Determination of moisture content in paints and paints
Paint and paint The paint contains pigments, most of which are insoluble in organic solvents and KF reagents. Latex paint will agglomerate in methanol and will not completely release moisture. Some paints and paints contain ketones and must be titrated with a non-alcoholic reagent (side reaction). Some glues and coatings require the addition of chloroform as a solubilizer. In addition, the active amines contained in the coating and/or paint increase the pH of the KF system too much. Salicylic acid can be added to the sample reagent to adjust the pH. Some inorganic pigments react with the reagents to release water. Mainly Ag2O, Pb3O4 (red lead) and ZnO. . Al2O3 and TiO2 did not interfere with the assay. In view of these factors, it is recommended to use a volumetric moisture analyzer to determine the moisture content of such samples (contaminated coulometric titration cells, special reagents are not always found, etc.). The moisture distribution in the paint is not uniform. Therefore, the sample should be homogenized before injection into the titration cell before sampling. Waterborne emulsion paint Samples containing such a mixture of vinyl acetate, acrylate or polyvinyl chloride and acrylate are not a problem in such coatings. Add 20 mL of methanol and 10 mL of formamide to the titration vessel and titrate to dryness. About 0.1 g of the sample was added by a syringe, and the moisture was measured. . Latex paint Latex paint will agglomerate in methanol. The assays in ASTM D4017-96 have proven to be suitable for most such samples. Homogenize and stir with a high frequency homogenizer. Methanol sufficient to pass the homogenizer head was added to the titration vessel and titrated to dryness. A 0.1...0.15 g sample was added using a dry syringe, and moisture was measured under the following conditions. The extraction time is 60 s, the stirring speed is small (zui is small), and the delay time is 20 s. The latex paint with a water content of <0.5% is determined by the following steps: A 20 g sample was weighed into a dry conical flask. About 70 g of a 1:1:1 methanol/p-xylene/chloroform mixed solvent and a magnetic stirrer were added. Immediately seal with a stopper, magnetically stir for 1 h, then let stand, take about 5 g of sample extract into the titration cup (containing titration to anhydrous methanol). It was also possible to place the flask in an ultrasonic shaker for 20 min without using a magnetic stirrer. The blank value of the mixed solvent should be determined and subtracted from the result. Insoluble coating pigments are analyzed as follows: About 2 g of the pre-powdered sample was weighed into a dry Erlenmeyer flask and extracted with about 75 g of dry methanol. Seal with a stopper, simply mix and place in an ultrasonic shaker for 20 min. Add 1...2g of sample extract to the titration cell (requires solvent blank value, and subtracted from the result). The ketone-containing paint is determined by an aldehyde-ketone-specific reagent. Multi-component paints of basic polybasic compounds, isocyanate hardeners and diluents can be analyzed as follows: Add 20 ml of pyridine and 1 ml of 1-ethylpyridine to the titration vessel and titrate to dryness. A 1...3 g sample was added using a syringe and the moisture was measured. It is also possible to determine the moisture of the adhesive: The polyurethane binder can be titrated in methanol. A polyurethane chlorinated banana warfare agent and a cyanoacrylate companion (rapid binder) were used as a titration solvent with 10 ml of methanol and 20 ml of chloroform.
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