ASTM_E_2945_-_14.pdf

Designation:E294514Standard 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 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 fabric 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 represents 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 UnitsThe 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 appro-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Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD1898 Practice for Sampling of Plastics(Withdrawn 1998)3E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 Definitions:3.1.1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,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 coeffcient,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 amembrane 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 through a unit area(for example,1 cm2)of filmmembrane 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 phase 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 during 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(weeks)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.Published 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 version 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 States1 equilibrium.Linear regression of data may be used to calculatethe mass transfer coefficient(MTC).Alternatively,an analyti-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.Signif