oSIST prEN ISO 1628-3:2026
(Main)Plastics - Determination of the viscosity of polymers in dilute solution using capillary viscometers - Part 3: Polyethylenes and polypropylenes (ISO/DIS 1628-3:2026)
- Abstract
ISO 1628-3:2010 defines particular conditions for determining the reduced viscosity (also known as viscosity number) and intrinsic viscosity of polyethylenes and polypropylenes at 135 °C in dilute solution.
The viscosity of polymer solutions may be affected by additives present in the sample. The value of a reduced viscosity determined by this method may therefore be unreliable if the sample contains fillers or other additives.
- Status
- Not Published
- Public Enquiry End Date
- 04-Sep-2026
- Technical Committee
- IPMA - Polimer materials and products
- Current Stage
- 4020 - Public enquire (PE) (Adopted Project)
- Start Date
- 14-Jul-2026
- Due Date
- 01-Dec-2026
- Completion Date
- 07-Sep-2026
oSIST prEN ISO 1628-3:2026 is a SIST draft aligned with ISO/DIS 1628-3:2026 for plastics testing. It specifies how to determine the reduced viscosity, also called viscosity number, and intrinsic viscosity of polyethylenes and polypropylenes in dilute solution using capillary viscometers.
The document is aimed at laboratories, quality teams, and buyers who need comparable viscosity data for PE and PP materials. It covers both a manual efflux time method and an alternative differential pressure method.
What does oSIST prEN ISO 1628-3:2026 specify?
oSIST prEN ISO 1628-3:2026 defines the test conditions for polyethylenes and polypropylenes in dilute solution at elevated temperature. It also warns that fillers and other additives can make the reduced viscosity result unreliable, so filled or modified materials need careful interpretation.
The document is organized into clauses 1 to 10 plus a bibliography. Clause 4 explains the principle, clause 5 covers solvents, clause 6 the apparatus, clause 7 the test sample, clause 8 the procedure, clause 9 the expression of results, and clause 10 the test report.
What are the key requirements of oSIST prEN ISO 1628-3:2026?
Test conditions and method choice
Clause 4 states that ethylene polymers and isotactic polypropylenes are not soluble at room temperature in known solvents, so the dissolution and test temperatures must be chosen to avoid precipitation. That matters because any precipitation changes the effective concentration and distorts the viscosity result.
oSIST prEN ISO 1628-3:2026 offers two procedures:
- Method A - Efflux time method measures the flow times of solvent and polymer solution in an Ubbelohde viscometer at 135 °C.
- Method B - Differential pressure method measures pressure differences across paired capillaries at the same elevated temperature.
Solvent control and sample preparation
Clause 5 makes decahydronaphthalene the reference solvent for the manual method and allows chlorinated solvents such as 1,2-dichlorobenzene and 1,2,4-trichlorobenzene. It also requires antioxidant addition and filtration, which helps keep the solvent and solution stable during high-temperature testing.
Clause 7 requires dry powder or very small pieces. Manufactured articles may be tested as a whole, or as separate surface and interior portions when the viscosity may vary through the part. This is important for molded parts and for materials that may be affected by crosslinking.
Apparatus and measurement setup
Clause 6 specifies the equipment needed: thermostatic baths at 135 °C and 20 °C, a temperature-measuring device, timer, analytical balance, shaker, and the appropriate viscometer. For the efflux time method, the standard recommends an Ubbelohde viscometer of specific sizes; for the differential pressure method, it uses a relative viscometer with two capillaries at the same temperature.
The differential pressure method allows a larger capillary for PE-UHMW and PP-UHMW, which helps with high-viscosity materials. That is useful when flow is slow and pressure readings need to stay stable.
Procedure, calculation, and reporting
Clause 8 controls solution concentration and dissolution time. The chosen concentration must give flow times in the specified range, and the solution must be clear enough for testing; if dissolution takes more than 2 h, that has to be reported.
Clause 9 gives the calculation of reduced viscosity and intrinsic viscosity, including the Solomon-Ciutà formula as an option for intrinsic viscosity. The calculated values are rounded to the nearest whole number. Clause 9.3 also states that the precision is not known from inter-laboratory data, so the method should be used carefully in specifications or disputes.
Clause 10 requires a report that identifies the material, the method used, solvent and temperature, sample preparation, whether filtration was used, the results, and any deviations from the procedure.
What terms does oSIST prEN ISO 1628-3:2026 define?
- Reduced viscosity / viscosity number - the viscosity value calculated from the solution measurement and reported in mL/g; the note also calls it the Staudinger function (Jg).
- Intrinsic viscosity - the extrapolated viscosity measure, written [η], used to compare polymer samples; the note also calls it the Staudinger index (J).
- Efflux time method - the manual procedure that compares solvent and solution flow times in an Ubbelohde viscometer.
- Differential pressure method - the alternative procedure that uses pressure differences across two capillaries to determine viscosity.
- Viscosity ratio increment, ηsp - the measured signal used in the differential pressure method to calculate reduced viscosity.
- Decahydronaphthalene - the reference solvent for the manual procedure, stabilized with antioxidant before use.
Who uses oSIST prEN ISO 1628-3:2026?
This standard is used by plastics laboratories, polymer producers, compounders, and third-party test houses that measure the viscosity of PE and PP materials. Quality managers and buyers use it to compare supplier data, check batch consistency, and document material identity. It is also relevant for testing molded or extruded articles when viscosity may differ between the surface and the interior.
What changed in oSIST prEN ISO 1628-3:2026 from the previous edition?
This fourth edition cancels and replaces the third edition. The main change stated in the foreword is the addition of the differential pressure method, following the same change made in ISO 1628-1:2024.
Which standards are used with oSIST prEN ISO 1628-3:2026?
- ISO 1628-1:2024 - provides the general principles for dilute-solution viscosity testing with capillary viscometers and is the main companion part for this method.
- ISO 3105:1994 - gives the specifications and operating instructions for glass capillary kinematic viscometers used in the efflux time method.
- ISO 1628 series - the foreword lists the other related parts: PVC resins, polycarbonate materials, thermoplastic polyester materials, and methyl methacrylate polymers.
What does the oSIST prEN ISO 1628-3:2026 document contain?
The document includes the test principle, solvent guidance, apparatus requirements, sample preparation, and procedures for both the efflux time and differential pressure methods. It also contains concentration guidance tables, formulas for mass, reduced viscosity, and intrinsic viscosity, and a test report checklist.
It refers to figure-based apparatus layouts and to cleaning instructions in Annex C of ISO 1628-1:2024. The bibliography cites the Solomon and Ciutà paper used for the intrinsic viscosity relationship.
Relations
- Effective Date
- 18-Dec-2024
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Frequently Asked Questions
oSIST prEN ISO 1628-3:2026 is a draft published by the Slovenian Institute for Standardization (SIST). Its full title is "Plastics - Determination of the viscosity of polymers in dilute solution using capillary viscometers - Part 3: Polyethylenes and polypropylenes (ISO/DIS 1628-3:2026)". This standard covers: ISO 1628-3:2010 defines particular conditions for determining the reduced viscosity (also known as viscosity number) and intrinsic viscosity of polyethylenes and polypropylenes at 135 °C in dilute solution. The viscosity of polymer solutions may be affected by additives present in the sample. The value of a reduced viscosity determined by this method may therefore be unreliable if the sample contains fillers or other additives.
ISO 1628-3:2010 defines particular conditions for determining the reduced viscosity (also known as viscosity number) and intrinsic viscosity of polyethylenes and polypropylenes at 135 °C in dilute solution. The viscosity of polymer solutions may be affected by additives present in the sample. The value of a reduced viscosity determined by this method may therefore be unreliable if the sample contains fillers or other additives.
oSIST prEN ISO 1628-3:2026 is classified under the following ICS (International Classification for Standards) categories: 83.080.20 - Thermoplastic materials. The ICS classification helps identify the subject area and facilitates finding related standards.
oSIST prEN ISO 1628-3:2026 has the following relationships with other standards: It is inter standard links to SIST EN ISO 1628-3:2012. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
oSIST prEN ISO 1628-3:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2026
Polimerni materiali - Ugotavljanje viskoznosti polimernih materialov v razredčeni
raztopini z uporabo kapilarnega viskozimetra - 3. del: Polietileni in polipropileni
(ISO/DIS 1628-3:2026)
Plastics - Determination of the viscosity of polymers in dilute solution using capillary
viscometers - Part 3: Polyethylenes and polypropylenes (ISO/DIS 1628-3:2026)
Kunststoffe - Bestimmung der Viskosität von Polymeren in verdünnter Lösung durch ein
Kapillarviskosimeter - Teil 3: Polyethylen und Polypropylen (ISO/DIS 1628-3:2026)
Plastiques - Détermination de la viscosité des polymères en solution diluée à l'aide de
viscosimètres à capillaires - Partie 3: Polyéthylènes et polypropylènes (ISO/DIS 1628-
3:2026)
Ta slovenski standard je istoveten z: prEN ISO 1628-3
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 1628-3
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 3:
Polyethylenes and polypropylenes
Plastiques — Détermination de la viscosité des polymères en
solution diluée à l'aide de viscosimètres à capillaires —
Partie 3: Polyéthylènes et polypropylènes
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
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This document is circulated as received from the committee secretariat.
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Reference number
ISO/DIS 1628-3:2026(en)
DRAFT
ISO/DIS 1628-3:2026(en)
International
Standard
ISO/DIS 1628-3
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 3:
Polyethylenes and polypropylenes
Plastiques — Détermination de la viscosité des polymères en
solution diluée à l'aide de viscosimètres à capillaires —
Partie 3: Polyéthylènes et polypropylènes
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
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Published in Switzerland Reference number
ISO/DIS 1628-3:2026(en)
ii
ISO/DIS 1628-3:2026(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 General .1
4.2 Method A – Efflux time method . .1
4.3 Method B – Differential pressure method.2
5 Solvent . 2
6 Apparatus . 2
6.1 Efflux time method .2
6.2 Differential pressure method .4
7 Test sample . 5
8 Procedure . 5
8.1 Efflux time method .5
8.1.1 Cleaning the viscometer .5
8.1.2 Measurement of efflux time of solvent .5
8.1.3 Choice of polymer solution concentration .5
8.1.4 Preparation of the solution .6
8.1.5 Measurement of efflux time of solution .7
8.2 Differential pressure method .7
8.2.1 Choice of polymer solution concentration .7
8.2.2 Viscosity ratio increment . . .7
8.2.3 Determination of the polymer solution concentration .7
9 Expression of results . 8
9.1 Reduced viscosity, I .8
9.2 Intrinsic viscosity, [η] .8
9.3 Precision . . .9
10 Test report . 9
Bibliography .10
iii
ISO/DIS 1628-3:2026(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 1628-3 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 9, Thermoplastic
materials.
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.
ISO 1628 consists of the following parts, under the general title Plastics — Determination of the viscosity of
polymers in dilute solution using capillary viscometers:
— Part 1: General principles
— Part 2: Poly(vinyl chloride) resins
— Part 3: Polyethylenes and polypropylenes
— Part 4: Polycarbonate (PC) moulding and extrusion materials
— Part 5: Thermoplastic polyester (TP) homopolymers and copolymers
— Part 6: Methyl methacrylate polymers
iv
DRAFT International Standard ISO/DIS 1628-3:2026(en)
Plastics — Determination of the viscosity of polymers in
dilute solution using capillary viscometers —
Part 3:
Polyethylenes and polypropylenes
1 Scope
This part of ISO 1628 defines particular conditions for determining the reduced viscosity (also known as
viscosity number) and intrinsic viscosity of polyethylenes and polypropylenes at elevated temperatures
(135 °C – 160 °C) in dilute solution.
The viscosity of polymer solutions can be affected by fillers or additives present in the sample. The value of
a reduced viscosity determined by this method can therefore be unreliable if the sample contains fillers or
other additives.
NOTE Reduced viscosity is also known as the Staudinger function (J ) and intrinsic viscosity as the Staudinger
v
index (J ).
g
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 1628-1:2024, Plastics — Determination of the viscosity of polymers in dilute solution using capillary
viscometers — Part 1: General principles
ISO 3105:1994, Glass capillary kinematic viscometers — Specifications and operating instructions
3 Terms and definitions
There are no terms and definitions in this document.
4 Principle
4.1 General
Ethylene polymers and isotactic polypropylenes are not soluble at room temperature in any known solvents.
Precautions shall therefore be taken during the test to avoid any precipitation of polymer, which would give
an incorrect solution concentration.
The dissolution and test temperatures shall be chosen with the above precautions.
4.2 Method A – Efflux time method
The times of flow of a solvent and a solution of polymer at a specified concentration in that solvent are
measured at elevated temperature. The reduced viscosity and intrinsic viscosity are calculated from
these measurements and from the known concentration of the solution, using an appropriate Ubbelohde
viscometer.
ISO/DIS 1628-3:2026(en)
4.3 Method B – Differential pressure method
The differential pressure across each of the 2 capillaries connected in series, one of them receiving the
solvent having the differential pressure ∆p , the other receiving the polymer solution having the differential
pressure ∆p, are measured at elevated temperature. The reduced viscosity and intrinsic viscosity are
calculated from these measurements and from the known concentration of the solution.
5 Solvent
5.1 The solution viscosity obtained by this method depends on the solvent used, although the solution
viscosities of polyolefin in different solvents are correlated. The reference solvent is decahydronaphtalene
which is primarily used in the manual efflux time method, while chlorinated solvents may be used and allow
the application of online concentration detectors in automated instruments.
5.2 Decahydronaphthalene, analytical-reagent grade, re-distilled at a temperature not higher than 65 °C
and a pressure of approximately 500 Pa; its per-oxidation shall be prevented by suitable means, for example
distilling in the presence
...