laboratories should be compared using the appropriate statis-tical analysis and an acceptable probability level chon by the two parties before testing is begun.If a bias is found,either its cau must be found and corrected,or the purchar and the supplier must agree to interpret future test results with consid-eration of the known bias.
5.2Air permeability is an important factor in the perfor-mance of such textile materials as gasfilters,fabrics for air bags,clothing,mosquito netting,parachutes,sails,tentage,and vacuum cleaners.Infiltration,for example,efficiency is directly related to air permeability.Air permeability also can be ud to provide an indication of the breathability of weather-resistant and rainproof fabrics,or of coated fabrics in general, and to detect changes during the manufacturing process.
5.3Performance specifications,both industrial and military, have been prepared on the basis of air permeability and are ud in the purcha of fabrics where permeability is of interest.
5.4Construction factors andfinishing techniques can have an appreciable effect upon air permeability by causing a change in the length of airflow paths through a fabric.Hot calendaring can be ud toflatten fabric components,thus reducing air permeability.Fabrics with different surface textures on either side can have a different air permeability depending upon the direction of airflow.
5.4.1For woven fabric,yarn twist also is important.As twist increas,the circularity and density of the yarn increas,thus reducing the yarn diameter and the cover factor and increasing the air permeability.Yarn crimp and weave influence the shape and area of the interstices between yarns and may permit yarns to extend easily.Such yarn extension would open up the fabric, increa the free area,and increa the air permeability.
5.4.2Increasing yarn twist also may allow the more circular, high-density yarns to be packed cloly together in a tightly woven structure with reduced air permeability.For example,a worsted gabardine fabric may have lower air permeability than
a woolen hopsacking fabric.
6.Apparatus
6.1Air Permeability Testing Apparatus5consisting of the following:
6.1.1Test Head that provides a circular test area of38.3 cm2(5.93in.2)60.3%.
N OTE2—Alternate test areas may be ud,such as5cm2(0.75in.2), 6.45cm2(1.0in.2),and100cm2(15.5in.2).
6.1.2Clamping System to Secure Test Specimens,of differ-ent thickness under a force of at least5065N(1161lbf) to the test head without distortion and minimal edge leakage underneath the test specimen.
6.1.2.1A suitable means to minimize edge leakage is to u a55Type A durometer hardness polychloroprene(neoprene) clamping ring20mm(0.75in.)wide and3mm(0.125in.) thick around the test area above and underneath the test specimen.
N OTE3—Since air leakage may affect test results,precautions must be taken,especially with very heavy or lofty fabrics,to prevent leakage.The u of a weighted ring and rubber gaskets on the clamp surfaces has been found to be helpful.Test Method F778describes a ries of usable clamping adaptions to eliminate edge leakage.Gaskets should be ud with caution becau in some cas,and with repeated-u gaskets may deform resulting in a small change in test area.A weighted ring can be ud with fabrics,such as knits or tho that readily conform to the test head.T
he weighted ring is not recommended for lofty or stiff fabric. 6.1.3Means for drawing a steadyflow of air perpendicu-larly through the test area and for adjusting the airflow rate that preferably provides pressure differentials of between100and 2500Pa(10and250mm or0.4and10in.of water)between the two surfaces of the fabric being tested.At a minimum,the test apparatus must provide a pressure drop of125Pa(12.7 mm or0.5in.of water)across the specimen.
6.1.4Pressure Gage or Manometer,connected to the test head underneath the test specimen to measure the pressure drop across the test specimen in pascals(millimetres or inches)of water with an accuracy of62%.
6.1.5Flowmeter,volumetric counter or measuring aperture to measure air velocity through the test area in cm3/s/cm2 (ft3/min/ft2)with an accuracy of62%.
6.1.6Calibration Plate,or other means,with a known air permeability at the prescribed test pressure differential to verify the apparatus.
6.1.7Means of calculating and displaying the required results,such as scales,digital display,and computer-driven systems.
6.2Cutting Dies or Templates,to cut specimens having dimensions at least equal to the area of the clamping surfaces of the test apparatus(optional).
7.Sampling and Test Specimens
7.1Lot Sample—As a lot sample for acceptance testing, randomly lect the number of rolls or pieces of fabric directed in an applicable material specification or other agreement between the purchar and the supplier.Consider the rolls or pieces of fabric to be the primary sampling units.In the abnce of such an agreement,take the number of fabric rolls or pieces specified in Table1.
N OTE4—An adequate specification or other agreement between the purchar and the supplier requires taking into account the variability between rolls or pieces of fabric and between specimens from a swatch from a roll or piece of fabric to provide a sampling plan with a meaningful producer’s risk,consumer’s risk,acceptable quality level,and limiting quality level.
7.2Laboratory Sample—For acceptance testing,take a swatch extending the width of the fabric and approximately1 m(1yd)along the lengthwi direction from each roll or piece in the lot sample.For rolls of fabric,take a sample that will exclude fabric from the outer wrap of the roll or the inner wrap around the core of the roll of fabric.
5Suitable apparatus is commercially available.TABLE1Number of Rolls or Pieces of Fabric in the Lot Sample Number of Rolls or Pieces in
Lot,Inclusive
Number of Rolls or Pieces
in Lot Sample
1to3all
4to244
25to505
over5010%to a maximum of10rolls or
pieces
7.3Test Specimens—From each laboratory sampling unit, take ten specimens unless otherwi agreed upon between purchar and supplier.U the cutting die or template de-scribed in6.2,or if practical,make air permeability tests of a textile fabric without cutting.
7.3.1Cutting Test Specimens—When cutting specimens,cut having dimensions at least equal to the area of the clamping mechanism.Label to maintain specimen identity.
7.3.1.1Take specimens or position test areas reprenting a broad distribution across the length and width,preferably along the diagonal of the laboratory sample,and no nearer the edge than one tenth its width unless otherwi agreed upon between the purchar and supplier.Ensure specimens are free of folds, creas,or wrinkles.Avoid getting oil,water,grea,and so forth,on the specimens when handling.
8.Preparation of Test Apparatus and Calibration
8.1Set-up procedures for machines from different manufac-turers may vary.Prepare and verify calibration of the air permeability tester as directed in the manufacturer’s instruc-tions.
8.2When using microprocessor automatic data gathering systems,t the appropriate parameters as specified in the manufacturer’s instructions.
8.3For best results,level the test instrument.
8.4Verify calibration for the range and required water pressure differential that is expected for the material to be tested.
9.Conditioning
9.1Precondition the specimens by bringing them to ap-proximate moisture equilibrium in the standard atmosphere for preconditioning textiles as specified in Practice D1776.
9.2After preconditioning,bring the test specimens to mois-ture equilibrium for testing in the standard atmosphere for testing textiles as specified in Practice D1776or,if applicable, in the specified atmosphere in which the testing is to be performed.
9.3When it is known that the material to be tested is not affected by heat or moisture,preconditioning and conditioning is not required when agreed upon in a material specification or contract order.
10.Procedure
10.1Test the conditioned specimens in the standard atmo-sphere for testing textiles,which is2161°C(
7062°F)and 6562%relative humidity,unless otherwi specified in a material specification or contract order.
10.2Handle the test specimens carefully to avoid altering the natural state of the material.
10.3Place each test specimen onto the test head of the test instrument,and perform the test as specified in the manufac-turer’s operating instructions.
10.3.1Place coated test specimens with the coated side down(towards low pressure side)to minimize edge leakage.
10.4Make tests at the water pressure differential specified in a material specification or contract order.In the abnce of a material specification or contract order,u a water pressure differential of125Pa(12.7mm or0.5in.of water).
10.5Read and record the individual test results in SI units as cm3/s/cm2and in inch-pound units as ft3/min/ft2rounded to three significant digits.
10.5.1For special applications,the total edge leakage un-derneath and through the test specimen may be measured in a parate test,with the test specimen covered by an airtight cover,and subtract
ed from the original test result to obtain the effective air permeability.
10.6Remove the tested specimen and continue as directed in10.3-10.5until ten specimens have been tested for each laboratory sampling unit.
10.6.1When a95%confidence level for results has been agreed upon in a material specification or contract order,fewer test specimens may be sufficient.In any event,the number of tests should be at least four.
11.Calculation
11.1Air Permeability,Individual Specimens—Calculate the air permeability of individual specimens using values read directly from the test instrument in SI units as cm3/s/cm2and in inch-pound units as ft3/min/ft2,rounded to three significant digits.When calculating air permeability results,follow the manufacturer’s instructions as applicable.
N OTE5—For air permeability results obtained600m(2000ft)above a level,correction factors may be required.
11.2Air Permeability,Average—Calculate the average air permeability for each laboratory sampling u
nit and for the lot.
11.3Standard Deviation,Coeffıcient of Variation—Calculate when requested.
11.4Computer-Procesd Data—When data are automati-cally computer-procesd,calculations are generally contained in the associated software.It is recommended that computer-procesd data be verified against known property values and its software described in the report.
12.Report
devil什么意思12.1Report that the air permeability was determined in accordance with Test Method D737.Describe the material or product sampled and the method of sampling ud.
北京电脑学校12.2Report the following information for each laboratory sampling unit and for the lot as applicable to a material specification or contract order:
12.2.1Air permeability.
12.2.2When calculated,the standard deviation or the coef-ficient of variation.
12.2.3Pressure differential between the fabric surfaces. 12.2.4For computer-procesd data,identify the program (software)ud.
12.2.5Manufacturer and model of test instrument.
12.2.6Any modification of this test method or equipment including changing or adding gaskets.
13.Precision and Bias
13.1Summary—In comparing two averages,the differences should not exceed the single-operator precision values shown in Table2for the respective number of tests,and for fabrics having averages similar to tho shown in Table3,in95out of 100cas when all the obrvations are taken by the
same
well-trained operator using the same piece of equipment and specimens randomly drawn from the sample of fabrics.Larger differences are likely to occur under all other circumstances.
13.2Woven Fabrics,Interlaboratory Test Data—An inter-laboratory test was run in1994through1995in which randomly drawn samples of three fabrics were tested in each of eight laboratories.Two operators in each laboratory each tested eight specimens of each fabric using this test method.Four of the eight specimens were tested on one day,and four speci-mens were tested on a cond day.Analysis of the data was conducted using Practices D2904and D2906and the adjunct Tex-Pac.The components of variance for air permeability expresd as standard deviations were calculated to be the values listed in Table3.The three woven fabric types were: Material5—S/2438,Plain Weave,Oxford,Spun Yarns
Material6—S/0002H,Plain Weave,Spun Yarns
Material7—S/28305,Plain Weave,Continuous Filament Yarns
13.3Nonwoven Fabrics,Interlaboratory Test Data—An interlaboratory test was run in1994in which randomly drawn samples of eight fabrics were tested in each participating laboratory.Two operators in each laboratory each tested eight specimens of each fabric using this test method.Four of the eight specimens were tested on one day and four specimens were tested on a cond day.Analysis of the data was conducted using Practices D2904and D2906and the adjunct Tex-Pac.The componen
ts of variance for air permeability of nonwoven fabrics expresd as standard deviations were cal-culated to be the values listed in Table3.The eight fabric types and number of participating laboratories were as follows: Nonwoven Material Number of Participating Laboratories Hydroentangled5
Dry-Laid5
Meltblown5
Needlepunched5
Resin-Bonded2
Spun-Bonded4
Thermal4
Wet-Laid5
13.4Precision—For the components of variance reported in Table3,two averages of obrved values
should be considered significantly different at the95%probability level if the difference equals or exceeds the critical differences listed in Table2.There were sufficient differences related to the fabric type and structure to warrant listing the components of variance and the critical differences parately.Conquently, no multi-fabric comparisons were made.
N OTE6—The tabulated values of the critical differences should be considered to be a general statement,particularly with respect to between-laboratory precision.Before a meaningful statement can be made about two specific laboratories,the amount of statistical bias,if any,beteween them must be established with each comparison being bad on recent data
TABLE2Air Permeability,ft3/min/ft2,Critical Differences A for the
Conditions Noted
Materials
Number of
Obrvations
in Each
Average
Single-
Operator
Precision
Within-
Laboratoryinct
Precision
Between-
Laboratory
Precision
Woven Fabrics
Plain,Oxford spun
yarns,Material5
128.834.159.3
220.327.455.7
512.922.453.4
109.120.552.6 Plain,spun yarns,
Material6
19.713.030.4
2 6.911.029.6
5 4.39.629.1
10 3.19.129.0 Plain,continous
filament yarns,
Material7
1 2.8 2.8 4.4
alcantara2 2.0 2.0 3.8
5 1.3 1.3 3.5
100.90.9 3.4 Nonwoven Fabrics
Hydroentangled127.633.952.0
219.527.748.2
512.323.345.8
108.721.645.0
Dry-laid151.355.673.4
236.342.163.8
523.031.357.2
1016.226.854.9 Meltblown18.89.321.5
2 6.2 6.920.6
5 4.0 4.920.0
10 2.8 4.019.8 Needlepunch1100.7112.4113.4
271.287.088.2
545.067.368.8
1031.859.261.0 Resin-bonded1162.7179.8189.2
2115.1138.1150.1
without you 歌词
572.8105.4120.8
1051.592.0109.3 Spun-bonded1234.6234.6251.2
2165.9165.9188.7
5104.9104.9138.1never too young
1074.274.2116.5 Thermal1206.2232.3232.2
2145.8180.8180.8
新的开始 英文
592.2141.2141.2
做鬼脸 英语新东方在线课堂1065.2125.2125.2 Wet-laid1 1.34 2.80 3.24
20.95 2.63 3.10
50.60 2.52 3.01
100.43 2.49 2.98
A The critical differences were calculated using t=1.960,which is bad on infinite degrees of freedom.
TABLE3Air Permeability,ft3/min/ft2
Materials
Grand
Average
Components of Variance Expresd as
Standard Deviations A
Single-
Operator
Component
Within-
Laboratory
Component
Between-
Laboratory
Component Woven Fabrics
Plain,Oxford
spun yarns Mat5
217.010.4 6.617.5
Plain,spun yarns
Mat6
90.0 3.5 3.19.9
Plain,continous
filament yarns
Mat7
8.3 1.00.0 1.2
Nonwoven Fabrics
Hydroentangled220.09.97.114.2
Dry-laid402.018.57.717.3 Meltblown72.7 3.2 1.07.0 Needlepunch278.036.018.0 5.3 Resin-bonded948.058.727.521.3 Spun-bonded474.084.60.032.4 Thermal564.074.438.60.0
Wet-laid17.20.50.90.6
A The square roots of the components of variance are being reported to express the variability in the appropriate units of measure rather than as the squares of tho units of
measure.
year是什么意思obtained on specimens taken from a lot of fabric to the type being
evaluated so as to be as nearly homogeneous as possible,and then
randomly assigned in equal numbers to each of the laboratories.
N OTE 7—Since the interlaboratory test for resin-bonded nonwoven
fabric included only two laboratories and the spun-bonded and thermal
nonwoven fabrics included only four laboratories,estimates of between
laboratory precision may be either underestimated or overestimated to a
considerable extent and should be ud with special caution.13.5Bias —The value of air permeability only can be defined in terms of a test method.Within this limitation,this test method has no known bias.14.Keywords 14.1air permeability;fabric
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