Interphase mass transfer between liquid-liquid counter-current flows. II. Mass transfer kinetics

A theoretical analysis of mass-transfer kinetics based on the method of similarity variables for a liquid-liquid counter-current flow has been made. The numerical results obtained for the mass-transfer rate (Sherwood number) in the case of a laminar boundary layer with a flat interphase are compared with analogous results for a co-current flow. The ratio between the mass-transfer rate and the energy dissipation in the boundary layer is determined. The advantages of the co-current flow due to lower energy losses compared with the case of the counter-current one are shown. Published in Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 86–90, July–August, 2007.     

Interphase heat transfer between low-temperature plasma and disperse materials in a plasma reactor

Data on heat transfer of plasma flows in a cylindrical channel of a reactor with a three-jet mixing chamber are analyzed. Experimental results are also presented on interphase heat transfer between plasma flows and disperse particles, and two possible methods of generalization of the results are shown. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 3, pp. 462–468, May–June, 1997.     

Interphase mass transfer between liquid-liquid counter-current flows. I. Velocity distribution

A theoretical analysis of liquid-liquid counter-current flow in laminar boundary layers with a flat interphase based on the similarity-variables method has been made. The numerical results for the velocity distribution in both phases are obtained. The dissipation energy in a boundary layer is found and the results corresponding to counter-current and co-current flows are compared. The comparison shows significant differences in the dissipation energy values in the cases of co-current and counter-current flows. Published in Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 80–85, July–August, 2007.     

Interphase mass and heat transfer in a compact disperse system

Limiting relations are derived for the Sherwood number, which characterizes convective diffusion to a solid sphere, a droplet, or a bubble in a constricted stream, applicable to low values of the Reynolds number and high values of the Peclet number.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 25, No. 4, pp. 594–600, October, 1973.     

Poly(acrylonitrile butadiene styrene)/poly(vinylidene fluoride) binary blends films with superior breakdown strength and discharge efficiency

Poly(vinylidene fluoride) (PVDF) ferroelectric polymer with high dielectric constant has been emerged as promising candidate for advanced electrostatic capacitors. However, the intrinsic high ferroelectric loss of PVDF can cause suppressed discharge efficiency, which greatly hinders its applicability. In this work, a polymer-blending approach using linear dielectric component poly(acrylonitrile butadiene styrene) (ABS) is proposed to alleviate the low discharge efficiency issue in PVDF. The ABS-containing high-polarity acrylonitrile monomer demonstrates to show excellent compatibility with PVDF and reduce PVDF ferroelectric domains. With weakened ferroelectric domains coupling, the blends perform significantly enhanced discharge efficiency. For instance, with a moderate discharge energy density of 5.7 J/cm³, a rather high discharge efficiency of 82% can be obtained in blends with a composition content of 50/50 under 400 MV/m while that of PVDF is only 55%. Additionally, the blends exhibit superior operation reliability against pure PVDF, suggesting its feasibility as viable capacitor.

     

iCVD growth of poly(N-vinylimidazole) and poly(N-vinylimidazole-co-N-vinylpyrrolidone)

The imidazole group plays an important role in α-chymotrypsin catalysis, metal-ion complexation, counterion or dye binding. Poly(N-vinylimidazole), PVI, is also a good model polymer interacting with neutral salts. The poly(N-vinylimidazole-co-N-vinylpyrrolidone) copolymer P(VI-co-VP), can be used to produce highly functionalized polymers.PVI and P(VI-co-VP) thins films were achieved via initiated chemical vapor deposition (iCVD), a solvent-free process to form films under mild conditions. The polymerization was initiated by hot wire heated tert-butyl peroxide (TBPO). The chemical structure and compositions of the polymers were analyzed using FTIR and XPS. The growth rate of PVI as a function of the pressure inside the iCVD reactor was measured to be 1 nm/h mTorr. The XPS results show that the functional groups were retained in the polymer deposited. For the P(VI-co-VP) deposition, there are more VI groups found in the co-polymer chain even when the reacting monomers were fed in the same ratio.     

Nano-structure of polyimide and poly(isobutyl methacrylate) monolayer films studied by interlayer electron transfer between porphyrin and pyromellitic diimide moieties

Hetero-multilayers composed of porphyrin-containing poly(isobutyl methacrylate) (PiBMA) and polyimide (PI) monolayers were prepared by using the Langmuir-Blodgett technique, and the interlayer electron transfer process from photo-excited porphyrins to pyromellitic diimide moieties in PI layers was observed by fluorescence spectroscopy. The efficiency of the electron transfer showed strong dependence on the number of PI layers, suggesting the presence of defects in the PI plane, which were filled with PI after the successive deposition of PI monolayers. The three-dimensional and two-dimensional active sphere models (Perrin model) well explained the interlayer electron transfer phenomena. We discussed the nano-structures of the multilayer films in terms of the thickness of each layer and the location of hydrophobic porphyrins in the PiBMA monolayer.     

聚乙二醇改性聚乳酸的合成与性能表征

以外消旋乳酸(D,L-LA)和不同数均分子量(Mn)的聚乙二醇(PEG)为原料,通过熔融缩聚法,合成了系列聚乳酸聚乙二醇(PLEG)。最佳工艺条件为:以(Sn(Oct)2)为催化剂,m(Sn(Oct)2)为0.8%,n(PEG)∶n(D,L-LA)=1∶600,聚合温度170℃,压力0.096 MPa条件下,反应8h。用特性粘度测试、FT-IR、XRD、接触角等对其进行表征,实验结果表明系列PLEG中PLEG-800接触角为63°,表明其亲水性能最好;PEG-800和乳酸共聚合成的PLEG的粘均分子量最大,可达48997,与PDLLA相比,结晶度有较大提高,亲水性得到改善。     

Synthesis and characterization of poly(3-hexylthiophene)/poly(3-(trimethoxysilyl)propyl methacrylate) rod-coil block copolymers by using atom transfer radical polymerization

In this study, polythiophene based rod-coil block copolymers (P3HT)47-b-(PMSMA)34 are synthesized by atom transfer radical polymerization (ATRP). The effects of altering the mix of solvent and processing temperature on the morphologies and photophysical properties of the block copolymers in both solution and solid state are investigated. The chemical structure of the prepared block copolymers is confirmed by NMR and FTIR analysis. TEM results show that different morphologies of aggregates can be obtained by varying the toluene/methanol ratios. Such aggregation leads to a significant red shift on the optical absorption and photoluminescence spectra of the P3HT-b-PMSMA in mixed solvents. The results of AFM, UV-Vis, and PL show that the morphologies and photophysical properties of P3HT-b-PMSMA films are also significantly affected by the curing temperature. Blue shifts on the optical absorption and photoluminescence spectra are observed upon increasing the curing temperature.     

低热膨胀聚(苯并噁唑-酰亚胺)薄膜与铜黏结性能EI北大核心CSCD

采用氧等离子体活化聚(苯并噁唑-酰亚胺)(PI)薄膜,以此为基底,通过离子注入和化学电镀铜工艺制备高黏结性、耐锡焊性的无胶柔性单面覆铜板(FCCL)。控制气流压强,研究处理功率、处理时间对薄膜表面结构、化学成分及其与Cu层黏结性能的影响。结果表明:氧等离子体改性对改善PI薄膜黏结性能有重要影响,控制压强30 Pa,处理功率100 W,时间10 min,表面引入含氧极性基团,蚀刻明显,使薄膜的浸润性增强;PI薄膜与铜离子形成络合物,进一步赋予FCCL优良的黏结性能,其剥离强度比现有FCCL提高60%以上。     

Synthesis and characterization of poly(ether sulfone ether ketone ketone) grafted poly(sulfopropyl methacrylate) for proton exchange membranes via atom transfer radical polymerization

A series of copolymers of poly(ether sulfone ether ketone ketone) grafted poly(sulfopropyl methacrylate) (PESEKK-g-PSPMA) were successfully synthesized by atom transfer radical polymerization (ATRP) of sulfopropyl methacrylate (SPMA) after chloromethylation of poly(ether sulfone ether ketone ketone) (PESEKK) backbone. The structure of the chloromethyl PESEKK and the copolymers were carefully investigated. Variation of the polymerization time leads to the formation of copolymers with different degree of sulfonation (DS). The properties of the proton exchange membranes such as water uptake, ion exchange capacity, proton conductivity, and methanol permeability are studied with compared to those of Nafion 117 membranes and could be modulated simply by control of the ATRP time. The copolymers exhibited much lower methanol permeability and higher proton conductivity as compared with Nafion 117.     

Plasma surface treatments of poly(l-lactic acid) (PLLA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)

The surfaces of poly(l-lactic acid) (PLLA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) were modified by oxygen and nitrogen plasma treatments. The physical and chemical surface characteristics were evaluated by contact angle tests, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The plasma treatments caused an increase in both contact angle and roughening, altered the surface morphology, inserted polar groups, and, consequently, enhanced the hydrophilicity for both PLLA and PHBV polymers.