Electrical Single Particle Aerodynamic Relaxation Time Research Articles

Effect of Surface Treatment of Carrier on Toner Charging Characteristics

Nowadays the two-component developers are widely used in electrophotography. In two-component developing system toner is tribo-electrically charged by contacting with carrier. In this study, two types of crushed toners categorized according to the constitution of external additives and four types of carriers which are also categorized according to the surface treatment were used for the experiment. The toner charge distribution is changed by the type of carrier coating and concentration of external additives as well. The Aerodynamic size and electrostatic charge distribution of the toner particles are measured individually by E-SPART (Electrical Single Particle Aerodynamic Relaxation Time) analyzer.

Toner Charge Distribution Change on Toner Mixing Time: Effect of carrier charging ability

Toner tribocharging characteristics are affected by various factors : charging method, materials, environment and others. The toner charge stability is important for keeping a good image quality. Toner charge distribution is one of important factors in electrophotographic printing process. The toner charge distribution is changed by toner mixing conditions of toner weight % and toner mixing time. In this study, aerodynamic size and electrostatic charge distribution of the toner particles are measured individually by E-SPART (Electrical Single Particle Aerodynamic Relaxation Time) analyzer. It is found that two peaks in toner charge histogram arise in some conditions.

Size Dependence on Toner Charge in Two-Component Developer

In the electrophotographic process, two-component developers are widely used for commercial machines. Quantity of tribo-electric charge on toner is one of the factors to affect image quality for copies. Effects of toner components and size on tribo-charging are important to evaluate electrophotographic developers. In this study, size dependence on toner charge is examined by a modified E-SPART (Electrical Single Particle Aerodynamic Relaxation Time) analyzer based on a laser Doppler velocimetric method for toner particles of styrene-acrylic copolymer in the size region from 6μ m to 10μ m. As a carrier, a polymer coated ferrite type or a non-coated type is used. From the experimental results, charge to mass ratio q/m decreases from 10 μ C at 6.4μ m to 4.6 μ C at 9.5μ m for toner without silica coating and CCA additives and the reverse m/q shows approximately a linear increase with diameter of toner in a two-component developer combined with a coated carrier. In case of a non-coated carrier, the n-th power size dependence on toner charge is shown to be about 2.7 for the toner with silica coating and CCA additives and about 2.2 for the toner without CCA additives. The results are explained to be consistent with prediction from the surface state theory.

Particle Size and Charge Distribution Analysis of Pharmaceutical Aerosols Generated by Inhalers

Aerosol particles generated by inhalers for respiratory drug delivery acquire electrostatic charge during the dispersion process. The electrostatic charge distribution of the particles can affect the efficiency of drug delivery by influencing both the transport and deposition of inhaled particles in the human lung. To analyze the electrostatic charge acquired by the aerosol particles, two sets of metered-dose inhaler (MDI) and dry powder inhaler (DPI) devices were investigated. Both the particle size and charge distributions were measured simultaneously by using an electrical single-particle aerodynamic relaxation time (E-SPART) analyzer. The analyzer was calibrated with particles of known size, which were generated by a vibrating orifice aerosol generator (TSI Inc.) and charge using the Faraday cup method. The charge distributions of the pharmaceutical aerosols from both the DPI and MDI devices were bipolar in nature. Although the net charge-to-mass ratio was less than 0.2 μC/g, the individual particles were charged with a relatively high charge: −2 to + 2 μC/g. The count mean aerodynamic diameter of the aerosols generated from these devices was 3–5 μm.

E-SPART Analyzer for Mars Mission: A New Approach in Signal Processing and Sampling

This paper introduces a novel electrical single particle aerodynamic relaxation time (E-SPART) analyzer for dust particle analysis in the Mars mission. The new E-SPART analyzer is based on a stationary-fringe laser Doppler velocimeter that can simplify the system hardware and reduce its physical size and weight. This paper presents the new operational principle and the signal processing methods. The requirement of the size of sensing volume is discussed by considering pedestal removal and the required time duration of a Doppler signal burst. Experimental results are given to confirm the effectiveness of the principle.

Bipolar charge distribution of a mixture of particles with different electrostatic characteristics in gas–solids pipe flow

Electrostatic charge distribution of fine particles in gas–solids pipe flow has been studied experimentally. The powders used were fly ash, 4.2 μm count median diameter (CMD), and alumina powder, 3.9 μm CMD. These powders were fully dispersed and pneumatically transported in a spiral stainless steel pipe, 6 mm in inner diameter. The average air velocity was in the range from 20 to 39 m/s, and the mass flow ratio of particles to air was 5×10 −4. The particles were charged by contact with the inner wall of the pipe. The charge and the diameter of individual particles were measured with an electrical-single particle aerodynamic relaxation time (E-SPART) analyzer. The experimental results showed that the charge on the particles increased with pipe length and reached an equilibrium (maximum) value. The fly ash was generally charged negatively, and the alumina powder was charged positively. However, the value of the charge of each powder was widely distributed having charge of opposite sign. Furthermore, a bipolar charge distribution was measured using a mixture of fly ash and alumina particles, showing that the charge distribution in a dilute phase transport system could be explained by the linear additivity of the charge distribution of each powder.

Charging Characteristics of Polymerized and Pulverized Toner in the Roller Rotation Mixing System of Toner and Carrier

Toner charge is very important in electrophotographic printing process. Although many studies on toner charging have been carried out, the process is very complex and the understanding of toner charging characteristics is not yet sufficient. In this paper, toner charge distribution is measured by E-SPART (Electrical Single Particle Aerodynamic Relaxation Time) analyzer, which can measure the size and charge of toner. The measured toners are polymerized and pulverized type. Charging is carried out as follows : the toner is mixed with the carrier and the mixture is bottled into the roller, and mixed by rotating the roller. Toner charge dependences on toner wt% are compared between polymerized and pulverized toner.

Toner Charging Characteristics in the Rotation Mixing System of Toner and Carrier

Toner charge is very important in electrophotographic printing process. Many studies on toner charging mechanism have been carried out. However, understanding of toner charging characteristics is not yet sufficient. Toner charge distribution is measured by E-SPART (Electrical Single Particle Aerodynamic Relaxation Time) which can measure and analyze the size and the charge of respective toner. The measured toner is of a crushing type. Charging is carried out as follows: the toner is mixed with carriers in a bottle and mixed by the rotation of the bottle. Average toner charge of each channel of the toner diameter is estimated. It is found that the average toner charge is proportional to the square of toner diameter and shows a saturation as the diameter increases. The experiment of adding the toner after the toner is charged to nearly stationary is carried out. It is found that toner charge distribution becomes a new value due to charge exchange between the toner and the toner/carrier.

Electrostatic Effects on Dispersion, Transport, and Deposition of Fine Pharmaceutical Powders: Development of an Experimental Method for Quantitative Analysis

Currently, there is no standard method for testing the electrostatic properties of pharmaceutical powders. The objective of this study was to develop a method of characterizing the dispersion, charging, and transport properties of fine powder flowing through tubes of different materials. Powders of known composition and size distribution were dispersed pneumatically and transported through a short section of tubing containing spiral baffle inserts of the same material to simulate powder flow in long sections of horizontal and vertical tubes with bends. The test powder was dispersed using ring jet suction and passed through the baffled tube to a sampling chamber, from which the powder cloud was sampled for particle size and electrostatic charge distribution measurement using an Electrical Single Particle Aerodynamic Relaxation Time (E-SPART) analyzer. Experimental data on the tribocharging and transport properties of different powders are presented along with an explanation of the charging mechanisms. Analyses of particle size and electrostatic charge distributions in real time and on a single particle basis using the E-SPART analyzer coupled with surface structure analyses with XPS and UPS showed that: (1) most powders are charged bipolarly with relatively high charge-to-mass ratio (Q/M) values that would have a strong effect on transport and deposition of powders; and (2) surface structures, particularly adsorbates, influence the work function and tribocharging of powder. Different methods, including plasma treatment, with minimal changes or contamination of the bulk properties of the powders are also suggested. pharmaceutical powders tribocharging dispersion work function charge distributions charge decay plasma treatment

Electrostatic charge distribution of particles in gas–solids pipe flow

A model for the tribo-charging in gas–solids pipe flow to analyze the electrostatic charge distribution of particles has been presented. The model is based on the charge transfer caused by particle impacts on the wall surface and takes into account three probability density functions: (i) the number of collisions of a particle with the wall, (ii) initial particle charge, and (iii) the impact electrification factor characterizing the transferred charge. These functions individually affect the electrostatic charge distribution, and hence key parameters on the particle electrification can be determined from the charge distribution. Furthermore, the relevant experiments have been carried out using fly ash particles, 7 μm in count median diameter. The charge distributions, which were measured with the electrical-single particle aerodynamic relaxation time (E-SPART) analyzer, agreed with the theoretical ones, and by analyzing the key parameters determined from the experimental data, the states of the particle electrification were evaluated quantitatively.

E-SPART Analysis of Poly (D, L-lactide-co-glycolide) Microspheres Formulated for Dry Powder Aerosols

ABSTRACT Electrical-single particle aerodynamic relaxation time (E-SPART) analysis was studied as a tool in formulation screening of diy powders for use in aerosol delivery to the lung. The respirable fraction (RF) of drugs delivered by dry powder inhalers (DPIs) can be improved more effectively by using hydrophobic microspheres as carriers. Poly (D,L-lacttde-co-grycolide) microspheres (PLGA) prepared in die respirable size range (3-7 mm) were treated with poryamino acids and isopropanol in order to obtain particles of surface charge suitable for use in DPIs. The powder formulations were evaluated for their degree of aggregation by cascade impaction following delivery by the Pfeifler® DPI. The IPA treated PLGA microspheres had a significantly higher RF (12.9%) as compared to the PL and PGA treated microspheres (3.3 and 2.4%, respectively), and untreated microspheres (3.8%). Results of electrostatic charge determined by E-SPART analysis suggested that die higher RF for the IPA formulation may be due to hs highly unipolar nature (+ 56.3 mC/g).

Effect of surface treatment on the respirable fractions of PLGA microspheres formulated for dry powder inhalers

An investigation of the degree of aggregation of dry powders with different surface charge and moisture contents was carried out using poly( d,l-lactide-co-glycolide) (PLGA) microspheres. Microspheres were prepared in the respirable size range (3–7 μm) with an estimated zeta potential (ZP) of −30.6 mV. Suspensions of polylysine (PL) and polyglutamic acid (PGA) in isopropanol were used to treat the microspheres to obtain ZPs of ±60 mV, respectively. Treatment with isopropanol (IPA) alone yielded a ZP of −36.7 mV, which was similar to the untreated microspheres −30.6 mV. Respirable fractions (RFs) were determined by cascade impaction using a prototype DPI. The IPA-treated formulation was the most deaggregated of the studied samples as indicated by a significantly higher RF (12.9) compared to the PL and PGA formulations (3.29 and 2.42, respectively) and the untreated PLGA microspheres (3.84). Microspheres with moisture contents in the range of 0.40–2.47% were studied and a moisture content of 0.66% resulted in the highest relative deaggregation of the PLGA microspheres. Measurement of the surface charge and mass median aerodynamic diameter in the dry state by electrical-single particle aerodynamic relaxation time analysis (E-SPART) suggested that the higher RF for the IPA formulation may be due to its highly unipolar nature, i.e. a net charge of +56.3 μC/g, as compared to net charges in the range of 34.3–38.4 μC/g for the other microspheres. Formulation of microspheres for use in DPIs must proceed on a case by case basis as certain approaches can enhance aggregation.

Characterization of tribocharging properties of powder paint

The charge-to-mass ratio (q/m) of individual particles plays a vital role in the powder coating process. Simultaneous measurements of particle size and electrostatic charge were performed on triboelectrically charged powder paint and other powders in the particle size range 1.0 to 65.0 /spl mu/m in diameter. An electrical single particle aerodynamic relaxation time (ESPART) analyzer was used to measure electrostatic charge (q) and aerodynamic size (d/sub a/) distributions on a single particle basis and in a noninvasive manner. The powders were triboelectrically charged against nonconducting surfaces. Experimental data show that (1) the magnitude of the charge increases linearly with the surface area of the particle and consequently, the charge-to-mass ratio of the particles decreases inversely with respect to d/sub a/ in the entire size range, and (2) twenty to sixty percent of the particles were charged with opposite polarity. The average charge attained by particles larger than 4.0 /spl mu/m in diameter was less than the Gaussian limit of saturation charge. The charge-to-mass ratio of the bulk powder sample depends upon the range of particle size in the sample. The mass median aerodynamic diameter of the sample studied was 30.0 /spl mu/m with the geometric standard deviation of 2.0. >

Measurement of particle size and electrostatic charge distributions on toners using E-SPART analyzer

Performance characteristics of a laser-based instrument called the electrical-single particle aerodynamic relaxation time (E-SPART) analyzer for measuring aerodynamic size and electrostatic charge distribution of particles in real time and on a single-particle basis are described. Applications of this analyzer along with experimental data of the characterization of different toners for their size and charge distributions are presented, including operational principles and methods of data acquisition. Size distribution ranged from 2.0 to 20.0 mu m in aerodynamic diameter, and the charge-to-mass distribution ranged from 0 to +or-20 mu C/g. The method is noncontact and provides both magnitude and polarity of electrostatic charge on an individual particle basis. The aerodynamic diameter and charge are measured simultaneously at an average count rate of approximately 100 particles/s. >