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Volume 41, Issue 10
Displaying 1-5 of 5 articles from this issue
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Hisashi HOTTA, Takashi SATAKE, Masaru MANIWA1968 Volume 41 Issue 10 Pages 483-490
Published: October 30, 1968
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSViscosity is of importance to the paint applicability. The shear rate of enamel under application is very high, reaching above 6×104sec-1 in such a case as roller coating. The viscosity of clear enamels was studied as a function of shear rate with a Burrel-Severs type viscometer, which was compared with a # 4 Ford Cup Viscometer. Clear enamels of a phenol-epoxy thermosetting resin were used at the solids contents of 30, 26. 7, 24. 1 and 19.9%. Solvents used were four binnry systems, butyl cellosolve-solvesso # 100, isophorone-solvesso # 150, butyl cellosolve-xylene and isophorone-xylene. Viscosities were measured at temperatures of 0 to 50°:C.
At the solids content 30% the enamel was a Newtonian at temperatures above 20°:C and a non-Newtonian at 0°:C. The relationship between concentration and logarithm of viscosity below the solids content 30% was expressed by log ηa = AC + log η0
where ηa, is the apparent viscosity in poises of the enamel, ηa the viscosity of the solvent, C the concentration (wt. %) and A a constant. Apparent activation energies for the flow of solvents and enamels were about 3 and 7 kcal/mol, respectively. These values were not appreciably affected by the kind of solvent and concentration. A good agreement was obtained between the viscosity values determined with the two viscometers at higher temperatures and lower concentrations. Little cor relation was found between the solvent viscosity and the enamel viscosity. Solubility of the enamel in the solvent appeared to be important, and a good correlation was found between the solubility parameter of the resin and those of the solvents.View full abstractDownload PDF (955K) -
Kaichiro MIYAZAWA, Shoji MATSUO, Mamoru SAITO1968 Volume 41 Issue 10 Pages 491-497
Published: October 30, 1968
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSLead chromates were prepared by simultaneously adding 125 ml of 0.25 molar Na2Cr2O7 solution and 125 ml of 0.5 molar Pb (NO3) 2 solution to 500 ml of water kept at 25-80°C. The Na2O/CrO3 and N2O5/PbO ratios in the solutions were controlled by the addition of NaOH and HNO3, respectively. The pH of the resulting solution was 3. 2 when the alkali and acid mole ratios were 1.0. With the increase in pH the red hue of the precipitates dried at 110°C decreased in the range pH 1-3 and increased in the range pH becoming very stronger at pH 8. The green hue and brightness increased between pH 1 and 2, becoming unchanged between pH 3 and 6 and then decreasing above pH 7. The effects of reaction temperature on colour depended on the pH at which the precipitates were prepared.
Solubilities of the precipitates in 0. 125 molar NaOH, 0. 204 molar H2SO4 and 1.0 molar AcOH were determined. The amount of CrO3 dissolved in the NaOH solution from the precipitates produced at pH 1-5 was not affected by the pH, the amount however decreased with the increase in pH in the range pH 5-7. The amount of CrO3 dissolved in the H2SO4 solution increased constantly with the increase in pH. The amount of PbO dissolved in the AcOH solution from the precipitates produced at pH 1-5 was negligible, while a gradual increase in the amount was observed in the range pH 5-7. The precipitates produced at pH 8 were very soluble in the H2SO4 and AcOH solutions, and very insoluble in the NaOH solution.
The PbO/CrO3 mole ratios of the precipitates produced at pH 1-5, pH 5.7-7. 4 and pH 8.3 were 0.98-1.0, 1.01-1.03 and 1.28, respectively. The X-rays diffraction patterns indicated the absence of basic lead chromate in the precipitates produced at pH 1-4, a trace of it was first detected at pH 5. 7, and in the precipitates prepared at higher pH values lead chromate became predominant.
From the change in the X-rays diffraction patterns by the H2SO4 and NaOH treatments of the precipitates, it is suggested that the behaviours against acid and alkali and colours of the precipitates produced at various pH values are caused mainly by the presence of basic or acidic lead chromates in the precipitates produced at pH below 3.2, respectively.View full abstractDownload PDF (827K) -
Takumi NAGATA1968 Volume 41 Issue 10 Pages 498-506
Published: October 30, 1968
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSSmall circular depressions on paint films or craters are caused very often by dusts or enamel drops which comprise surface active materials such as silicone oil. The relations between cratering tendency and such factors as size of dust contaminated with silicone, surface tension, enamel viscosity, and thickness of wet film, were studied.
A white enamel with no additives, 0.1% methylsilicone added and 0.3% ethylcellulose added were used for the study. A glass bead of 0.8 mm in diameter and the enamel placed in a flat-bottomed beaker of 12 cm in diameter were used as the models of dust and wet film, respectively. The beaker was inclined to obtain the depth of enamel layer of 0.4 to 2.0 mm. The enamel in beaker was divided into about 6×5 sections by lattice-like barriers. The glass bead coated with the methylsilicone was dropped in each section of the enamel layer at regular intervals. The intervals were calculated from the empirical equation, ds/dt=za+βD, where ds/dt is the increase in enamel solids per min., D the depth of enamel layer, and a, β the constants.
When the paint layers were sufficiently shallower than the bead diameter, large craters with holes appeared with the enamels without the methylsilicone ; when the paint layers were sufficiently deeper, craters without holes appeared with all the enamels, although the diameters were much smaller with the methylsilicone-added enamel. The diameter reached a maximum at the apparent enamel viscosity of 700-800 poises. With the enamels without the methylsilicone the diameter was increased after the enamel was cured, while with the methylsilicone-added enamel no change was observed. The value ds/dt of the enamel without any additives was considerably affected by the thickness of paint layer as compared with the other enamels.View full abstractDownload PDF (1169K) -
Taiichi TSURITANI1968 Volume 41 Issue 10 Pages 507-518
Published: October 30, 1968
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSDownload PDF (1523K) -
High Molecular Weight CompoundsHiroshi KAKIUCHI1968 Volume 41 Issue 10 Pages 519-523
Published: October 30, 1968
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSDownload PDF (618K)
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