ASTM D789-98
(Test Method)Standard Test Methods for Determination of Relative Viscosity and Moisture Content of Polyamide (PA)
Standard Test Methods for Determination of Relative Viscosity and Moisture Content of Polyamide (PA)
SCOPE
1.1 These test methods cover the determination of relative viscosity, and moisture content as they apply to polyamide (PA).
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. For a specific statement on safety, see 10.4.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
Designation:D 789–98
Standard Test Methods for
Determination of Relative Viscosity and Moisture Content of
Polyamide (PA)
This standard is issued under the fixed designation D 789; 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 (ϵ) indicates an editorial change since the last revision or reapproval.
1. Scope* D 4000D 4000 lists materials that would be applicable to the
tests contained in these test methods.
1.1 These test methods cover the determination of relative
viscosity and moisture content as they apply to polyamide
5. Test Specimen
(PA).
5.1 Test specimens for the various tests shall conform to the
1.2 The values stated in SI units are to be regarded as the
requirements prescribed herein.
standard. The values given in parentheses are for information
only.
6. Number of Tests
1.3 This standard does not purport to address all of the
6.1 Duplicate determinations, using two separate samples,
safety concerns, if any, associated with its use. It is the
shall be considered sufficient for testing each molding powder
responsibility of the user of this standard to establish appro-
batch or resin lot.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. For a specific
7. Sampling
statement on safety, see 10.4.
7.1 Unless otherwise agreed upon between the purchaser
NOTE 1—There is no similar or equivalent ISO standard.
and the seller, sample the materials in accordance with the
sampling procedure prescribed in Practice D 1898D 1898.
2. Referenced Documents
Adequatestatisticalsamplingshallbeconsideredanacceptable
2.1 ASTM Standards:
alternative.Abatch or lot of resin shall be considered as a unit
D 883 Terminology Relating to Plastics
of manufacture as prepared for shipment and may consist of a
D 1898 Practice for Sampling of Plastics
blend of two or more “production runs” of material.
D 4000 Classification System for Specifying Plastic Mate-
8. Conditioning
rials
8.1 Test Conditions—Do not remove samples from sealed,
3. Terminology
airtight containers until ready for testing.
3.1 Definitions—The definitions used in these test methods
TEST METHODS
are in accordance with Terminology D 883D 883.
4. Significance and Use 9. Relative Viscosity
9.1 General—Determine the relative viscosity of the nylon
4.1 These test methods are intended for use as control and
acceptance tests. They may be used also in the partial evalua- polymer by either the pipet viscometer method (9.2)orthe
Brookfield viscometer method (9.3). The pipet viscometer
tion of materials for specific end uses and as a means for
detecting changes in materials due to specific deteriorating method is the referee method.
9.2 Pipet Viscosity:
causes.
4.2 Since some materials require special treatment, refer- 9.2.1 Apparatus:
9.2.1.1 Constant-Temperature Water Bath, set to operate at
ence should also be made to theASTM test methods applicable
to the material being tested. Classification System 25 6 0.1°C.
9.2.1.2 Precision Thermometer, calibrated, for use in the
water bath.
9.2.1.3 Pipet Viscometer, calibrated, 25-mL.
These test methods are under the jurisdiction of ASTM Committee D20 on
Plastics and are the direct responsibility of Subcommittee D20.15 on Thermoplastic
Materials (Section D20.15.09).
Current edition approved Nov. 10, 1998. Published January 1999. Originally A Brookfield viscometer is available from Brookfield Engineering Laborato-
published as D 789 – 44 T. Last previous edition D 789 – 97. ries, Inc., 240 Cushing St., Stoughton, MA 02072.
2 5
Annual Book of ASTM Standards, Vol 08.01. Drawing No. 66-1644, available from the Scientific Glass Apparatus Co., 51
Annual Book of ASTM Standards, Vol 08.02. Ackerman St., Bloomfield, NJ 07003.
*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.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
D789–98
9.2.1.4 Ostwald Viscometer, calibrated.
f = kinematic viscosity of S-20 oil, mm /s (cST)/t ,
20 20
9.2.1.5 Pycnometer, calibrated, 50-mL.
f = kinematic viscosity of S-60 oil, mm /s (cST)/t ,
60 60
9.2.1.6 Automatic Pipet, calibrated, 100-mL.
t = average efflux time of S-20 oil, s, and
9.2.1.7 Erlenmeyer Flasks, 250-mL, heat-resistant glass. t = average efflux time of S-60 oil, s.
9.2.1.8 Shaking Machine.
This value shall be used in calculating the relative viscosity
9.2.1.9 Rubber Bulbs.
of a polymer solution, as shown in 9.2.7.
9.2.1.10 Timer, accurate to 0.2 s.
9.2.4 Calibration of Ostwald Viscometer—Add to the vis-
9.2.1.11 With the exception of the pipet and Ostwald
cometer 10 mL of Oil S-3 at approximately 25°C from a
viscometers, apparatus capable of equivalent accuracy may be
volumetric pipet. Immerse the viscometer in the constant-
substituted.
temperature bath at 25 6 0.1°C and allow it to remain at least
9.2.2 Reagents and Materials:
20 min. Apply air pressure to the large diameter leg by means
9.2.2.1 Acetone, commercial grade.
ofarubberbulbuntiloilisabovetheuppertimingmark.Allow
9.2.2.2 Chromic Acid Cleaning Solution—Dissolve sodium
the oil to flow down. Repeat several times to ensure thorough
dichromate Na CrO·2H O, technical grade, in concentrated
2 7 2
wetting of the viscometer. Again, force oil above the upper
sulfuric acid (H SO , sp gr 1.84).
2 4
9.2.2.3 m-Cresol, having a viscosity of 12.83 cP at 25°C timing mark, and observe the time (to 0.2 s) required for the
and a density of 1.029 6 0.0011 g/mL at 25°C. liquid to fall from the upper timing mark to the lower timing
9.2.2.4 Formic Acid (90 6 0.2 %) —Clear, water-white.
mark. Repeat until three successive values agree within 0.5 %,
ACS-grade formic acid with the following additional require-
and record the average for Oil S-3 at 25°C as t . Remove the
ments: Methyl formate content 0.2 % maximum; density
viscometer from the bath, clean and dry the inside surfaces
1.1985 6 0.001 g/mL at 25°C; viscosity 1.56° 6 0.02 cP at
thoroughly, and repeat the above procedure, using 10 mL of
25°C.
90 % formic acid. Record the average efflux time as t .
f
9.2.2.5 Standard Viscosity Oils—Use Cannon Instrument
Calculate the absolute viscosity of the 90 % formic acid as
Company standard viscosity oils S-3, S-20, K-50, S-60, and
follows:
S-200. The approximate kinematic viscosities at 25°C are 4.0,
η 5 f ·d ·t (2)
f t f f
35, 90, 120, and 480 cSt, respectively.
9.2.2.6 Stopcock Lubricant.
where:
9.2.3 Calibration of Pipet Viscometer—Use Oil S-20. As-
η = absolute viscosity of formic acid, kPa · s (cP),
f
semble the pipet viscometer so that the lowest mark on the
f = viscometer tube factor, mm /s (cSt)/s = η /t ,
t 3 3
pipet aligns with the 50-mL mark on the reservoir to the pipet.
η = kinematic viscosity of Oil S-3, mm /s (cSt),
Place the assembly in the water bath adjusted to a temperature t = average efflux time for Oil S-3 at 25°C, s,
of 25 6 0.1°C. After at least 20 min, apply air pressure to the d = density of 90 % formic acid at 25°C, g/mL, = 1.1975,
f
and
reservoirorvacuumtothecapillary,bymeansofarubberbulb,
t = average efflux time for 90 % formic acid at 25°C, s.
to drive the oil up into the pipet above the upper timing mark.
f
Place a finger over the top of the pipet, and release the pressure
9.2.5 Preparation of Solutions:
by opening the system to air. Remove the finger and allow
9.2.5.1 Preparation of Nylon Polymer-Formic Acid
pipet to drain. Repeat at least three times to wet the pipet
Solutions—Weigh 11.00 g of nylon polymer into a clean, dry,
thoroughly, and then record the time (to 0.2 s) for the liquid
250-mL, ground-glass stoppered Erlenmeyer flask (see Note
leveltofallfromtheuppertimingleveltothelower.Determine
2). Add, by means of the calibrated 100-mL automatic pipet,
the efflux time, t , repeating until three successive values
100 mL of 90 % formic acid at 25 6 1°C. Slowly shake the
agree within 0.5 %, and record the average. Repeat the
flask while adding the acid to prevent the polymer from
procedure with Oil S-60 to obtain t . Calculate the viscometer
forming a gelatinous mass. Set the flask in an oven at 50°C for
tube factor as follows:
15 min, if needed, to obtain complete solutions. Then put
tube factor 5 ~f 1 f !/2 (1)
20 60
stopcock lubricant on the glass stopper, insert it tightly into the
flask, and place the flask and contents on a shaking machine.
where:
Agitate until the solution is complete (see Note 3).
9.2.5.2 The procedure for the preparation of n-alkoxy-alkyl
6 nylon 6:6 and nylon 6:12 polymers in m-cresol is the same as
The compound m-cresol is used with n-alkoxyalkyl nylon 6:6 resin because
formic acid tends to crosslink this nylon. It is used with nylon 6:10 resin because of for the preparation of formic acid solutions, except that the
this nylon’s insolubility in formic acid. It is available as No. 5072 from Matheson,
quantity of nylon polymer shall be 9.44 g instead of 11.00 g,
Coleman, and Bell Co., East Rutherford, NJ 07073.
7 and the m-cresol shall be specified as the solvent instead of
Available in drums from Union Carbide Corp., Chemical and Plastics Div.,
Moorestown, NJ 08057. Available in smaller quantities from Polyscience, Incorpo- formic acid.
rated, Paul Valley Industrial Park, Warrington, PA 18976. Matheson, Coleman, and
Bell 97 to 100 % formic acid, diluted with water and checked by titration to
NOTE 2—The polymer should contain less than 0.28 % moisture. If it
90.0 6 0.2 %, has also been found satisfactory.
contains more than 0.28 %, the polymer should be dried. Normally, drying
Suitable standard viscosity oils are available from Cannon Instrument Co., P.O.
at 70°C in a vacuum for 4 to6hor 90°C for 20 min is adequate.
Box 16, State College, PA 16801.
NOTE 3—Heating may be continued for a maximum of 2 h while
“Cello-Grease,” available from the Fisher Scientific Co., 717 Forbes St.,
Pittsburgh, PA 15219, has been found satisfactory for this purpose. shaking at a temperature not exceeding 50°C.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
D789–98
9.2.6 Procedure—Fill the reservoir bottle of a dry, clean 9.3.1.1 Constant-Temperature Water Bath, set to operate at
pipet viscometer to the 50-mL mark with the nylon polymer- 25 6 0.1°C.
formic acid solution. Insert the pipet and reservoir top and
9.3.1.2 Precision Thermometer, calibrated, for use in water
fasten securely. Determine the efflux time, t , as described in
bath.
p
9.2.4.
9.3.1.3 Brookfield Synchro-Lectric Viscometer, Model LVF.
9.2.7 Calculation of Relative Viscosity—The relative vis-
9.3.1.4 Viscometer, Cannon-Fenske type, Size 75, uncali-
cosity, η , is the ratio of the absolute viscosity of the polymer
brated.
r
solution to that of the formic acid:
9.3.1.5 Automatic Pipet, 200-mL.
η 5~η /η!5~f ·d ·t !/η (3)
9.3.1.6 Shaking Machine, reciprocating type.
r p f t p p f
9.3.1.7 Stopwatch, having divisions of at least 0.1 s or 0.01
where:
min and accuracy of at least 0.05 %.
d = density of formic acid-polymer solution at 25°C (see
p
9.3.1.8 Bottles, 8-oz, round, wide-mouth with caps contain-
9.2.8), and
ing polyethylene liners.
t = average efflux time for formic acid-polymer solution,
p
9.3.1.9 With the exception of the Brookfield and Cannon-
s.
Fenske viscometers, apparatus capable of equivalent accuracy
Calculate the relative viscosity of n-alkoxyalkyl nylon 6:6
may be substituted.
and nylon 6:12 resins using m-cresol as the comparison base,
9.3.2 Reagents and Materials—Same as described in 9.2.2.
not formic acid. Substitution of proper constants in the calcu-
9.3.3 Determination of Absolute Viscosity of Formic Acid:
lation formulas will then be necessary.
9.3.3.1 Add 10.0 mL (pipet) of 90 6 0.2 % formic acid (at
9.2.8 Density of Nylon Polymer-Formic Acid Solution:
25.0 6 0.5°C) to a Size 75 Cannon-Fenske viscometer. The
9.2.8.1 Prepare the nylon polymer-formic acid solution as
viscometer may be calibrated as described in 9.3.3.3. Suspend
described in 9.2.5.1.
the viscometer from the lid of the constant-temperature water
NOTE 4—Calibration of the pyknometer used to determine density is
bath in a vertical position so that the upper bulb is well-
made by repeating the procedure specified in 9.2.8.2 and 9.2.8.3, using
immersed in the bath at 25 6 0.1°C. Allow 20 to 30 min for
distilled water in place of the nylon polymer-formic acid solution.
temperature equilibrium to be reached. Apply suction (bulb or
vacuum) to the small leg of the viscometer and draw the liquid
9.2.8.2 Weigh (to 60.1 mg) a clean, dry, calibrated 50-mL
pyknometer, and fill it with the nylon polymer-formic acid above the upper timing mark. Allow to drain. Repeat twice to
ensure complete wetting of the tube. Observe and record the
solution at a temperature slightly below (1 to 2°C) the test
temperature. Stopper or cap the pyknometer, leaving the time required for the meniscus of liquid to fall from the upper
timing mark to the lower timing mark. Repeat until three
overflow orifice open. Take care to prevent the formation of
bubbles in the pyknometer. Immerse the filled pyknometer (the successive readings agree within 0.5 %. Average the results;
record the efflux time as t.
neck of the pyknometer shall be above the water line) into a
f
constant-temperature water bath, maintained at 25 6 0.1°C.
9.3.3.2 Calculation of Absolute Viscosity for Formic Acid:
Allow 20 to 30 min for temperature equilibrium to be reached.
η 5 f ·d ·t (6)
f t f f
9.2.8.3 Remove the pyknometer from the water bath, and
where:
wipe away any overflow with paper towels or other absorbent
η = viscosity of formic acid, kPa · s (cP),
f
material, taking care not to remove any subsequent overflow
f = tube factor, mm /s (cSt)/s (9.3.3.3),
t
that may be caused in this step. Dry the pyknometer thor-
d = density of formic acid at 25 6 0.1°C, g/cm = 1.1975,
f
oughly, and weigh immediately (60.1 mg).
and
9.2.8.4 The density of the nylon polymer-formic acid solu-
t = efflux time of formic acid, s.
f
tion, in grams per cubic centimetre, is calculated by the
9.3.3.3 Calibration of Viscometer, Cannon-Fenske, Size
following formulas:
75—Determine the efflux time of the standard Cannon viscos-
m 2m
p o
ity Oil S-3, following the procedures of 9.3.3.1. Record the
d 5 (4)
p
V
efflux time as t.
and
f 5 η /t (7)
t d d
m 2m
w o
V
...
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