Effect of oxygen plasma treatment on surface charge and wettability of PVC blood bag—In vitro assay

Wettability and zeta potential studies were performed to characterize the hydrophobicity and surface charge of PVC blood bag samples and evaluate the effect of these properties on fibroblast cells growth. The surface properties of PVC and plasma treated PVC were compared by water drop contact angle and zeta potential measurement. Light microscopy was used to study the behavior of cell attachment and growth on these surfaces. Water drop contact angle measurement shows that the plasma treated PVC becomes more hydrophilic and wettability increased. Zeta potential and in vitro cell culture measurements noticed that the plasma treated PVC surface is more negatively charge and consequently attachment of the L929 fibroblast cells decreased on this surface.     

Modified suspension‐PVC particles as absorbents of ortho‐dichlorobenzene from water

Modified porous PVC particles are studied as absorbents of o‐dichlorobenzene (DCB), from water. The modified particles were produced by an in‐situ stabilizer‐free polymerization/crosslinking of a monomer/crosslinker/peroxide solution absorbed within commercial porous suspension‐type PVC particles. The modifying monomers used include styrene with divinyl benzene (DVB) as a crosslinking comonomer, methyl methacrylate (MMA), butyl acrylate (BA), or ethylhexyl acrylate (EHA) with ethylene glycol dimethacrylate (EGDMA) as a crosslinking comonomer. The effect of the nature of the monomers, morphology, porosity, surface area and composition of the modified PVC particles on DCB absorption was studied. Batch experiments (absorption rate and isotherms) were used to screen the PVC absorbents on the basis of absorption rate and absorption capacity. Continuous absorption column experiments were conducted to study the parameters characterizing the absorption process. Both the unmodified and modified PVC particles absorb DCB from water. The PBA and PEHA‐modified PVC particles approach equilibrium capacity faster and have greater absorption capacity than neat PVC, PS‐modified PVC and PMMA‐modified PVC particles. The absorption characteristics are influenced by the modifying polymer's T_g. The rubbery nature of PBA and PEHA yields better absorption in spite of the significantly lower surface area and porosity obtained in the modified PVC particles. Thus, indicating that fast adsorption followed by bulk absorption of DCB is taking place. A clear influence of the crosslinking effect was not established. The continuous absorption experiments were found more efficient than the batch absorption experiments. Copyright © 2003 John Wiley & Sons, Ltd.     

Pressure drop in CIM disk monolithic columns

Pressure drop analysis in commercial CIM disk monolithic columns is presented. Experimental measurements of pressure drop are compared to hydrodynamic models usually employed for prediction of pressure drop in packed beds, e.g. free surface model and capillary model applying hydraulic radius concept. However, the comparison between pressure drop in monolith and adequate packed bed give unexpected results. Pressure drop in a CIM disk monolithic column is approximately 50% lower than in an adequate packed bed of spheres having the same hydraulic radius as CIM disk monolith; meaning they both have the same porosity and the same specific surface area. This phenomenon seems to be a consequence of the monolithic porous structure which is quite different in terms of the pore size distribution and parallel pore nonuniformity compared to the one in conventional packed beds. The number of self-similar levels for the CIM monoliths was estimated to be between 1.03 and 2.75.     

Isotherms of phospholipid monolayers measured by a pendant drop technique

The Axisymmetric Drop Shape Analysis (ADSA) has been used to study the surface pressure/area isotherms of insoluble surfactant monolayers. The continuous measurement of surface tension as a function of surface area by increasing and decreasing the drop volume allows to investigate the phase transitions in monolayers. The isotherms of two phospholipids, dipalmitoyl phosphatidyl choline (DPPC) and dimyristoyl phosphatidyl ethanolamine (DMPE), show good agreement with those measured by using a conventional Langmuir-Blodgett film balance, except in the coexistence region. The observed disagreements are discussed in terms of differences in compression rate, curvature of the surface and effect of impurities. Evidence of possible geometric effects on monolayer domain formation and growth is given on the basis of BAM images.Due to the small total surface area, the ADSA technique provides advantages as regards homogeneity of temperature, surface pressure, surface concentration and the symmetry of area changes.     

Effect of instant controlled pressure drop treatments on the oligosaccharides extractability and microstructure of Tephrosia purpurea seeds

The study of the oligosaccharides extracted from Tephrosia purpurea seeds was undertaken using the instant controlled pressure drop (DIC) as a pre-treatment prior to conventional solvent extraction. This DIC procedure provided structural modification in terms of expansion, higher porosity and improvement of specific surface area; diffusion of solvent inside such seeds and availability of oligosaccharides increase notably. In this paper, we investigated and quantified the impact of the different DIC operative parameters on the yields of ciceritol and stachyose extracted from T. purpurea seeds. The treatment could be optimized with a steam pressure (P) (P=0.2 MPa), initial water content (W) (W=30% dry basis (DB)) and thermal treatment time (t) (t=30s). By applying DIC treatment in these conditions, the classic process of extraction was intensified in both aspects of yields (145% of ciceritol and 185% of stachyose), and kinetics (1h of extraction time instead of 4h for conventional process). The scanning electron microscopy micrographs provided evident modifications of structure of seeds due to the DIC treatment.     

Enhanced electrorheological activity of mesoporous Cr-doped TiO2 from activated pore wall and high surface area

To enhance electrorheological (ER) activity by improving interfacial polarization, we prepared a new mesoporous Cr-doped TiO2 ER material by a copolymer-templated sol-gel method. The material was characterized by differential scanning calorimeter and thermogravimetric (DSC-TG) analysis, Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption, and X-ray photoelectron spectroscopy (XPS) techniques. The ER activity was studied by the rheological curve and yield stress under an electric field. The results showed that the mesoporous Cr-doped TiO2 ER material possessed a high surface area over 200 m2/g and a crystalline anatase pore wall doped by different valent Cr ions. The ER activity of mesoporous Cr-doped TiO2 was higher than that of nonporous Cr-doped TiO2. The yield stress and ER efficiency of the mesoporous Cr-doped TiO2 ER suspension was 3 times as high as that of the nonporous Cr-doped TiO2 ER suspension, 7 times as high as that of the mesoporous undoped TiO2 ER suspension, and 20 times as high as that of the nonporous pure TiO2 ER suspension. Furthermore, the ER activity of mesoporous Cr-doped TiO2 showed a dependence on surface area, and the high porosity or surface area samples showed higher ER activity. The dielectric spectra analysis showed that the mesoporous Cr-doped TiO2 ER suspension possessed a significantly larger interfacial polarizability compared with the nonporous Cr-doped TiO2 ER suspension, and the regular change of polarizability with surface area or porosity was in accordance with the change of ER activity with surface area or porosity. The improvement of dielectric properties or polarization could well explain the enhancement of the ER activity of mesoporous Cr-doped TiO2.     

Suspension polymerization of vinyl chloride and the processibility of poly(vinyl chloride)

The most important technological procedure in the production of PVC is the suspension polymerization of vinyl chloride, as processibility of the polymer may be influenced to a considerable extent by the choice of polymerization conditions. Structure heterogeneities in PVC powders manifest themselves in plasticized PVC by the occurrence of “fish eye” particles. This review concerns the formation and properties of these particles and discusses the causes of their difficult processibility. Also, the relation between polymerization process and PVC dehydrochlorination is discussed and a new mechanism of its initiation based on the reactivity of cisoid enone structures is proposed. These structures catalyze elimination of hydrogen chloride from regular units of PVC by an interchain enzyme-like mechanism giving rise to chloroallyl structures.     

Forced desorption of nanoparticles from an oil-water interface

While nanoparticle adsorption to fluid interfaces has been studied from a fundamental standpoint and exploited in application, the reverse process, that is, desorption and disassembly, remains relatively unexplored. Here we demonstrate the forced desorption of gold nanoparticles capped with amphiphilic ligands from an oil-water interface. A monolayer of nanoparticles is allowed to spontaneously form by adsorption from an aqueous suspension onto a drop of oil and is subsequently compressed by decreasing the drop volume. The surface pressure is monitored by pendant drop tensiometry throughout the process. Upon compression, the nanoparticles are mechanically forced out of the interface into the aqueous phase. An optical method is developed to measure the nanoparticle area density in situ. We show that desorption occurs at a coverage that corresponds to close packing of the ligand-capped particles, suggesting that ligand-induced repulsion plays a crucial role in this process.     

Thermal degradation of poly(vinyl chloride) synthesized with a titanocene catalyst

PVC was synthesized using a trichloroindenyltitanium-methylaluminoxane catalyst at room temperature, and its degradation was monitored along with a commercial sample at 160, 170 and 180 °C under air or nitrogen atmosphere. The process was followed by HCl evolution, yellowing index, colour formation and thermogravimetric analysis. The produced polymer had a lower molecular weight and higher surface area, compared with a commercial PVC, while ¹H NMR and T_g values show minimal differences between materials. The HCl evolution degradation studies indicate that produced PVC has a lower thermal resistance than commercial PVC, while TGA reveals the opposite behaviour. Yellowing index and colour evaluation give evidence that nitrogen atmosphere and high surface area in produced PVC allow the polyene growth, whereas low surface area and air atmosphere generate shorter polyenes and chromophoric species. Differences in degradation performance are thought to be due to chemical origin, inherent morphology and differences in instrumentation.     

Effect of crystallization behavior of polyethylene glycol 6000 on the properties of granules prepared by fluidized hot-melt granulation (FHMG)

The objective of this study was to investigate the effect of the crystallization behavior of Macrogol 6000 (polyethylene glycol 6000; PEG 6000), used as a binder, during the solidification process on the properties of mononucleic granules prepared by the fluidized hot-melt granulation (FHMG) technique. Crystallization of PEG 6000 from molten liquid was investigated using differential scanning calorimetry (DSC) and hot stage microscopy. The results obtained from the measurement of isothermal crystallization demonstrated that crystallization of PEG 6000 was either slow or rapid. Analysis based on solid-state decomposition showed that slow crystallization was due to the two-dimensional growth of nuclei mechanism, while rapid crystallization was due to the three-dimensional growth of nuclei mechanism. Observation of the crystallization of PEG 6000 by hot stage microscopy supported the existence of two different crystallization mechanisms. Granules containing PEG 6000 that underwent rapid crystallization during FHMG showed a significantly higher fraction powder under 150 microm in diameter. This was caused by the loss of powder particles from the surface of mononucleic granules during the solidification process, because many cracks were observed after crystallization of PEG 6000 with a short isothermal crystallization time (ICT) due to the reduced of sticking of particles. The results of this study suggested that the crystallization behavior of the binder during the solidification process of FHMG can influence the properties of the resultant granules, such as particle size distribution, content uniformity or taste masking. It was also indicated that measuring the ICT using DSC was a useful method to classify PEG 6000.     

Effect of nano‐size nodular structure induced by CNT‐promoted phase separation on the fabrication of superhydrophobic polyvinyl chloride films

The nonsolvent‐induced phase separation (NIPS) method was employed to fabricate the porous films based on polyvinyl chloride loaded with carbon nanotubes (CNTs). The combinational addition of CNTs and a proper nonsolvent (ethanol) resulted in a porous surface layer with the nano‐size nodular structure possessing an exact superhydrophobic behavior (water contact angle [WCA] = 157° and sliding angle [SA] <5°). The size of PVC nodules at the surface layer varies in the range of 200 to 800 nm depending on the nonsolvent concentrations, and polymer molecular weight. The effects of various nonsolvent concentrations as well as PVC molecular weight on the surface properties of the films were also investigated. Morphological and roughness analyses revealed the pronounced role of PVC molecular weight on the size of nodules, and the structural uniformity of the surface morphology based on the thermodynamic parameters such as relaxation time and dynamic of polymer chains. The concurrent use of CNTs and nonsolvent led to promote the NIPS process due to the nucleating role of CNTs, which were localized within the polymer‐rich phase leading to an ultra‐fine and packed nodular surface structure. Transmission electron microscopy results also proved the very well dispersion quality of CNTs. Glass transition temperature of PVC was also assessed, and the results were correlated to the associating ability of CNTs with polymer chains during the phase separation process. Overall, the promising potential of CNT/ethanol combination on the surface porosity and hydrophobicity of PVC nanocomposite films was revealed in this study, which could further extend its application window.     

Filtration application from recycled expanded polystyrene

Water-in-oil emulsion with drop size less than 100 mum is difficult to separate. Coalescence filtration is economical and effective for separation of secondary dispersions. Coalescence performance depends on flow rate, bed depth, fiber surface properties, and drop size. The amount of surface area of the fibers directly affects the efficiency. A new recycling method was investigated in the previous work in which polystyrene (PS) sub-mum fibers were electro-spun from recycled expanded polystyrene (EPS). These fibers are mixed with micro glass fibers to modify the glass fiber filter media. The filter media are tested in the separation of water droplets from an emulsion of water droplets in oil. The experimental results in this work show that adding nanofibers to conventional micron sized fibrous filter media improves the separation efficiency of the filter media but also increases the pressure drop. An optimum in the performance occurs (significant increase in efficiency with minimal increase in pressure drop) with the addition of about 4% by mass of 500 nm diameter PS nanofibers to glass fibers for the filters.     

二乙烯苯交联大孔聚甲基丙烯酸羟乙酯的合成及其结构性能的研究

选用反应性单体甲基丙烯酸羟乙酯（ＨＥＭＡ），以二乙烯苯（ＤＶＢ）作为交联剂。在致孔剂甲苯和环己烷存在下，用经典悬浮聚合的方法制得了一系列的大孔共聚物。通过测定树脂的孔结构性能及化学组成，讨论了不同交联剂用量和配比对共聚物结构的影响。     

二乙烯苯交联大孔聚甲基丙烯酸缩水甘油酯的合成及其结构性能的研究

选用反应性单体甲基丙烯酸缩水甘油酯（ＧＭＡ），以二乙烯苯（ＤＶＢ）作为交联剂。在致孔剂甲苯和正庚烷存在下，用悬浮聚合的方法制得了一系列大孔ＧＤ共聚物。通过测定树脂的孔结构性能及化学组成，讨论了不同交联剂用量和配比对共聚物结构的影响。     

Characteristics of the Porous Structure of Cement Stone

The complex study of filtration and electric properties of the samples of cement stone with different water-cement ratios is performed. It is established that filtration coefficient decreases by 4–6 times with an increase in a pressure drop and becomes constant at pressure drops above 3–3.5 MPa. The observed effect is interpreted as a reversible change in the internal structure of cement stone upon the filtration of a liquid through the stone. It is revealed that the filtration coefficient and porosity of samples decrease with time. Total open porosity and the most probable pore radius are determined by mercury porosity technique. Coefficients of structural resistance and pore tortuosity of the samples are determined from the comparison of through and total porosity. The values of streaming potential are measured and values of surface charge and potential of the samples of cement stone are calculated.     

Pore Modification in Porous Ceramic Membranes With Sol-Gel Process and Determination of Gas Permeability and Selectivity

Summary: The aim of the study was to investigate the variation in total surface area, porosity, pore size, Knudsen and surface diffusion coefficients, gas permeability and selectivity before and after the application of sol-gel process to porous ceramic membrane in order to determine the effect of pore modification. In this study, three different sol-gel process were applied to the ceramic support separately; one was the silica sol-gel process which was applied to increase porosity, others were silica-sol dip coating and silica-sol processing methods which were applied to decrease pore size. As a result of this, total surface area, pore size and porosity of ceramic support and membranes were determined by using BET instrument. In addition to this, Knudsen and surface diffusion coefficients were also calculated. After then, ceramic support and membranes were exposed to gas permeation experiments by using the CO₂ gas with different flow rates. Gas permeability and selectivity of those membranes were measured according to the data obtained. Thus, pore surface area, porosity, pore size and Knudsen diffusion coefficient of membrane treated with silica sol-gel process increased while total surface area was decreasing. Therefore, permeability of ceramic support and membrane treated with silica sol-gel process increased, and selectivity decreased with increasing the gas flow rate. Also, surface area, porosity, pore size, permeability, selectivity, Knudsen and surface diffusion coefficients of membranes treated with silica-sol dip coating and silica-sol processing methods were determined. As a result of this, porosity, pore size, Knudsen and surface diffusion coefficients decreased, total surface area increased in both methods. However, viscous flow and Knudsen flow permeability were detected as a consequence of gas permeability test and Knudsen flow was found to be a dominant transport mechanism in addition to surface diffusive flow owing to the small pore diameter in both methods. It was observed that silica-sol processing method had lower pore diameter and higher surface diffusion coefficient than silica-sol dip coating method.     

Structural aspects of suspension poly(vinyl chloride): Influence of temperature on the macro- and microstructure

The structural aspects of rigid suspension poly(vinyl chloride), PVC, have been investigated on the basis of two independent series of suspension PVC samples, polymerized at temperatures between 26 and 84°C. The reproducibility of the suspension polymerization process and the importance of the polymerization temperature with respect to the macro- and microstructure is demonstrated. Quantitative examination of the grain structure by small angle neutron scattering, Brunauer-Emmett-Teller absorption technique, and mercury porosimetry clarifies the gradual increase of the specific surface on lowering the polymerization temperature. A detailed WAXS study shows an increasing degree of crystallinity on lowering the polymerization temperature, which can be associated with the corresponding increase of the syndiotacticity. Furthermore, the presence of a polymerization history in the PVC powders with respect to the crystallinity is evidenced. This effect seems to be related to chain mobility restrictions during the polymerization process and is determined by the difference between the polymerization temperature and the glass-transition temperature (T_g) of rigid PVC. This so-called T_g effect is indicative of the fact that no appreciable swelling of PVC by its monomer occurs. © 1994 John Wiley & Sons, Inc.     

耐热聚氯乙烯的耐热机理研究

用悬浮聚合方法制得了氯乙烯 N 苯基马来酰亚胺 ( 丙烯腈 )共聚物 ,研究了该共聚物的维卡软化点、玻璃化温度、动态力学行为以及形态结构 .发现当耐热组分达到一定含量时 ,耐热性能的增加幅度发生变化、出现两个动态力学内耗峰、形态上出现双连续相结构 .基于这些实验现象 ,提出了“刚性有效网架”可以使耐热性能大幅度提高的观点 ,并探讨了耐热机理 ,给出了物理模型 .讨论了相容性对“刚性有效网架”形成的影响     

Membrane emulsification using membranes of regular pore spacing: Droplet size and uniformity in the presence of surface shear

During membrane emulsification it is shown that the size of the drops formed at the membrane surface may increase with increasing dispersed phase injection rate through the membrane, or it may decrease, depending on the prevailing conditions. This is illustrated using a paddle stirrer positioned above flat disc membranes with regular arrays of pores of 20 μm diameter and spacing between the pores of 80 and 200 μm. In the former case an additional mechanism for drop detachment is the push-off force, which is determined by the geometry of the drops as they deform at the membrane surface. When dispersing sunflower oil in to aqueous solutions containing Tween 20, drop sizes between 60 and 200 μm were produced, and in the case of the membrane when the push-off force was working the Coefficient of Variation of the drops formed was below 10%. The push-off force may be added to the shear-drag force to predict drop detachment. For the 200 μm pore spaced membrane this force is much less prominent than the 80 μm spaced membrane. The capillary-shear model has been modified to include this push-off force. The experimental study required the use of very low dispersed phase injection rates as well as very high rates. Hence, two different types of pumps were used to provide these: a peristaltic and syringe pumps. A small study comparing the drop size, and size distributions, showed that the pump type did not influence the drops produced by the membrane emulsification process.     

Preparation and characterization of a novel zeolite using hydrothermal synthesis in a stirred reactor

This paper describes the preparation of novel zeolite particles by the hydrothermal method in a stirred reactor. The variations between certain properties of the resulting zeolites, such as morphology by the scanning electron microscopy (SEM), pore properties (i.e., surface areas, pore volume, and porosity) by the surface area & porosity analyzer, crystallinity by the X-ray diffraction (XRD) and Si/Al ratio by the inductively coupled plasma-atomic absorption spectrometer (ICP-AES), and the process parameters, such as aging time, agitation speed, temperature and pressure, were studied at a specific gel composition. The optimal value of the Brunauer–Emmett–Teller (BET) surface area was found to be over 400 m²/g in the resulting microporous zeolite, indicating that the size was centered on about 0.5 nm. The XRD image was indicative of the probable formation of zeolite-P2 in the hydrothermal synthesis.