ASTM D5225-98
(Test Method)Standard Test Method for Measuring Solution Viscosity of Polymers with a Differential Viscometer
Standard Test Method for Measuring Solution Viscosity of Polymers with a Differential Viscometer
SCOPE
1.1 This test method covers the determination of the solution viscosity of polymers using a differential or the modified differential viscometer. It is applicable to all polymers that dissolve completely without chemical reaction or degradation to form solutions that are stable with time and temperature. Results of the test are usually expressed as specific viscosity, intrinsic viscosity (limiting viscosity number), inherent viscosity (logarithmic viscosity number), or relative viscosity (viscosity ratio).
1.2 Since there is more than one type of viscometer available to measure a differential pressure, follow the manufacturers' directions applicable to the equipment being used.
1.3 The solution viscosity values are comparable with those obtained using a glass capillary of Test Method D2857. This test method differs from the glass capillary in that the solvent and the solution are compared at the same time that a test is run. With a glass capillary, each solution must be referenced back to the solvent run in the same capillary at the same temperature.
1.4 This standard does not purport to address all of the safety problems, 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. For specific hazard statements, see Section 8.
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Designation: D 5225 – 98
Standard Test Method for
Measuring Solution Viscosity of Polymers with a Differential
Viscometer
This standard is issued under the fixed designation D 5225; 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 * E 691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1.1 This test method covers the determination of the solu-
tion viscosity of polymers using a differential or the modified
3. Terminology
differential viscometer. It is applicable to all polymers that
3.1 Definitions:
dissolve completely without chemical reaction or degradation
3.1.1 inherent viscosity—the ratio of the natural logarithm
to form solutions that are stable with time and temperature.
of the relative viscosity to the concentration. The IUPAC term
Results of the test are usually expressed as specific viscosity,
for inherent viscosity is logarithmic viscosity number.
intrinsic viscosity (limiting viscosity number), inherent viscos-
3.1.2 intrinsic viscosity—limit of the reduced and inherent
ity (logarithmic viscosity number), or relative viscosity (vis-
viscosities as the concentration of the polymeric solute ap-
cosity ratio).
proaches zero and represents the capacity of the polymer to
1.2 Since there is more than one type of viscometer avail-
increase viscosity. The IUPAC term for intrinsic viscosity is
able to measure a differential pressure, follow the manufactur-
limiting viscosity number.
er’s directions applicable to the equipment being used.
3.1.3 reduced viscosity—the ratio of the specific viscosity to
1.3 The solution viscosity values are comparable with those
the concentration. Reduced viscosity is a measure of the
obtained using a glass capillary of Test Method D 2857. This
specific capacity of the polymer to increase the relative
test method differs from the glass capillary in that the solvent
viscosity. The IUPAC term for reduced viscosity is viscosity
and the solution are compared at the same time that a test is
number.
run. With a glass capillary, each solution must be referenced
3.1.4 relative viscosity—the ratio of the polymer solution
back to the solvent run in the same capillary at the same
pressure to the pressure of the solvent.
temperature.
3.1.5 specific viscosity—the relative viscosity minus one.
1.4 This standard does not purport to address all of the
3.1.6 viscosity constant, K—baseline reading when solvent
safety concerns, if any, associated with its use. It is the
is present in both capillaries.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
4. Summary of Test Method
bility of regulatory limitations prior to use. For specific hazard
4.1 Differential Viscometer (Fig. 1):
statements, see Section 8.
4.1.1 The viscosity measurement with the differential vis-
NOTE 1—There is no ISO equivalent method.
cometer is based on a fluid analog of the Wheatstone Bridge.
Pure solvent at constant inlet pressure P enters a balanced
i
2. Referenced Documents
capillary network and flows through, producing a zero or
2.1 ASTM Standards:
baseline pressure on the differential pressure transducer. Solu-
D 1243 Test Method for Dilute Solution Viscosity of Vinyl
tion is loaded into the sample reservoir A and then injected
Chloride Polymers
onstream by means of the switching valve S . The differential
A
D 2857 Test Method for Dilute Solution Viscosity of Poly-
pressure begins to rise until it reaches a steady state value of
mers
DP proportional to the specific viscosity of the solution. The
differential pressure is monitored continuously on a strip chart
recorder or computer, providing a baseline where DP is
This test method is under the jurisdiction of ASTM Committee D-20 on Plastics
measured. The equation relating DP to specific viscosity is:
and is the direct responsibility of Subcommittee D20.70 on Analytical Methods.
Current edition approved July 10, 1998. Published January 1999. Originally
published as D 5225 – 92.
Annual Book of ASTM Standards, Vol 08.01.
3 4
Annual Book of ASTM Standards, Vol 08.02. Annual Book of ASTM Standards, Vol 14.02.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 5225
data acquisition system. When the valve is switched to the
INJECT position, solvent flowing from capillary 1 pushes the
sample into capillary 2. The differential pressure P will
increase due to the higher viscosity of the sample solution. The
steady state value of P /P then yields the value of relative
2 1
viscosity of the sample.
P
Relative Viscosity 5 (3)
KP
4.2.1.3 Absolute viscosity of the sample may be calculated
from relative viscosity, RV, assuming the viscosity of the
solvent is known.
h~sample! 5 RV · h~solvent! (4)
5. Significance and Use
5.1 Solution viscosity values for polymers are related to the
average molecular size of that portion of the polymer which
dissolves in the solvent.
NOTE—
6. Apparatus
R ,R ,R ,R = Matched SS Capillary Tubing
1 2 3 4
A, B = Solution Holdup Reservoirs
6.1 Differential Viscometer, Viscotek Model 100-01 viscom-
S ,S = Switching Valve
A B
eter, or equivalent; or Relative Viscometer, Viscotek Model
P = Solvent Inlet Pressure Transducer
i 5
Y-500, or equivalent,
DP = Differential Pressure Transducer
6.2 Kit for conversion to GPC Detector,
FIG. 1 Differential Viscometer
6.3 Computer, IBM PC or equivalent, with 640K RAM,
coprocessor, and graphics adapter,
4DP
6.4 PC Based Software, for data acquisition and processing.
h 5 (1)
sp
P 2 2DP
i
6.5 PC interface with Data Translation Board and external
4.1.2 Derivation of the equation is in Annex A1. signal box and cable,
4.2 Modified Differential Viscometer (Fig. 2): 6.6 Printer,
4.2.1 The modified differential viscometer has two stainless 6.7 Autosampler, Viscotek #100-06, or equivalent,
steel capillaries connected in series with a sample loading/ 6.8 Glass Vial,25mL,
injection valve before the second capillary. Two differential 6.9 Screw Type Cap, open top, size 24-400,
pressure transducers, P and P , are connected in parallel 6.10 Septa, aluminum foil (household grade) or acceptable
1 2
across the capillaries. A pump continuously supplies solvent substitute,
flow. The ratio of the pressures P and P is proportional to the 6.11 Balance, accurate to 0.0001 grams,
2 1
ratio of the viscosities of the fluid in capillary 2 to that in 6.12 Filter Funnel, and
capillary 1. 6.13 Filter medium, coarse filter paper or metal screen of
140 mesh or finer.
P h
2 2
5 K 5 K · Relative Viscosity (2)
P h
1 1
7. Reagents and Materials
4.2.1.1 K, the viscosity constant, is obtained from the
7.1 Polymer Sample.
baseline reading when solvent is present in both capillaries, so
7.2 Solvent.
h /h is unity.
2 1
7.3 Compressed Gas Cylinder of nitrogen or helium.
4.2.1.2 With the valve in LOAD position, the sample is
flushed through the sample loop by the syringe pump. A
8. Hazards
baseline reading is established and recorded by the computer
8.1 Flammable solvents are to be used in a hood or a well
ventilated area.
8.2 Solvents are to be dated and to be used on a first-in
first-out basis.
8.3 Stored solvents prone to develop peroxides should be
tested on a regular schedule for peroxid
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