Electrostatic Charge Accumulation Research Articles

Electrostatic characterisation of inhaled powders: Effect of contact surface and relative humidity

Electrostatic charge accumulation on drug and excipient powders arising from interparticulate collisions or contacts between particles and other solid surfaces often leads to agglomeration and adhesion problems during the manufacture and use of dry powder inhaler (DPI) formulations. The aim of this work was to investigate the role of triboelectrification in particle interactions between micronised drug (salbutamol sulphate or ipratropium bromide monohydrate) and excipient (α-lactose monohydrate, 63–90 μm) during mixing in cylindrical vessels constructed from stainless steel, polypropylene and acetal under selected relative humidity (rh) conditions (0–86%). The charge was found to depend on both the nature of the powders and the mixing vessel surface. In addition, coating the vessels with drug or excipient removed the influence of the vessel material on charge generation, thus providing a technique to investigate interactions between the drug and excipient substances. A triboelectric series of all materials used, placed ipratropium at the positive end and polypropylene at the negative end. Micronised drug profoundly altered the charging properties of lactose in drug (1.46%, w/w)/lactose DPI formulations. An increase in rh in the range 0–86% produced a corresponding decrease in charge and adhesion values for each drug, lactose and DPI formulation during triboelectrification with each mixing vessel surface. The results provide increased knowledge of the role of electrostatics in DPI technology.

A miniature charged plate for testing charge accumulation in hard disk drives

A technique for monitoring electrostatic charge accumulation inside a hard disk drive (HDD) is described: a miniature charged plate is built into the top cover of the HDD, connected to a charged plate monitor. Experiments show that the miniature plate technique can be used for detection and measurement of the voltage induced by the charge generated inside the grounded enclosure of a hard drive.

Electrostatic ignition hazards in the process industry

Fires and explosions continue to be triggered by the accumulation of electrostatic charge in different branches of the process industry. This is the case even though nowadays the electrostatic phenomena that give rise to ignition hazards in industrial practice are generally well known. This paper presents various reasons as to why this should be so and draws attention to the conflicts of interest, which arise, when other requirements need to be met. In addition, current trends and new results with respect to the assessment of electrostatic ignition hazards are reviewed. They include (i) incendivity and characterisation of discharges from insulating surfaces with and without contact to a conductive surface, (ii) incidents affecting the present assessment of occurrence and incendivity of propagating brush discharges in practice and (iii) characterisation, measurement method and ignition hazard assessment of modern packaging systems such as flexible and rigid intermediate bulk containers (FIBC and RIBC). Finally, the consequences of Directives issued at the European and national levels are appraised with respect to electrostatic ignition hazards.

Overcoming the Electrostatic Discharge in Hydraulic, Lubricating and Fuel-Filtration Applications by Incorporating Novel Synthetic Filter Media

Electrostatic charge generation occurs in fluid systems as a result of friction between the fluid and system components. The magnitude of charge generated by each component will depend on many interrelated factors, including environmental ones. It can occur during filtration of hydraulic and lubricating oils as well as diesel and gasoline fuels. This effect manifests itself in several ways, the most noticeable effect being an audible noise (clicking sound) as the discharge of electrostatic charge accumulation causes sparking internally within the system. Less-apparent effects involve migration of the electrical charge downstream of the filter, causing damage to system components and the filter itself when the charge dissipates by discharging itself to a grounded surface. Several methods have been investigated to overcome the aforementioned behavior and prevent the damage that can occur if the electrostatic discharge continues to operate unchecked. One of these methods involved adding an antistatic additive to the liquid, but this is restricted to fuel applications. Other methods involved surface modifications carried out directly on the filter media or the use of conducting materials such as meshes made from suitably selected conducting materials that can be incorporated into the construction of filter cartridges. The main aim of these modifications is to affect a discharge from the filter cartridge, before a hazardous potential accrues on the filter media, by lowering the voltage gap. Although this approach eliminates direct damage to the filter cartridge, it does not prevent charge migration into the oil where it subsequently accumulates. The approach we took involves designing the filter material to be electrostatic dissipative, which offers the advantage of eliminating filter damage entirely and significantly reducing migration of charge into the fluid.

Spacer devices for metered dose inhalers.

Spacer devices are attachments to the mouthpieces of pressurised metered dose inhalers (pMDIs), and range from tube spacers with a volume of <50 mL to holding chambers with a volume of 750 mL. Compared with a pMDI alone, spacers minimise coordination difficulties, reduce oropharyngeal deposition and often increase lung deposition. Spacers may not improve the clinical effect in patients able to use a pMDI properly, but may allow maintenance dosages of bronchodilators and corticosteroids to be reduced. Correct use of spacer devices is important, especially achieving control over electrostatic charge accumulation on the walls of plastic devices. In patients with severe acute asthma or severe chronic obstructive pulmonary disease, a pMDI plus large volume spacer may be a viable alternative to a nebuliser for delivering large bronchodilator doses. Although the addition of a spacer to every pMDI would not be justified, the use of large volume spacers has been recommended for any inhaled asthma drug in young children, and as a means of reducing systemic bioavailability of inhaled corticosteroids in adults and children alike.

Accumulation of Electrostatic Charge on YBa 2 Cu 3 O 6.8 Cuprate upon Its Reduction

Accumulation of Electrostatic Charge on YBa 2 Cu 3 O 6.8 Cuprate upon Its Reduction

Reduction of electrostatic charges in gas–solid fluidized beds

Reduction of electrostatic charge accumulation by increasing the humidity of fluidizing gas was investigated using single bubble injection in two- and three-dimensional fluidized beds. Both 321 μm glass beads and 378 μm polyethylene particles were found to be charged positively when fluidized by air. Electrostatic charges increased as the bubble size increased. Increasing the relative humidity of the fluidizing air to 40–80% reduced the accumulation of electrostatic charge by increasing the surface conductivity, thereby enhancing charge dissipation.

Hazards and problems associated with liquids

After paying tribute to the work of Helmut Krämer in the field of electrostatics, this paper examines the mechanisms involved in the accumulation and relaxation of electrostatic charge in liquids. Based on this, an assessment is then made of the ignition hazards when filling vessels with flammable nonpolar liquids, particularly when multiphase systems are involved or the liquids are sprayed.

SCALPEL mask-membrane charging

Electrostatic charge generation and accumulation in a:SiNx thin films irradiated by energetic (100 keV) electrons is investigated and kinetic equations describing the dynamic process are formulated. It is found that the incident electrons, inelastically scattered in the membrane, primarily generate plasmons. The plasmon decay creates electron-hole pairs and secondary electrons (SE). The escape of the SEs from the target leads to a positive electrostatic charge accumulation in the membrane. It is shown that SCALPEL^(R) mask-membrane charging is defined by the balance of the SE escape, hole trapping and transport processes.

Network Formation in Nanoparticulate Tin Oxide−Gelatin Thin Films

Electrostatic-charge accumulation and discharge can cause a variety of problems in imaging, electronic, and packaging materials and processes. Nanoparticulate antimony-doped tin oxide containing antistatic layers provide robust electronic conductivity that survives aqueous and thermal processing. Dielectric spectroscopy of tin oxide-gelatin (antistatic) thin films reveals relaxation processes that depend on tin oxide-to-gelatin ratios and upon tin oxide-gelatin film thickness. The frequency maxima of dielectric-loss peaks inversely correlate with surface electrical resistance (SER) measurements. A simple model of a layered heterogeneous dielectric explains the relative position of dielectric-loss peaks in terms of antistatic-layer conductivity. Dielectric measurements of antistatic layers do not require ohmic contact with such layers, and measurements on buried layers are straightforward. An observation of apparent percolation induced by variations in coverage, at constant tin oxide-to-gelatin weight ratio, suggests that the coating conditions and drying processes appear to play a role in network formation and nanoparticulate aggregation. Scaling of (inverse) SER and dielectric-loss peak frequencies above the percolation threshold conforms with scaling expected for electrical-conductivity percolation in three dimensions.

The effects of contaminants on the behaviour of conductivity improvers in hydrocarbons

Dangerous accumulation of electrostatic charge can occur due to high-speed pumping and microfiltration of jet fuel. This can be avoided by increasing the electrical conductivity of the fuel using conductivity improver additives. However, marked variations occur in the conductivity response of different fuels when doped to the same level with conductivity improver. This has been attributed to interactions of the conductivity improver with other fuel additives or fuel contaminants. The present work concentrates on the effects of fuel contaminants, in particular polar compounds, on the performance of the conductivity improver. Conductivity is the fuel property of prime interest. The conductivity response of model systems of the conductivity improver STADIS 450 in dodecane has been measured and the effect on this conductivity of additions of model polar contaminants sodium naphthenate, sodium dodecyl benzene sulphonate, and sodium phenate has been measured. The sodium salts have been found to have a complex effect on the performance of STADIS 450, reducing the conductivity at low concentrations to a minimum value and then increasing the conductivity at high concentrations of sodium salts. This work has focused on characterising this minimum in the conductivity values and on understanding the reason for its occurrence. The effects on the minimum conductivity value of the following parameters are investigated: (a) time, (b) STADIS 450 concentration, (c) sodium salt concentration, (d) mixed sodium salts, (e) experimental method, (f) a phenol, (g) individual components of STADIS 450. The complex conductivity response of the STADIS 450 to sodium salt impurities is discussed in terms of possible inter-molecular interactions.

Solar Wind Modulation of the Global Electric Circuit and Apparent Effects on Cloud Microphysics, Latent Heat Release, and Tropospheric Dynamics.

The solar wind modulation of the energy distribution and flux of galactic cosmic rays causes 11 year cycles in the latitude distribution of air-earth current density in the global electric circuit. Similar changes occur with solar activity on the day to day time scale. At least 3 independent data sets correlate changes in tropospheric winds and vorticity with measured and modelled changes in air-earth current density in the troposphere. These are (1) the decadal oscillations in winter in the North Atlantic region, with period averaging 11 ± 2 years over the last 120 years, and which appear to have been phase locked to the solar cycle except for a period of generally low solar activity prior to 1925; (2) the decrease in 500 mbar Vorticity Area Index (VAI) in winter at times of Forbush decreases of cosmic ray flux; and (3) decreases of 500 mbar VAI in winter at times of solar wind magnetic sector boundary passages, when volcanic aerosols from Agung and El Chicon were in the global stratosphere, together with solar wind sector modulated relativistic electron precipitation. One possible physical mechanism connecting changes in air-earth current density with changes in tropospheric dynamics is via the accumulation of electrostatic charge at cloud tops affecting the microphysics of ice nucleation and precipitation, with consequences for latent heat release and the intensification of winter cyclones.

Electrification analysis of a web or sheet moving between pinch rollers

Abstract A model is developed which provides a phenomenological understanding of the static electrification of a web or sheet by a pinch roller system through which it passes, in terms of the electrostatic characteristics of the separate regions comprising the system. The total pinch roller interaction is characterized by a matrix and vector which are derived from the characteristics of the component parts of the interaction. It is therefore possible to examine the effect on the electrostatic performance of the whole system caused by a change in one or more components. The mode of accumulation of electrostatic charge on a web subjected to many repeated passes through the pinch roller system is derived and reveals that a unique equilibrium charge density on each surface is approached regardless of the initial charge density configuration. However, the sequence of discrete charge density changes on each surface, by which the equilibrium charge configuration is approached, is a unique function of the initial charge density on each surface. The model should be useful in designing or improving pinch roller devices, i.e., in choosing roller materials and their physical configuration.

Stratospheric volcanic aerosols and changes in air‐earth current density at solar wind magnetic sector boundaries as conditions for the Wilcox tropospheric vorticity effect

A correlation between tropospheric dynamics and solar wind magnetic fields that disappeared in the early 1970s reappeared with a new injection of volcanic aerosols into the stratosphere. A similar pattern of correlation has been found for changes in current density in the global electric circuit and for changes in relativistic electron precipitation. Several other weather and climate variations have been found to correlate with changes in air‐earth current density due to solar wind modulation of the global electric circuit. The accumulation of electrostatic charge on supercooled droplets at cloud tops responds to air‐earth current density changes. A mechanism linking the effects of charge accumulation to changes in ice nucleation, precipitation efficiency, latent heat retention and perturbations in atmospheric dynamics is thus as an explanation for this and other solar wind ‐ atmospheric electricity ‐ weather and climate correlations.

Correlations of atmospheric dynamics with solar activity evidence for a connection via the solar wind, atmospheric electricity, and cloud microphysics

We respond to several criticisms of the view that there is a physical linkage between solar activity and the dynamics of the troposphere and lower stratosphere, and we provide further evidence in support of a mechanism for such a linkage involving atmospheric electricity and cloud microphysics. The main criticisms are (1) that the decadal time scale variations in stratified data result from aliasing introduced by the sampling process and are not responses to a decadal time scale physical input; (2) that the observed correlations are due to chance coincidence or an atmospheric periodicity that is not uniquely related to solar variability; and (3) that there are no plausible mechanisms that can amplify one of the weak solar‐varying inputs in the region where the correlations are found. We show that the aliasing criticism is inadequate because the real quasi‐biennial oscillation departs from an ideal sine wave in a way that reduces aliasing effects to insignificant levels. The nonuniqueness of identification of the 11‐year solar cycle as the period of the arctic forcing for the Arctic winter stratospheric temperatures is a problem only for the short 33‐year record of polar temperatures; in much longer time series of unstratified climate data the periods of 11 and 22 years are prominent. Highly unique signatures of solar wind forcing of tropospheric dynamics exist on the day‐to‐day time scale via two independent inputs to atmospheric electricity. These are (1) through changes in tropospheric ion production as a result of solar wind modulation of galactic cosmic rays and (2) through changes in the potential difference between the polar ionospheres and the surface, forced by the solar wind By component. The product of the cosmic ray flux and the ionospheric potential determines the vertical air‐earth electrical current. In the presence of clouds of large horizontal extent, this current determines the rate of polarization charging of the clouds via the accumulation of positive electrostatic charges on droplets near cloud tops. The observed correlations, and theoretical and laboratory results for the effects of electrostatic charges on droplets and aerosols on the rates of ice nucleation, are consistent with the postulate that for certain regions and seasons and atmospheric levels the large‐scale atmospheric electrical parameters have significant effects on the rates of initial ice nucleation. In such cases the chain of consequences includes changes in the rates of precipitation, net latent heat release, vertical motions, atmospheric vorticity, and ultimately in the general circulation. Much more work is required before the mechanism can be considered to have a secure basis in laboratory experiment and quantitative atmospheric modeling.

Experimental investigation of electrostatic fire accidents after aircraft landing and preventive measures

This work is an experimental investigation to determine the cause of electrostatic fire accidents after aircraft landing and to clarify the effects of various factors on the cause. This research work has conducted a series of ground simulation tests and actual flight tests under the fire and explosion environment conditions. The test results have indicated that the process of an aircraft landing run is the fundamental process of electrostatic charges generating in fuel tanks. After an aircraft comes to a stop, there is also a process of accumulation of electrostatic charges, while fuel charged with higher energy remains for a considerably long period, unable to dissipate. All kinds of unbonded conductors in the tank are electrodes for dangerous spark discharges. When an aircraft using RP-2 fuel flies in hot weather, the concentration of flammable vapor produced in the space above the fuel surface inside of the tank will, under certain conditions, come close to its chemical equivalent, thus possessing the condition of combustibles under which an electrostatic spark can cause fires and explosions. Some principles that should be followed in aircraft fuel system design are discussed.

A polymer with a copoly(ether‐ester‐amidic) structure. II. Laboratory spinning‐drawing operations and fibre characterization

AbstractPreparation and mechanical characterization of fibres from a new copoly(ether‐ester‐amide) are reported. The mechanical characteristics are slightly lower than those of polyamide 6, but satisfactory for textile use, and the fibres have larger moisture absorption. This gives rise to more comfortable fibres preventing the accumulation of electrostatic charges.

Identification of hazards caused by static electricity in dust chambers

A dust chamber is a room containing filtration sacks which are the final elements of dedusting chains. There is a real possibility of formation and retention of explosive dust-air mixtures in these chambers. In conjunction with this the problem arises of explosion initiation by electrostatic discharges. It was known so far that the dust becomes electrically charged in the processes of transport, pulverization and separation. Basing on material investigations and on comparative measurements of electrostatic fields outside filtration sacks, it was also possible to observe accumulation of electrostatic charges in filtration sacks. However, direct information on forming of electrostatic discharges, particularly inside sacks in conditions of dust layer separation was lacking hitherto. The problem outlined above was investigated experimentally on flax dusts. An indicator of electric discharges has been constructed and used for detection of spark discharges during separation of dust layers inside filtration sacks. The nature of the discharges was investigated on the laboratory stand and the discharge currents were recorded. Several parameters inclusively those of the equivalent discharge circuit were introduced for characterization of these discharges, basing on earlier own work. The applied investigation method allowed comparison between various filtration fabrics from the view-point of hazards caused by static electricity in dust chambers, which can find direct practical application when materials for filtration sacks are chosen.

Electrostatic ignition hazards in industry

Several accidents are described in which fires and explosions with electrostatic ignition sources have occured. These accidents are used to illustrate the precautions that should be taken to avoid the accumulation of dangerous electrostatic charges, and, in particular, nine simple rules are given, which, if followed, would reduce the electrostatic ignition risk in the majority of circumtances.

Low-cost conductive flooring for hospitals

A new type of electrically conductive flooring for use in hazardous locations in hospitals is designed to prevent the accumulation of electrostatic charges on personnel and equipment which would create an explosion hazard in areas where combustible anesthetics are stored or used. This discussion of the characteristics desired in such flooring, and of the results of tests which have been made, should prove interesting not only for hospital use, but for many other purposes, as an extrapolation of the basic principle.