The role of water vapor in the charge elimination process for flowing powders

Nguyen, Tuan; Nieh, Sen

doi:10.1016/0304-3886(89)90086-7

Cited by 31 publications

(23 citation statements)

References 11 publications

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“…[38][39][40][41][42][43][44][45] In powder flow, as flow speed increases, the influence of triboelectrification grows. Charge accumulated on the surface is continually relaxing with time, depending on the surface conductivity.…”

Section: Discussionmentioning

confidence: 99%

“…In fact, water vapor can be used to reduce the triboelectrification developed in powder flowing. [39] In this experiment, a PVP particle attached to an AFM cantilever was continually tapping a pharmaceutical particle, which is a good condition for the development of In Figure 4, the kinetic aspects of triboelectrification are noticeable only when RH is relatively low. As RH increases, water adsorption prevents triboelectrification from building up, which was noticeable in PVP/LT cases which showed a decrease at 15% RH in Figure 3.…”

Section: Discussionmentioning

confidence: 99%

“…Among them, electrostatic force can explain the increase in adhesion force with decreasing RH. [38][39][40][41][42][43][44][45] The amount of adsorbed water molecules on the surface of PVP and LT and the surface electric conductivity both decrease with reduced RH. As a result, surface triboelectrification can easily build up during the tapping movements of the tip, thereby distinctly increasing the adhesion force.…”

Section: Humidity Effects Of Pvpmentioning

confidence: 99%

“…Electrostatic force depends on many experimental kinetic variables. [38][39][40][41][42][43][44][45] A key variable investigated in this study was the time after contact (engaging) between the two surfaces. After a tip engaged a surface, the tip began to continually tap the surface, producing the displacement versus z-position curve that is illustrated in Figure 2.…”

Section: Contact Timementioning

confidence: 99%

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Intrinsic Adhesion Properties of Poly(vinyl pyrrolidone) to Pharmaceutical Materials: Humidity Effect

Lee

2005

Macromolecular Bioscience

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Poly(vinyl pyrrolidone) (PVP) is widely used for bioengineering and pharmaceutical applications, and its adhesion characteristics are critical. When used as a binder in pharmaceutical granulation, it covers the resultant granules and governs their surface properties. The intrinsic adhesion forces of PVP toward common hydrophobic (magnesium stearate) and hydrophilic (lactose) pharmaceutical materials have been studied as a function of relative humidity (RH). The effect of RH on adhesion force was more significant for the PVP/hydrophilic material than the PVP/hydrophobic material. Adhesion was lowest between 20 and 40% RH, and it increased at RH above 40% and below 20%. This is likely to be due to the development of capillary and triboelectrification forces, respectively. In a nano-indentation experiment using a silicon tip at room temperature, the PVP surface underwent a glass transition at 70% RH. This result suggests that surface softening contributes to the increased PVP adhesion at RH above 70%. To adjust the adhesion properties of PVP, humidity control should be an essential part of research and development. Effect of humidity on the adhesion forces between PVP and lactose (LT) or magnesium stearate (MS).

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Humidity Effects Of Pvpmentioning

confidence: 99%

Section: Contact Timementioning

confidence: 99%

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Intrinsic Adhesion Properties of Poly(vinyl pyrrolidone) to Pharmaceutical Materials: Humidity Effect

Lee

2005

Macromolecular Bioscience

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“…Uno de los retos actuales consiste en determinar como afectan tanto los parámetros de los polvos cerámicos como los factores externos a la generación de carga y a la disipación de la misma (8). Entre los diferentes parámetros relativos a los polvos cerámicos se consideran: tamaño de partícula, morfología (9), composición, I. LORITE; J. J. ROMERO; J. F. FERNáNDEz rugosidad (10), propiedades eléctricas y mecánicas (11).…”

Section: Introductionunclassified

Factores que afectan la carga electrostática en polvos cerámicos

Lorite¹,

Romero²,

Fernández³

2011

Bol. Soc. Esp. Ceram. Vidr.

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Los fenómenos de carga electroestática en polvos cerámicos se producen cuando las superficies de los mismos entran en contacto entre sí y con los elementos que las contienen. La acumulación de cargas electrostática es importante en polvos cerámicos dado su carácter aislante y debido al riesgo de explosiones por descarga. En este trabajo se estudian los principales factores que afectan a la aparición de carga neta y la tribocarga en las partículas de polvo cerámico. En polvos cerámicos de alúmina se ha comprobado que las partículas más finas presentan un aumento de la carga electrostática con una polaridad negativa. Se ha observado una correlación entre la naturaleza de los grupos OH -superficiales y la carga electrostática. La carga neta y la tribocarga en polvos cerámicos se pueden reducir si se compensan los sitios superficiales que soportan dicha carga. La dispersión en seco de nanopartículas sobre micropartículas permite la compensación de la carga superficial con una importante modificación del estado de aglomeración de los polvos cerámicos. Palabras clave: Polvos cerámicos, nanopartículas, carga electroestática, tribocarga, alúmina.Factors affecting the electrostatic charge of ceramic powders.Abstract. The phenomenon of electrostatic charge in ceramic powders takes place when the particle surfaces enter in contact between them or with the containers. The accumulation of electrostatic charge is of relevance in ceramic powders in view of their insulating character and the risk of explosions during the material handling. In this work the main factors that affect the appearance of intrinsic charge and tribo-charge in ceramic powder have been studied. In ceramic powders of alumina it has been verified that the smallest particle sizes present an increase of the electrostatic charge of negative polarity. A correlation has been observed between the nature of the OH -surface groups and the electrostatic charge. The intrinsic charge and the tribocharge in ceramic powders can be diminished by compensating the surface groups that support the charge. The dry dispersion of nanoparticles on microparticles allows surface charge compensation with a noticeable modification of the powder agglomeration.Key Words: ceramic powders, nanoparticles, electrostatic charge, tribocharge, alumina.a INTRODUCCIÓNLa electricidad estática es un fenómeno físico que ha sido ampliamente estudiado durante siglos. Actualmente, la acumulación de electricidad estática durante la manipulación de los polvos cerámicos en los procesos industriales conlleva un elevado factor de riesgo debido a la posibilidad de explosiones (1) provocadas por descargas electrostáticas de los materiales cercanos a combustibles o gases inflamables. Sin embargo, a pesar de tratarse de un proceso conocido, los problemas derivados de la presencia de carga electrostática no están totalmente resueltos aún.Existen diferentes explicaciones para la generación de la carga electrostática en las partículas de polvo cerámico (2). La carga electrostática se genera cuando dos superfic...

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