【国外标准】 Standard Test Method for Determination of the Weight Percent Individual Volatile Organic Compounds in Waterborne Air-Dry Coatings by Gas Chromatography

5.1 In using Practice D3960 to measure the volatile organic compound content of waterborne coatings, precision can be poor for low volatile organic compound content air-dry coatings if the volatile organic weight percent is determined indirectly. The present method directly identifies and then quantifies the weight percent of individual volatile organic compounds in air-dry coatings (Note 6). The total volatile organic weight percent can be obtained by adding the individual weight percent values (Note 7).NOTE 6: The present method may be used to speciate solvent-borne air-dry coatings. However, since these normally contain high, and often complex, quantities of solvent, precision tends to be better using other methods contained in Practice D3960, where the volatile fraction is determined by a direct weight loss determination.NOTE 7: Detectable compounds may result from thermal decomposition in a hot injection port or from reaction with the extraction solvent. If it can be shown that a material is a decomposition product, or is the result of a reaction with the extraction solvent, then results for that compound should be discounted from the volatile measured by Test Method D6886.1.1 This test method is for the determination of the weight percent of individual volatile organic compounds in waterborne air-dry coatings (Note 1).1.2 This method may be used for the analysis of coatings containing silanes, siloxanes, and silane-siloxane blends.1.3 This method is not suitable for the analysis of coatings that cure by chemical reaction (this includes two-component coatings and coatings which cure when heated) because the dilution herein required will impede the chemical reaction required for these types of coatings.1.4 Precision statistics for this method have been determined for waterborne coatings in which the volatile organic compound weight percent is below 5 percent. The method has been used successfully with higher organic content waterborne coatings and with solventborne coatings (Note 2).1.5 This method may also be used to measure the exempt volatile organic compound content (for example, acetone, methyl acetate, t-butyl acetate and p-chlorobenzotrifluoride) of waterborne and solvent-borne coatings. Check local regulations for a list of exempt compounds. The methodology is virtually identical to that used in Test Method D6133 which, as written, is specific for only exempt volatile compounds.1.6 Volatile compounds that are present at the 0.005 weight percent level (50 ppm) or greater can be determined. A procedure for doing so is given in Section 9.1.7 Volatile organic compound content of a coating can be calculated using data from Test Method D6886 but requires other data (see Appendix X2.)NOTE 1: Data from this method will not always provide the volatile organic compound content of a paint film equivalent to EPA Method 24. Some compounds and some semi-volatile compounds may be considered volatile using the GC conditions specified but will not fully volatilize during the one hour at 110°C conditions of EPA Method 24. Some or all of these materials remain in the paint film and therefore are not considered volatile organic compounds according to EPA Method 24. In addition, some compounds may decompose at the high inlet temperature of the GC. However, note the EPA Method 24 has poor precision and accuracy at low levels of volatile organic compounds.NOTE 2: This method measures volatile organic compound weight of air-dry coatings directly as opposed to other methods in Practice D3960 which measure the volatile organic compound weight percent indirectly. A direct measurement of the weight percent particularly in low volatile organic compound content waterborne coatings, generally gives better precision. California Polytechnic State University carried out an extensive study for the California Air Resources Board comparing the precision of the direct method with the indirect method (CARB Standard Agreement No. 04.329) Detailed results of this study may be found at http://www.arb.ca.gov/coatings/arch/Final_Report_6_11_09.pdf. This study may be used to decide if the present method or other methods in Practice D3960 are preferred for a specific coating.1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.