1、Designation: E2945 14Standard Test Method forFilm Permeability Determination Using Static PermeabilityCells1This standard is issued under the fixed designation E2945; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of the trans-mission of a gas through plastic membranes, sheeting, films,and fabri
3、c materials using a static sealed diffusion chamber.The test method monitors gas diffusion across a film membraneand provides measurements of (1) gas concentrations on eachside of the film membrane and (2) estimates of the masstransfer coefficient (MTC) for the tested gas and film material.The MTC r
4、epresents the film permeability and is independentof the concentration gradient used during testing, whichsimplifies some aspects of the experimental design.1.2 This test method permits the loading of mixed vaporsand simultaneous determination of the permeability of one filmto various gases.1.3 Unit
5、sThe values stated in SI units are to be regardedas the standard. No other units of measurement are included inthis standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish app
6、ro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD1898 Practice for Sampling of Plastics (Withdrawn 1998)3E691 Practice for Conducting an Interla
7、boratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 concentration, C, nchemical mass divided by thechamber volume.3.1.1.1 DiscussionCois the initial (t = 0) concentration inthe source chamber. The SI unit of concentration is g/cm3.3.1.2 concentration gradient
8、, ndifference in the concen-tration of gases across the film membrane divided by thetransport distance between the source and collection chambers(for example, usually considered to be the film thickness).3.1.2.1 DiscussionThe SI unit of the concentration gradi-ent is g/cm3-cm.3.1.3 mass transfer coe
9、ffcient, MTC, ngas diffusion rateconstant that relates the mass transfer rate, distance, andconcentration gradient as the driving force through a filmmembrane under the test conditions.3.1.3.1 DiscussionThe SI unit of the MTC is cm/hour.TheMTC expresses the ease of transmission of a gas through amem
10、brane under test conditions. The test conditions shall bestated, which include the ambient temperature, relativehumidity, film conditioning, sampling, and handling.3.1.4 mass transfer rate, J, nmass transfer rate, or fluxdensity, of a gas diffusing through a film membrane is the massof gas passing t
11、hrough a unit area (for example, 1 cm2)offilmmembrane per unit time interval (for example, 1 h). The SI unitof J is g/cm2hour.4. Summary of Test Method4.1 This test method uses a static sealed apparatus consist-ing of two chambers separated by the test-film membrane. Thetest chemical in the vapor ph
12、ase is added to the chamber on oneside of the film and the apparatus is incubated at constanttemperature during which the chemical diffuses through thetest membrane. This test method requires determination of therelative chemical concentrations on both sides of the mem-brane at several time points d
13、uring the incubation. Concentra-tions are monitored until equilibrium is reached or some otherpractical stoppage time. For permeable films, more frequentsampling is necessary because equilibrium may be reachedwithin minutes or hours. For films with very low permeability,longer incubation times (week
14、s) may be necessary to reach1This test method is under the jurisdiction of ASTM Committee E35 onPesticides, Antimicrobials, and Alternative Control Agents and is the directresponsibility of Subcommittee E35.22 on Pesticide Formulations and DeliverySystems.Current edition approved Feb. 1, 2014. Publi
15、shed April 2014. DOI: 10.1520/E2945-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved ver
16、sion of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1equilibrium. Linear regression of data may be used to calculatethe mass transfer coefficient (MTC). Alternatively, an analyt
17、i-cal solution to a mathematical model may be used to calculateMTC (see Appendix X1) for which a nonlinear least-squarealgorithm is available to fit concentrations derived from themathematical model to the observed concentrations. See Pa-piernik et al4,5for additional details.5. Significance and Use
18、5.1 This test method provides a simple approach for deter-mining the transmission properties of film membranes andsheeting over a range of permeability exceeding four orders ofmagnitude. This test method is described here to measure thepermeability of films used in soil fumigation, but it is alsoapp
19、ropriate for other gases and membranes if the analyticalmethods are appropriately modified.5.2 This test method can be used for single or mixedcompounds. This test method uses small quantities of testchemicals in vapor form, and microgram to milligram quanti-ties of each chemical may produce a suffi
20、cient amount of vaporfor each test depending on the analytical methods.5.3 Interlaboratory testing showed that the MTC estimatedby this test method is relatively insensitive to the laboratoryprocedures. The interlaboratory testing involved measuring theMTC for several soil fumigant compounds and a w
21、ide range offilm permeability. Analysts with prior experience handling andanalyzing gaseous fumigant compounds had lower coefficientsof variation (10 to 20 %) compared to less experienced analysts(20 to 50 %) based on triplicate tests. The coefficient ofvariation between laboratories was higher for
22、less permeablefilm materials than for films with high MTC. This wasattributed to the additional length of the experiments andpotential for increased leakage from the apparatus and wasmost pronounced for less experienced analysts.6. Apparatus6.1 A sealed apparatus is constructed of inert and imperme-
23、able material (for example, stainless steel) such that a sampleof test membrane is held between the two chambers in a closedsystem. The selection of material is dependent on the gasesbeing considered. The apparatus (see Fig. 1) enables samplingof the time rate of change in the gas concentration in e
24、achchamber and the mass transfer coefficient. The apparatus isconfigured as shown in Fig. 1.6.1.1 Permeability ApparatusStainless steel pipe (forexample, 0.3 to 0.6 cm thick, 10- to 15-cm diameter) is cut toform cylinders with height 2 to 6 cm. The volume of thechamber affects the time to reach equi
25、librium; therefore, tallercylinders are appropriate for testing permeable films, shortercylinders for less permeable films. The ends of the pipe aretrued and the mating surfaces smoothed. Each cylinder iswelded to a flat steel plate (for example, 0.3 cm thick) at oneend, as shown in Fig. 2.6.1.2 Sam
26、pling PortsHoles are drilled and threaded on theside of each cylinder to allow installation of sampling ports.The holes should be located near the mid-point height of thecylinder (Figs. 1 and 2).6.1.3 The purpose of the ports is to allow access to theinside of the chamber for spiking and sampling. D
27、uring othertimes, ports should be sealed to prevent leakage. This can beaccomplished using a septum port or sampling valve asdescribed in 6.1.3.1 and 6.1.3.2.6.1.3.1 Septum PortA 1.6-mm steel (or brass) unionconnector is installed in each hole. Before installation, thethreads of the union are coated
28、 with epoxy to ensure a gastightseal. One port is installed in the collection chamber and twoports (on opposite sides of the cylinder) are installed in thesource chamber. The second port is used to vent the sourcechamber during spiking. A septum and threaded nut areinstalled onto the 1.6-mm union an
29、d the union threads coatedwith epoxy. The threaded nut is covered by a Swagelok6capand a septum (Fig. 3A). Samples are collected with a syringe4Papiernik, S. K., Yates, S. R., and Gan, J., “An approach for estimating thepermeability of agricultural films,” Environmental Science and Technology, Vol 3
30、5,2001, pp. 1240-1246.5Papiernik, S. K., Ernst, F. F., and Yates, S. R., “An apparatus for measuring thegas permeability of films,” Journal of Environmental Quality, Vol 31, 2002, pp.358-361.6Swagelok is a registered trademark of the Swagelok Company, Cleveland,Ohio.FIG. 1 Schematic of Static Film P
31、ermeability Apparatus Consisting of Two Parts: A Source and Collection Chamber with a Film Mem-brane between ThemE2945 142by removing the outer septum and cap and piercing through theseptum behind the threaded nut (Fig. 3A). Between sampling,the nonpunctured septum and cap should be tightened over t
32、hethreaded nut to prevent leakage from the pierced septumbetween sampling times.6.1.3.2 Sampling Valve PortA gastight sampling valve isscrewed onto the union (Fig. Fig. 3A) or directly into thechamber wall and the threads sealed with epoxy (Fig. Fig. 3B).One valve is installed in the collection cham
33、ber and one valveis installed in the source chamber. The valve shall be made ofinert and impermeable material and produce a gastight connec-tion to the cylinder wall. A polytetrafluoroethylene stopcockscrewed onto the union allows sample introduction or removal.Astainless steel two-way valve (1.6 mm
34、) screwed directly intothe drilled hole could also be used to allow sample introductionor removal (Fig Fig. 3B). The air volume within the valveshould be minimized.NOTE 1Other configurations for the chamber access ports arepossible, but design criteria and testing should demonstrate that they: (1)ar
35、e constructed of inert materials, (2) are non-leaking between samplingtimes, (3) minimize leaking during sampling, and (4) maintain integrityduring routine laboratory handling.7. Materials7.1 The apparatus can be used to measure diffusion of anarbitrary gas through a film membrane. The specifics of
36、themethodology described in the following relate to fumigantFIG. 2 Top View of the Source ChamberA Stainless Steel Cylinder Is Welded to the Stainless Steel Bottom Plate Leaving One End ofthe Cylinder Open3A Sampling Port Design3b Sampling Port DesignFIG. 3 Sampling Port DesignE2945 143gases and fum
37、igation films, but the test method can bemodified to allow measuring the MTC for other gases and othermembranes.7.2 Fumigant ChemicalsIodomethane, 1,3-dichloropropene (mixture of cis and trans isomers), dimethyldisulfide, methyl isothiocyanate (transformation product ofmetam sodium or dazomet during
38、 fumigation), chloropicrin,methyl bromide, and sulfuryl fluoride.7.3 Gas-Mixing ChamberGastight 1-L glass containerwith valves on both ends and a side sampling port. Other typesof gastight containers with sampling ports may be used. If aclear glass container is used, it is recommended that the glass
39、container be wrapped with aluminum foil to protect thefumigants from light. Some fumigants are photodegradable.7.4 A constant-temperature environmental chamber is usedto maintain constant temperature during testing. Since thetemperature is known to affect the MTC value, the variation inthe temperatu
40、re set point should be no more than 62C.7.5 MiscellaneousAn assortment of gastight syringes (forexample, 10-Lto 100-mLcapacity), Tedlar bag with samplingport (for example, 0.6-L capacity), gas chromatograph au-tosampler vials, caps that are inert to the test gas, crimpers,timers, epoxy glue, aluminu
41、m adhesive tape.7.6 Gas Chromatograph/Mass Spectrometer Equipped withAppropriate Capillary ColumnA gas chromatograph (GC)with electron capture detector (ECD) can also be used foranalysis of halogenated fumigants, such as methyl bromide,iodomethane, chloropicrin, 1,3-dichloropropene, and sulfurylfluo
42、ride. Equipment that includes an autosampler providesadded convenience.7.7 Other Gases, appropriate sampling and detection equip-ment as needed.8. Potential Hazards8.1 GeneralAppropriate laboratory and chemical safetyprocedures should be followed and materials and gases shouldbe used in accordance w
43、ith information provided on productlabels, safety data sheets, and established laboratory safetyguidelines.8.2 Gases under PressureWhen using gases stored underhigh pressure, the dispensing equipment should be appropriatefor the intended use. The equipment should be rated for the gascylinder or gas-
44、line pressures, or both, and pressure-reducingvalves and regulators used where needed.8.3 Fumigation gases are a class of chemicals that posesignificant health hazards. They generally are irritants andtoxic. Adverse human health effects include harm if inhaled,swallowed, or absorbed through the skin
45、; appropriate safetyprocedures should be used.9. Sampling, Test Specimens, and Test Units9.1 Test specimens should be sampled in accordance withPractice D1898. Tested samples should be representative of thebulk material; free of wrinkles, stretches, pinholes, otherimperfections; and of uniform thick
46、ness. Surface condition anddifferences in materials or construction of each side of the filmshall be reported.9.2 Cut the film test specimens into approximately 15- by15-cm pieces.9.3 Information concerning the film composition (forexample, thickness, presence of ultraviolet UV stabilizers,barrier p
47、olymers and additives, and so forth) and manufactur-ing should be reported, when available.10. Preparation of Apparatus10.1 Mix together a small amount of the epoxy resin andhardener. Spread a thin layer of the well-mixed epoxy glueover the exposed rim of the open edge of the source chamberside of t
48、he permeability apparatus using a flat stainless steelspatula. Place the test film onto the edge containing the glue.Make sure the film is spread flat and evenly (not stretched andwith no crevices). Spread a thin layer of well-mixed epoxy glueover the exposed rim of the collection chamber of the per
49、me-ability apparatus. Carefully place the rim of collection chamberover the film and mate the two halves of apparatus by aligningand joining them together to form a gastight seal. Care shouldbe taken to place the film and mate the two chambers withminimal movement after contact.10.2 After the glue is cured (usually overnight), trim theexcess film with a razor blade. Apply aluminum tape to theoutside of the apparatus over the seam between chambers andburnish to provide additional support and sealing of theapparatus. Place the constructed apparatus inside a
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