ASTM D6188-97(2008)
(Test Method)Standard Test Method for Viscosity of Cellulose by Cuprammonium Ball Fall (Withdrawn 2017)
Standard Test Method for Viscosity of Cellulose by Cuprammonium Ball Fall (Withdrawn 2017)
SIGNIFICANCE AND USE
This test method is suitable for use as a rapid control test for pulp manufacture or for careful determination of the viscometric molecular weight of purified cotton or wood derived pulps.
This test method is applicable over a very large range of cellulose molecular weights because seven sample sizes are defined. (Sample weights are reduced as cellulose molecular weight increases.)
Cotton and high molecular weight pulps may be difficult to dissolve. (Warning—This test method is only valid if the sample dissolves completely without gels.)
SCOPE
1.1 This test method describes the procedure for estimating the molecular weight of cellulose by determining the viscosity of cuprammonium (CuAm) solutions of cellulosic materials, such as wood pulp, cotton, and cotton linters. This test method is suitable for rapid, routine testing of large numbers of samples with high accuracy and precision. This test method updates and extends the procedure reported by the American Chemical Society (ACS) .
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
WITHDRAWN RATIONALE
Formerly under the jurisdiction of Committee D01 on Paint and Related Coatings, Materials, and Applications, this test method was withdrawn in January 2017 in accordance with section 10.6.3 of the Regulations Governing ASTM Technical Committees, which requires that standards shall be updated by the end of the eighth year since the last approval date.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D6188 − 97 (Reapproved 2008)
Standard Test Method for
Viscosity of Cellulose by Cuprammonium Ball Fall
This standard is issued under the fixed designation D6188; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope in-process samples. Dry samples are wetted with demineral-
ized water. Samples are either squeezed or pressed to 20 to
1.1 This test method describes the procedure for estimating
40% consistency as necessary, then passed through a picker.
the molecular weight of cellulose by determining the viscosity
of cuprammonium (CuAm) solutions of cellulosic materials, 4.2 The wet pulp sample is dried with air whose maximum
such as wood pulp, cotton, and cotton linters.This test method temperature is 120°C and weighed under conditions that cause
is suitable for rapid, routine testing of large numbers of the specified quantity of sample to be obtained. The weighed
samples with high accuracy and precision. This test method sample is placed in a glass 120-mL(4-oz) bottle, steel shot are
updates and extends the procedure reported by the American added, a vacuum is pulled on the bottle, and 97 mL of
Chemical Society (ACS). cuprammonium solution are added to the bottle. The bottle is
placed on a shaker to mix and dissolve the pulp sample in the
1.2 The values stated in SI units are to be regarded as the
CuAm solution.
standard. The values given in parentheses are for information
only. 4.3 The dissolved sample is transferred to a glass viscosity
tube. The tube is mounted vertically with a bright light behind
1.3 This standard does not purport to address all of the
the tube. A special glass bead (see 7.13) is dropped into the
safety concerns, if any, associated with its use. It is the
center of the solution in the tube. The time is measured in
responsibility of the user of this standard to establish appro-
seconds(s)fortheglassbeadtopassbetweentwomarksonthe
priate safety and health practices and determine the applica-
tubewhichare20cmapart.Thistime(s)istheuncorrected“as
bility of regulatory limitations prior to use.
is” cuprammonium ball fall viscosity. The temperature of the
2. Referenced Documents solution is determined, and the correction factor for this
3 temperature is multiplied by the uncorrected viscosity of the
2.1 ASTM Standards:
sample. This gives the “as is” cuprammonium ball fall viscos-
D1193Specification for Reagent Water
ity value.
D1695Terminology of Cellulose and Cellulose Derivatives
4.4 The “as is” viscosity value for the sample size used is
E438Specification for Glasses in Laboratory Apparatus
converted to the 2.50-g ACS viscosity by the equations
3. Terminology
provided in 14.4. The viscosity is reported in “ACS seconds.”
3.1 This standard terminology of cellulose and cellulose
5. Significance and Use
derivatives, see Terminology D1695.
5.1 Thistestmethodissuitableforuseasarapidcontroltest
4. Summary of Test Method
for pulp manufacture or for careful determination of the
4.1 An in-process or finished product sample is taken. All viscometric molecular weight of purified cotton or wood
cooking and bleaching chemicals must be washed out of
derived pulps.
5.2 Thistestmethodisapplicableoveraverylargerangeof
cellulose molecular weights because seven sample sizes are
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and Related Coatings, Materials, andApplications and is the direct responsibility of defined. (Sample weights are reduced as cellulose molecular
Subcommittee D01.36 on Cellulose and Cellulose Derivatives.
weight increases.)
Current edition approved June 1, 2008. Published June 2008. Originally
approved in 1997. Last previous edition approved in 2003 as D6188–97(2003). 5.3 Cottonandhighmolecularweightpulpsmaybedifficult
DOI: 10.1520/D6188-97R08.
to dissolve. (Warning—This test method is only valid if the
Carver et al., “A Standard Method for Determining the Viscosity of Cellulose
sample dissolves completely without gels.)
in Cuprammonium Hydroxide,” Industrial and Engineering Chemistry, Analytical
Edition, Vol 1, No 1, 1929, pp. 49-51.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 6. Interferences
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
6.1 High temperature drying of pulp causes a reduction in
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. viscosity. Therefore, limit the maximum temperature of the air
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6188 − 97 (2008)
TABLE 2 Effect of Volume Errors on Viscosity Error
usedtodrythesampleto120°Candthemaximumdryingtime
to 20 min to keep viscosity loss to a minimum.All in-process Volume Percent Viscosity Error
Error, (mL) Low Volume High Volume
samples must be washed to remove cooking and bleaching
1 4.0 3.9
chemicals,becausethepresenceofchemicalswhiledryingwill
2 8.2 7.6
increase viscosity loss. 5 21.8 17.9
10 48.3 32.6
6.2 The weight of sample used with this test method is
critical. The effect of incorrect sample weight on viscosity is
shown in Table 1.
TABLE 3 Temperature Correction Factors
6.2.1 If the pulp sample is properly weighed but a small
Temperature Correction Factor
amount fails to dissolve, the viscosity will be incorrect by at Error, °C Low Temperature High Temperature
1 0.971 1.030
least the percentage of the sample that failed to dissolve.
2 0.943 1.061
3 0.915 1.093
6.3 The volume of cuprammonium solution used is also
4 0.888 1.126
critical.Theeffectofincorrectvolumeonviscosityisshownin
5 0.863 1.159
Table 2.
6.4 Use the temperature correction factors given in Table 3
to correct the cuprammonium viscosities to 25°C, assuming
that a 1°C increase causes a 3% decrease in the measured
viscosity of the solution. Correction for temperatures off by
more than 5°C is not recommended. Samples should be
retested, ensuring than the CuAm solution is within tempera-
ture limits.
7. Apparatus
7.1 Testing Laboratory, maintained at 25 6 2°C.
7.2 Picker, suitable for shredding pulp without damaging it.
The picker must have provisions that permit sample remaining
afterpickingiscompletedtobeblownoutwithcompressedair.
7.3 Drier, suitable for pulp sample that dries the pulp with
hot air whose temperature is never permitted to get higher that
120°C.
7.4 Analytical Balance, capable of weighing to 60.001 g.
7.5 Bottles, wide mouth, glass, for use with an approxi-
matelyNo.5rubberstopper,andwithacapacityofatleast120
mL (4 oz). The type of bottle must be selected such that it is
suitable for dissolving pulps in cuprammonium solution as
specified in this test method.
7.6 Steel Balls, chrome alloy, Grade 25, 3.2-mm ( ⁄8-in.)
FIG. 1 Solution Filling System
diameter.
7.7 Automatic Pipet, special made, capable of delivering 97
horizontalposition,anditsdesignandoperationshouldbesuch
61mLofCuAmsolution,whichispartofthecuprammonium
thatin-processpulpswillbecompletelydissolvedafter20min
solution filling system (see Fig. 1).
of shaking.
7.8 Rubber Stopper Assembly, (see Fig. 2).
7.11 Transfer Assembly, for transferring the
7.9 VacuumSource,capableofpullingavacuumof686mm
cuprammonium-cellulose solution from the bottle to the vis-
Hg.
cosity tube (see Fig. 3).
7.10 Shaker, capable of shaking bottles of cuprammonium
7.12 Viscosity Tube, specially made (see Fig. 4).
solution containing pulp. The shaker is to hold the bottles in a
7.13 Glass Viscosity Beads, for ACS cuprammonium vis-
cosity determination. These beads are to be ground to a
diameter that causes the viscosity of each second of bead fall
TABLE 1 Effect of Weight Errors on Viscosity Error
timeincuprammonium-cellulosesolutiontoequal22cP.(This
Pulp Weight Percent Viscosity Error
will mean that a sample that has a bead fall time of 10 s will
Error, % Underweight Overweight
1 3.8 3.9 have a viscosity of 220 cP, and a sample that has a bead fall
2 7.4 8.0
timeof50swillhaveaviscosityof1100cP).Sincethedensity
5 17.4 21.1
of various shipments of glass beads will vary somewhat, the
10 31.8 45.6
diameter of the beads will have to be varied to compensate for
D6188 − 97 (2008)
10. Sampling
10.1 The sample for this test may consist of a wet pulp or a
dry, finished product sample. Take a representative portion of
the pulp sample that contains at least 10 and not more than
25 g of dry pulp.
10.2 If the sample is an in-process pulp sample, thoroughly
wash out any process chemicals (acids, bases, or bleach),
which may be present. Drain the excess water out of the wet
pulp sample (see 10.3).
10.3 If any sample is above 40% consistency, wet it with
demineralized water. If the sample is below 20% consistency,
hand squeeze it or press it until the consistency is between 20
to 40%.
10.4 Seven sample sizes are authorized by this test method.
These sizes, in g, are 0.85, 1.00, 1.25, 1.50, 2.20, 2.40, and
3.50. Select the sample size which will be used for the test.
Generally, select a sample size which will give a CuAm
viscosity between 15 and 60 s. Never use a sample size that
gives a CuAm viscosity of less than 10 or more than 100 s. (If
FIG. 2 Rubber Stopper Assembly In Bottle
atestresultisnotwithintheselimits,anewsamplesizeshould
the variation in the density of the glass. Generally the beads
be selected.)
will be about 3.3 mm in diameter, and they will weigh about
10.5 In order to ensure that traces of the last sample passed
0.046 g.
through the picker will not contaminate the new sample, pick
7.14 Moisture Balance—Apparatus to determine the dry
enough of the present sample that an amount equal to at least
weight of cellulose.
1 g of dry pulp has passed through the picker. Discard all of
7.15 pH Meter.
this portion of the sample. Then, pick enough of the sample to
carry out the viscosity test. Immediately after each sample has
7.16 ViscosityTubeHolder/LightingAssembly—Thisdevice
been passed through the picker, turn on the compressed air
holdstheviscositytubeverticallywithabrightlightbehindthe
going into the picker for at least 2 s. (This is to blow out as
tube so that the bead falling through the cuprammonium
much as possible of the sample before it has time to dry and
solution can be easily seen.
stick to the surfaces of the picker.)
7.17 Bead Centering Apparatus—This consists of a small
corrosion resistant funnel topped tube having an internal 10.6 Dry the picked sample with air as follows:
diameter just sufficient to permit the beads to fall through
10.6.1 Temperature does not exceed 120°C, and
freely.
10.6.2 Time does not exceed 20 min.
7.18 Timer, accuracy/precision: 630sover1h.
10.7 Weigh the sample in a manner that will consistently
7.19 PlasticSieve,with0.250mmopenings,thesameasUS
give weighed samples which contain dry pulp weights within
Alternate No. 70, Tyler 60 mesh sieve.
the specifications of Table 4.
7.20 Plastic Container, 2500 to 3500 mL graduated poly-
10.8 More accurate and precise results will be obtained if
ethylene beaker with handle.
the pulp sample is conditioned to an equilibrium moisture
8. Reagents and Materials content and the consistency of the sample determined by
moisture balance. This modification provides better weight
8.1 Cuprammonium Solution, containing 20 6 1 g/L of
control, but is not suited for rapid turn-around process control.
copper (expressed as copper) and 200 6 2 g/L of ammonium
hydroxide (expressed as ammonium).
11. Calibration and Standardization
8.2 Water, potable.
11.1 Selectcontrolpulpsamplesforwhicharelativelylarge
8.3 Water,reagent(inaccordancewithSpecificationD1193)
supply is available. Ensure that the cuprammonium viscosities
with an electrical resistance of at least 1 000 000Ω-cm. This
of these samples are sufficiently different so that different
water is used to determine the pH of the film left after acid
sample weights are required. Determine the cuprammonium
washing.
viscosityofeachsampleusingexactlythesameprocedurethat
9. Hazards
would be used for testing unknown samples. Record the
9.1 CuAmsolutioniscorrosive,andthusharmfultotheskin cuprammonium viscosity in a log book. Keep a separate
and eyes. Wear safety glasses or goggles while working with control chart of the cuprammonium viscosity values (or loga-
thissolution.Glovesandlaboratorycoatorchemicalapronare rithm of the values) for each of the samples. Measure these
recommended. control samples at a convenient frequency.
D6188 − 97 (2008)
FIG. 3 Solution Transfer Assembly In Bottle
12. Conditioning/Preparation cuprammonium solution to the bottle. Be sure that there is no
CuAm solution in the filling system below the stopcock on the
12.1 Conditioning of dry samples to an equilibrium mois-
automatic pipet before the addition is begun, and be sure that
ture content will give more accurate and precise results.
all of the CuAm solution in the filling system is added to the
12.2 It is usually necessary to treat bottles, stopper
bottle and that none remains in any part of the filling system.
assemblies, and viscosity tubes with a solution of sulfuric acid
However, do not let air into the bottle after all of the CuAm
tocoagulatetheCuAm-cellulosesolutionbeforethisapparatus
solution has entered the bottle. (Never apply vacuum to the
can be cleaned. (Warning—It is very important that this
bottle after the addition of the CuAm solution is begun, since
apparatus be thoroughly washed to remove all of the sulfuric
thismayresultinthelossofseveralmillilitresofthemeasured
acidbeforeitisdried.Ifthereisasmallamountofsulfuricacid
97 mL of CuAm solution that was supposed to have been
remaining on the surface of any apparatus when it dries, a thin
added to the bottle.)
film of sulfuric acid will remain on the surface of the
13.5 Place a hose clamp on the rubber hose on the stopper
apparatus.)
assembly to prevent air from entering the bottle (see Fig. 2),
13. Procedure and disconnect the hose on the stopper assembly from the
fillingassembly.Placethebottleintheshakersothatthebottle
13.1 Carry out the following operations in a room main-
is in a horizontal position, and shake for 25 6 3 min. Stop the
tained at 25 6 2°C (77 6 3.6°F).
shaker and remove the bottle. Observe the bottle to see if there
13.2 This test method defines clean, dry bottles; clean, dry
is any indication of undissolved material in the solution. If
stopper assemblies; and clean, dry viscosity tubes as ones that
there is any indication of undissolved material, discard
appeartobeclean,dono
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