ASTM_F_1249_-_13.pdf

Designation:F124913Standard Test Method forWater Vapor Transmission Rate Through Plastic Film andSheeting Using a Modulated Infrared Sensor1This standard is issued under the fixed designation F1249;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 a procedure for determining therate of water vapor transmission through flexible barriermaterials.The method is applicable to sheets and films up to 3mm(0.1 in.)in thickness,consisting of single or multilayersynthetic or natural polymers and foils,including coatedmaterials.It provides for the determination of(1)water vaportransmission rate(WVTR),(2)the permeance of the film towater vapor,and(3)for homogeneous materials,water vaporpermeability coefficient.NOTE1Values for water vapor permeance and water vapor perme-ability must be used with caution.The inverse relationship of WVTR tothickness and the direct relationship of WVTR to the partial pressuredifferential of water vapor may not always apply.1.2 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prior to use.2.Referenced Documents2.1 ASTM Standards:2D374 Test Methods for Thickness of Solid Electrical Insu-lation(Withdrawn 2013)3D1898 Practice for Sampling of Plastics(Withdrawn 1998)3E96/E96M Test Methods for Water Vapor Transmission ofMaterialsE104 Practice for Maintaining Constant Relative Humidityby Means of Aqueous SolutionsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE178 Practice for Dealing With Outlying ObservationsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 Definitions:3.1.1 water vapor permeability coeffcientthe product ofthe permeance and the thickness of the film.The permeabilityis meaningful only for homogeneous materials,in which caseit is a property characteristic of bulk material.3.1.1.1 DiscussionThis quantity should not be used unlessthe relationship between thickness and permeance has beenverified in tests using several thicknesses of the material.Anaccepted unit of permeability is the metric perm centimeter,or1 g/m2per day per mm Hgcm of thickness.The SI unit is themol/m2sPamm.The test conditions(see 3.1)must be stated.3.1.2 water vapor permeancethe ratio of a barriersWVTR to the vapor pressure difference between the twosurfaces.3.1.2.1 DiscussionAn accepted unit of permeance is themetric perm,or 1 g/m2per day per mm Hg.The SI unit is themol/m2sPa.Since the permeance of a specimen is generally afunction of relative humidity and temperature,the test condi-tions must be stated.3.1.3 water vapor transmission rate(WVTR)the time rateof water vapor flow normal to the surfaces,under steady-stateconditions,per unit area.3.1.3.1 DiscussionAn accepted unit of WVTR is g/m2perday.The test conditions of relative humidity and temperaturewhere the humidity is the difference in relative humidity acrossthe specimens,must be stated.4.Summary of Test Method4.1 A dry chamber is separated from a wet chamber ofknown temperature and humidity by the barrier material to betested.The dry chamber and the wet chamber make up adiffusion cell in which the test film is sealed.Water vapordiffusing through the film mixes with the gas in the drychamber and is carried to a pressure-modulated infrared sensor.This sensor measures the fraction of infrared energy absorbedby the water vapor and produces an electrical signal,the1This test method is under the jurisdiction ofASTM Committee F02 on FlexibleBarrier Packaging and is the direct responsibility of Subcommittee F02.10 onPermeation.Current edition approved Oct.1,2013.Published November 2013.Originallyapproved in 1989.Last previous edition approved in 2011 as F1249 06(2011).DOI:10.1520/F1249-13.2For 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 amplitude of which is proportional to water vapor concentra-tion.The amplitude of the electrical signal produced by the testfilm is then compared to the signal produced by measurementof a calibration film of known water vapor transmission rate.This information is then used to calculate the rate at whichmoisture is transmitted through the material being tested.5.Significance and Use5.1 The