Testing permeation

Testing for the presence of permeated chemical contaminants requires that pieces (in the case of contaminated soil this would be typically those that visually indicate contamination) of the protective garments be sent to a laboratory for analysis. 

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R is the gas constant Dq and activation energy Eu are constants derived from an Arrhenius plot for diffusion coefficients applying at different temperatures, and solubility coefficient was obtained from a separate permeation test at TiK. Suitable testing using a specially constmcted permeation cell water-cooled at one end provided good validation data. 

Diffusion and Permeation Testing 23.4.4.1 Kinetics of Liquid Diffusion Tests... 

MERL s interest in employing these tests has included (1) the quantifying of D to enable certain predictions to be made (see Section 23.4.6), (2) testing at high temperature and pressures to simulate service realism (see Section 23.5.1.3), and (3) to provide data for use in estimating permeation rates while not needing to conduct actual permeation tests (see Section 23.4.4.3). 

Water permeability is tested by transmission permeation tests, standard test ASTM E 96 being widely used. The water which permeates is absorbed in a desiccant and its weight—or alternatively, the loss of weight of the water supply from a container (or permeation cup ) sealed by the sheet test sample—is determined. The same procedure is applied for the transmission of volatile liquids in standard ISO 6179 (BS 903 A46)—see Eigure 23.7. 

For gases, both permeation and diffusion data are best measured by permeation tests, many different types been described elsewhere. The same sheet membrane permeation test can quantify permeation coefficient Q, diffusion coefficient D, solubility coefficient s, and concentration c. The membrane, of known area and thickness, must be completely sealed to separate the high-pressure (initial) region from that containing the permeated gas it may need an open-grid support to withstand the pressure. The permeant must be suitably detected and quantified (e.g., by pressure or volume buildup, infrared (IR) spectroscopy, ultraviolet (UV), gas chromatography, etc.). 

FIGURE 23.10 Permeated volume versus time for gas permeation test. 

FIGURE 23.11 Schematic of high-pressure gas permeation testing system. 

Values from high-pressure permeation tests can give useful information regarding the selecting of elastomer types to withstand potential explosive (rapid gas) decompression damage (Sections... 

When testing, the permeation equation shown for conical samples in Section 23.4.2 is used to provide permeation coefficient Q. Measured values showed that the more normal methods employed for high-pressure permeation testing at MERE and elsewhere, using a sample support sinter, are likely to give underestimates of true permeation rates by a factor of about three. 

For single-component systems, permeation testing can be divided into four broad categories ... 

Although many chemical permeation tests have been conducted by the NTP over the past several years, the time and cost of... 

Forsberg s electronic book consists of information from over 5,000 permeation tests on 6A0 chemicals or mixtures of chemicals. Over 7,000 breakthrough times and/or permeation rates are recorded. Along with this information are over 25,000 pieces of associated data such as the test material, manufacturer, model number, thickness, comments, a performance index number, and references. Over 200 different models of CPC are represented. 

By a combination of tank redesign and surface fluorination the problems were overcome and today a number of local motor car manufacturers are using surface-fluorinated LLDPE petrol tanks. These tanks performed exceptionally well in petrol permeation tests in which control tanks lost about 16g/day, while fluorinated tanks lost less than 0.5g/day at 40°C. With advanced fluorination techniques mass loss values of less than 0.1 g/day have already been achieved for some of these fluorinated tanks. 

A total of four Co and Fe based alloys were procured from a commercial source. Disks were punched from the foil and mounted into VCR vacuum fittings, with a nickel gasket on one surface and the sample in direct contact with the VCR sealing surface on the other. The sample assemblies were leak tested and verified leak tight to 2x10 7 sscm He prior to intallation in the permeation test apparatus. 

Figure 2. SRNL Gaseous Permeation Test Rig (a) photo and (b) schematic...

Gaseous hydrogen permeation testing of similar V-Ti-Ni alloys once again demonstrated permeabilites on par with commercially available Pd/Pd-alloy membrane materials. 

Permeation testing of the Fe-/Co-based metallic glass alloys demonstrated permeabilities slightly lower than Pd/Pd-alloys however, the cost savings afforded by these materials (approximately 650X lower) warrants further study/evaluation of this class of materials. 

Table 19.1 Composition of various buffer systems possibly eligible for combined dissolution and permeation testing. Concentrations may vary from reference to reference. Composition of FaSSIF and FeSSIF is shown as reported by Galia et al. [3] in the meantime, several publications denoted a change from potassium to sodium as the main cation [91] or others changes. Abbreviations are given in the text. 

Historical Evolution of Combined Dissolution and Permeation Testing... 

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