Voltage rupture

In this first part of this study the properties considered were the aqueous and solvent solution properties, rupture voltage, wet film resistance, film thickness and weight, coulombic efficiency, and surface appearance. The viscosities and the aqueous solution conductivity and haze are summarized in Table I. Because of their solubility characteristics ... 

Table III. Rupture Voltages of Epoxy Ester Solutions...

The effect of solvent concentration and type on rupture voltage appears in Table III. At the low solids concentration 2-butoxyethanol gives the poorest results. However, as the solid concentration increases, the rupture voltage also increases dramatically compared with the other solvents examined. 2-(2-Butoxyethoxy) ethanol, is relatively unaffected by concentration. 

The only solvent of the nine candidates which compared favorably with 2-butoxyethanol was 2-(2-butoxyethoxy) ethanol. As pointed out in Figure 4, solution viscosity was not a major factor. It was noted from Table 3, however, that this solvent gives a higher rupture voltage at lower solvent concentrations. This could be important if a compromise were needed between throwing power and the handling or let down requirements of the resin solution for the plant. Figure 8 shows that this solvent... 

Two of the alcohols, sec-butyl alcohol and methyl isobutyl carbinol, gave very high rupture voltages and wet film resistances but poor film appearance. Thus, these solvents should be considered in mixtures, and further investigation along these lines may be warranted. 

Table IV shows the rupture voltages of the various solvents at different solids concentrations. At all concentrations 2-ethoxyethanol is clearly superior, but diacetone alcohol shows some advantages at the lower solids concentrations. Figure 11 illustrates the effect of voltage and solids content on film thickness. This property did not vary markedly with any of the solvents evaluated. In all cases the contour lines had a slope which approximates the curve of rupture voltages vs. non-volatile concentration. Figures 12 and 13 show the wet film resistances for 2-butoxyethanol and...

The rupture voltages for the various resin-solvent combinations are shown in Table V. Of the candidates under consideration 2-ethoxyethanol and hexylene glycol gave the highest values. This is also reflected somewhat in the plots of film thickness as a function of voltage and... 

Two solvents used in this evaluation, 2-butoxyethanol and 2-(2-butoxyethoxy) ethanol, were the most versatile. Except for the film appearance of the trimellitic alkyd, satisfactory coating systems could be made with each of the three resins. The 2-butoxyethanol has slightly lower viscosity and lower cost. On the other hand 2-(2-butoxyethoxy)-ethanol gave slightly higher rupture voltages. With the acrylic resin and... 

One of the main differences of electrodeposition paints with conventional water soluble paints is their lower solids and thus solvent content. A typical binder content is around 10%w, the amount of solvent approximately 5%. The rest, apart from pigmentation, is water. The influence of solvent in the early stages of binder/paint formulation is very similar to the effects described for conventional aqueous paints which is also started from an approx. 70% solids binder solution in coupling solvent(s). The choice of the solvent (blend) is, however, less influenced by its evaporation characteristics as the deposited paint film does not contain much water and is stoved after application. Of more importance are paint stability and electrical properties (conductivity, rupture voltage). 

Solvents should preferably be water miscible - butanol is commonly used but it is only partly water soluble and so can lead to problems v th film resistance and rupture voltage. The propanols are water miscible, but their low boiling point can give problems with choice of a suitable initiator. Probably the best solvents to use are the glycol ethers, which have reasonable boiling points and good water miscibility. 

Electrolyte contamination is a serious problem in an electrodeposition tank and quantities of the order of 50 ppm will give rise to fill defects, as well as reducing the rupture voltage and the coulombic efficiency. This is a matter which is relevant to running the tanks rather than formulating either resins or paints. 

One of the important design parameters affecting rupture voltage is the correct choice of type and level of co-solvent. Another factor is the degree of neutraUsation. with higher amine levels giving lower rupture voltages. 

After the heat treatment for Cr diffusion, the films were taken to the electrical characterization. From the varistor responses, shown in Figure 15, it was observed that the heat treatment used after the chromium deposition influenced the improvement of the nonlinear coefficient of the samples. All films had lower rupture voltage less than 65 V and a low leakage current. 

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