ASTM D4243-23

Standard Test Method for Measurement of Average Viscometric Degree of Polymerization of New and Aged Electrical Papers and Boards

SIGNIFICANCE AND USE
5.1 This test method applies to all papers made from unmodified cellulose, as used in transformer, cable, or capacitor manufacture. It applies to new or aged papers. For information, Appendix X1 shows an example of statistical distribution of  values for new papers intended for the insulation of transformers, together with information relative to cable and capacitor papers. Nevertheless, where evaluating the decomposition stage of aged papers, take care to use, as a reference, the  value of the new paper of the very same origin;  of new papers being a function, among other factors, of their specific gravity and of their manufacturing process.  
5.2 This test method can also be used for the determination of the intrinsic viscosity of solutions of chemically modified papers, provided that these dissolve completely in the selection solvent. Use this test method with caution when it is applied to papers with mineral fillers.
SCOPE
1.1 This test method describes a standard procedure for determining the average viscometric degree of polymerization (abbreviated ) of new or aged electrical papers. The determination is made by measuring the intrinsic viscosity of a solution of the paper in an appropriate solvent.  
1.2 The degree of polymerization (or the degree of condensation) of a particular cellulose molecule is the number of anhydro-β-glucose monomers, C6H10O5, in the cellulose molecule. Within a sample of paper, not all the cellulose molecules have the same degree of polymerization so that the mean value measured by viscometric methods is not necessarily the same as that which are obtained by other methods.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. See Section 9.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Apr-2023
• ICS: 29.035.10 - Paper and board insulating materials
• Technical Committee: D09 - Electrical and Electronic Insulating Materials
• Drafting Committee: D09.01 - Electrical Insulating Products

Relations

• Refers: ASTM D445-24 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 01-Apr-2024
• Refers: ASTM D1711-24 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Mar-2024
• Refers: ASTM D445-23 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 01-Nov-2023
• Refers: ASTM D445-16 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 15-Dec-2016
• Refers: ASTM D1711-15 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2015
• Refers: ASTM D1711-14a - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2014
• Refers: ASTM D445-14e1 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 01-Jul-2014
• Refers: ASTM D445-14 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 01-Jul-2014
• Refers: ASTM D1711-14 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-May-2014
• Refers: ASTM D1711-13 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2013
• Refers: ASTM D445-12 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 15-Apr-2012
• Refers: ASTM D1711-11a - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Aug-2011
• Refers: ASTM D1711-08 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-May-2008
• Refers: ASTM D445-06 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 15-May-2006
• Refers: ASTM D445-04e1 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and the Calculation of Dynamic Viscosity)
• Effective Date: 01-Nov-2004

Overview

ASTM D4243-23 specifies the standard test method for the measurement of the average viscometric degree of polymerization (DP) of new and aged electrical papers and boards. This method is crucial for evaluating the quality and aging state of cellulose-based electrical insulation materials used in transformers, cables, and capacitors. The degree of polymerization is a key indicator of mechanical and electrical properties, making this standard essential for manufacturers and users concerned with material performance and longevity.

The method involves determining the intrinsic viscosity of a solution of the paper in an appropriate solvent, typically cupriethylene-diamine (CED). The test applies to both new and aged unmodified cellulose papers, as well as to some chemically modified papers under specific conditions.

Key Topics

• Degree of Polymerization (DP): Statistical average of the number of anhydro-β-glucose units in cellulose molecules of the sample. DP correlates with the mechanical strength and electrical insulation quality of the paper or board.
• Viscometric Analysis: The degree of polymerization is indirectly measured by determining the intrinsic viscosity of a paper solution in CED using viscometry.
• Applicability: Suitable for all electrical papers made from unmodified cellulose, whether new or aged, and applicable with caution for papers containing mineral fillers or that are chemically modified.
• Reference Standards: Measurements for aged materials should be referenced against new paper from the same source, due to variability introduced by manufacturing processes and physical characteristics.
• Sample Preparation: Guidelines for preparing both impregnated and non-impregnated samples, including solvent extraction, cutting of samples, and humidity control.
• Validity and Repeatability: The method stipulates conditions for result acceptance, including agreement between duplicate tests and minimal insoluble residue.

Applications

• Transformer and Power Cable Manufacturing: Used to monitor the quality of insulating papers, ensuring optimal electrical performance and long service life. Regular DP assessment allows early detection of degradation.
• Aging Studies: Essential for assessing aging or decomposition in insulation materials through comparison of new and service-aged samples, assisting in preventive maintenance and lifecycle analysis.
• Capacitor Insulation: Evaluates material integrity in high-reliability electronic components, maintaining safety and functionality.
• Quality Assurance: Environmental and operational factors can influence DP. Manufacturers and users apply this standard to certify compliance with internal and industry requirements.
• R&D and Material Development: Supports development of advanced insulating products by providing a reliable means of benchmarking polymerization levels.

Related Standards

• ASTM D445: Test Method for Kinematic Viscosity of Transparent and Opaque Liquids.
• ASTM D1711: Terminology Relating to Electrical Insulation, providing definitions relevant to this test method.
• IEC 60450: International standard for measuring the average viscometric degree of polymerization of new and aged electrical papers, which ASTM D4243 aligns closely with.

Practical Value

The intrinsic viscosity-based DP measurement provided by ASTM D4243-23 delivers a non-destructive, reliable method for evaluating unmodified and some modified cellulose insulation used in critical electrical infrastructure. By standardizing sample preparation, solution protocols, and measurement conditions, this method minimizes variability and enhances comparability across laboratories and organizations. Periodic testing according to this method helps extend the operational life of transformers, cables, and capacitors, reduces failure risks, and supports industry compliance with quality, safety, and performance standards.

Keywords: ASTM D4243, degree of polymerization, electrical papers, intrinsic viscosity, transformer insulation, cable insulation, viscometric analysis, aging, cellulose insulation, quality assurance.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D4243 − 23
Standard Test Method for
Measurement of Average Viscometric Degree of
Polymerization of New and Aged Electrical Papers and
Boards
This standard is issued under the fixed designation D4243; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope D1711 Terminology Relating to Electrical Insulation
1.1 This test method describes a standard procedure for 2.2 Other Document:
determining the average viscometric degree of polymerization IEC 60450 Measurement of the Average Viscometric Degree
¯
of Polymerization of New and Aged Electrical Papers
(abbreviated DP ) of new or aged electrical papers. The
v
determination is made by measuring the intrinsic viscosity of a
3. Terminology
solution of the paper in an appropriate solvent.
3.1 Definitions—For definitions of terms used in this test
1.2 The degree of polymerization (or the degree of conden-
method, refer to Terminology D1711.
sation) of a particular cellulose molecule is the number of
anhydro-β-glucose monomers, C H O , in the cellulose mol-
6 10 5
ecule. Within a sample of paper, not all the cellulose molecules 4. Summary of Test Method
have the same degree of polymerization so that the mean value
4.1 This test method measures the specific viscosity of a
measured by viscometric methods is not necessarily the same
solution of the paper in cupriethylene–diamine. From this
as that which are obtained by other methods.
measurement the intrinsic viscosity of the solution is deduced,
1.3 This standard does not purport to address all of the and from this the degree of polymerization is easily calculated.
safety concerns, if any, associated with its use. It is the
4.2 This test method follows very closely the procedures
responsibility of the user of this standard to establish appro-
specified in IEC 60450.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
5. Significance and Use
See Section 9.
5.1 This test method applies to all papers made from
1.4 This international standard was developed in accor-
unmodified cellulose, as used in transformer, cable, or capaci-
dance with internationally recognized principles on standard-
tor manufacture. It applies to new or aged papers. For
ization established in the Decision on Principles for the
information, Appendix X1 shows an example of statistical
Development of International Standards, Guides and Recom-
¯
distribution of DP values for new papers intended for the
mendations issued by the World Trade Organization Technical v
insulation of transformers, together with information relative to
Barriers to Trade (TBT) Committee.
cable and capacitor papers. Nevertheless, where evaluating the
2. Referenced Documents
decomposition stage of aged papers, take care to use, as a
2 ¯
reference, the DP value of the new paper of the very same
2.1 ASTM Standards:
v
¯
origin; DP of new papers being a function, among other
D445 Test Method for Kinematic Viscosity of Transparent
v
and Opaque Liquids (and Calculation of Dynamic Viscos- factors, of their specific gravity and of their manufacturing
process.
ity)
5.2 This test method can also be used for the determination
of the intrinsic viscosity of solutions of chemically modified
This test method is under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and is the direct responsibility of
papers, provided that these dissolve completely in the selection
Subcommittee D09.01 on Electrical Insulating Products.
solvent. Use this test method with caution when it is applied to
Current edition approved May 1, 2023. Published May 2023. Originally
papers with mineral fillers.
approved in 1983. Last previous edition approved in 2016 as D4243 – 16. DOI:
10.1520/D4243-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4243 − 23
6. Interferences Cu NH 2 CH 2 CH 2 NH OH (2)
@ ~ ! #~ !
2 2 2 2
2 2
6.1 Lignins, that are present in measurable amounts in most
This implies a molar ratio of 2 between the concentration of
papers and boards, have an effect on the test results, depending
ethylene-diamine and the concentration of copper:
upon concentration and composition. For this reason, it is
~C /C ! 5 2 (3)
ED cu
important in aging studies to use as a reference samples of the
8.1.2 Cupriethylene-diamine solution is available for pur-
unaged paper as mentioned in 5.1.
chase commercially at several different concentrations. At a
6.2 Under some conditions of heat and atmosphere, cross
concentration greater than 1 M it is suitable to be kept for one
linking of cellulose molecules occur, resulting in erratic test
year in the dark. It is diluted to 1 M when required for use.
values. This effect has been observed for capacitor tissue in
Alternatively the CED solution can be made in the laboratory
vacuum at temperatures as low as 110 °C and for other papers
at its working strength of 1 M by the methods described in
aged in air at higher temperatures.
Annex A1.
8.1.3 The 1 M solution will keep only for a limited time. As
7. Apparatus
often as necessary check the solution by:
7.1 Apparatus for Solution:
8.1.3.1 Using the method described in Annex A2 to verify
7.1.1 Round-Bottomed or Flat-Bottomed 50 mL Flask, pref-
that the ratio
erably with a short narrow neck, or a narrow-necked 50 mL
C /C 5 2.060.1. (4)
ED Cu
Erlenmeyer flask.
7.1.2 Rubber Stopper, fitting the neck of the flask, through
8.1.3.2 Verify that there is no precipitate in the solution.
which passes a capillary tube fitted with a small-bore cock
Remove any precipitate by filtering or by decanting.
glass cock; or a ground stopper, fitted with a small-bore cock is
suitable for use with a ground-neck flask.
9. Preparation of Specimens
NOTE 1—In lieu of a small-bore cock a capillary tube with constant
9.1 Impregnated Papers:
nitrogen flow may be used. The use of constant nitrogen flow requires both
9.1.1 Using a Soxhlet extractor, degrease the paper with
an inlet and an outlet capillary to avoid pressure build-up in the flask.
hexane or, if necessary, with chloroform. (Warning—
7.1.3 Glass Balls, 4 mm to 6 mm diameter, that shall not be
Chloroform is toxic, and hexane is flammable. Adequate
able to enter the bore of the cock.
precautions must be taken to avoid exposure to vapors and to
7.1.4 Mechanical Stirrer, to rotate the solution flask with a
prevent fire.)
uniform circular motion with a horizontal axis between 20 and
9.1.2 Allow the solvent to evaporate in air at room tempera-
40 r/min. The flask shall be mounted so that its axis is normal
ture.
2 2
to the axis of rotation, and the radius of gyration shall not be
9.1.3 Cut the sample into small pieces (1 mm or 2 mm )
greater than 200 mm.
with scissors, using gloves to avoid touching the paper.
7.2 Apparatus for Measurement of Viscosity:
NOTE 2—Optionally, to assist in the separation of fibers the specimen
7.2.1 Apparatus for Measurement of Kinematic Viscosity, as
may be fluffed in a suitable blender or grinder. Care shall be taken to
ensure any temperature increase caused by the fluffing process does not
described in Test Method D445. The viscometer shall have a
negatively affect the specimen.
calibration constant, C, of from 0.00010 or 0.00013 St/s (10 ×
−9 −9 2 2
9.1.4 Keep the sample in a controlled-humidity atmosphere
10 to 13 × 10 m /s ).
7.2.2 This constant shall be determined by measuring the until it reaches equilibrium water content before removing the
efflux-time T (seconds) of a liquid of known dynamic viscosity material required for test purposes.
2 3
(Ns/m ) and density ρ (g/cm ). It is given by the formula:
9.2 Nonimpregnated Papers:
2 2
η 9.2.1 Cut the sample into small pieces (1 mm or 2 mm )
C 5 (1)
ρ·T with scissors, using gloves to avoid touching the paper.
NOTE 3—Optionally, to assist in the separation of fibers the specimen
7.2.3 Constant-Temperature Water Bath, regulated at 20 °C
may be fluffed in a suitable blender or grinder. Care shall be taken to
6 0.1 °C.
ensure any temperature increase caused by the fluffing process does not
7.2.4 Stopwatch, with an accuracy of 0.1 s.
negatively affect the specimen.
7.3 Apparatus for Measurement of Water Content of Paper
9.2.2 Keep the sample in a controlled-humidity atmosphere
Sample:
until it reaches equilibrium water content before removing the
7.3.1 Weighing Containers, impermeable to water vapor,
material required for test purposes.
with airtight lids.
7.3.2 Ventilated Drying Oven, thermostatically controlled at
10. Procedure
105 °C 6 2 °C.
10.1 Determination of Viscosity:
7.3.3 Desiccator.
10.1.1 Test Specimen—Weigh to the nearest 0.1 mg an
amount (m) of paper, in equilibrium with the controlled
8. Reagents
atmosphere, of about:
8.1 Cupriethylene-Diamine Solution:
¯
10.1.1.1 125 mg when DP lies between 100 and 300,
v
8.1.1 The formula ascribed to cupriethylene-diamine (CED)
¯
is: 10.1.1.2 50 mg when DP lies between 300 and 700, and
v
D4243 − 23
¯
10.1.5 Make all tests in duplicate, making up two separate
10.1.1.3 25 mg when DP lies between 700 and 1500.
v
solutions from separately weighed specimens.
10.1.2 Solution:
10.2 Determination of Water Content of Paper:
10.1.2.1 Put a few glass balls in the flask.
10.1.2.2 Add the weighed test specimen.
10.2.1 Test Specimen:
10.1.2.3 Carefully shake or stir by hand to ensure the small
10.2.1.1 Weigh to the nearest milligram approximately 2 g
pieces of paper are separated and evenly distributed.
of paper in equilibrium with the controlled-humidity
10.1.2.4 Add between 20 mL and 25 mL, measured to the
atmosphere, and in a closed weighing container that has been
neared 0.1 mL, of distilled water.
dried and tared.
10.1.2.5 Again shake or stir by hand to disintegrate and wet
10.2.1.2 If the paper sample is too small for 2 g to be
all the paper completely.
reserved for determining its water content, use a smaller
10.1.2.6 Leave for ⁄2 h to allow thorough impregnation with
specimen. However, if the amount of paper is only sufficient
water.
for the viscometric measurements, its water content is deduced
10.1.2.7 Add the same volume (60.1 mL) of 1 M solution
from the moisture equilibrium curves and the relative humidity
of cupriethylene-diamine that was previously added of distilled
of the conditioning atmosphere with which the paper was in
water.
equilibrium. If equilibrium curves are not available for the
10.1.2.8 Add a number of glass balls so that, when the particular paper tested, the following average values are used
as a first approximation for temperatures between 20 °C and
stopper with capillary tube, and so forth, is fitted, the liquid
will entirely fill the flask and reach the bore of the cock. Do not 27 °C.
allow any pieces of paper to enter the capillary, for such paper
Relative Humidity of Air, % Water Content of Air, %
50 6
will not be dissolved.
65 8
10.1.2.9 Close the cock or initiate nitrogen flow.
10.2.2 Measurement of Water Content:
10.1.2.10 Allow the specimen to dissolve with mechanical
stirring as described in 7.1.4. The preferred solution time is 2 h; 10.2.2.1 After weighing, open the container and place it,
however, when the specimen is not satisfactorily dissolved, with the weighed test specimen and its cap, in the oven and
increase the solution time may be increased to a maximum of heat at 105 °C 6 2 °C until it reaches constant mass. This will
18 h. For a specimen of an aged paper, there is little risk of
normally require from 4 h to 18 h.
further measurable degradation due to this increase of solution
10.2.2.2 After drying, replace the cap on the container and
time.
allow it to cool in a desiccator for about 45 min. After cooling,
10.1.3 Measurement of Viscosity:
equalize the air pressures inside and outside the container by
10.1.3.1 After the period of stirring and before filling the
raising and lowering the cap quickly. Weigh the container with
viscometer, allow the solution to stand for 1 h at the tempera-
the specimen.
ture of measurement, 20 °C 6 0.1 °C.
10.2.3 Alternative procedures are suitable for use to deter-
10.1.3.2 Take the required volume of solution and transfer it
mine the water content of the paper sample provided that it can
to the viscometer reservoir. Assemble the viscometer and place
be verified that the procedure used will give results that differ
the assembly in the thermostatic bath.
from the results used in 10.2.2 by no more than 0.5 %.
10.1.3.3 Wait 15 min before beginning the measurements.
Then raise the liquid level above the upper mark of the
11. Calculation
viscometer either by means of air pressure or slight vacuum.
11.1 Concentration, c, of Dry Paper in the Solution:
Measure the efflux time between the upper and lower marks.
11.1.1 The water content H of the paper, as a proportion of
Make three successive measurements. The difference between
the dry weight, is as follows:
the maximum and minimum time of flow shall be less than
0.5 s. If this repeatability is not achieved, clean the viscometer
H 5 ~M 2 M /M ! (5)
0 0
as described in 10.1.4. Take a second specimen of the solution
where:
that has been kept at the measurement temperature and make a
M = mass of the test sample used for determining the water
further series of three measurements. If again the difference is
content before drying, g and
not less than 0.5 s, take a new specimen of paper and prepare
M = mass of this sample after drying, g.
a fresh solution.
10.1.3.4 Under the same conditions, measure the flow time
11.1.2 Knowing the mass, m, in grams of the test specimen
of the solvent. This shall be between 90 s and 110 s for the
and its water content, H, the concentration c (g/100 mL), of dry
viscometer constant C stated in 6.2 (0.00010 ≤ C ≤ 0.00013).
paper in the solution is given by:
10.1.4 Cleaning the Viscometer:
c 5 m·100/45 · 1/11H (6)
~ ! ~ !
10.1.4.1 By aspiration, fill the tube with chromic-acid mix-
11.2 Specific Viscosity, η —The densities of the solvent and
ture and immediately empty it again.
s
of the solution a
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4243 − 16 D4243 − 23
Standard Test Method for
Measurement of Average Viscometric Degree of
Polymerization of New and Aged Electrical Papers and
Boards
This standard is issued under the fixed designation D4243; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method describes a standard procedure for determining the average viscometric degree of polymerization
¯
(abbreviated DP ) of new or aged electrical papers. The determination is made by measuring the intrinsic viscosity of a solution
v
of the paper in an appropriate solvent.
1.2 The degree of polymerization (or the degree of condensation) of a particular cellulose molecule is the number of
anhydro-β-glucose monomers, C H O , in the cellulose molecule. Within a sample of paper, not all the cellulose molecules have
6 10 5
the same degree of polymerization so that the mean value measured by viscometric methods is not necessarily the same as that
which are obtained by other methods.
1.3 This standard may involve hazardous materials, operations, and equipment. 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 to safety, health, and environmental practices and determine the applicability of regulatory
limitations prior to use. See Section 9.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D445 Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
D1711 Terminology Relating to Electrical Insulation
2.2 Other Document:
IEC 60450 Measurement of the Average Viscometric Degree of Polymerization of New and Aged Electrical Papers
3. Terminology
3.1 Definitions—For definitions of terms used in this test method, refer to Terminology D1711.
This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of Subcommittee
D09.01 on Electrical Insulating Products.
Current edition approved Nov. 1, 2016May 1, 2023. Published November 2016May 2023. Originally approved in 1983. Last previous edition approved in 20092016 as
D4243 – 99 (2009).D4243 – 16. DOI: 10.1520/D4243-16.10.1520/D4243-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4243 − 23
4. Summary of Test Method
4.1 This test method measures the specific viscosity of a solution of the paper in cupriethylene–diamine. From this measurement
the intrinsic viscosity of the solution is deduced, and from this the degree of polymerization is easily calculated.
4.2 This test method follows very closely the procedures specified in IEC 60450.
5. Significance and Use
5.1 This test method applies to all papers made from unmodified cellulose, as used in transformer, cable, or capacitor manufacture.
¯
It applies to new or aged papers. For information, Appendix X1 shows an example of statistical distribution of DP values for new
v
papers intended for the insulation of transformers, together with information relative to cable and capacitor papers. Nevertheless,
¯
where evaluating the decomposition stage of aged papers, take care to use, as a reference, the DP value of the new paper of the
v
¯
very same origin; DP of new papers being a function, among other factors, of their specific gravity and of their manufacturing
v
process.
5.2 This test method can also be used for the determination of the intrinsic viscosity of solutions of chemically modified papers,
provided that these dissolve completely in the selection solvent. Use this test method with caution when it is applied to papers with
mineral fillers.
6. Interferences
6.1 Lignins, that are present in measurable amounts in most papers and boards, have an effect on the test results, depending upon
concentration and composition. For this reason, it is important in aging studies to use as a reference samples of the unaged paper
as mentioned in 5.1.
6.2 Under some conditions of heat and atmosphere, cross linking of cellulose molecules occur, resulting in erratic test values. This
effect has been observed for capacitor tissue in vacuum at temperatures as low as 110°C110 °C and for other papers aged in air
at higher temperatures.
7. Apparatus
7.1 Apparatus for Solution:
7.1.1 Round-Bottomed 50-mL or Flat-Bottomed 50 mL Flask, preferably with a short narrow neck, or a narrow-necked
50-mL50 mL Erlenmeyer flask.
7.1.2 Rubber Stopper, fitting the neck of the flask, through which passes a capillary tube fitted with a small-bore cock glass cock;
or a ground stopper, fitted with a small-bore cock is suitable for use with a ground-neck flask.
NOTE 1—In lieu of a small-bore cock a capillary tube with constant nitrogen flow may be used. The use of constant nitrogen flow requires both an inlet
and an outlet capillary to avoid pressure build-up in the flask.
7.1.3 Glass Balls, 4 to 6-mm4 mm to 6 mm diameter, that shall not be able to enter the bore of the cock.
7.1.4 Mechanical Stirrer, to rotate the solution flask with a uniform circular motion with a horizontal axis between 20 and 40 r/min.
The flask shall be mounted so that its axis is normal to the axis of rotation, and the radius of gyration shall not be greater than
200 mm.
7.2 Apparatus for Measurement of Viscosity:
7.2.1 Apparatus for Measurement of Kinematic Viscosity, as described in Test Method D445. The viscometer shall have a
−9 −9 2 2
calibration constant, C, of from 0.00010 or 0.00013 St/s (10 × 10 to 13 × 10 m /s ).
7.2.2 This constant shall be determined by measuring the efflux-time T (seconds) of a liquid of known dynamic viscosity (Ns/m )
and density ρ (g/cm ). It is given by the formula:
D4243 − 23
η
C 5 (1)
ρ·T
7.2.3 Constant-Temperature Water Bath, regulated at 20 6 0.1°C.20 °C 6 0.1 °C.
7.2.4 Stopwatch, with an accuracy of 0.1 s.
7.3 Apparatus for Measurement of Water Content of Paper Sample:
7.3.1 Weighing Containers, impermeable to water vapor, with airtight lids.
7.3.2 Ventilated Drying Oven, thermostatically controlled at 105 6 2°C.105 °C 6 2 °C.
7.3.3 Desiccator.
8. Reagents
8.1 Cupriethylene-Diamine Solution:
8.1.1 The formula ascribed to cupriethylene-diamine (CED) is:
Cu NH 2 CH 2 CH 2 NH OH (2)
@ ~ ! #~ !
2 2 2 2 2 2
This implies a molar ratio of 2 between the concentration of ethylene-diamine and the concentration of copper:
~C /C !5 2 (3)
ED cu
8.1.2 Cupriethylene-diamine solution is available for purchase commercially at several different concentrations. At a concentration
greater than 1 M it is suitable to be kept for one year in the dark. It is diluted to 1 M when required for use. Alternatively the CED
solution can be made in the laboratory at its working strength of 1 M by the methods described in Annex A1.
8.1.3 The 1 M solution will keep only for a limited time. As often as necessary check the solution by:
8.1.3.1 Using the method described in Annex A2 to verify that the ratio
C /C 5 2.060.1. (4)
ED Cu
8.1.3.2 Verify that there is no precipitate in the solution. Remove any precipitate by filtering or by decanting.
9. Preparation of Specimens
9.1 Impregnated Papers:
9.1.1 Using a Soxhlet extractor, degrease the paper with hexane or, if necessary, with chloroform. (Warning—Chloroform is
toxic, and hexane is flammable. Adequate precautions must be taken to avoid exposure to vapors and to prevent fire.)
9.1.2 Allow the solvent to evaporate in air at room temperature.
2 2
9.1.3 Cut the sample into small pieces (1(1 mm or 2 mm2 mm ) with scissors, using gloves to avoid touching the paper.
NOTE 2—Optionally, to assist in the separation of fibers the specimen may be fluffed in a suitable blender or grinder. Care shall be taken to ensure any
temperature increase caused by the fluffing process does not negatively affect the specimen.
9.1.4 Keep the sample in a controlled-humidity atmosphere until it reaches equilibrium water content before removing the material
required for test purposes.
9.2 Nonimpregnated Papers:
2 2
9.2.1 Cut the sample into small pieces (1(1 mm or 2 mm2 mm ) with scissors, using gloves to avoid touching the paper.
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NOTE 3—Optionally, to assist in the separation of fibers the specimen may be fluffed in a suitable blender or grinder. Care shall be taken to ensure any
temperature increase caused by the fluffing process does not negatively affect the specimen.
9.2.2 Keep the sample in a controlled-humidity atmosphere until it reaches equilibrium water content before removing the material
required for test purposes.
10. Procedure
10.1 Determination of Viscosity : Viscosity:
10.1.1 Test Specimen—Weigh to the nearest 0.1 mg an amount (m) of paper, in equilibrium with the controlled atmosphere, of
about:
¯
10.1.1.1 125 mg when DP lies between 100 and 300,
v
¯
10.1.1.2 50 mg when DP lies between 300 and 700, and
v
¯
10.1.1.3 25 mg when DP lies between 700 and 1500.
v
10.1.2 Solution:
10.1.2.1 Put a few glass balls in the flask.
10.1.2.2 Add the weighed test specimen.
10.1.2.3 Carefully shake or stir by hand to ensure the small pieces of paper are separated and evenly distributed.
10.1.2.4 Add 22.5 mL between 20 mL and 25 mL, measured to the neared 0.1 mL, of distilled water.
10.1.2.5 Again shake or stir by hand to disintegrate and wet all the paper completely.
10.1.2.6 Leave for ⁄2 h to allow thorough impregnation with water.
10.1.2.7 Add 22.5 mL the same volume (60.1 mL) of 1 M solution of cupriethylene-diamine.cupriethylene-diamine that was
previously added of distilled water.
10.1.2.8 Add a number of glass balls so that, when the stopper with capillary tube, and so forth, is fitted, the liquid will entirely
fill the flask and reach the bore of the cock. Do not allow any pieces of paper to enter the capillary, for such paper will not be
dissolved.
10.1.2.9 Close the cock.cock or initiate nitrogen flow.
10.1.2.10 Allow the specimen to dissolve with mechanical stirring as described in 7.1.4. The preferred solution time is 2 h;
however, when the specimen is not satisfactorily dissolved, increase the solution time may be increased to a maximum of 18 h.
For a specimen of an aged paper, there is little risk of further measurable degradation due to this increase of solution time.
10.1.3 Measurement of Viscosity:
10.1.3.1 After the period of stirring and before filling the viscometer, allow the solution to stand for 1 h at the temperature of
measurement, 20 6 0.1°C.20 °C 6 0.1 °C.
10.1.3.2 Take the required volume of solution and transfer it to the viscometer reservoir. Assemble the viscometer and place the
assembly in the thermostatic bath.
10.1.3.3 Wait 15 min before beginning the measurements. Then raise the liquid level above the upper mark of the viscometer either
by means of air pressure or slight vacuum. Measure the efflux time between the upper and lower marks. Make three successive
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measurements. The difference between the maximum and minimum time of flow shall be less than 0.5 s. 0.5 s. If this repeatability
is not achieved, clean the viscometer as described in 10.1.4. Take a second specimen of the solution that has been kept at the
measurement temperature and make a further series of three measurements. If again the difference is not less than 0.5 s, 0.5 s, take
a new specimen of paper and prepare a fresh solution.
10.1.3.4 Under the same conditions, measure the flow time of the solvent. This shall be between 9090 s and 110 s for the
viscometer constant C stated in 6.2 (0.00010 ≤ C ≤ 0.00013).
10.1.4 Cleaning the Viscometer:
10.1.4.1 By aspiration, fill the tube with chromic-acid mixture and immediately empty it again.
10.1.4.2 Rinse thoroughly with distilled water.
10.1.4.3 Rinse twice with acetone or alcohol.
10.1.4.4 Dry by means of compressed gas from a cylinder or dust-and-oil-free compressed air.
10.1.5 Make all tests in duplicate, making up two separate solutions from separately weighed specimens.
10.2 Determination of Water Content of Paper:
10.2.1 Test Specimen:
10.2.1.1 Weigh to the nearest milligram approximately 2 g of paper in equilibrium with the controlled-humidity atmosphere, and
in a closed weighing container that has been dried and tared.
10.2.1.2 If the paper sample is too small for 2 g 2 g to be reserved for determining its water content, use a smaller specimen.
However, if the amount of paper is only sufficient for the viscometric measurements, its water content is deduced from the moisture
equilibrium curves and the relative humidity of the conditioning atmosphere with which the paper was in equilibrium. If
equilibrium curves are not available for the particular paper tested, the following average values are used as a first approximation
for temperatures between 20 and 27°C.20 °C and 27 °C.
Relative Humidity of Air, % Water Content of Air, %
50 6
65 8
10.2.2 Measurement of Water Content:
10.2.2.1 After weighing, open the container and place it, with the weighed test specimen and its cap, in the oven and heat at 105
6 2°C105 °C 6 2 °C until it reaches constant mass. This will normally require from 44 h to 18 h.
10.2.2.2 After drying, replace the cap on the container and allow it to cool in a desiccator for about 45 min. After cooling, equalize
the air pressures inside and outside the container by raising and lowering the cap quickly. Weigh the container with the specimen.
10.2.3 Alternative procedures are suitable for use to determine the water content of the paper sample provided that it can be
verified that the procedure used will give results that differ from the results used in 10.2.2 by no more than 0.5 %.
11. Calculation
11.1 Concentration, c, of Dry Paper in the Solution:
11.1.1 The water content H of the paper, as a proportion of the dry weight, is as follows:
H 5 M 2 M /M (5)
~ !
0 0
D
...