Adhesion measurements centrifugal

Results obtained by different methods of adhesion measurement (with the same materials and imder the same conditions) are similar. Thus, the adhesive forces for glass particles sticking to a metal surface (brass and steel) are approximately the same, despite differences in the method of detachment (vibration and centrifuging) the adhesive forces measured with a relative air humidity of 50-60%, using the centrifuge method to remove the glass particles, are the same as those obtained by the method of detaching individual particles. 

Some of the disadvantages were overcome by the use of the colloidal probe technique to measure adhesion forces (review Ref. [216]). The colloidal probe technique offers the advantage that the same particle can be used for a series of experiments and its surface can be examined afterwards. The accessible range of particle size is typically limited to a range between 1 /zm and 50 pm. The tedious sample preparation, limits the number of different particles used within one study, for practical reasons. Therefore the colloidal probe and centrifugal methods complement each other. 

The method proposed by Horii et al.13 was used for the measurement of free amino acid. The SC was stripped with adhesive cellophane tape (Cello-tape, Nichiban Co. Ltd., Tokyo, Japan). The tape was immersed in toluene to remove the SC, which was then washed with toluene several times and dried in a vacuum desiccator. One milligram of dried sample of SC was precisely weighed and homogenized with 0.1 % of sulfosalicylic acid. After centrifugation the supernatant was analyzed with a high-speed amino acid analyzer (Model 835, Hitachi, Tokyo, Japan) to determine the level of total... 

In near infrared spectroscopic (NIR) cure rate studies, a small amount (10-15 g) of sample was manually combined using the indicated ratio of materials. After the bubbles had been removed via centrifugation, the mixture (about 1 g) was poured onto a microscope slide prepared with a 1 mm spacer window cut from foam tape with adhesive on both sides. Another slide was placed on top, and a zero-time measurement was made on the Cary 14 spectrophotometer. The absorption at 2.205A was used as a measure of the amount of unreacted epoxy resin. The sample was kept at the appropriate temperature and spectra were measured at the indicated times. 

A measure of platelet adhesion. Hematocrit is a tube calibrated to facilitate determination of the volume of red cells in centrifuged blood expressed as corpuscular volume percent. 

The adhesive force is numerically equal and opposite to the force required in order to detach particles from a surface. Therefore, if we measure the latter (i.e., the force at the instant of detachment) by varying the slope of the surface or by centrifugal, vibrational, or pulse methods, we may determine the adhesive force. 

The centrifugal method of measuring the value of the detaching force is the principal method used in determining forces of adhesion. The advantages of this method lie in its simplicity and accessibility, and also in the reliability of the results and the rapidity of the measurements. In addition to this, a variety of conditions may be created in the centrifuge test tubes (humidity, temperature, pressure, etc.), which widens the experimental potentialities of the method. However, in order to obtain the integral adhesion curve several measurements must be made with different numbers of revolutions. 

There are several techniques available for the measurement of the adhesion force of particles on substrates. These techniques involve both the study of individual particles (as in the microbalance technique) and of multiple particles by statistical counting (as in the centrifuge method). In each type of study the conditions of both the particles and the substrates must be known with high precision. The exact chemistry, physical size and shape, surface condition, temperature, and properties of the surrounding gas are vital parameters that must be quantified in order to obtain reproducibility. 

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