ASTM D2857-95(2001)
(Practice)Standard Practice for Dilute Solution Viscosity of Polymers
Standard Practice for Dilute Solution Viscosity of Polymers
SCOPE
1.1 This practice covers the determination of the dilute solution viscosity of polymers. There are several ASTM standards (Test Methods D789, D1243, D1601, and D4603, and Practice D3591) that describe dilute solution viscosity procedures for specific polymers, such as nylon, poly(vinyl chloride), polyethylene, and poly(ethylene terephthalate). This practice is written to augment these standards when problems arise with which the specific procedure is not concerned, or when no standard is available for the polymer under investigation.
1.2 This practice is applicable to all polymers that dissolve completely without chemical reaction or degradation to form solutions that are stable with time at a temperature between ambient and 150°C. Results are usually expressed as relative viscosity (viscosity ratio), inherent viscosity (logarithmic viscosity number), or intrinsic viscosity (limiting viscosity number) (see 3.1).
1.3 For polyamides, relative viscosity values by this procedure are not equivalent to those determined by Test Methods D789.
1.4 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.
Note 1—This standard and ISO 1628, "Plastics-Determination of Viscosity Number and Limiting Viscosity Number," are technically equivalent.
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Designation:D2857–95 (Reapproved 2001)
Standard Practice for
Dilute Solution Viscosity of Polymers
This standard is issued under the fixed designation D2857; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D789 Test Methods for Determination of Relative Viscos-
ity, and Moisture Content of Polyamide (PA)
1.1 This practice covers the determination of the dilute
D883 Terminology Relating to Plastics
solution viscosity of polymers. There are several ASTM
D1243 Test Method for Dilute Solution Viscosity of Vinyl
standards (Test Methods D789, D1243, D1601, and D4603,
Chloride Polymers
and Practice D3591) that describe dilute solution viscosity
D1600 Terminology for Abbreviated Terms Relating to
procedures for specific polymers, such as nylon, poly(vinyl
Plastics
chloride), polyethylene, and poly(ethylene terephthalate). This
D1601 Test Method for Dilute Solution Viscosity of Eth-
practice is written to augment these standards when problems
ylene Polymers
arise with which the specific procedure is not concerned, or
D3591 Practice for Determining Logarithmic Viscosity
when no standard is available for the polymer under investi-
Number of Poly(Vinyl Chloride) (PVC) in Formulated
gation.
Compounds
1.2 This practice is applicable to all polymers that dissolve
D4603 Test Method for Determining Inherent Viscosity of
completely without chemical reaction or degradation to form
Poly(Ethylene Terephthalate) (PET) by Glass Capillary
solutions that are stable with time at a temperature between
Viscometer
ambient and 150°C. Results are usually expressed as relative
D5226 Practice for Dissolving Polymer Materials
viscosity (viscosity ratio), inherent viscosity (logarithmic vis-
E1 Specification for ASTM Thermometers
cosity number), or intrinsic viscosity (limiting viscosity num-
2.2 ISO Standard:
ber) (see 3.1).
1628/1 Guidelines for the Standardization of Methods for
1.3 For polyamides, relative viscosity values by this proce-
the Determination of Viscosity Number and Limiting
dure are not equivalent to those determined by Test Methods
Viscosity Number of Polymers in Dilute Solution
D789.
2.3 National Institute of Standards and Technology Docu-
1.4 This standard does not purport to address all of the
ment:
safety concerns, if any, associated with its use. It is the
Circular No. C602 Testing of Glass Volumetric Apparatus
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
3. Terminology
bility of regulatory limitations prior to use.
3.1 Definitions—Terms and definitions in Terminology
NOTE 1—This standard and ISO 1628, “Plastics—Determination of
D883andabbreviationsinTerminologyD1600areapplicable
Viscosity Number and Limiting Viscosity Number,” are technically
tothispractice.Thefollowingdefinitions areapplicabletothis
equivalent.
practice.
3.1.1 inherent viscosity, h , n—the ratio of the natural
2. Referenced Documents
inh
logarithm of the relative viscosity to the mass concentration of
2.1 ASTM Standards:
the polymer, c: h =(ln h )/c.
inh r
D445 Test Method for Kinematic Viscosity of Transparent
3.1.1.1 Discussion—Also known as the logarithmic viscos-
and Opaque Liquids
ity number, h . See also 3.1.3.
ln
D446 Specifications and Operating Instructions for Glass
3.1.2 intrinsic viscosity, [h], n—the limiting value of the
Capillary Kinematic Viscometers
reduced viscosity or the inherent viscosity at infinite dilution
lim lim
ofthepolymer: [h] 5 ~h /c! 5 h .
c→0 i c→0 inh
ThispracticeisunderthejurisdictionofASTMCommitteeD20onPlasticsand
is the direct responsibility of Subcommittee D20.70 on Analytical Methods.
Current edition approved February 15, 1995. Published April 1995. Originally Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
published as D 2857–70. Last previous edition D2857–93. 4th Floor, New York, NY 10036.
2 4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from National Institute of Standards and Technology (NIST), 100
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Bureau Dr., Stop 3460, Gaithersburg, MD 20899-3460.
Standards volume information, refer to the standard’s Document Summary page on International Union of Pure and Applied Chemistry, Compendium of Macro-
the ASTM website. molecular Nomenclature,BlackwellScientificPublications,Oxford,England,1991.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D2857–95 (2001)
3.1.2.1 Discussion—Also known as the limiting viscosity 5.3 For polymers meeting the restrictions of 5.2, empirical
number and in the literature as the Staudinger index. See also relationships can be developed between the dilute solution
3.1.3. viscosity of a polymer and its hydrodynamic volume or
3.1.3 reduced viscosity, n—theratiooftherelativeviscosity average chain dimension (radius of gyration or end-to-end
increment to the mass concentration of the polymer, c, that is, distance). Such relationships depend upon any variables influ-
h /c. encing this molecular size of the dissolved polymer. The most
i
important of these variables are solvent type and temperature.
3.1.3.1 Discussion—Also known as the viscosity number.
The unit must be specified; cm /g is recommended. Thus, the solution viscosity of a given polymer specimen
dependsonthechoiceofthesevariables,andtheymustalways
3.1.3.2 Discussion—This quantity and those defined in
3.1.1 and 3.1.2 are neither viscosities nor pure numbers. The be specified with the viscosity for complete identification.
5.4 The solution viscosity of a polymer of sufficiently high
terms are to be looked upon as traditional names. Any
replacement by consistent terminology would produce unnec- molecular weight may depend on rate of shear in the viscom-
eter, and the viscosity of a polyelectrolyte (polymer containing
essary confusion in the polymer literature.
3.1.4 relative viscosity, h , n—the ratio of the viscosity of ionizable chemical groupings) will depend on the composition
r
and ionic strength of the solvent. Special precautions beyond
the solution, h, to the viscosity of the solvent, h , that is, h
s r
the scope of this practice are required when measuring such
= h/h .
s
polymers.
3.1.4.1 Discussion—Also known as the viscosity ratio.
5.5 Finally, the viscosity of polymer solutions may be
3.1.5 relative viscosity increment, h , n—the ratio of the
i
affected drastically by the presence of recognized or unrecog-
differencebetweentheviscositiesofsolutionandsolventtothe
nized additives in the sample, including but not limited to
viscosity of the solvent, that is, h =(h− h )/h .
i s s
colorants, fillers, or low-molecular-weight species.
3.1.5.1 Discussion—The use of the term specific viscosity
for this quantity is discouraged, since the relative viscosity
6. Apparatus
increment does not have the attributes of a specific quantity.
6.1 Volumetric Flasks, 100-mLor other size found conve-
nient.
4. Summary of Practice
6.2 Transfer Pipets, sizes between 1 and 25 mL, as re-
4.1 General procedures are given for the determination of
quired. Transfer pipets for use with polymer solutions should
the dilute solution viscosity of polymers, including descrip-
haveabout2mmcutfromtheirlowertipstopermitmorerapid
tions of apparatus, reagents and materials, and sample prepa-
transfer of the solution to the viscometer.
ration, as well as measurement procedures and calculations.
6.3 Constant-Temperature Bath, capable of maintaining
4.2 Ifdetailedtestmethodsareavailableforthepolymersof
60.01°C at the desired temperature (usually between 25 and
interest, such as those mentioned in 1.1, this practice provides
150°C). Less stringent temperature control (60.02°C) is satis-
information of a general nature to augment the detailed
factory upon demonstration that the precision of results is not
treatments in the relevant test methods.
affected.
6.4 Viscometer, glass capillary type, as described in Speci-
5. Significance and Use
fications D446. Efflux time for the solvent and temperature
5.1 The determination of dilute solution viscosity provides
used shall be greater than 200 s (except that efflux time for
oneitemofinformationtowardsthemolecularcharacterization
semimicro viscometers shall be greater than 80 s), to eliminate
of polymers.When viscosity data are used in conjunction with
the need for kinetic energy corrections.
other molecular parameters, the properties of polymers de-
6.4.1 Two types of viscometers are commonly used: One is
pending on their molecular structure may be predicted.
a constant-volume device of simple construction, recom-
5.2 Viscosityisdependentonmolecularweightdistribution,
mended for use where solution viscosity is to be measured at a
so with certain restrictions, satisfactory correlations can be
single concentration, as for determination of the reduced
obtained between dilute-solution viscosity and molecular pa-
viscosity (viscosity number) or inherent viscosity (logarithmic
rameters such as molecular weight or chain length. The most
viscosity number). It may also serve for the determination of
limiting restrictions that must be observed are as follows:
the intrinsic viscosity (limiting viscosity number) through
5.2.1 It must be known that the polymers used to establish
measurement of several solutions having different concentra-
the correlations and those to which they are applied do not
tions.
consist of or contain branched species. Basically a measure of
6.4.2 The second type viscometer, commonly called a
molecular size and not molecular weight, the dilute solution
dilution viscometer, is a time-saving device for the determina-
viscosity can be correlated appropriately with molecular
tion of intrinsic viscosity (limiting viscosity number) since it
weight or chain length only if there is a unique relationship
does not require constant liquid volume for operation. Several
between the mass and the size of the dissolved polymer
concentrations of a polymer solution can be tested by adding a
molecules. This is the case for linear, but not for most
knownquantityofthesolventatthetesttemperaturedirectlyto
branched, polymers.
the viscometer, mixing, measuring the viscosity, and then
5.2.2 For reasons similar to those outlined in 5.2.1, it must
be required that the polymers to which the correlations are
applied have the same chemical composition as those used in
Glassware should conform to the standards of accuracy in National Institute of
establishing the relationships. Standards and Technology Circular No. C602.
D2857–95 (2001)
NOTE 5—Solution concentrations for some common polymers are
making the next dilution. The viscosity of the pure solvent
recommendedinAppendixX1.Sinceothersizesofvolumetricflasksmay
must be measured separately.
be used, depending on the viscometer size and the amount of sample
6.4.3 An alternative procedure is to start with the minimum
available, adjust sample weights and the solvent and solution volumes
volumeofthepuresolvent,thenaddaliquotsofaconcentrated
accordingly.
stocksolutiontotheviscometertoobtainvaluesoftherelative
NOTE 6—For greater reliability of results, select the sample size on the
viscosity (viscosity ratio) at successively higher concentra-
basis of experiment to give a relative viscosity (viscosity ratio) near 1.5.
tions. The choice of procedures is dictated by the range of
If several concentrations of a solution of a single sample are to be used
(Note 8), select them so that the relative viscosity (viscosity ratio) falls in
volumes with which the viscometer will operate and the range
the range from 1.2 to 2.0.
of concentrations desired for test.
NOTE 7—Preparation of a single solution may often suffice, either for
6.5 Timer, graduated in divisions of 0.1 s or less, as
determining the relative viscosity (viscosity ratio) or inherent viscosity
described in Test Method D445.
(logarithmic viscosity number), or as a stock solution for use in a dilution
6.6 Thermometer, suitable for the specified test temperature
viscometer to determine the intrinsic viscosity (limiting viscosity num-
and conforming to the specifications of Specification E1,
ber). If more than one solution concentration is desired, weigh a series of
Kinematic Viscosity Thermometers ASTM 110C (for use at
specimens (often four) into separate flasks, selecting specimen weights to
give the desired solution concentration.
135°C) and 118C (for use at 30°C).
6.7 Fritted Glass Filter Funnel, coarse grade, or equiva- 3
9.2 Add approximately 50 cm of solvent to each specimen
lent.
flask, purge with nitrogen if necessary, and shake on a
laboratory shaker. Elevated temperature may enhance the
7. Reagents and Materials
solutionrateassuggestedinAppendixX1,PracticeD5226,or
7.1 Solvents, as required, or as recommended in Appendix
specific test methods, but this approach should be used with
X1.
caution. Some polymers and solvents have limited high-
7.2 Heat Transfer Liquid, for constant temperature bath.
temperature stability. If solution preparation requires an el-
evated temperature, subject a flask of pure solvent to the same
NOTE 2—The following materials have been used as heat-transfer
liquids: (1) silicone oil, (2) mineral oil, (3) peanut oil, (4) water, and (5) conditions as the polymer solution.
water-miscible liquid, such as glycerin or ethylene glycol. The material
NOTE 8—Caution:Complete solution of all of the specimen is essen-
selected must not discolor or smoke on prolonged exposure at the test
tial. When solution appears complete, examine the flask with care to be
temperature; in some cases discoloring may be inhibited by the use of an
sure that no undissolved material, gel particles, or foreign matter is
antioxidant. The use of water or a water-miscible liquid facilitates
present.
cleaning glassware used in the test.
9.3 Place the volumetric flasks containing the solution(s)
7.3 Nitrogen, for purging.
and the pure solvent in the constant-temperature bath main-
8. Sample Preparation tained at the test temperature. After temperature equilibrium
has been achieved (10 to 30 min) complete the dilution to the
8.1 Do not predry or condition the sample unless the
100-cm mark by adding solvent maintained at the bath
material is known to be hygroscopic.
temperature, using a transfer pipet. Mix the contents of the
8.2 If it is known that the sample dissolves only slowly in
flask(s) thoroughly.
the selected solvent, pretreating the s
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