Electrical conductivity in iodine-doped ethyl cellulose

The electrical conductivity of solution-grown ethyl cellulose (EC) films, 5–30 μm thick, has been studied in the sandwich configuration (metal–EC–metal) as a function of iodine concentration from 0.5 to 5.0 wt% ratio. The studies were conducted in the temperature range 333–383 K, while the field was varied over the range (3.0–5.5) × 10⁴V/cm. Aluminium was used as the lower electrode, while the upper electrode was of Al, Ag, Cu, Au or Sn. Certain transient effects such as a large burst of current immediately after the application of field were observed. An attempt was made to identify the nature of the current by comparing the observed dependence on electric field, electrode material and temperature with the respective characteristic features of the existing theories of electrical conduction. The results show that the electrical conduction follows Ohm's law at lower fields, while at higher fields, space-charge limited current (SCLC) was observed. It was also found that Richardson–Schottky emission was responsible, to some extent, for the transport of charge carriers in the polymer. The conductivity of the films increased on doping with iodine. The dopant molecules are considered to act as additional trapping centes and provide links between the polymer molecules in the amorphous region, thus resulting in the formation of charge transfer complexes.     

The isothermal crystallization kinetics of ethyl cellulose /poly(ethylene oxide)/ ethyl cellulose sandwich films

Isothermal crystallization of the sandwich films in the form of ethyl cellulose/poly(ethylene oxide)/ethyl cellulose (EC/PEO/EC) was traced by differential scanning calorimeter (DSC). A primary turning point was found in the Avrami plot and the Avrami analysis shows that the primary turning point is an indication of transformation of crystal growth geometry from the three-dimensional mode to the two-dimensional one. A mathematical model was proposed to predict if the primary turning point would emerge in the Avrami plot. The model is related to an expression that involves the sample thickness and the average distance between adjacent nuclei. The presence of the primary turning point and the prediction of the model were confirmed by using the computer simulation method.     

Interaction between iodine and ethyl cellulose

Interaction between iodine and ethyl cellulose was investigated by immersing ethyl cellulose membranes in aqueous iodine–iodide solution (iodine doping) and incorporating iodine in the solution from which the membrane was cast. Oxygen and nitrogen permeabilities in iodine‐doped ethyl cellulose decrease with an increase in the concentration of iodine in the dopant solution up to 0.003 mol L⁻¹ and increase sharply at higher iodine concentrations, and ultraviolet–visible and far‐infrared spectra indicate formation of a charge transfer complex. Differential scanning calorimetry of both types of membrane shows changes in the characteristic phase transitions of ethyl cellulose after iodine treatment, including the crystal–liquid crystal transition that has been reported to occur in ethyl cellulose. Further evidence for liquid crystal phases has been found from circular dichroism. X‐ray photoelectron spectroscopy of iodine‐doped ethyl cellulose films indicates that the iodine is present in two different chemical states, probably l and l₂. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1303–1314, 1999     

Viscometric behavior of ternary concentrated solutions of hydroxypropyl cellulose and ethyl cellulose in m-cresol

The shear viscosity of blend solutions of hydroxypropyl cellulose (HPC) and ethyl cellulose (EC) in m-cresol (both HPC/m-cresol and EC/m-cresol systems form lyotropic liquid crystals) was determined by cone-plate-type and capillary-type viscometers. The textures for the same systems at rest and undergoing shear were also observed with a polarized microscope. At shear rate of 1 s^?1, viscosity exhibited a maximum and a minimum with respect to temperature, and this suggested that the phase of the matrix dominated the viscometric behavior of the ternary systems; the blend composition dependence of the viscosity was not additive, and this suggested that HPC and EC were immiscible. At relatively high shear stress, the blend composition dependence of the viscosity greatly depended on the total polymer concentration of the solutions and was quite different from that at low shear rate; the texture of the anisotropic solutions was also different from that at low shear rate. Our findings suggested that the dependence of viscosity on shear and concentration for pure HPC solution was different from that for pure EC solution.     

Study on mass transfer of ethyl acetate in polymer adsorbent by experimental and theoretical breakthrough curves

A new polymeric adsorbent with highly hypercrosslinked structure was developed for the removal of VOCs from polluted air. The purpose of this work is to obtain the intraparticle mass transfer coefficient of the adsorbent particles. Adsorption experiments for obtaining breakthrough curves were carried out with a fixed bed system. A dynamic mathematical model for the fixed bed adsorption system was developed. By model fitting, the overall mass transfer coefficient was determined when the deviation error was minimum. Then, the intraparticle mass transfer coefficient of the adsorbent was determined when the external mass transfer resistance was eliminated at higher velocities. Furthermore, a linear relationship of the intraparticle mass transfer coefficient and equilibrium coefficient at lower inlet gas concentrations range was correlated. Moreover, an equation for predicting external mass transfer coefficient at low Reynolds number range at room temperature was obtained.     

乙基纤维素与聚苯乙烯共混体系的相溶性研究

用紫外光谱、X射线衍射和DSC、偏光显微锐、相差显微镜和电镜等方法研究了乙基纤维素-聚苯乙烯共混体系的相溶性。结果表明该体系为部分相溶体系。     

Open- and short-circuit thermally stimulated currents in ethyl cellulose

Thermally stimulated currents (TSCs) in short-circuit and open-circuit configuration for ethyl cellulose samples (≈40 µm thick) have been studied as a function of polarizing field (25–100kV/cm) and polarizing temperature (323–353K). The thermograms have been found to be characterized by two prominent peaks located around 70 ± 10°C and 140 ± 10°C and the appearance of anomalous current in the high temperature region of the short-circuit TSC thermograms. The observed behaviour has been explained in terms of the existence of heterocharge due to dipole orientation and ionic homocharge drift, together with the injection of charge carriers from electrodes and their subsequent localization in surface and bulk traps.     

A structure rheological study of cellulose trinitrate in ethyl acetate

A structure rheological analysis was undertaken with cellulose trinitrates dissolved in ethyl acetate. Empirical scaling laws with molecular mass and concentration were found for the zero shear viscosity η_o and the critical shear rate $ \dot \gamma _C $ at the onset of shear thinning. Values for the apparent chain element A' were calculated from the concentration dependent network strand M_e and extrapolated to zero concentration. They were compared with dilute solution data. From the concentration dependence of the mass of network strand M_e a network with hindered penetration was inferred.     

Transient currents in charging and discharging modes in ethyl cellulose

Transient current in vacuum aluminized ethyl cellulose foil samples of thickness 75 μm were investigated in charging and discharging modes at different temperatures and fields. The occurrence of a peak in the current–time characteristics of charging current (I_c), and the dependence of such currents on field, characterized by a negative resistance region and followed by a superlinear region, are considered to indicate injection controlled transient currents modified by space-charge arising from the localization of carriers in various traps. Carrier mobility values calculated from a knowledge of the peak in the charging current versus time characteristics were found to range from 10^?11 to 10^?9 cm²/V s. As times larger than the peak time, the charging current follows the relation I ∝ t^?n at low temperatures with different poling fields (V_p). However, the current increases with time and finally tends to saturate for samples poled at higher temperatures with higher values of field. The isochronal characteristics (i.e. current–temperature plots at fixed times) constructed from discharge current versus time plots are characterized by a peak at 70°C or 100°C, depending upon the poling field values.     

Mass transfer effects on kinetics of nonideal liquid phase ethyl tert-butyl ether formation

Ethyl tert-butyl ether (ETBE) is an alternative fuel oxygenate that can be produced in the liquid phase by addition of ethanol to isobutene catalyzed by sulfonic acid ion exchange resins. A generalized Langmuir-Hinshelwood rate expression is formulated in terms of the liquid phase activities of the reactants that is quasi-autocatalytic due to ethanol. This microkinetic model is combined with the generalized Maxwell-Stefan equations for a detailed investigation of the influence of multicomponent mass transfer limitations inside the macropores of the heterogeneous catalyst. The model is used for revision of experimental rate data for ETBE synthesis in the literature. The analysis reveals that reverse diffusion of isobutene can occur by strong interaction with ethanol and the catalyst effectiveness factor can exceed unity.     

Corona-induced graft polymerization of ethyl acrylate onto cellulose film

Ethyl acrylate was readily grafted from an aqueous solution onto cellophane film previously treated in a corona discharge at atmospheric pressure. The effect was found when the corona treatment was carried out not only in air but also in pure nitrogen. The observed grafting was not promoted but depressed by the presence of ferrous ion, which indicated that peroxide radicals were not initiating the graft. A high grafting efficiency was obtained, and the grafted surface was covered with a smooth uniform layer of polymer.     

Rapid expansion of cellulose triacetate from ethyl acetate solutions

Rapid‐expansion‐of‐supercritical‐solution (RESS) experiments were performed for solutions of cellulose triacetate [CTA; weight‐average molecular weight = 145,700, polydisperity = 2.07] in ethyl acetate [EA] over a range of concentrations and conditions of polymer–solvent phase behavior. Solid‐solubility experiments were carried out beforehand and identified hot and compressed liquid EA at approximately 175°C as a good solvent for CTA. Cloud‐point measurements were then used to locate the region of liquid–liquid equilibrium (LLE) for this system. The RESS results indicate that the phase state of the pre‐expansion mixture determines the product size, and the overall concentration of the pre‐expansion mixture determines the product morphology. However, we have also discovered a new constraint: for the production of well‐formed fibers and particles, the rapid‐expansion path must include penetration into a region of LLE, which must exist over a sufficient pressure range so that a separate, polymer‐rich liquid phase has time to develop before the onset of vapor–liquid equilibrium (VLE). If rapid expansions are carried out at temperatures near or below the lower critical end point, the expansion path leads directly into a region of VLE, and a disruptive vapor expansion occurs within the continuous liquid phase. In this case, hollow particles, hollow structures, and even foams are produced. By the proper choice of operating conditions, we were able to produce continuous CTA fiber from a 5 wt % solution in EA at 250°C and 69 bar. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 290–299, 2005     

Antioxidant capacity of robust polyaniline–ethyl cellulose films

Ethyl cellulose films containing up to 17% polyaniline (PANI EC film) were prepared from ethanolic solutions. The antioxidant capacity of the PANI EC films was examined using the oxygen radical absorbance capacity (ORAC) assay, and the films demonstrated very efficient peroxyl free radical scavenging activity. A good correlation was also obtained between the net ORAC curve area and the size of the tested film, indicating the homogenous dispersion of active PANI powder across the film. Reduced PANI presented greater peroxyl radical scavenging activity than more oxidized as-prepared forms. The influence of the PANI EC films on the oxidation of Ropufa oil was determined after incubation at 60 °C for several days. The oil stored in the presence of a PANI EC film was found to exhibit a lower peroxide value than in the absence of PANI, indicating that the conducting polymer can inhibit the oxidation of fish oil.     

Gas-liquid mass transfer in trickle-bed reactors: Gas-side mass transfer

New data of gas-liquid mass transfer for cocurrent downflow through packed beds of non-porous particles are presented. Mass transfer parameters for air/carbon dioxide/water and air/carbon dioxide/sodium hydroxide systems were evaluated by least squares fit of the calculated CO₂ concentration profiles in the gas phase to the experimental values. The dependence of k_Ga on gas and liquid flow rates is caused by the dependence of gas-liquid interfacial area, not by the gas-side mass transfer coefficient k_G. In the case of the absorption of dilute carbon dioxide the gas-side resistance is considerably smaller than the liquid-side resistance. In the pulse flow regime, gas-liquid interfacial area calculated from k_La and k_L values obtained by physical, respectively, chemical absorption are lower than the gas-liquid interfacial area evaluated from the measurements under reaction conditions.     

基于乙基纤维素大分子RAFT试剂的n-BMA细乳液聚合

以大分子乙基纤维素基RAFT试剂(EC-CPADB)为链转移剂,采用可逆加成-断裂链转移聚合(RAFT)聚合法,合成了乙基纤维素接枝聚甲基丙烯酸丁酯(PBMA)细乳液。通过凝胶渗透色谱(GPC)、动态光散射激光粒度仪(DLS)、原子力显微镜(AFM)、差示扫描量热仪(DSC)、拉伸测试等进行表征。结果表明,纤维素大分子RAFT试剂EC-CPADB在细乳液聚合中发挥了一定的活性控制的作用,得到的聚合物分子量为141 100,并且分子量分布窄,PDI为2. 82,聚合物的玻璃化转变温度为21℃。大分子RAFT试剂EC-CPADB的加入,对聚合体系有一定的缓聚作用,但体系反应效率高,反应2 h,转化率大于90%;大分子RAFT试剂EC-CPADB的存在,对乳液粒子的形貌没有明显影响,乳液粒径大小约为100 nm,呈规则的圆球状,分布较均一。膜循环拉伸实验显示,聚合物弹性恢复系数能够达到90%以上,具有较好的弹性力学性能。     

Effect of solvent on morphology of electrospinning ethyl cellulose fibers

The influence of the composition of a multicomponent solvent on the surface morphology and diameter distribution of ethyl cellulose fibers produced by electrospinning technology was investigated. The results showed that the average diameter of the fibers using the multicomponent solvent was thinner than when using either of the two components and the diameter distribution of the fibers became narrower. Tiny tubercles formed on the fiber surface, which may improve the specific surface area and broaden the applications. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1292–1297, 2005