ASTM D1795-96
(Test Method)Standard Test Method for Intrinsic Viscosity of Cellulose
Standard Test Method for Intrinsic Viscosity of Cellulose
SCOPE
1.1 This test method covers the determination of the intrinsic viscosity of purified celluloses such as bleached wood pulps, cotton linters, and regenerated cellulose. It is applicable to all cellulose samples with an intrinsic viscosity of 15 dl/g or less. Most native (unpurified) celluloses have intrinsic viscosity values too high for measurement by this test method.
Note 1—The use of cuprammonium hydroxide solution for regular viscosity determination is described in Method T 206 m-55 of the Technical Association of Pulp and Paper Industry on "Cuprammonium Disperse Viscosity of Pulp," and Joint Army-Navy Specifications JAN-C-206.
1.2 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.
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Designation: D 1795 – 96
Standard Test Method for
Intrinsic Viscosity of Cellulose
This standard is issued under the fixed designation D 1795; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Significance and Use
1.1 This test method covers the determination of the intrin- 4.1 This test is a sensitive measure of the degradation of
sic viscosity of purified celluloses such as bleached wood cellulose resulting from the action of heat, light, acids, alkalies,
pulps, cotton linters, and regenerated cellulose. It is applicable oxidizing and reducing agents, and the like, used in its
to all cellulose samples with an intrinsic viscosity of 15 dl/g or processing or purification. The intrinsic viscosity value may be
less. Most native (unpurified) celluloses have intrinsic viscos- converted to degree of polymerization (DP) or to intrinsic
ity values too high for measurement by this test method. fluidity, if desired.
4.2 Solutions of cellulose are not Newtonian liquids; that is,
NOTE 1—The use of cuprammonium hydroxide solution for regular
their viscosity depends upon the rate-of-shear or velocity
viscosity determination is described in Test Methods D 539, Method
gradient during measurement. This effect is smaller for samples
T 206 m-55 of the Technical Association of Pulp and Paper Industry on
“Cuprammonium Disperse Viscosity of Pulp,” and Joint Army-Navy of low molecular mass (DP) and at low concentrations than for
Specifications JAN-C-206.
high-DP samples and at high concentrations. For the celluloses
and concentrations included within the limits set forth in this
1.2 This standard does not purport to address all of the
test method, the effect of rate-of-shear is assumed to be
safety concerns, if any, associated with its use. It is the
negligible for referee purposes. For other conditions and for
responsibility of the user of this standard to establish appro-
research purposes this assumption may be invalid, but to
priate safety and health practices and determine the applica-
discuss ways of accounting for this effect is beyond the scope
bility of regulatory limitations prior to use.
of the present test method.
2. Referenced Documents
5. Apparatus
2.1 ASTM Standards:
5.1 Viscometer, Glass, Capillary Type— The Cannon-
D 445 Test Method for Kinematic Viscosity of Transparent
Fenske, Ubbelohde, or similar capillary type instrument as
and Opaque Liquids (and the Calculation of Dynamic
described in Test Method D 445 is recommended. Viscometers
Viscosity)
described in Test Methods D 539 are also suitable. In order to
D 539 Test Methods for Apparent Fluidity of Dispersions of
avoid correction for the kinetic energy effect, choose a viscom-
Cellulose Fibers
eter with a small enough capillary to give an outflow time of 80
D 629 Test Methods for Quantitative Analysis of Textiles
s or more for the Cannon-Fenske type. (A size 100 viscometer
E 1 Specification for ASTM Thermometers
is normally used for the sample solution and a size 50 for the
3. Summary of Test Method
solvent.)
5.2 Thermometer—ASTM Kinematic Viscosity Thermom-
3.1 A weighed sample of the material is dissolved in a 0.5 M
eter for use at 25°C, having a range from 19 to 27°C and
cupriethylenediamine hydroxide solution. The viscosity of this
conforming to the requirement for Thermometer 17C as
solution, and also that of the solvent, is determined at 25°C by
prescribed in Specification E 1.
means of a calibrated glass capillary-type viscometer. The
5.3 Bath—A constant-temperature bath at 25°C suitable for
relative viscosity is calculated and the corresponding intrinsic
immersion of the viscometer so that the reservoir or the top of
viscosity is read from a table.
the capillary, whichever is uppermost, is immersed at least 50
mm, and with provision for visibility of the instrument and the
thermometer. Firm supports for the viscometer shall be pro-
This test method is under the jurisdiction of ASTM Committee D-1 on Paint
and Related Coatings, Materials, and Applications and is the direct responsibility of
vided; or the viscometer may be sealed in as an integral part of
Subcommittee D01.36 on Cellulose and Cellulose Derivatives.
the bath. Either a liquid bath with thermostatic regulation and
Current edition approved Nov. 10, 1996. Published January 1997. Originally
a stirrer or a vapor bath with pressure regulation is permissible.
published as D 1795 – 60. Last previous edition D 1795 – 94.
Annual Book of ASTM Standards, Vol 05.01. The efficiency of the stirring and the balance between heat
Discontinued, see 1973 Annual Book of ASTM Standards, Part 24.
losses and heat input must be such that the temperature of the
Annual Book of ASTM Standards, Vol 07.01.
bath medium does not vary by more than 60.1°C over the
Annual Book of ASTM Standards, Vol 14.03.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 1795
NOTE 4—Calibration of the viscometers may be avoided if both solvent
length of the viscometer, or from viscometer to viscometer in
and solution are measured in the same instrument. Then the relative
the various bath positions. If a vapor bath is used, there must
viscosity is nearly the ratio of outflow times for solution and solvent,
be no temperature gradient over the length of the viscometer
respectively. This simplification involves two assumptions. The first, that
greater than that permitted in a liquid bath.
the densities of solution and solvent are equal, holds very well for the
5.4 Timer—A stop watch or other spring-activated timing
dilute solutions used in these tests. The second, that the kinetic energy
device or electrical timing device shall be used, graduated in
correction is zero, depends upon the choice of viscometer. If the one used
divisions of 0.2 s or less, and accurate to within 0.05 % when gives convenient outflow times for the solution of less than 150 s, then it
will be too fast for the solvent. The kinetic energy correction is zero,
tested over not less than a 10-min period. Such electrical
depending upon flow. On the other hand, if one is chosen so that the
timing devices shall be used only on electrical circuits of
outflow time for the solvent is large enough (80 s or more), then the times
continuously controlled frequency. Frequency-controlled de-
for the solutions will in most cases be inconveniently long. For some
vices of suitable capacity for laboratory purposes, accurate to
work, however, it may be desirable to make some sacrifice in accuracy or
within 1 part in 10 000 should be used. Errors exceeding
in convenience during measurement in order to avoid calibration and
0.05 % of a 10-min interval may occur in timing devices
using two sizes of viscometers.
actuated by electrical synchronous motors driven by most
8.2 By means of a pipet, add 7.0 mL of the calibrating liquid
public power systems, which are intermittently and not con-
to the viscometer, in a constant-temperature bath at 25 6 0.1°C
tinuously controlled.
(or fill as described in Test Method D 445, Appendix A).
8.3 When the liquid has reached temperature equilibrium
6. Reagent
with the bath (in about 5 min), determine the outflow time t by
6.1 Cupriethylenediamine Hydroxide Solution (1.00 6 0.01
drawing the top meniscus of the liquid above the mark between
M), in copper, with the molar ratio of ethylenediamine to
the two bulbs and measuring the time required for the meniscus
copper of 2 6 0.1 to 1. This solvent may be prepared in the
to pass from this mark to the mark below the lower bulb. Take
laboratory as described in Test Methods D 539. It is also
the average of two or more observations, which should differ
commercially available.
by not more than 0.2 s.
7. Reference Materials 8.4 Determine the viscometer constant C by the equation:
C5h/dt (1)
7.1 Viscosity Oil Standards—Calibrating oils in the speci-
fied ranges of viscosity. Aqueous solutions of glycerol may be
where:
used instead of standardized oils; the compositions for various
h = viscosity of the calibrating liquid, cP,
viscosities are given in chemical handbooks. The applicable
d = density, g/mL, and
viscosity oil standards (Note 2) are listed in Table 1.
t = time, s.
TABLE 1 Viscosity Oil Standards
9. Preparation of Sample
Viscometer Viscosity Oil Standard
9.1 To avoid undesirable effects from long heating at high
Approximate
Absolute Viscosity
temperature, samples should be air-dried and the moisture
Size Designation Absolute Viscosity
A
Range, cP
at 77°F (25°C), cP
content determined on a portion that is not used for measure-
50 0.9 to 3.5 S-3 3.3
ment of viscosity. The mass of air-dried samples is then
100 3.3 to 13.3 S-6 7.7
corrected for moisture to obtain the mass of oven-dried
A
For solution with density of 0.9.
cellulose used to calculate concentration.
9.2 Soft, sheeted pulp should be picked apart with tweezers
NOTE 2—The viscosity oil standards are available only as 1-pt (4.7- m
or scraped with a dull knife. Hard-pressed or harsh pulp should
3) samples. More than 1 pt of any given oil (for example, duplicate
6 be slurried in water, formed into thin sheets on a Büchner
samples) are supplied only when it is established that 1 pt is inadequate.
funnel, and dried at a temperature below 100°C (preferably
8. Calibration of Viscometer
room temperature). Loose pulp should be picked apart by hand
to break up any lumps. Slurried or slush pulps should be
8.1 The following directions apply to the Cannon-Fenske
formed into thin sheets and dried. Yarn and staple should be
viscometer (Note 3). They should be modified according to the
washed in warm water containing a little detergent to remove
operating instructions for other types of viscometers. The
the finish, rinsed thoroughly, dried (at low temperature), and
viscometers shall be calibrated (Note 4) by means of liquids
fluffed. (It will be found helpful to cut yarn and long staple into
having known viscosities approximately equal to those of the
short lengths, say ⁄2 in. (13 mm), before washing.) Fabrics
solvent and cellulose solutions respectively (1.2 and 12 cP,
should be cut into small pieces, desized (see Test Methods
approximately).
D 629, Section 8), thoroughly washed, and dried. Raveling will
NOTE 3—Detailed specifications and directions for filling, calibrating,
be helpful before dissolving samples that tend to get in the
and measurement with types of capillary viscometers most used are given
solvent. Materials containing a considerable amount of non-
in Test Method D 445.
cellulosic matter must first be purified; such treatments lie
outside the scope of this test method.
The sole source of supply of the viscosity oil standards known to the committee
at this time is Cannon Instrument Co., P. O. Box 16, State College, PA 16801. If you
10. Preparation of Solution
are aware of alternative suppliers, please provide this information to ASTM
10.1 The sample size is dependent upon the nature of the
Headquarters. Your comments will receive careful consideration at a meeting of the
responsible technical committee, which you may attend. material, smaller masses of high-viscosity celluloses and larger
D 1795
TABLE 2 Intrinsic Viscosities of Typical Samples on fritted-glass filters have been observed to give erratic results. Inad-
equate dispersion of the sample is apparently the cause, and two
Intrinsic Approximate
modifications in procedure have been recommended in such cases. One is
Type of Material Viscosity, Concentration,
dL/g g/dL to add about 0.04 % wetting agent to the water used to wet out the
sample. The other requires use of cupriethylenediamine solutions of two
Regenerated cellulose (rayons) 2 to 3 1
concentrations: The sample is wetted out with one solution that is 0.167 M
Dissolving pulps:
Low viscosity 3 to 4 1 in copper and dispersion is completed by adding the second solution,
Regular viscosity 4 to 7 0.5
1.000 M in copper, in such volume as to make the final copper
High viscosity 7 to 10 0.3
concentration 0.500 M (see Section 14 of Test Methods D 539).
Cotton linters, for rayon and acetate 6 to 9 0.4
Paper (wood) pulps 3 to 8 0.4
11. Measurement of Viscosity
A
Native celluloses 15 to 30 0.1 to 0.2
A
11.1 Transfer 7.0 mL of the solution by means of a syringe
Serious error may be introduced when this test method, which neglects effects
of rate of shear upon viscosity, is used for native celluloses of high intrinsic
or pipet to a viscometer previously placed in the bath at 25°C
viscosity.
and flushed with nitrogen (or fill as described in Test Method
D 445, Appendix A). Allow at least 5 min for the solution to
masses of low-viscosity celluloses being used in order to keep
reach bath temperature.
the viscosity of the solutions within rather narrow limits.
11.2 By applying either pressure (with nitrogen) or suction,
(Working at nearly constant viscosity reduces the effect of rate
draw the solution into the lower bulb of the viscometer until the
of shear upon the measurements.) The concentration for each
top meniscus is a little above the mark between the two bulbs.
sample is chosen according to the rule:
Measure the time t required for the meniscus to pass from this
@h#c 5 3.09 6 0.5 (2) mark to the mark below the lower bulb. Repeat at least twice
and average the observations, which should not differ by more
where:
than 0.3 %.
[h] = intrinsic viscosity, dL/g, and
11.3 In the same way, measure the outflow time t for the
c = cellulose concentration, g/dL.
solvent. This of course must be determined not for the 1.00 M
Obviously, use of this rule requires knowledge of the
solvent as prepared or purchased, but for this solvent diluted
approximate intrinsic viscosity of the sample before the con-
with an equal volume of water.
centration can be estimated. In routine control work, such
information is available. If it is not, Table 2 will serve as an
12. Calculations
approximate guide.
12.1 Calculate the viscosity, h, in centipoises, as follows:
10.2 Make up a preliminary solution of about the indicated
h5 Ctd (3)
concentration, and determine the viscosity as described in
Sections 11 and 12. From the relative viscosity thus obtained,
where:
find the approximate value of the intrinsic viscosity by means
C = viscometer constant (Section 8),
of Table 3. From this determine the concentration needed to
t = outflow time, s, and
give: [h] c = 3.0. If this preliminary solution does not give a
d = density, g/mL.
value of [h]c of 3.0 6 0.5, prepare a second solution of the
Calculate the relative vi
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