Static contact process

Fig. 1.16. Crystallization kinetics of potassium bitartrate analyzed by measuring the drop in conductivity of a wine according to the type of treatment or fining. Samples were stored at 2°C, seeded with 5 g/1 of KTH and subjected to the static contact process for four hours (Maujean et ah, 1986)...

Rapid Cold Stabilization Static Contact Process... 

The static contact process is a very flexible system. It is possible to run 2-3 cycles per day with volumes of 50-100 hi in each batch. This technology is advisable for small and mediumsized wineries. The weak point of this system is the price of cream of tartar, but costs may be reduced by recycling tartrate. 

Chemical reactions in boundary lubrication are different from static reactions even if the reactive substances involved are the same. The temperature to activate a chemical reaction on rubbing surfaces is usually lower than that required in the static chemical process. Some believe this is because of the naked surfaces and structural defects created by the friction/wear process, which are chemically more active. Kajdas proposed a new concept that accumulations of stress and strain in friction contacts could cause emission of low-... 

The basic theories of elastic deformations associated with various contact forces under static contact conditions have been introduced in the last section. Assuming that an impact process of two solids can be regarded as quasi-static, the theories given in 2.3 are used directly to link the dynamic deformations of the colliding solids with the impact forces. In this section, the collisions of elastic spheres are described. 

Contact electrification. A second static electrification process is contact electrification. Here electrons migrate from clean, dry surfaces of dis-... 

Figure 26.8 The effects of plasma polymerization coatings on the wettability of conventional polymers given by the cosine of the static advancing contact angle, 0s each value of the static contact angle was taken for the largest droplet size attained during the advancing process whereby the droplet size dependence is small, dotted lines indicate the mean cos 0s of the TMS and (TMS + O2) treated polymers.

There are several rapid cold stabilization processes for precipitating tartrates (static and dynamic contact processes). These techniques have certain economic advantages, but are not easy to implement. They are described elsewhere (Sections 1.7.3 and 1.7.4). 

In the process industry there are numerous procedmes by which badly conducting materials enter into mutual contact. Processes in which gas-solid mixtures or dusts are used or pneumatic transport should be mentioned in this context. Hence, the following areas where static electricity is to be expected are identified ... 

The hydrophilic stability of surface-modified PDMS was described by Bodas et al. [13]. Three different modification processes, namely, conventional oxygen-plasma treatment, two-step modification using O2 -I- C2F6, and chemical modification using HEMA, were considered in the study. AU of the surfaces were characterized using static contact angle measurements and ATR-FTIR spectroscopy. Oxygen-plasma modification resulted in hydrophilic stability for about 2 days. The hydrophobic recovery in this case... 

The applicability of these models remains limited. Indeed, they are only devoted to the calculation of static contact angles. They do not consider friction forces that will affect the dynamic dewetting process. In addition, the impact of the accumulation of particles on... 

Note that up to this point nothing has been said on the dynamics of the processes only static configurations have been taken into account. In fact, in all the above expressions, the static contact angle 0 is the advancing one if the dry solids have been immersed in the liquid, but the receding contact angle must be used if the solids have been extracted out of the liquid bath. 

The relation between the normal load and the real area Is much less dependent upon the complex process of friction. It may be obtained, as far as static contact Is concerned, from a clearly defined problem In solid mechanics if the surface topography and the deformation properties of the materials are known. In the case of sliding contacts, it would be necessary to modify the analysis in order to make use of Green s conditions, that the surfaces slide in parallel planes. It appears however, that the essential features of the analysis are not different from those in the case of static contact. The notions involved in the analysis of static contacts will be mentioned In the following. 

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