prEN ISO 1628-2

• Abstract:

  1.1 This document specifies conditions for the determination of the reduced viscosity (also known as viscosity number) and K-value of PVC resins. It is applicable to resins in powder form which consist of homopolymers of the monomer vinyl chloride and copolymers, terpolymers, etc., of vinyl chloride with one or more other monomers, but where vinyl chloride is the main constituent. The resins may contain small amounts of unpolymerized substances (e.g. emulsifying or suspending agents, catalyst residues, etc.) and other substances added during the course of the polymerization. This document is not applicable, however, to resins having a volatile-matter content in excess of 0,5 % ± 0,1 %, when determined in accordance with ISO 1269. In addition to this, it is not applicable to resins which are not entirely soluble in cyclohexanone.; 1.2 The reduced viscosity and K-value of a particular resin are related to its molecular mass, but the relationship varies depending on the concentration and type(s) of other monomer(s) present. Hence, homopolymers and copolymers having the same reduced viscosity or K-value might not have the same molecular mass.; 1.3 The values determined for reduced viscosity and K-value, for a particular sample of PVC resin, are influenced differently by the concentration of the solution chosen for the determination. Hence the use of the procedures described in this document only gives values for reduced viscosity and K-value that are comparable when the concentrations of the solutions used are identical.; 1.4 Limiting viscosity number is not used for PVC resins.; 1.5 The experimental procedures described in this document can also be used to characterize the polymeric fraction obtained during the chemical analysis of a PVC composition. However, the values calculated for the reduced viscosity and K-value in these circumstances might not indicate the actual values for the resin used to produce the composition because of the impure nature of the recovered polymer fraction.

• Status: Not Published
• Publication Date: 11-Jan-2028
• ICS: 83.080.20 - Thermoplastic materials
• Technical Committee: CEN/TC 249 - Plastics
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 08-Sep-2026
• Completion Date: 08-Sep-2026
• Ref Project: oSIST prEN ISO 1628-2:2026 - Plastics - Determination of the viscosity of polymers in dilute solution using capillary viscometers - Part 2: Poly(vinyl chloride) resins (ISO/DIS 1628-2:2026)

• Revises: EN ISO 1628-2:2020 - Plastics - Determination of the viscosity of polymers in dilute solution using capillary viscometers - Part 2: Poly(vinyl chloride) resins (ISO 1628-2:2020)
• Effective Date: 18-Dec-2024

Overview

prEN ISO 1628-2:2026 titled Plastics - Determination of the viscosity of polymers in dilute solution using capillary viscometers - Part 2: Poly(vinyl chloride) resins is a draft standard developed by CEN and ISO. This document establishes standardized conditions for determining the reduced viscosity (also known as viscosity number) and K-value of poly(vinyl chloride) (PVC) resins in powder form. The standard covers both homopolymer and copolymer forms of vinyl chloride, provided the vinyl chloride monomer is the primary component. Accurate measurement of these properties is essential for quality control and characterizing the molecular properties of PVC materials in industrial applications.

Key Topics

• Scope and Applicability

  • Applies to PVC resins in powder form, consisting predominantly of vinyl chloride.
  • Also covers copolymers and terpolymers where vinyl chloride is the main monomer.
  • Excludes resins with volatile matter content above 0.5% (as per ISO 1269) and those not completely soluble in cyclohexanone.

• Test Methods

  • Efflux time method: Utilizes a Ubbelohde or equivalent capillary viscometer to measure the flow times of dilute polymer solutions.
  • Differential pressure method: Based on measuring differential pressures in capillary tubing for both solvent and polymer solution.

• Key Results

  • Reduced viscosity (viscosity number) and K-value are determined, which are indicators of the polymer's molecular characteristics.
  • Both results are meaningful only if the test solution concentrations used in the determination are identical.

• Standardization Features

  • Procedures for solution preparation, equipment calibration, and data expression to ensure comparability.
  • Provides conversion tables for viscosity ratio to reduced viscosity and K-value.
  • Requires documentation of the specific method, instrument used, and any deviations from the standard procedure.

Applications

• Quality Control

  • Used by manufacturers and processors to verify the consistency and molecular characteristics of PVC resins.
  • K-value and reduced viscosity are critical for assessing processability and end-use performance.

• Product Development

  • Helps researchers and product developers understand the relationship between polymer molecular structure and product behavior.
  • Facilitates formulation of PVC compounds for various applications by providing standardized metrics.

• Chemical Analysis

  • The procedures may also be applied for characterizing polymer fractions obtained during the chemical analysis of complex PVC compositions, enabling assessment of material purity and composition variability.

• Regulatory Compliance

  • Following standardized test procedures assists in meeting global regulatory requirements and facilitates international trade of PVC resins.

Related Standards

• ISO 1628-1:2024
  Plastics - Determination of the viscosity of polymers in dilute solution using capillary viscometers - Part 1: General principles

• ISO 1269:2006
  Plastics - Homopolymer and copolymer resins of vinyl chloride - Determination of volatile matter (including water)

• Other Parts of ISO 1628 Series
  Covering determination of viscosity for other types of polymers using similar methodologies.

Practical Value

Implementing prEN ISO 1628-2 ensures consistent, reproducible measurement of PVC resin viscosity and K-value, supporting quality assurance throughout the supply chain. This standard is vital for industries dealing with PVC-based products such as piping, profiles, films, and cables, where material performance depends on precise molecular characteristics. Adhering to this internationally recognized standard not only streamlines product specification and comparison but also underpins compliance in regulated markets.

For laboratories, manufacturers, and quality control professionals, the adoption of prEN ISO 1628-2 delivers accurate, comparable polymer viscosity data. This is crucial for efficient production, product innovation, and successful entry to global markets for PVC materials and products.

SLOVENSKI STANDARD
01-september-2026
Polimerni materiali - Ugotavljanje viskoznosti polimerov v razredčenih raztopinah
s kapilarnimi viskozimetri - 2. del: Polivinilklorid (ISO/DIS 1628-2:2026)
Plastics - Determination of the viscosity of polymers in dilute solution using capillary
viscometers - Part 2: Poly(vinyl chloride) resins (ISO/DIS 1628-2:2026)
Kunststoffe - Bestimmung der Viskosität von Polymeren in verdünnter Lösung unter
Verwendung von Kapillarviskosimetern - Teil 2: Vinylchlorid-Polymere (ISO/DIS 1628-
2:2026)
Plastiques - Détermination de la viscosité des polymères en solution diluée à l'aide de
viscosimètres à capillaires - Partie 2: Résines de poly(chlorure de vinyle) (ISO/DIS 1628-
2:2026)
Ta slovenski standard je istoveten z: prEN ISO 1628-2
ICS:
83.080.20 Plastomeri Thermoplastic materials
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 1628-2
ISO/TC 61/SC 9
Plastics — Determination of
Secretariat: KATS
the viscosity of polymers in
Voting begins on:
dilute solution using capillary
2026-06-16
viscometers —
Voting terminates on:
2026-09-08
Part 2:
Poly(vinyl chloride) resins
Plastiques — Détermination de la viscosité des polymères en
solution diluée à l'aide de viscosimètres à capillaires —
Partie 2: Résines de poly(chlorure de vinyle)
ICS: 83.080.20
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 1628-2:2026(en)
DRAFT
ISO/DIS 1628-2:2026(en)
International
Standard
ISO/DIS 1628-2
ISO/TC 61/SC 9
Plastics — Determination of
Secretariat: KATS
the viscosity of polymers in
Voting begins on:
dilute solution using capillary
2026-06-16
viscometers —
Voting terminates on:
2026-09-08
Part 2:
Poly(vinyl chloride) resins
Plastiques — Détermination de la viscosité des polymères en
solution diluée à l'aide de viscosimètres à capillaires —
Partie 2: Résines de poly(chlorure de vinyle)
ICS: 83.080.20
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 1628-2:2026(en)
ii
ISO/DIS 1628-2:2026(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
4.1 Efflux time method .2
4.2 Differential pressure method .2
5 Materials . 2
6 Apparatus . 2
6.1 Efflux time method .2
6.2 Differential pressure method .3
7 Sampling . 3
8 Number of determinations . 3
9 Procedure . 3
9.1 Preparation of solution .3
9.2 Efflux time method: determination of efflux times .4
9.3 Differential pressure method .4
10 Expression of results . 4
10.1 Reduced viscosity .4
10.2 K-value .5
11 Precision . 5
12 Test report . 6
Annex A (informative) Conversion of viscosity ratio (VR) to reduced viscosity (I) and K-value . 7

iii
ISO/DIS 1628-2:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent
rights identified during the development of the document will be in the Introduction and/or on the ISO list of
patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 9, Thermoplastic
materials, in collaboration with the European Committee for Standardization (CEN) Technical Committee
CEN/TC 249, Plastics, in accordance with the Agreement on technical cooperation between ISO and CEN
(Vienna Agreement).
This fourth edition cancels and replaces the third edition, which has been technically revised.
The main change is the incorporation of an alternative procedure, the differential pressure method
(following same change in ISO 1628-1:2024), based on comparing the differential pressure in capillary
tubing due to the flow of polymer solution and neat solvent simultaneously.
A list of all parts in the ISO 1628 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
DRAFT International Standard ISO/DIS 1628-2:2026(en)
Plastics — Determination of the viscosity of polymers in
dilute solution using capillary viscometers —
Part 2:
Poly(vinyl chloride) resins
1 Scope
1.1 This document specifies conditions for the determination of the reduced viscosity (also known
as viscosity number) and K-value of PVC resins. It is applicable to resins in powder form which consist of
homopolymers of the monomer vinyl chloride and copolymers, terpolymers, etc., of vinyl chloride with one
or more other monomers, but where vinyl chloride is the main constituent. The resins can contain small
amounts of unpolymerized substances (e.g. emulsifying or suspending agents, catalyst residues, etc.) and
other substances added during the course of the polymerization. This document is not applicable, however,
to resins having a volatile-matter content in excess of 0,5 % ± 0,1 %, when determined in accordance
with ISO 1269:2006. In addition to this, it is not applicable to resins which are not entirely soluble in
cyclohexanone.
1.2 The reduced viscosity and K-value of a particular resin are related to its molecular mass, but the
relationship varies depending on the concentration and type(s) of other monomer(s) present. Hence,
homopolymers and copolymers having the same reduced viscosity or K-value can have different molecular
masses.
1.3 The values determined for reduced viscosity and K-value, for a particular sample of PVC resin, are
influenced differently by the concentration of the solution chosen for the determination. Hence the use
of the procedures specified in this document only gives values for reduced viscosity and K-value that are
comparable when the concentrations of the solutions used are identical.
1.4 The experimental procedures specified in this document can also be used to characterize the polymeric
fraction obtained during the chemical analysis of a PVC composition. However, the values calculated for the
reduced viscosity and K-value in these circumstances can deviate form the correct values for the resin used
to produce the composition because of the impure nature of the recovered polymer fraction.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 1269:2006, Plastics — Homopolymer and copolymer resins of vinyl chloride — Determination of volatile
matter (including water)
ISO 1628-1:2024, Plastics — Determination of the viscosity of polymers in dilute solution using capillary
viscometers — Part 1: General principles
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1628-1:2024 apply.

ISO/DIS 1628-2:2026(en)
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Principle
4.1 Efflux time method
A test portion shall be dissolved in a solvent. The reduced viscosity and the K-value shall be calculated from
the efflux times for the solvent and the solution in a Ubbelohde viscometer.
4.2 Differential pressure method
A test portion shall be dissolved in a solvent. The reduced viscosity and the K-value shall be calculated from
the differential pressures for the solvent and the solution in a relative viscometer.
5 Materials
−6 2 –1
Cyclohexanone, having a viscosity/density ratio (kinematic viscosity) between 2,06 × 10 m s and
−6 2 –1 2 –1 2 –1
2,33 × 10 m s (2,06 mm s and 2,33 mm s ) at 25 °C. The specified boiling point shall be 155 °C.
The solvent shall be stored in the dark in a dark-coloured bottle fitted with a ground-glass stopper. The
kinematic viscosity shall be checked before use.
6 Apparatus
6.1 Efflux time method
6.1.1 The apparatus required to carry out viscosity measurements on polymers in dilute solution shall be
in accordance with ISO 1628-1:2024, Clause 5. In addition, the following particular items are required for the
procedures specified in this document.
6.1.2 Viscometer. The viscometer model 1C specified in ISO 1628-1:2024, shall be used as the reference
viscometer.
Other viscometers specified in ISO 1628-1:2024 may be used provided the correlation between the chosen
viscometer and the reference viscometer has been established over the range of reduced viscosities and
K-values to be measured, and the results are corrected accordingly.
6.1.3 Graduated flask (one-mark volumetric flask), class A, as specified in ISO 1042, with a volume of
50 ml.
NOTE The use of a flask calibrated at a temperature of 20 °C, as specified in ISO 1042, causes a systematic error
which can, however, be neglected.
6.1.4 Filter funnel, with fritted-glass filter disc of medium porosity (pore size 40 µm to 50 µm), or glass
funnel with paper filter.
6.1.5 Mechanical agitator, equipped with a heating device to keep the flask (6.1.3) and its contents at a
temperature between 80 °C and 85 °C.
As an alternative, a rotary agitator or shaker may be placed in an oven at a temperature between 80 °C and
85 °C.
ISO/DIS 1628-2:2026(en)
6.1.6 Analytical balance, accurate to 0,1 mg.
6.1.7 Temperature-regulated bath, capable of being set at 25,0 °C ± 0,5 °C in steps of 0,1 °C and
maintaining a stability of ± 0,05 °C around the set temperature.
6.1.8 Thermometer, capable of reading to 0,05 °C in the range to be used and in a known state of
calibration, is suitable. Other thermometric devices of at least equal precision may be used.
6.1.9 Time-measuring device, with a sensitivity of 0,1 s.
6.2 Differential pressure method
6.2.1 Analytical balance, accurate to 0,1 mg.
6.2.2 A schematic diagram of a relative viscometer used in this method is depicted in ISO 1628-1:2024.
The reference/solvent capillary and the measurement/polymer solution capillary shall be kept at the same
temperature of 25 °C, enclosed in a proper temperature-controlled device with variations from the specified
temperature lower than ± 0,2 K. The nominal inside diameter of the capillaries shall be 0,5 mm, or 0,75 mm,
and length 80 mm to 600 mm.
7 Sampling
A sample shall be taken which is representative of the resin whose properties are to be determined and
which is large enough for at least two determinations.
8 Number of determinations
Two complete determinations shall be carried out, starting each with a fresh test portion.
9 Procedure
9.1 Preparation of solution
General requirements for the dissolution of polymer in solvent are given in ISO 1628-1:2024. A solution shall
3 3
be prepared with a concentration of 5 kg/m ± 0,1 kg/ m at 25 °C ± 1 °C, as follows.
0,250 g ± 0,005 g of resin shall be weighed to the nearest 0,2 mg, and transferred quantitatively to the
50 ml flask (6.1.3). About 40 ml of cyclohexanone shall be added (Clause 5) to the flask, swirling the flask by
hand to prevent coagulation or the formation of lumps. The dissolution shall be continued by agitating for
1 h between 80 °C and 85 °C using the agitator (6.1.5). The completion of the dissolution shall be checked
visually. If gelatinized particles are still visible, the procedure shall be started again with a new portion of
the resin. The solution shall be cooled to 25 °C ± 1 °C and made up to the mark with cyclohexanone at the
same temperature. The solution shall be mixed thoroughly by shaking.
The actual concentration of the solution shall be checked to an accuracy of ± 0,1 %.
If a mass of 0,250 g ± 0,000 25 g is taken and made up to 50 ml of solution as described above, Table A.1 in
Annex A may be used to read off the reduced viscosity and K-value from the ratio of the efflux time of the
solution to that of the solvent (the so-called viscosity ratio).
Alternative methods for the preparation of the solution may be used, for example the addition of a measured
volume of solvent to a measured mass of test portion, provided that the values obtained for the reduced
viscosity and K-value can be shown to be equivalent to those obtained with the method of solution
preparation described above. Such alternative methods of solution preparation requires the amounts of

ISO/DIS 1628-2:2026(en)
solvent and test portion taken to be determined by experiment, and can also require compensation for loss
of solvent by evaporation during the dissolution process.
With resins having K-values greater than 85, the ratio of the efflux time of the solution to that of the solvent
will exceed the maximum value of 2,0, which is contrary to the requirement specified in ISO 1628-1:2024.
In order to ensure uniformity of testing for PVC, this non-conformity shall be ignored, and all currently
available resins shall be tested using the same test-portion mass.
9.2 Efflux time method: determination of efflux times
The procedure is specified in ISO 1628-1:2024.
The temperature of the thermostat (6.1.7) shall be set such that the actual temperature which is measured
by the thermometer (6.1.8) lies in the range 25 °C ± 0,5 °C. The measured temperature shall be stable to
±0,05 °C around the temperature at which the thermostat has been set.
When filling the viscometer, the solvent and the solution shall be filtered using a filter funnel or a glass
funnel and paper filter (see 6.1.4).
Particular care shall be taken over viscometer cleaning, which shall be based on the procedure specified in
ISO 1628-1:2024. Efflux times with the control solvent cyclohexanone shall remain constant to within 0,2 s
for a given viscometer. With the solution, the measurement of the efflux time shall be repeated until two
successive measurements differ by less than 0,25 %. The first efflux time reading shall always be discarded.
NOTE This is a manual procedure. Proprietary equipment is available which will organize the charging of the
viscometer with solution and solvent and measure the respective efflux times automatically. The use of such equipment
is included in the scope of this document provided that all the procedures and verification checks described above are
followed by the automated procedure.
9.3 Differential pressure method
In general, automated sample preparation is used with this method. The guidelines for time and temperature
as in 9.1 shall be used.
The general procedure as specified in ISO 1628-1:2024 shall be followed, with reference to the manufacturer
instructions in case of automated systems, to obtain the value of the viscosity ratio increment for the tested
solution. A flow rate of 0,5 to 3,0 ml/min shall be applied for the determination.
10 Expression of results
10.1 Reduced viscosity
In the efflux time method the reduced viscosity, I, shall be calculated for each test portion as specified in
ISO 1628-1:2024, using Formula (1):
(1)
where
t and t are the efflux times, in seconds, of the solution and solvent, respectively;
3 3 3
c is the concentration of the solution, in 10 kg/m , i.e. g/cm .
The reduced viscosity I for the sample shall be calculated as the mean value of the two individual values
obtained in the two determinations, expressing the result to the nearest whole number. If the I values
obtained in the two determinations deviate by more than ± 0,4 % from the mean value, these results shall be
rejected and further determinations carried out with fresh test portions.
3 3
If the solution concentration is 5 kg/m ± 0,005 kg/m , it is more convenient to read off the values of I from
3 −3 3
Table A.1, expressing I in (m /kg) · 10 , i.e. cm /g, rounded to the first place of decimals.

ISO/DIS 1628-2:2026(en)
When the differential pressure method is applied, calculate the reduced viscosity I using the calculated
solution viscosity ratio increment according to Formula (2):
(2)
where
η is the viscosity ratio increment of the tested polymer solution;
sp
c is the concentration of the polymer, in grams per millilitre of solution.
Or from the viscosity ratio increment peak area according to Formula (3):
(3)
where
A(η (V)) is peak area of the continuous viscosity ratio increment signal as a function of elution volume,
sp
V;
M is the mass of polymer injected into the measurement capillary.
inj
10.2 K-value
For each test portion, the K-value shall be calculated as specified in ISO 1628-1:2024, using Formula (4):
(4)
where
is the ratio of the viscosities (efflux times) of the solution and solvent;
t and t are the efflux times, in seconds, of the solution and solvent, respectively;
3 3 3
c is the concentration of the solution, in 10 kg/m , i.e. g/cm .
The K-value for the sample shall be calculated as the mean value of the two individual K-values obtained in
the two determinations, expressing the result to the first place of decimals. If the K-values obtained in the
two determinations deviate by more than ± 0,4 % from the mean value, these results shall be rejected and
further determinations carried out with fresh test portions.
3 3
If the solution concentration is 5 kg/m ± 0,005 kg/m , it is more convenient to read off the K-value from
Table A.1, rounding to the second place of decimals.
11 Precision
Inter laboratory trials were conducted on three resins in 11 laboratories on four different dates. These inter
laboratory trials gave the following results for the repeatability standard deviation s (within the same
r
laboratory) and the reproducibility standard deviation s (among different laboratories).
R
See Table 1.
Table 1 — Results for s , s of K-value and reduced viscosity
r R
K-value Reduced viscosity
Approximately Approximately Approximately Approximately Approximately Approximately
50 70 90 61 124 227
s 0,132 0,115 0,120 0,313 0,458 0,742
r
s 0,420 0,291 0,495 0,984 1,202 3,042
R
ISO/DIS 1628-2:2026(en)
12 Test report
The test report shall include the following information:
a) a reference to this document, including the year of publication;
b) all details necessary
...