ASTM D8171-18

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D8171 − 18
Standard Test Methods for
Density Determination of Flax Fiber
This standard is issued under the fixed designation D8171; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 These test methods cover two procedures for determi-
nation of the density of flax fiber and are applicable to fibers of
2. Referenced Documents
any length.
2.1 ASTM Standards:
1.1.1 Test Method A—Gas Pycnometry—This is the more
D1577 Test Methods for Linear Density of Textile Fibers
accurate method of density measurement and is preferred in
D3800 Test Method for Density of High-Modulus Fibers
cases in which specimen conditioning (oven drying) can be
D3878 Terminology for Composite Materials
applied or outgassing effects can be mitigated by purge
D6798 Terminology Relating to Flax and Linen
settings. The level of accuracy for the test methods can be
E12 Terminology Relating to Density and Specific Gravity
assessed from the precision and bias tables. Outgassing effects
of Solids, Liquids, and Gases (Withdrawn 1996)
can be assessed by performing a purge cycle, pressurization,
E177 Practice for Use of the Terms Precision and Bias in
and pressure stability check on the sample. If the pressure
ASTM Test Methods
increases in an isolated sample chamber, outgassing may affect
E1309 Guide for Identification of Fiber-Reinforced
the accuracy of results. Oven dry specimens below 55 ºC to
Polymer-Matrix Composite Materials in Databases (With-
equilibrium with a 0 % relative humidity (RH) environment or
drawn 2015)
use longer purge methods, or both, to eliminate outgassing
effects.
3. Terminology
1.1.2 Test Method B—Buoyancy (Archimedes) Method—
This is acceptable as an alternative to Test Method A in 3.1 Definitions—Terminology D3878 defines terms relating
applications in which less accurate results are sufficient, as tocompositematerials.TerminologyE12definestermsrelating
represented in the precision and bias tables. Test Method B is to density. Terminology D6798 defines terms relating to flax
preferred in cases in which outgassing effects inTest MethodA and linen. Practice E177 defines terms relating to statistics. In
cannot be addressed by oven drying or purge settings and
theeventofaconflictbetweenterms,TerminologyD3878shall
prevent Test Method A from producing valid results. have precedence over other standards.
3.1.1 impurity, n—any material (such as, but not limited to,
1.2 The values stated in SI units are to be regarded as
water, shive, or dirt) present in the sample that, if not removed
standard. No other units of measurement are included in this
or accounted for, would obfuscate the density measurement of
standard.
the targeted material in the sample.
1.3 This standard does not purport to address all of the
3.2 Symbols:
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
M = weight of suspension wire in air, g.
priate safety, health, and environmental practices and deter-
M = weight of suspension wire in liquid (to immer-
mine the applicability of regulatory limitations prior to use.
sion point), g.
Specific hazard statements are given in Sections 9 and 17.
M = weight of suspension wire plus item whose
1.4 This international standard was developed in accor-
density is to be determined (in air), g.
dance with internationally recognized principles on standard-
M = weight of suspension wire plus item whose
ization established in the Decision on Principles for the
density is to be determined (in liquid), g.
Development of International Standards, Guides and Recom-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
These test methods are under the jurisdiction of ASTM Committee D13 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Textiles and are the direct responsibility of Subcommittee D13.17 on Flax and Standards volume information, refer to the standard’s Document Summary page on
Linen. the ASTM website.
Current edition approved Jan. 1, 2018. Published February 2018. DOI: 10.1520/ The last approved version of this historical standard is referenced on
D8171-18. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8171 − 18
the second, lower pressure, P , is again noted. The ratio of the
M –M = weight of item for density to be determined in
3 1
pressure change P /P , is directly related to the volume of the
air, g. 1 2
sample chamber displaced by the specimen. The difference
M –M = weight of item for density to be determined in
4 2
between this volume and the geometric volume of the speci-
liquid, g.
men is a measure of the sample volume.
ρ = density of fiber, g/cm .
f
ρ = density of the impurities, g/cm .
4.2.2 The sample is weighed to determine the sample mass
i
ρ = density of the combined fiber and impurities,
and the density of the sample is calculated by dividing the
if
g/cm .
sample mass by the sample volume.
ρ = density of standard, g/cm .
s
4.3 Test Method B—Buoyancy (Archimedes) Method:
ρ = density of liquid, g/cm .
l
3 4.3.1 The sample is weighed in air and weighed in certified
ρ = density of surfactant, g/cm .
sur
soybean oil that will thoroughly wet the sample and is of a
ρ = density of water, g/cm .
w
lower density.
P = equilibrium pressure of the sample chamber
4.3.2 The difference in weight of the samples in the two
after closing the input valve, kPa.
media is the buoyancy force. This force is converted to sample
P = equilibrium pressure of the sample and expan-
volume by dividing it by the soybean oil density. The sample
sion volume chambers after opening the connec-
weight in air divided by the sample volume equals the sample
tion valve, kPa.
density.
s = standard deviation.
V = volume of the calibrated expansion volume
e
5. Significance and Use
chamber, cm .
5.1 Fiberdensityisusefulintheevaluationofnewmaterials
V = measured volume of the fiber specimen, cm .
f
V = equipment specific minimum volume of solid attheresearchanddevelopmentlevelandisoneofthematerial
min
material required in each test to produce accu- properties normally given in fiber specifications.
rate results.
5.2 Fiberdensitycanbeusedtodeterminefiberstrengthand
V = volume of the calibrated sample chamber, cm .
s
modulus of a single fiber or bundle of fibers. These properties
W = weight of specimen before testing, g.
are based on load or modulus slope over an effective area.
W = weight of specimen after testing, g.
Fiber density, when used with the lineal mass of the specimen,
�W = changeinweightofthespecimenduringthetest,
g
can calculate an approximate, total effective area for the
g.
specimen.
x = mass of impurity as a percentage of the total
i
mass of the measured fiber, g.
5.3 In composite applications, fiber density is used as
constituent property when determining reinforcement volume
4. Summary of Test Methods and void volume based on reinforcement mass and laminate
density.
4.1 General—TestMethodAisthemoreaccuratemethodof
density measurement in cases in which specimen conditioning
6. Interferences
(oven drying) can be followed or outgassing can be mitigated
6.1 General (All Methods):
by purge settings. Outgassing, such as the release of water
6.1.1 Removal of Impurities—A bias will exist if impurities
vapor from unconditioned fibers when exposed to a dry gas,
are not removed as the measured fiber density will be a
will reduce the precision of Test Method A by introducing
combination of the average densities of the fiber and impurity.
vapor pressure to the gas pressure being used for measurement.
Eq 1 may be used to calculate the effect of the impurity on the
In cases in which outgassing cannot be addressed by oven
density of the material.
drying the sample or increasing the purge cycle/time, the
~100 2 x !ρ 1x ~ρ !
results from Test Method A are invalid. Test Method B can be i f i i
ρ 5 (1)
if
used as an alternative to Test Method A in applications in
which high precision is not required. Test Method B has a
6.2 Test Method A:
similar method and equipment setup to Test Method D3800,
6.2.1 The presence of components that can outgas during
but has been augmented to provide more accurate results for
testing, such as water vapor or volatile organic compounds,
flax fibers.
interfere with the measurement of the gas pressure and, if not
mitigated, can invalidate the results. Typically, oven drying
4.2 Test Method A—Pycnometry Method:
specimens at a temperature higher than the density testing
4.2.1 Sample volume is determined by the application of
temperature or increasing the amount/time of purge cycles will
Boyle’s Law, which states that the increase in volume of a
sufficiently reduce the effect of outgassing in typical samples.
confined gas results in a proportionate decrease in pressure.
6.2.2 Changes in temperature can cause changes in volume.
The apparatus consists of two chambers of known volume
The equipment and specimens should be given sufficient time
connected by a valve. One of the chambers, the calibrated
to a reach a steady state condition.
samplechamber,isaccessibleforinsertionofthetestspecimen
and is connected to a source of high purity (at least 99.99 %) 6.3 Test Method B:
dry gas, such as nitrogen. The pressure in the sample chamber 6.3.1 Temperature—The temperature of the certified soy-
is increased to a predetermined pressure and this value, P,is bean oil shall remain constant within a tolerance of 61 ºC,
noted.The valve between the two chambers is then opened and since the soybean oil density will change with temperature.
D8171 − 18
6.3.2 Sample Wetting (Entrapped Air)—Since this test 8. Reagents and Materials
method is very dependent on buoyancy, any entrapped air in
8.1 Purity of Reagents—Reagent-grade chemicals shall be
the sample will change the measured density and not give a
used in all tests. Unless otherwise indicated, it is intended that
true material density. Ensure visually that the sample does not
all reagents shall conform to the specifications of the Commit-
contain entrapped air bubbles.
tee onAnalytical Reagents of theAmerican Chemical Society,
6.3.3 Immersion Point—The distance the sample is lowered
where such specifications are available. Other grades may be
into the soybean oil and overall liquid level should be the same
used, provided it is first ascertained that the reagent is of
throughout determinations for Procedure A. This may be done
sufficiently high purity to permit its use without lessening the
byputtingalineforthedesiredsoybeanoillevelontheoutside
accuracy of the determination.
of the container.
8.2 Nitrogen, dry and of 99.99 % purity.
TEST METHOD A—GAS PYCNOMETRY
NOTE 1—Helium is a commonly used gas in gas pycnometer systems
and providing that it is dry and of 99.9 % purity, it can be used instead of
nitrogen; however, in some cases, molecules may be sufficiently small
7. Apparatus
enough to penetrate the cell walls of the fibers. This phenomenon can be
identified when both of the following occur: P decreases slowly after the
7.1 Test Method A:
sample chamber was sealed (helium entering the solid) and P ’s value will
7.1.1 Commercial pycnometer instruments are available
rise following the initial drop after the valve between the two chambers is
from several manufacturers. The commercial instruments or
opened (helium being released from the solid). If helium penetration
custom laboratory setups should include, at minimum, the occurs, it is recommended that a lower pressure, longer equilibrium time,
or nitrogen be used.
following:
7.1.1.1 Calibrated sample volume chamber—a chamber
9. Hazards
having a volume suitable to the sample size and calibrated to
3 9.1 Appropriate precautions should be taken when handling
the nearest 0.1 cm . The chamber shall be accessible to the
compressed gases.
operator such that a sample can be loaded into the chamber and
then sealed for testing. The chamber should have a known
10. Sampling, Test Specimens, and Test Units
volume (V cm ).
s
10.1 Specimens should be chosen to represent the larger
7.1.1.2 Calibrated expansion volume chamber,achamberof
3 bulk sample from which it is taken.
known volume (V cm ) that is calibrated to the nearest 0.1
e
10.2 For statistical purposes, a minimum of five specimens
cm .
for each sample should be tested.
7.1.1.3 Pressure transducer, capable of measuring 0 to 175
kPa with minimum volume displacement and linear within
10.3 Tests should not use a volume less than V for each
min
0.1 %.
specimen. For the best results, the maximum amount of solid
volume that can reasonably be packed into the sample chamber
7.1.1.4 Pressure relief valve, used to avoid the overpressur-
ization of the transducer. should be used for each specimen.
7.1.1.5 Filter, prevents powder or dust from contaminating
11. Calibration and Standardization
the transducer and valves.
11.1 The apparatus should be calibrated following the
7.1.1.6 Input flow control valve, controls the rate of pres-
manufacturer’s recommendations for procedure and frequency.
surization.
Because of the low packing density of fibers, alternate calibra-
7.1.1.7 Output flow control valve, controls the rate of
tion routines may need to be selected or modified to improve
depressurization.
precision when the solid volume of specimen in the chamber is
7.1.1.8 Connection valve, connects the calibrated sample
lower than the manufacturer’s recommended loading.
volume chamber with the calibrated expansion volume cham-
11.2 For highest precision results, perform a calibration
ber.
routine before testing.
7.1.1.9 Nonporous calibration standard(s), object(s) of
11.3 It is recommended that a leak check be done before a
known volume that can be used in different configurations to
series of tests.
calibrate the chambers for different volumes of sample.
7.1.1.10 Digital meter, used for reading the pressure to
12. Conditioning
0.007 kPa.
12.1 Before testing, fibers should be conditioned to equilib-
7.1.1.11 Analytical balance,capableofweighingto0.001g.
rium at 0 % relative humidity (RH) at the temperature the
7.1.2 The minimum volume of solid material (V ) re-
min
testing will occur. This will remove moisture that can outgas
quired to produce accurate measurements is equipment specific
and shall be known before conducting testing. The volume can
be based on manufacturer recommendations or determined
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
through testing. If done through testing, V would be the
min
listed by the American Chemical Society, see Analar Standards for Laboratory
volume in which increasing the volume of the solid material
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
beingmeasureddoesnotchangethevalueoftheresultsbeyond
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
what would fall within sample or standard deviation. MD.
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