ASTM Committee D01 reports of June 2007 subcommittee activities

JCT CoatingsTech, Jan, 2008

The method has been evaluated with a variety of waterborne and solventborne multi-component coatings. A comparison of the results obtained with expected results is very good. D01.06 will form a new task group to develop the method. G. Janezic has tentatively agreed to chair this new task group.

The group on Volatile Organic Compound (VOC) Content in Waterborne Coatings by Static Headspace Sampling, L. Mink, Chair, discussed the most recent version (Draft 5) of the proposed test method. The following changes were highlighted: A statement was added regarding the need to insure the inertness of all surfaces in the headspace unit that contact the analytes; the solvent used for standard preparation was changed to 50% water/50% tetrahydrofuran to insure that the water content in the samples and standards was similar. In addition, the calibration was changed from a single point to a three point calibration; and a statement was added defining the minimum signal-to-noise at which peaks must be integrated.

Results were distributed on the determination of VOC weight fraction in five waterborne architectural coatings. The results included one set of liquid injection GC results acquired using D 6886 and two sets of headspace GC results from two laboratories. In reviewing the results, it was noted that headspace 1 results agreed fairly well with the liquid injection results, with the exception of Texanol, which was consistently lower by the headspace method. This was expected because under the conditions of the headspace method it has been shown that Texanol is not fully evolved from the paint matrix. In comparing the two sets of headspace results, it was noted that the headspace 2 values were consistently higher than headspace 1 results. This was attributed to the difference in the solvent used for standard preparation. For the headspace 1 measurements, the standards were prepared in 50% water/50% tetrahydrofuran, while for the headspace 2 measurements 100% organic solvent was used. Previous experiments have shown that the water content in the headspace vial has a significant effect on signals obtained for very polar, water soluble compounds. An investigation of the effects of the calibration solvent will be investigated by the method collaborators. Once this issue is resolved, a larger round robin will be conducted.

The group on Water in Paint by Calcium Hydride, T. Lynn, Chair, was told that the purpose of this task group is to explore the utility of a calcium hydride based method as an alternative to Karl Fischer for the determination of water in paint. At the previous meeting in January, the task group voted to ballot the method concurrently. At this meeting Mr. Lynn discussed the results of the ballot: There were two negatives and several comments. The negative votes both related to the use of the term "water-reducible" in the title of the method, the fact that the method was based on a sole source and how that was handled in the method as well as the presentation of the statistical analysis in the "Precision and Bias" sections. The comments concerned the same issues with additional editorial corrections that improved the method. In discussing their comments with them, the task group chair arrived at a resolution to the relevant issues with the two negative voters, R. Montemayor and N. Rogers. The resulting revised method also included all of the editorial changes suggested by the other voters. As the changes were more than editorial, the ballot was withdrawn and the method will be re-balloted. After the chairman's summary there was some further discussion of the presentation of the statistical analysis in the "Precision and Bias" section. At the end of the discussion, it was decided to leave the section as is and re-ballot the rewritten method.