The effect of atmospheric‐pressure air plasma discharge power on adhesive properties of aramid fibers

After exposure to the atmospheric‐pressure air plasma at different discharge powers, the adhesion characteristics of Twaron aramid fibers were investigated. For the 12 s‐300 W plasma treatment, the interlaminar shear strength of Twaron fiber reinforced thermoplastic poly(phthalazinone ether sulfone ketone) was increased from 46.0 to 61.7 MPa by 34.1%, and the diffusion of water molecule into the resulting composites was proved to be effectively prevented. These results showed that surface adhesive properties of the plasma‐treated aramid fibers were improved. At the power level of 300 W, X‐ray photoelectron spectroscopy analysis revealed the increases in concentrations of oxygen and nitrogen polar groups on the fiber surface, and atomic force microscopy observations led to the conclusion that the fiber surface morphology was changed and the surface roughness was greatly increased. These new polar and irregular surface structures accounted for the better adhesion between the fiber and the matrix, while due to the reasonability of this discharge power level applied to the surface modification, the measured fiber tensile strength only decreased by 2.0%. POLYM. COMPOS., 37:620–626, 2016. © 2014 Society of Plastics Engineers     

The effect of interstitial air on the in vitro thrombogenicity of ePTFE vascular grafts

Gas trapped in the interstices of the biomaterials used for vascular prostheses causes thrombosis, and the process of eliminating this gas is known as denucleation. An apparatus was developed for testing in the in vitro effects of denucleation on 4 mm I.D. expanded polytetrafluoroethylene (ePTFE) Vitagraft (Johnson and Johnson). The apparatus was designed to ensure that neither the blood nor the grafts came in contact with air. Blood from a single donor was incubated with control and denucleated grafts for 5, 10, 15, 20, and 30 minutes. The thrombus volume in the graft lumen was measured with a computer assisted videometric system. Little thrombus formed by 5 or 10 minutes, but there was less thrombus in the denucleated graft than in the control graft at all times. The differences were statistically significant at 15 and 20 minutes (p < 0.05). Denucleation nearly doubled the thrombus formation time. Thrombus was more adherent to denucleated grafts than to control grafts. These results are consistent with in vivo observations in the rat where denucleation decreased thrombus formation and increased patency duration.     

Calculation of air discharge from the mold

A procedure is proposed in the paper whereby the quantity of air forced into a pressed blank can be calculated. The calculations are done in the general form and with reference to a specific example, using the compaction pressure, compaction ratio, gas content, and gas permeability of the pressed work. Graphs are constructed which relate the variables of compaction and adiabatic discharge of air from the pressed work to the compaction pressure and the duration of the pressing operation.     

Experimental analysis of static pressure in bins

A pressure transducer with a pressure-high sensitive semiconductor gauge was used to measure distribution of vertical pressure at the base and horizontal wall pressure in a bin packed with glass beads, which are typical cohesionless particles.Even when the glass beads were uniformly supplied to the bin, the vertical pressure at the base was distributed unevenly, with the maximum and minimum values. This seems to be attributable to the “arching” which results from its nonhomogeneous configuration. In addition, the results indicate that the larger the diameter of the bin, the more numerous the extreme values of vertical and horizontal pressure become.This implies that the distribution of particles is the principal mechanism affecting the distribution of pressure in a powder bed. Consequently, to analyze the mechanism of a powder bed, the transference of force among the particles should be evaluated considering the distribution of the particles and paying careful attention to each of the particles in the powder bed.     

A consideration of the effect of air pressure on solids flow from storage vessels

Based on a simplified block-flow model, the mechanism of flow of particles through an aperture is generally analyzed under the influence of air pressure. As a result, the effect of air pressure on the flow criterion and the flow rate of particles can be evaluated in terms of material properties, vessel geometry and operational conditions. Computed results satisfy previous data. Solids flow under air pressure is treated as a fluctuation phenomenon just as under gravity alone or tapping.     

The effect of interstitial gas on milling

In a research program on the influence of interstitial gas on the handling of fine powders, particle diameter less than 100 μm, the effect on milling is also investigated.The influence of the interstitial gas is exhibited through the drag force, due to velocity differences, which the gas exerts on the solid particles of the powder. These forces strongly influences the behavior of the powder.Our investigations of milling showed that the milling parameters, i.e. the specific rates of breakage and the breakage parameter, were dependent on the powder flow behavior. Two extremes were the regime of free-flowing powder, where the rate of breakage was high and the grinding of the individual particles was rather ineffective, and the regime in which the powder did not flow at all, where the rate of breakage was low, but where the grinding of the single particles was rather fine.     

Phenol decomposition in water cathode of DC atmospheric pressure discharge in air

We studied phenol decomposition in aqueous solution under the action of DC discharge at atmospheric pressure in air. The decomposition efficiency was 0.017 molecules per 100 eV. When the kinetics of forming destruction products was studied in detail, the peculiarities of air plasma action were revealed for the first time. Plasma action not only results in the formation of oxygen-containing products, which are usually formed under oxygen plasma action (hydroxyhenols, carboxylic acids, aldehydes), but also the formation of nitro phenols. The treatment is accompanied by hydrogen peroxide formation, a pH decrease, and nitric and nitrous acids formation. We also discussed the possible mechanism of the processes and the role of some active species in chemical transformations after determining some parameters of the discharge.     

池壁间隙砖漏风对窑压和油耗的影响

池壁间隙砖炸裂漏风，造成窑压偏大和油耗高，对其产生原因进行分析。采取对池壁间隙砖进行密封。取得明显效果。     

Minimizing the pressure gradients in capsule pipelines

The pressure gradients due to cylindrical capsules were reduced by up to 80% by providing them with plastic instead of steel surfaces or by fitting them with collars. The power requirements of a capsule pipeline depend greatly on the capsule density, and if the capsules were constructed so that a third of the volume consisted of voids, the power needed to transport two teragrammes (2 million tons)/year of solid with a density of 1500 kg.m^?3 (S.G. = 1.50) in a 254 mm (10 in.) pipeline would be reduced by over 90%. The pressure gradients and power required to transport spherical capsules were generally much smaller than those required for even the smoothest cylinders of the same specific gravity.     

Determining the pressure of refractory bodies at discharge from the feed tubes

Conclusions For the design of presses, the height of the column of body in the feed tubes during filling needs to be fixed at not less than a certain level calculated for the dryest body which can be pressed in the press.In existing presses the permissible height of body in the tube can be taken as the lowest, in accordance with the results of our experiments for each body.A mathematical relationship was established for the pressure at the bottom and on the walls of the pipe and the height of the column of body in the pipe.     

The removal of dichloromethane from atmospheric pressure air streams using plasma-assisted catalysis

Plasma-assisted catalysis was used for the destruction of 500 ppm of dichloromethane, CH₂Cl₂ (DCM), in gas streams of air using a non-thermal, atmospheric pressure plasma utilising a dielectric packed bed. The combination of plasma and catalyst gave improved destruction of DCM. Eight catalysts which including alumina, TiO₂ and various zeolites were investigated with the finding that alumina in a one-stage reactor configuration and TiO₂ and HZSM-5 in two-stage configurations gave the best DCM destructions. The sodium zeolites are capable of reducing by 50% the unwanted NO_x by-products, formed by plasma processing in air. The nature of the catalyst is important in terms of the destruction efficiency, end-product selectivity and NO_x reduction.     

The vertical force of bulk solids on objects in bins

The vertical force exerted on discs, spheres and horizontal square bars in test bins was measured during gravity flow of bulk solids. Approximate methods for estimating the vertical force on such objects were developed from the equation which expressed the stress in a conical mass flow hopper. With three adjustable parameters, good agreement was obtained between experimental and computed results for discs, provided the disc diameter was more that five times as large as the particle diameter. Identical parameters for a given material were found to be applicable in analyses for spheres and horizontal square bars.     

The effect of interstitial gas on milling. Part 2

In a previous paper results were presented on the effect of interstitial gas on the milling characteristics of one specific fine powder in a ball mill. This second paper gives more data on two other powders, cracking catalyst and hematite, together with those on the powder used in the earlier experiments, quartz sand. The effects found are similar for each of the three powders: increasing gas pressure or viscosity of the gas or both inside the mill increases the rate of breakage and decreases the fineness of the daughter particles of a milling event. The overall milling speed or production rate as well as the ultimate fineness of the product are both improved by increasing pressure or viscosity.On the basis of these results a comparison is made with wet milling. It appears that pressurized milling, pressure around 10 bar, is a good alternative for the milling of fine powders.     

The effect of electrolyte constituents on contact glow discharge electrolysis

Ordinary electrolysis developed spontaneously to contact glow discharge electrolysis (CGDE) at sufficiently high voltage, with glow discharge taking place around a thin platinum anode which was in contact with electrolyte solution. During this transition, the critical voltage (V_D) was an important parameter for the onset of CGDE. The results indicated that V_D decreased with the increasing conductivity and then maintained a certain value. The different dimension and material of cathode had little effect on V_D. When the electrolyte conductivity was 5.0 mS/cm, V_D was hardly affected by electrolyte composition. And the concentrations of H₂O₂ producing in the anolyte were close in different inert electrolyte. However, the concentrations of H₂O₂ in NaCl, NaAc, Na₂CO₃ and NaHCO₃ solution were lower than that in Na₂SO₄ solution. And the concentration of H₂O₂ in the anolyte was also decreased by adding a minute amount of CH₃OH.     

The effect of air on the packing structure of fine particles

A numerical study of the effect of air on the packing structure of fine particles has been performed by a combined continuum and discrete numerical model. The forces considered are gravity, contact force, drag force, and van der Waals forces. The results are analyzed in terms of particle rearrangement, local porosity, coordination number, radial distribution function, and the distribution of contact forces. The results indicate the degree to which drag and van der Waals forces promote mean porosity increases and mean coordination number decreases. Drag forces allow contacts of particles reaching a state of rest in a packing to be closer to the Coulomb failure criterion for shear displacement when van der Waals forces are small. Increasing van der Waals forces imposes contact conditions that are far away from the Coulomb failure criterion. Increased drag and van der Waals forces tends to lead to more heterogeneous structure. It is demonstrated that average normal contact force is related to the ratio of van der Waals forces to particle weight.     

The effect of air distribution on the induced air flotation of fine oil in water emulsions

The induced air flotation (IAF) of a highly stabilized oil in water (o/w) emulsion has been studied experimentally in a batch column 10 cm in diameter and 150 cm in height. Column performance was strongly affected by the method of air distribution. The main variables investigated were the type of air distributor (either porous plate, single hole plate, or multi-hole plate), initial oil concentraton (30-600 mg/L), oil drop size distribution of feed (1.0-30 μm), surfactant type, and gas superficial velocity. Results were successfully analyzed in terms of a first order kinetic rate model which yielded a removal rate constant (K₁) that varied from 2.0 to 60.0 h^?1. Corresponding total organic carbon (TOC) removal efficiencies went from 20 to 99.9 percent, illustrating the wide performance range for the flotation cell.     

Atmospheric pressure plasma treatment of polyethylene via a pulse dielectric barrier discharge: Comparison using various gas compositions versus corona discharge in air

Modification of polyolefin surfaces is often necessary to achieve improved printability, lamination, etc. Although corona discharge and flame treatments can produce the higher surface energy needed for these applications, the properties of the resulting surfaces are not always optimal. Atmospheric pressure plasma is a surface modification technique that is similar to corona discharge treatment, but with more control, greater uniformity, and higher efficiency. Using an atmospheric pressure plasma unit with a dielectric barrier discharge generated using an asymmetric pulse voltage, the effects of different gases, powers, and linespeeds on polyethylene surface treatment were studied. Our results show that atmospheric pressure plasma can be used to achieve higher long‐term wettability, higher surface oxygen and nitrogen, and a greater range of surface chemistries with better robustness versus standard corona treatment. Atomic force microscopy results suggest significant differences in the mechanism of surface functionalization versus etching and ablation depending on the gases used. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 319–331, 1999     

The pressure swing adsorption drying of compressed air

An experimental and theoretical study of the drying of compressed air by a granular silica gel adsorbent was carried out using pressure swing adsorptio This process uses a portion of the dried air expanded to a lower pressure to purge the saturated bed for regeneration purposes. The effect of the volum ratio purge flow/feed flow on the dry air humidity when the process has reached quasi-steady state was investigated over the range 0.85–1.48. These humidities were predicted successfully by a simplified dynamic adsorption model using previously determined equilibrium and rate data. The approach to this steady state was also predicted. The calculated values of the humidity of the outlet regeneration flow indicate the potential of this process for the enrichment of trace adsorbates.     

Surface degradation and hydrophobic recovery of polyolefins treated by air corona and nitrogen atmospheric pressure glow discharge

The surface degradation and production of low molecular weight oxidized materials (LMWOM) on biaxially oriented polypropylene (BOPP) and low‐density polyethylene (LDPE) films was investigated and compared for two different dielectric barrier discharge (DBD) treatment types, namely air corona and nitrogen atmospheric pressure glow discharge (N₂ APGD). Contact angle measurements, X‐ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) analyses were performed in conjunction with rinsing the treated films in water. It is shown that N₂ APGD treatments of both polyolefins result in much less surface degradation, therefore, allowing for a significantly higher degree of functionalization and better wettability. Hydrophobic recovery of the treated films has also been studied by monitoring their surface energy (γ_s) over a period of time extending up to several months after treatment. Following both surface modification techniques, the treated polyolefin films were both found to undergo hydrophobic recovery; however, for N₂ APGD modified surfaces, γ_s ceases to decrease after a few days and attains a higher stable value than in the case of air corona treated films. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1291–1303, 2004