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Daniel H. Annal,a,b
Edward T. Zellers,a
Robert Sulewski,a
ASTM (American Society for Testing and Materials) Method F739-96 specifies a test-cell design and procedures for measuring the permeation resistance of chemical protective clothing. Among the specifications are open-loop collection stream flow rates of 0.050 to 0.150 Umin for a gaseous medium. At elevated temperatures the test cell must be maintained within 10degC of the set point. This article presents a critical analysis of the effect of the collection stream flow rate on the measured permeation rate and on the temperature uniformity within the test cell. Permeation tests were conducted on four polymeric glove materials with 44 solvents at 25degC. Flow rates >0.5 Umin were necessary to obtain accurate steady-state permeation rate (SSPR) values in 25% of the tests. At the lower flow rates the true SSPR typically was underestimated by a factor of two or less, but errors of up to 33-fold were observed. No clear relationship could be established between the need for a higher collection stream flow rate and either the vapor pressure or the permeation rate of the solvent, but test results suggest that poor mixing within the collection chamber was a contributing factor. Temperature gradients between the challenge and collection chambers and between the bottom and the top of the collection chamber increased with the water-bath temperature and the collection stream flow rate. Use of a test cell modified to permit deeper submersion reduced the gradients to<=0.5degC. It is recommended that all SSPR measurements include verification of the adequacy of the collection stream flow rate. For testing at nonambient temperatures, the modified test cell described here could be used to ensure temperature uniformity throughout the cell.
Keywords: ASTM, glove, permeation, polymer, protective clothing, solvent
STM (American Society for Testing and Materials) Method F739, Standard Test Method for Resistance of Protective Clothing Materials to Permeation by Liquids or Gases Under Conditions of Continuous Contact, was first published in 1981(1,2) and subsequently revised in 1985, 1991, and 1996 by the ASTM F23 Committee3-5 It provides specifications for the design of a test cell and for the evaluation and documentation of the barrier effectiveness of chemical protective clothing (CPC) materials when exposed to liquid or gaseous chemicals. The materials intended for evaluation...