|Industrial Chemicals Committee Focuses on Analyzing Glycols; Participation Requested
ASTM Committee E15 on Industrial and Specialty Chemicals has recently focused on the analysis of glycols, with standards under development and tests recently published. Of particular importance in the area of industrial chemicals is monoethylene glycol (MEG), which is used in numerous industrial applications and serves as a chemical intermediate in the manufacture of polyester fibers, plastics, automobile coolants and resins. One standard under development covers glycol impurities. Participation is requested for an interlaboratory study on this draft as well as for the revision of a second standard. In addition, two standards recently published by E15 address ultraviolet transmittance and aldehydes, which are critical product quality parameters in many applications involving glycols.
WK1069, Draft Test Method for Glycol Impurities in Mono-, Di- and Triethylene Glycol (Gas Chromatographic Method) takes advantage of the different boiling points among the small amounts of diethylene glycol and even triethylene glycol that are co-produced with MEG in the manufacturing process. These co-products are separated by distillation, but small amounts can be found in the preferred MEG product. The method separates these materials and allows detection of the individual compounds, which can affect performance or upset the end users process. Interested stakeholders are requested to participate in an interlaboratory study for this method. When completed, this method should replace E 611 mentioned below.
Recently completed WK1480 was an action to reinstate the previously withdrawn standard E 611, Test Method for Low Concentrations of Diethylene Glycol in Ethylene Glycol by Gas Chromatography, with revisions to the precision and bias statements. The impurities in the glycols method, WK1069 above should supersede this method when approved.
E 202, Test Methods for the Analysis of Ethylene Glycols and Propylene Glycols, covers the chemical and physical analysis of the commonly available grades of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and dipropylene glycol. Analyses included are purity of reagents, specific gravity, distillation range, acidity, water, iron, color and gas chromatographic analysis. The standard is currently being reviewed and updated primarily to incorporate the technology now being used in the industry and to remove outdated techniques. Participation is sought for interlaboratory studies to work on the precision and bias statements for this method.
Recently published E 2193, Test Method for Ultraviolet Transmittance of Monoethylene Glycol (Spectrophotometric Method), provides a measure of the purity of the sample with respect to ultraviolet absorbing compounds. The compounds measured by this technique are in trace quantities in the parts per billion ranges and cannot be measured directly. UV is extensively measured during the MEG production process, product release and product acceptance because glycol that has poor UV transmittance can produce color problems in the final polyester product.
Also recently published is E15 standard E 2313, Test Method for Aldehydes in Monoethylene Glycol (Spectrophotometric Method), which provides a measure of sample purity. Aldehydes are a class of chemical compounds known as carbonyls, and the three aldehydes of interest found in glycol are formaldehyde, acetaldehyde and glycolaldehyde, which are produced in trace quantities in the manufacturing process. Aldehydes react differently than glycol and may affect a users process that in turn could cause inferior products (poor color or product performance) or interfere with overall process performance. In addition, the presence of aldehydes can also represent an environmental problem as they may be rejected from the process into waste streams that require disposal.
For further technical information or to participate in the interlaboratory studies, contact Deborah Passwater, chemist, Shell Chemical LP, Houston, Texas (phone: 281/544-6740). Committee E15 meets March 8-9 in conjunction with the Chlorine Institute in Houston, Texas, and Oct. 4-5 in Amelia Island, Fla. For meeting or membership details, contact Diane Rehiel, manager, Technical Committee Operations, ASTM International (phone: 610/832-9717). //
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