1、Designation: D8171 18Standard Test Methods forDensity Determination of Flax Fiber1This standard is issued under the fixed designation D8171; 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 par
2、entheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover two procedures for determi-nation of the density of flax fiber and are applicable to fibers ofany length.1.1.1 Test Method
3、AGas PycnometryThis is the moreaccurate method of density measurement and is preferred incases in which specimen conditioning (oven drying) can beapplied or outgassing effects can be mitigated by purgesettings. The level of accuracy for the test methods can beassessed from the precision and bias tab
4、les. Outgassing effectscan be assessed by performing a purge cycle, pressurization,and pressure stability check on the sample. If the pressureincreases in an isolated sample chamber, outgassing may affectthe accuracy of results. Oven dry specimens below 55 C toequilibrium with a 0 % relative humidit
5、y (RH) environment oruse longer purge methods, or both, to eliminate outgassingeffects.1.1.2 Test Method BBuoyancy (Archimedes) MethodThis is acceptable as an alternative to Test Method A inapplications in which less accurate results are sufficient, asrepresented in the precision and bias tables. Te
6、st Method B ispreferred in cases in which outgassing effects in Test MethodAcannot be addressed by oven drying or purge settings andprevent Test Method A from producing valid results.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisst
7、andard.1.3 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, health, and environmental practices and deter-mine the applicability of regulatory limitations prior
8、 to use.Specific hazard statements are given in Sections 9 and 17.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mend
9、ations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1577 Test Methods for Linear Density of Textile FibersD3800 Test Method for Density of High-Modulus FibersD3878 Terminology for Composite MaterialsD6798 Terminology Re
10、lating to Flax and LinenE12 Terminology Relating to Density and Specific Gravityof Solids, Liquids, and Gases (Withdrawn 1996)3E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in Databases (W
11、ith-drawn 2015)33. Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto composite materials. Terminology E12 defines terms relatingto density. Terminology D6798 defines terms relating to flaxand linen. Practice E177 defines terms relating to statistics. Inthe event of a conflict betw
12、een terms, Terminology D3878 shallhave precedence over other standards.3.1.1 impurity, nany material (such as, but not limited to,water, shive, or dirt) present in the sample that, if not removedor accounted for, would obfuscate the density measurement ofthe targeted material in the sample.3.2 Symbo
13、ls:M1= weight of suspension wire in air, g.M2= weight of suspension wire in liquid (to immer-sion point), g.M3= weight of suspension wire plus item whosedensity is to be determined (in air), g.M4= weight of suspension wire plus item whosedensity is to be determined (in liquid), g.1These test methods
14、 are under the jurisdiction of ASTM Committee D13 onTextiles and are the direct responsibility of Subcommittee D13.17 on Flax andLinen.Current edition approved Jan. 1, 2018. Published February 2018. DOI: 10.1520/D8171-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact
15、 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
16、Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by
17、 the World Trade Organization Technical Barriers to Trade (TBT) Committee.1M3M1= weight of item for density to be determined inair, g.M4M2= weight of item for density to be determined inliquid, g.f= density of fiber, g/cm3.i= density of the impurities, g/cm3.if= density of the combined fiber and imp
18、urities,g/cm3.s= density of standard, g/cm3.l= density of liquid, g/cm3.sur= density of surfactant, g/cm3.w= density of water, g/cm3.P1= equilibrium pressure of the sample chamberafter closing the input valve, kPa.P2= equilibrium pressure of the sample and expan-sion volume chambers after opening th
19、e connec-tion valve, kPa.s = standard deviation.Ve= volume of the calibrated expansion volumechamber, cm3.Vf= measured volume of the fiber specimen, cm3.Vmin= equipment specific minimum volume of solidmaterial required in each test to produce accu-rate results.Vs= volume of the calibrated sample cha
20、mber, cm3.W1= weight of specimen before testing, g.W2= weight of specimen after testing, g.glyph507Wg= change in weight of the specimen during the test,g.xi= mass of impurity as a percentage of the totalmass of the measured fiber, g.4. Summary of Test Methods4.1 GeneralTest MethodAis the more accura
21、te method ofdensity measurement in cases in which specimen conditioning(oven drying) can be followed or outgassing can be mitigatedby purge settings. Outgassing, such as the release of watervapor from unconditioned fibers when exposed to a dry gas,will reduce the precision of Test Method A by introd
22、ucingvapor pressure to the gas pressure being used for measurement.In cases in which outgassing cannot be addressed by ovendrying the sample or increasing the purge cycle/time, theresults from Test Method A are invalid. Test Method B can beused as an alternative to Test Method A in applications inwh
23、ich high precision is not required. Test Method B has asimilar method and equipment setup to Test Method D3800,but has been augmented to provide more accurate results forflax fibers.4.2 Test Method APycnometry Method:4.2.1 Sample volume is determined by the application ofBoyles Law, which states tha
24、t the increase in volume of aconfined gas results in a proportionate decrease in pressure.The apparatus consists of two chambers of known volumeconnected by a valve. One of the chambers, the calibratedsample chamber, is accessible for insertion of the test specimenand is connected to a source of hig
25、h purity (at least 99.99 %)dry gas, such as nitrogen. The pressure in the sample chamberis increased to a predetermined pressure and this value, P1,isnoted. The valve between the two chambers is then opened andthe second, lower pressure, P2, is again noted. The ratio of thepressure change P1/P2, is
26、directly related to the volume of thesample chamber displaced by the specimen. The differencebetween this volume and the geometric volume of the speci-men is a measure of the sample volume.4.2.2 The sample is weighed to determine the sample massand the density of the sample is calculated by dividing
27、 thesample mass by the sample volume.4.3 Test Method BBuoyancy (Archimedes) Method:4.3.1 The sample is weighed in air and weighed in certifiedsoybean oil that will thoroughly wet the sample and is of alower density.4.3.2 The difference in weight of the samples in the twomedia is the buoyancy force.
28、This force is converted to samplevolume by dividing it by the soybean oil density. The sampleweight in air divided by the sample volume equals the sampledensity.5. Significance and Use5.1 Fiber density is useful in the evaluation of new materialsat the research and development level and is one of th
29、e materialproperties normally given in fiber specifications.5.2 Fiber density can be used to determine fiber strength andmodulus of a single fiber or bundle of fibers. These propertiesare based on load or modulus slope over an effective area.Fiber density, when used with the lineal mass of the speci
30、men,can calculate an approximate, total effective area for thespecimen.5.3 In composite applications, fiber density is used asconstituent property when determining reinforcement volumeand void volume based on reinforcement mass and laminatedensity.6. Interferences6.1 General (All Methods):6.1.1 Remo
31、val of ImpuritiesA bias will exist if impuritiesare not removed as the measured fiber density will be acombination of the average densities of the fiber and impurity.Eq 1 may be used to calculate the effect of the impurity on thedensity of the material.if5100 2 xi!f1xii!100(1)6.2 Test Method A:6.2.1
32、 The presence of components that can outgas duringtesting, such as water vapor or volatile organic compounds,interfere with the measurement of the gas pressure and, if notmitigated, can invalidate the results. Typically, oven dryingspecimens at a temperature higher than the density testingtemperatur
33、e or increasing the amount/time of purge cycles willsufficiently reduce the effect of outgassing in typical samples.6.2.2 Changes in temperature can cause changes in volume.The equipment and specimens should be given sufficient timeto a reach a steady state condition.6.3 Test Method B:6.3.1 Temperat
34、ureThe temperature of the certified soy-bean oil shall remain constant within a tolerance of 61 C,since the soybean oil density will change with temperature.D8171 1826.3.2 Sample Wetting (Entrapped Air)Since this testmethod is very dependent on buoyancy, any entrapped air inthe sample will change th
35、e measured density and not give atrue material density. Ensure visually that the sample does notcontain entrapped air bubbles.6.3.3 Immersion PointThe distance the sample is loweredinto the soybean oil and overall liquid level should be the samethroughout determinations for Procedure A. This may be
36、doneby putting a line for the desired soybean oil level on the outsideof the container.TEST METHOD AGAS PYCNOMETRY7. Apparatus7.1 Test Method A:7.1.1 Commercial pycnometer instruments are availablefrom several manufacturers. The commercial instruments orcustom laboratory setups should include, at mi
37、nimum, thefollowing:7.1.1.1 Calibrated sample volume chambera chamberhaving a volume suitable to the sample size and calibrated tothe nearest 0.1 cm3. The chamber shall be accessible to theoperator such that a sample can be loaded into the chamber andthen sealed for testing. The chamber should have
38、a knownvolume (Vscm3).7.1.1.2 Calibrated expansion volume chamber, a chamber ofknown volume (Vecm3) that is calibrated to the nearest 0.1cm3.7.1.1.3 Pressure transducer, capable of measuring 0 to 175kPa with minimum volume displacement and linear within0.1 %.7.1.1.4 Pressure relief valve, used to av
39、oid the overpressur-ization of the transducer.7.1.1.5 Filter, prevents powder or dust from contaminatingthe transducer and valves.7.1.1.6 Input flow control valve, controls the rate of pres-surization.7.1.1.7 Output flow control valve, controls the rate ofdepressurization.7.1.1.8 Connection valve, c
40、onnects the calibrated samplevolume chamber with the calibrated expansion volume cham-ber.7.1.1.9 Nonporous calibration standard(s), object(s) ofknown volume that can be used in different configurations tocalibrate the chambers for different volumes of sample.7.1.1.10 Digital meter, used for reading
41、 the pressure to0.007 kPa.7.1.1.11 Analytical balance, capable of weighing to 0.001 g.7.1.2 The minimum volume of solid material (Vmin) re-quired to produce accurate measurements is equipment specificand shall be known before conducting testing. The volume canbe based on manufacturer recommendations
42、 or determinedthrough testing. If done through testing, Vminwould be thevolume in which increasing the volume of the solid materialbeing measured does not change the value of the results beyondwhat would fall within sample or standard deviation.8. Reagents and Materials8.1 Purity of ReagentsReagent-
43、grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is first
44、ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.8.2 Nitrogen, dry and of 99.99 % purity.NOTE 1Helium is a commonly used gas in gas pycnometer systemsand providing that it is dry and of 99.9 % purity, it can be used inste
45、ad ofnitrogen; however, in some cases, molecules may be sufficiently smallenough to penetrate the cell walls of the fibers. This phenomenon can beidentified when both of the following occur: P1decreases slowly after thesample chamber was sealed (helium entering the solid) and P2s value willrise foll
46、owing the initial drop after the valve between the two chambers isopened (helium being released from the solid). If helium penetrationoccurs, it is recommended that a lower pressure, longer equilibrium time,or nitrogen be used.9. Hazards9.1 Appropriate precautions should be taken when handlingcompre
47、ssed gases.10. Sampling, Test Specimens, and Test Units10.1 Specimens should be chosen to represent the largerbulk sample from which it is taken.10.2 For statistical purposes, a minimum of five specimensfor each sample should be tested.10.3 Tests should not use a volume less than Vminfor eachspecime
48、n. For the best results, the maximum amount of solidvolume that can reasonably be packed into the sample chambershould be used for each specimen.11. Calibration and Standardization11.1 The apparatus should be calibrated following themanufacturers recommendations for procedure and frequency.Because o
49、f the low packing density of fibers, alternate calibra-tion routines may need to be selected or modified to improveprecision when the solid volume of specimen in the chamber islower than the manufacturers recommended loading.11.2 For highest precision results, perform a calibrationroutine before testing.11.3 It is recommended that a leak check be done before aseries of tests.12. Conditioning12.1 Before testing, fibers should be conditioned to equilib-rium at 0 % relative humidity (RH) at the temperature thetesting will occur. This will remove moist
