen content is explained by their crystalline stratification.

Dynamo-optical and electro-optical properties of cellulose nitrate molecules in solutions

A study was made of flow birefringence, refringence in electric field and intrinsic viscosity in dioxane and cyclohexanone, diffusion and sedimentation in methylethylketone of solutions of a cellulose nitrate sample with a nitrogen content of 10·7%. The electro-optical and dynamo-optical properties of cellulose nitrate solutions observed are typical of all chain molecules which are rigid from an equilibrium and kinetic point of view, including a number of other cellulose esters. Experimental results are discussed using the theory of translational friction and the viscosity of worm-like chains and the theory of Maxwell effect and Kerr effect in rigid-chain polymer solutions. Equilibrium and kinetic rigidity, optical anisotropy and dipole moments of cellulose nitrate molecules are determined.

A method for measuring personnel neutron doses through induced changes in molecular weight of cellulose nitrate

In this work, a new method for measuring fast neutron doses has been achieved through measuring the induced changes in the average molecular weight of cellulose nitrate (CN) foils after being irradiated with fast neutrons. The mean molecular weight of the irradiated CN samples has been determined through measuring changes in viscosity of CN solutions in ethyl acetate of different concentrations. An empirical formula for calculating the change in the mean molecular weight of CN after being irradiated with fission neutrons, and to doses over the range 0.6–10 4 Rad, has been proposed and found to fit the experimental data within ±6.3%. The effect of neutron energies on the induced changes in the mean molecular weight of CN has been studied. Moreover, the fading of these changes after storage at temperatures of 40 and 60°C and for periods up to 48 h have been investigated.