Surface treatment of granular materials by dielectric barrier discharge in view of triboelectric charging improvement (original) (raw)
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Journal of Electrostatics, 2017
The aim of this paper is to point out the influence of dielectric barrier discharge treatment on tribocharging of granular insulating materials. Particles of Polyvinyl Chloride (PVC) and Polypropylene (PP) were subjected to an AC dielectric barrier discharge (DBD) plasma treatment in ambient airprior to tribocharging in a vibratory device. The charge to mass ratio was measured for treated and untreated materials. Electrostatic separation of a mixture of granular materials (PVC and PP) to measure the effectiveness of DBD treatment was evaluated by processing treated and untreated PVC/PP granular mixtures in a free-fall electrostatic separator. The obtained results clearly indicate that DBD has the capability to influence surface charging proprieties of polymer granular materials. In case of short treatment time, typically less than 3 s, a marked increase in the charge to mass ratios was observed for both PVC (about 35%) and PP (roughly 45%). In the same way, the quantity of DBD-treated materials, recovered after electrostatic separation, was increased by about 104% and 30% for PVC and PP, respectively, as compared to untreated case. The DBD treatment time is a key factor to increase the tribo electric effect.
2018
Effective triboelectric charging is a prerequisite of the successful electrostatic separation of granular insulating materials. If the triboelectric effect imparted them high levels of charge of opposite polarities, the particles can be easily separated in a high-intensity electric field. The dielectric barrier discharge (DBD), commonly used for ozone production, air depollution or surface treatment is able to change the triboelectric properties of plastics. Depending on the conditions of DBD treatment (amplitude and frequency of the voltage applied to the electrode system, the duration of the exposure...) the triboelectric charge of plastics can be improved or decreased. The aim of this study is to compare the results of triboelectric charging and electrostatic separation of DBD-treated and untreated plastic particles originating from WEEE. Triboelectric series were established for nine different plastics (ABS, HIPS, PC, Cristal PC, PE, PP, PS, Cristal PS and PVC) using a rotating ...
Journal of Physics: Conference Series, 2019
The dielectric barrier discharge (DBD) is a convenient way to modify the surface properties of polymers. The aim of this study is to evaluate the effect of atmospheric DBD treatment on the triboelectric properties of polymers in sliding contact. The experiments were carried out on two polymers that were rubbed against each other: PP and PE. The pairs of samples were exposed to the DBD, and then taken to a triboelectric test bench for friction charging. The distribution of electric potential at the surface of the tribocharged samples was measured by an electrostatic voltmeter. The triboelectric behavior of the considered polymers depends on the conditions of DBD treatment: thickness of the dielectric barrier and duration of the exposure to the non-thermal plasma.
2017
Triboelectric charging is used for many applications including electrostatic separation of granular insulating materials. For this application, the granules should get the highest electric charge, so that the electric field for ces could easily separate them. Triboelectric charging is a surface phenomenon and dielectric bar rier discharge (DBD) is known for its ability to change surface properties of different materials. This study is focused on the evaluation of the DBD factors that might enhance the triboelectric charging properties of Polypropylene (PP) mm-size granules: the discharge duratio n, as well as the frequency and the amplitude of the high-voltage. After having been exposed to the DBD, the granules were tribocharged in a vibratory device for 5 min. Then, the charge was measured by a Faraday pail connected to an electrostatic voltmeter. The result s show that under optimal operating conditions, DBD exposure can enhance the triboelectric c harging by about 30%.
Journal of Electrostatics, 2018
Tribocharging of insulating materials is a pivotal step in several electrostatic applications in which the charge value has an important consequence on the outcome of the process. The Dielectric Barrier Discharge (DBD) at atmospheric pressure is an excellent energetic plasma source having the aptitude to change surface properties and, thereby, to enhance triboelectric charging of granular insulating materials. This paper aimed to investigate the influence of dielectric barrier geometrical parameters on the triboelectric charge of the DBD-treated Polypropylene (PP) and Polyvinyl Chloride (PVC) mm-size granules. The studied parameters include the air gap between the upper barrier and the surface of the granular layer, the number of granular layers, as well as the material forming the dielectric barrier and its position. After being treated for 3 s, the granules were triboelectrically charged in a vibratory device for 2 min. The charge the DBD-treated and untreated particles acquire by tribocharging was measured using a Faraday pail connected to an electrometer. Experimental results show that the air gap and the properties of the dielectric barrier can influence the mean value of the discharge current and enhance significantly the triboelectric charge of DBD-treated granules. Best results were obtained when the air gap did not exceed 4 mm and material with high permittivity was used as a barrier.
The European Physical Journal Applied Physics
The aim of this paper is to quantify the effects of dielectric barrier discharge (DBD) exposure on the physico-chemical and tribo-electric properties of polymers. The study was conducted in atmospheric air on polypropylene, polyethylene and polyvinyl-chloride. These three types of polymers are widely used in industry. The polymers were characterized by means of an optical profilometer, a fourier-transform infrared (FTIR) spectrometer and an electric charge measurement system. The latter is composed of a Faraday pail connected to an electrometer. The profilometer analyses showed that the DBD plasma treatment has increased the surface roughness of the three polymers. FTIR revealed that oxygen atoms and polar groups were grafted on their surfaces, thereby conferring them a hydrophilic character. The short (2 sec) DBD plasma treatment has considerably improved the electrostatic charge acquired by the polymers during electrostatic tribo-charging, while longer exposures conferred the poly...
Advanced Powder Technology, 2018
The manufacturing and handling of polyethylene (PE) powders is associated with undesired charging, 29 resulting in agglomeration of charged particles, wall sheeting and eventually leading to plugging of reac-30 tors/conveyors. In this work, we measured the triboelectric charging of PE powders using both sliding and 31 shaking apparatuses in dependence on humidity, impact velocity of colliding particles and temperature 32 of the colliding particles or of the wall. As expected, saturation charge of PE particles is reduced with 33 increasing air humidity. However, in a more detailed study we observed that whenever we change the 34 humidity, the saturation charge rapidly reaches the equilibrium value and no hysteresis in charging that 35 might be caused, for example, by adsorption/desorption thermodynamics is observed. Saturation charge 36 is believed to be independent of impact velocity; however, we show that the saturation charge is propor-37 tional to impact velocity in the system of PE particles of non-spherical shape. The charging is more pro-38 nounced as the temperature of PE particles increases, however, it is unchanged if only the metal wall in 39 contact with the particles is heated. That is a different trend than observed for spherical metal particles 40
IOP Conference Series: Materials Science and Engineering
One of the factors affecting the electric charge acquired through friction between the polymers is their surface roughness. The dielectric barrier discharge (DBD) treatment is known to modify the surface characteristics of polymers. The aim of this study is to quantify the effect of atmospheric DBD exposure, in a well-defined configuration on the triboelectric behavior of polymers. Thus, Polytetrafluoroethylene (PTFE) plate samples characterized by different surface roughness were rubbed against bronze plate samples in a triboelectric test bench and then the electric potential at their surface was measured. The results were compared with those obtained for surfaces previously exposed to DBD treatment duration of which did not bring any change in their roughness. It was found that the roughness of the surface of the treated polymers hardly changed for rather short DBD exposure time (a few minutes). Significant changes were noticed for longer treatment duration (30 minutes and more). ...
Powder Technology, 2020
The understanding of triboelectric charging of industrially important powders can help in avoiding or controlling the particle agglomeration and wall sheeting. We developed a new experimental approach to study both samematerial particle-particle (P\ \P) and different-material particle-wall (P\ \W) charging of nascent polyethylene (PE) particles born by catalytic polymerization. We constructed a simple tribocharger consisting of a metal box divided inside into several compartments filled with the PE sample and attached to the vibration shaker. The particle charge distribution was characterized by a self-constructed electrostatic separator. This way, we investigated the charging dynamics of PE particles colliding with other PE particles as well as with metal walls of the box compartments. Both P\ \P and P\ \W charging were measured either separately, or in sequence, and in combination of simultaneous P\ \P and P\ \W. The different-material P\ \W charging produced unipolarly charged particles and was much faster than the same-material P\ \P charging leading to bipolar particle charge distribution.