Casting thickness

Cobalt-60 5.3 years 1.1, 1.3 14.4 Heavy castings, thick weldments... 

FIGURE 13.9 Velocity profile in the tape casting gap for a Newtonian fluid at different dimensionless pressures. For cast thickness versus pressure, see curve A in Figure 13.10(b). 

For these reasons, operation of a nearly dry second doctor blade may lead to tape cast thickness fluctuations. Much more stable operation can be obtained from operating with only one doctor blade with a full doctor box and control of tape speed and applied pressure. 

Using a suspension of hard spheres immersed in water at a volume fraction of 45% determine the cast thickness if the suspension is tape cast with a doctor blade 10 cm long and 1 cm wide onto a moving piece of mylar which is 0.2 cm from the doctor blade. The mylar is moving with a velocity of 5 cm/sec and the heif t of the suspension in the doctor box is 5 cm. No gas pressure is applied to the doctor box. 

In this process, final membrane thickness is only a fraction of the as-cast thickness owing to solvent loss and the resultant Increase in the concentration of polymer per unit volume. However, because of the inclusion of voids, the final membrane thickness is substantially greater than the thickness of a dense membrane containing an equivalent amount of polymer. The weight and thickness as functions of evaporation time for a typical CN membrane casting are shown in Table I. 

Cumulative pore volume and pore size distribution for PPO membranes, calculated from the thermograms. (The numbers 0.15 and 0.20 Indicate the casting thickness (nm) during preparation of the membranes). 

As cast thickness Casting speed Evaporation period Evaporation temperature Precipitant Bath temperature... 

Machining allowances should be detailed on the part drawing so as to ensure adequate stock and avoid excessive differences in casting thickness. 

We have applied high-precision diffraction analysis to monomers, oligomers, and polymers based on thiophene residues, in the form of single crystals, of powders, of cast thick films, and even as thin films prepared using the Langmuir-Blodgett technique. Preliminary results encourage us to perform further detailed studies on diffraction techniques suitable for well-ordered thin films, which are of interest for non-linear optics and for electronic applications. 

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