Measuring Powder Adhesion Using Centrifugal Separation with an Ultra Centrifuge
In the manufacturing sector and during the product design phase, the dust-holding capacity of products is particularly important. For example, to measure the adhesion of printer toners, the centrifugal method is generally accepted as the first choice. In this method, centrifugal force applied in various stages is used to make particles adhere to a flat surface.
Erhan Doruk - Biologist / Sales Engineer - Ant Teknik Cihazlar Ltd. Şti. Measurement of Powder Adhesion Using Centrifugal Separation Method with Ultra Centrifuge
Equipment used: CS-FNX series compact ultra
centrifuge, S110AT angled rotor and NS-C200 adhesion measurement equipment.
In the manufacturing sector and during the product design phase, the dust retention capacity of products is particularly important. For example, to measure the adhesion of printer toners, the centrifugal method is generally accepted as the first choice.
In this method, centrifugal force applied at various levels is used to cause particles to adhere to a flat surface. In recent years, with the reduction in particle size used in toners, adhesion has become stronger.
The electrostatic charge application and Van der Waals method used in applying toner to paper have resulted in adhesion that is too strong to be measured by general-purpose centrifuges.
This article presents the results of measuring adhesion at a centrifugal force of 691,000×g obtained by centrifuging particles with very strong adhesion using an ultra centrifuge.
Contents
1. Sample: Black color toner available on the market.
2. Test Conditions:
Centrifuge: CS150FNX compact ultra centrifuge,
Rotor: S110AT angled rotor.
Figure 1. Adapter: T-AL adapter (particle adhesion surface made of acrylic material).
Centrifugal Steps: Seven steps were used at speeds of 10,000, 16,000, 32,000, 64,000, 128,000, 256,000 and 512,000×g.
Time: 5 minutes, Temperature: 25°C Adhesion Measurement Equipment: NS-C200 (Tele-centric lens, image analysis system and other components. Manufactured by Nano Seed Corp.)
3. Adhesion Measurement Method
a) Toner is applied to a plate and a photograph is taken with the NS-C200 equipment.
b) The plate is centrifuged at various speeds for 5 minutes.
c) A photograph of the remaining toner on the plate is taken again and recorded.
d) The remaining toner area (or particle count) on the plate after centrifugation is compared with the previous photograph to calculate the remaining toner ratio.
e) Toner adhesion calculation method:
The centrifugal force applied to the particles causes the toners adhering to the plate to separate. The force causing separation is calculated by the following equation.
F(N) = (π/6) • p •d³ • r • (2Πn/60)²
p: Particle density (kg/m³) d: Particle diameter (m) r: Centrifuge radius (m) N: Speed (rpm)
f) Average adhesion ratio calculation: In this method, the ratio of toner remaining after centrifugation is written on the horizontal axis of the graph. The separating force (×g) applied to the toner is written on the vertical axis. From the 50% residue ratio point on the graph (F 50), the average adhesion force is calculated. If this method is used in calculating average particle size, reaching a conclusion in a series of samples becomes much easier (Figure 1).
4. Results
Average adhesion F50=98 nM (using the areas in the graph) was calculated. According to this result, basic measurement of toner particles was performed using the centrifugal separation method with an ultra centrifuge, and separation of damaged or electrostatically adhered toners can be easily achieved.
References:
1. Takeuchi, M., et al., Discussion on Powder, Collected Articles for Lectures 31, p.59, 1993.
2. Limura, H., Study of Adhesion of Toner, Ricoh Technical Report 26, p.34, 2000.
3. Chemical Toner, edited by the Imaging Society of Japan, Tokyo Denki University Press,
p.177, 2008.
4. Jinbo, G., Materials - 16, Society of Materials Science - Japan, p.291, 1967.
5. Asakawa, S., et al., Materials - 16, Society of Materials Science - Japan, p.358, 1967.
* The data was obtained in cooperation with Nano Seeds Corp.
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