1、Designation: F 2476 05Standard Test Method forthe Determination of Carbon Dioxide Gas Transmission Rate(Co2TR) Through Barrier Materials Using An InfraredDetector1This standard is issued under the fixed designation F 2476; the number immediately following the designation indicates the year oforigina
2、l adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This method covers a procedure for determination of thesteady-sta
3、te rate of transmission of carbon dioxide gas throughplastics in the form of film, sheeting, laminates, coextrusions,or plastic-coated papers or fabrics. It provides for the determi-nation of (1) carbon dioxide gas transmission rate (CO2TR),(2) the permeance of the film to carbon dioxide gas (PCO2),
4、and (3) carbon dioxide permeability coefficient (P”CO2)inthecase of homogeneous materials.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 practic
5、es and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1898 Practice for Sampling of Plastics3E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 Carbon d
6、ioxide permeability coeffcient (P”CO2)theproduct of the permeance and the thickness of film. Thepermeability is meaningful only for homogeneous materials, inwhich case it is a property characteristic of the bulk material.This quantity should not be used unless the relationshipbetween thickness and p
7、ermeance has been verified on testsusing several different thicknesses of the material. The SI unitof carbon dioxide permeability is the mol/msPa. The testconditions (see 3.1.3) must be stated.3.1.2 Carbon dioxide permeance (PCO2)the ratio of theCO2TR to the difference between the partial pressure o
8、f CO2on the two sides of the film. The SI unit of permeance is themol/(m2sPa). The test conditions (see 3.1.3) must be stated.3.1.3 Carbon dioxide transmission rate (CO2TR)Thequantity of carbon dioxide gas passing through a unit area ofthe parallel surfaces of a plastic film per unit time under thec
9、onditions of the test. The SI unit of transmission rate is themol/(m2s). The test conditions, including temperature andcarbon dioxide partial pressure on both sides of the film, mustbe stated.3.1.3.1 DiscussionA commonly used metric unit ofCO2TR is the cc(STP)/(m2day) at one atmosphere drivingforce
10、pressure differential where: 1 cc(STP) is 44.62 mol. 1atm is 0.1013 MPa. and one day is 86.4 x 103s. CO2TR in SIunits is obtained by multiplying the value in metric units by5.164 x 10-10or the value in inch-pound units (cm3(STP)/100in2day) by 8.004 x 10-9.4. Summary of Test Method4.1 The carbon diox
11、ide gas transmission rate is determinedafter the sample has equilibrated in a dry-test environment. Inthis context, a “dry” environment is considered to be one inwhich the relative humidity is less than 1 %.4.2 The specimen is mounted as a sealed semi-barrierbetween two chambers at ambient atmospher
12、ic pressure. Onechamber is slowly purged by a stream of nitrogen and the otherchamber with carbon dioxide.As carbon dioxide gas permeatesthrough the film into the nitrogen carrier gas, it is transportedto an infrared detector where an electrical output is producedwhose magnitude is proportional to t
13、he amount of CO2flowinginto the detector per unit of time.5. Significance and Use5.1 Carbon dioxide gas transmission rate (CO2TR) is animportant determinant of the packaging protection afforded bybarrier materials. It is not, however, the sole determinant, andadditional tests, based on experience, m
14、ust be used to correlate1This test method is under jurisdiction of ASTM Committee F02 on FlexibleBarrier Materials and is the direct responsibility of Subcommittee F02.10 onPermeation.Current edition approved May 1, 2005. Published May 2005.2For referenced ASTM standards, visit the ASTM website, www
15、.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.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United S
16、tates.packaging performance with CO2TR. It is suitable as a refereemethod of testing, provided that purchaser and seller haveagreed on sampling procedures, standardization procedures,test conditions and acceptance criteria.6. Apparatus6.1 Carbon Dioxide Gas Transmission Apparatus, as dia-grammed in
17、Fig. 1 or Fig. 2, with the following:6.1.1 Diffusion Cellshall consist of two metal halves,which, when closed upon the test specimen, will accuratelydefine a circular area. A typical acceptable diffusion cell area is50 cm2. The volume enclosed by each cell half, when clamped,in not critical: it shou
18、ld be small enough to allow for rapid gasexchange, but not so small that an unsupported film thathappens to sag or bulge will contact the top or bottom of thecell.6.1.1.1 O-Ring Groovean appropriately sized groove, ma-chined into the CO2(or test gas) side of the diffusion cell,retains an elastomer O
19、-ring. The test area is considered to bethat area established by the inside contact diameter of thecompressed O-ring when the diffusion cell is clamped shutagainst the test specimen. The area, A, can be obtained bymeasuring the inside diameter of the imprint left by the O-ringon the specimen after i
20、t has been removed from the diffusioncell.6.1.1.2 The nitrogen (or carrier gas) side of the diffusion cellshall have a flat raised rim. Since this rim is a critical sealingsurface against which the test specimen is pressed, it shall besmooth and flat, without radial scratches.6.1.1.3 Diffusion Cell
21、Pneumatic Fittingseach half of thediffusion cell shall incorporate suitable fittings for the intro-duction and exhaust of gases without significant loss orleakage.6.1.1.4 It is desirable to thermostatically control the diffu-sion cell. Because the transmission rate is a function oftemperature, it sh
22、all be controlled to within 6 0.1C.6.1.1.5 Experience has shown that arrangements using mul-tiple diffusion cells are a practical way to increase the numberof measurements that can be obtained from an infrared sensor.A valving manifold connects the carrier gas side of eachindividual diffusion cell t
23、o the sensor in a predeterminedpattern. Carrier gas is continually purging the carrier gas sideof those cells that are not connected to the sensor. Either testgas or carrier gas, as is appropriate, purges the test gas chamberof any individual cell.6.1.2 Flowmetera means shall be provided to establis
24、hand maintain test gas and carrier gas flows. An operating rangein the order of 5 to 100 ml/min for CO2and up to 300 ml/minfor N2.6.1.3 Flow Switching Valvesneeded to perform the tasksof (1) purging, (2) accumulating, if needed, for static ordynamic testing methods, and (3) maintaining flow for con-
25、tinuous flow methods.6.1.4 Infrared sensora 4.3 m infrared filter to measurethe quantity of CO2in the carrier gas going to the sensor.NOTE 1The infrared sensor is not an absolute measuring device.Therefore, some standard has to be used to establish a point of reference.FIG. 1 A practical arrangement
26、 of components for the measurement of carbon dioxide transmission rate using a non-computerizedsystemF2476052A means of providing a known quantity of CO2has been used and hasbeen found satisfactory for this application. The use of a calibrated valveenables the system to establish the point of refere
27、nce against which theunknown film is compared or the system may also be calibrated with areference film4.6.1.5 Recording devicea strip chart recorder or, if thesystem is computer- controlled, a monitor and a printer havebeen found to be adequate.7. Reagents and Materials7.1 Nitrogen gasgrade need no
28、t be higher than “HighPurity” or “Extra Dry,” which is readily available in most ofthe principle cities at low cost. A regulator with auxiliarymetering valve and outlet fittings for18 in. tubing should beused.7.2 Carbon Dioxide gasa carbon dioxide concentration of99.9 % or greater is suitable for th
29、is application.7.3 Sealing Greasea high-viscosity silicone stopcockgrease or high-vacuum grease for sealing the specimen film inthe diffusion cell.7.4 Aluminum Foil Reference BlankThe term “referenceblank” or “blocking plate” refers to a non-transmitting, zeroreference aluminum foil sheet. Used in s
30、ome instruments toestablish system zero prior to testing film specimens.8. Precautions8.1 Temperature is a critical parameter affecting the mea-surement of CO2TR. Careful temperature control will help tominimize variations due to temperature fluctuations. Duringtesting, the temperature shall be main
31、tained within 6 0.1C.The average temperature and the range of temperatures foundduring a test shall both be reported. Accurate temperaturecontrol is easier to maintain if the instrument is placed in atemperature-controlled environment.8.2 The sensor will require time to stabilize to a low readingcha
32、racteristic of a good CO2barrier after it has been used totest a high transmission barrier. For this reason, materials ofcomparable gas transmission qualities should be tested to-gether.8.3 Calibration should be performed with the appropriateamount of CO2that is comparable to the CO2TR of thespecime
33、ns being tested.9. Sampling9.1 The sampling units used for the determination ofCO2TR shall be representative of the quantity of product forwhich the data are required, in accordance with Recommended4The sole source of supply of the reference material known to the committee atthis time is MOCON, 7500
34、 Boone Ave. North, Minneapolis, MN 55428. If you areaware of alternative suppliers, please provide this information to ASTM Interna-tional Headquarters. Your comments will receive careful consideration at a meetingof the responsible technical committee1, which you may attend.FIG. 2 A practical arran
35、gement of components for the measurement of carbon dioxide transmission rate using a computerized systemF2476053Practice D 1898. Care shall be taken to ensure that samples arerepresentative of conditions across the width and along thelength of a roll of film.10. Test Specimens10.1 Test specimens sha
36、ll be representative of the materialsbeing tested and shall be free of defects, including wrinkles,creases, and pinholes, unless these are a characteristic of thematerial being tested.10.2 Average thickness shall be determined to the nearest2.5 m (0.0001 in.), using a digital micrometer (or equivale
37、nt)at a minimum of five points distributed over the entire test area.Maximum, minimum, and average values shall be recorded.10.3 If the test specimen is of an asymmetrical (multilayer)construction, the two surfaces shall be marked by appropriatedistinguishing marks and the orientation of the test sp
38、ecimen inthe diffusion cell shall be reported (for example, “side 2 wasmounted facing the CO2side of the diffusion cell”).11. Conditioning11.1 If a specific conditioning procedure is used, it shouldbe included in the report.12. Calibration12.1 Computerized instrumentsSystems that utilize com-puter l
39、inearization technology allow a one-point calibration fora wide range of CO2TR values. This one-point reference isaccomplished by utilizing a known value reference film4.12.1.1 Systems that utilize computer linearization technolo-gies normally require calibration to be accomplished before thesamples
40、 are tested, or during the test of a sample. Follow themanufacturers standard calibration procedure as called out inthe manufacturers operating manual.12.2 Non-computerized instrumentsBecause the IR sen-sor voltage output on non-computerized systems is dependenton variables such as detector response
41、 and carrier gas flow, acalibrated point of reference must be determined against whichthe unknown can be compared. This is achieved through theuse of a measured quantity of CO2being injected into thesystem, utilizing a calibration valve (the volume of which hasbeen determined) or with a known value
42、reference film.12.2.1 On the manually operated systems, calibration isperformed after the samples have been tested and before thetest cells have been opened and the samples removed. Followthe manufacturers standard calibration procedure as called outin the manufacturers operating manual.12.2.2 It sh
43、ould be noted that the system response may notbe perfectly linear. Therefore, the amount of CO2injected intothe system during the calibration cycle should be as close to theestimated value as possible.13. Test Procedure13.1 Trim the test specimen to a size appropriate for thediffusion cell in which
44、it will be mounted. In general, thismeans that the seal around the edge of the diffusion cell shouldnot be impaired if the specimen bulges or sags slightly.13.2 Unclamp the diffusion cell and open it. Apply a thinlayer of sealing grease around the raised rim of the diffusioncell. Place the test spec
45、imen upon the greased surface, takingcare to avoid creases or wrinkles. Clamp both halves of thediffusion cell tightly together.13.3 In some instruments, it may be necessary to establish asystem zero prior to testing. This is accomplished by using analuminum foil reference blank that is free from wr
46、inkles,creases, scratches and pinholes. This foil is mounted in onediffusion cell using sealing grease. The output of this cell,where there is no contribution from permeation since foil isessentially impervious, is the system zero.If a system zero is not required prior to testing, proceed to13.4.13.
47、4 Introduce carbon dioxide gas into the test gas side ofthe diffusion cell, following the manufacturers instructions.This marks the start of the conditioning period during which agradient is established within the film and a steady-statetransmission rate is achieved. The length of time it takes toac
48、hieve a steady-state condition is dependent on many factors,such as temperature and thickness of the film. Steady state isdefined as the point at which the transmission rate no longerchanges with time. Users will initially have to experiment withconditioning times to establish a suitable time for th
49、eir mate-rials.13.5 Depending on the equipment used, the following isoffered as a guide when testing flat materials with a manualsystem (non-computerized):Static accumulationA method generally used for testinglow transmitting barriers (transmission rates of less that 50cc/m2/day).Dynamic accumulationA method applied to barriers ofmoderate transmission rate generally greater than 50 cc/m2/daybut less than 300 cc/m2/day.Continuous FlowA method suited to measurement ofmoderate-to-high transmitting barriers (300 cc/m2/day to 10000 cc/m2/day).Pleas
