prEN ISO 1628-3
(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
- Publication Date
- 05-Dec-2027
- Technical Committee
- CEN/TC 249 - Plastics
- Current Stage
- 4060 - Closure of enquiry - Enquiry
- Start Date
- 08-Sep-2026
- Completion Date
- 08-Sep-2026
prEN ISO 1628-3 is the draft standard for determining the reduced viscosity, also called viscosity number, and intrinsic viscosity of polyethylenes and polypropylenes in dilute solution using capillary viscometers. It is aimed at laboratories, polymer producers, and quality teams that need a controlled way to compare PE and PP materials at elevated temperature. The document specifies the solvent, sample preparation, test methods, calculation steps, and reporting items needed to make the result usable in practice.
What does prEN ISO 1628-3 specify?
prEN ISO 1628-3 specifies how to measure the viscosity behaviour of polyethylenes and polypropylenes in dilute solution at elevated temperature, with the main scope covering 135 °C to 160 °C. It organizes the work from scope and references through principle, solvent, apparatus, sample preparation, procedure, result calculation, and test report.
The document is structured in Clauses 1 to 10:
- Clause 1 Scope
- Clause 2 Normative references
- Clause 3 Terms and definitions
- Clause 4 Principle
- Clause 5 Solvent
- Clause 6 Apparatus
- Clause 7 Test sample
- Clause 8 Procedure
- Clause 9 Expression of results
- Clause 10 Test report
What are the key requirements of prEN ISO 1628-3?
Sample, solvent, and temperature control
Clause 1 limits the method to polyethylenes and polypropylenes, and warns that fillers or additives can affect the solution viscosity. In practice, that means the method is best suited to clean polymer materials, not highly filled compounds.
Clause 4 states that these polymers do not dissolve at room temperature in known solvents, so dissolution and testing must be done at elevated temperature without precipitation. That matters because any precipitation changes the concentration and makes the result invalid.
Clause 5 sets decahydronaphthalene as the reference solvent for the manual efflux time method and allows chlorinated solvents such as 1,2-dichlorobenzene and 1,2,4-trichlorobenzene. The solvent must be stabilized with antioxidant and filtered, so the lab has to control oxidation as well as temperature.
Method A and Method B
Clause 4.2 defines the efflux time method: the laboratory measures the flow time of the solvent and the polymer solution in an Ubbelohde viscometer, then calculates reduced viscosity and intrinsic viscosity from those times and the known concentration. This is the classic manual route when a viscometer setup is available.
Clause 4.3 defines the differential pressure method: the laboratory measures differential pressure across two capillaries, one for solvent and one for polymer solution, and calculates the same viscosity results. This gives an alternative procedure for automated instruments and changes the way the flow signal is collected.
Clause 6 sets the apparatus for each method. For the efflux time method it specifies Ubbelohde viscometers, thermostatic baths, a timer, balance, shaker, flask, pipette, and filter funnel. For the differential pressure method it requires matched capillaries held at the same temperature, with larger capillaries for PE-UHMW or PP-UHMW when needed.
Concentration, preparation, and reporting
Clause 8 gives the concentration choices and preparation steps. For the efflux time method, the solution concentration is selected so the solution-to-solvent efflux time ratio stays in the stated range, and if the viscosity is unknown the method starts from a low concentration. For the differential pressure method, the concentration can be lower, and the instrument maker’s instructions guide the calculation of the injected mass or concentration.
Clause 7 requires dry powder or very small pieces. For manufactured articles, the standard allows either testing the whole article as a homogenized grind or testing surface and interior separately. That is important when the surface has a different history from the core.
Clause 9 gives the calculation of reduced viscosity and intrinsic viscosity and says to round the values to the nearest whole number. It also notes that precision is not established from interlaboratory data, so the method should be used carefully for disputes or strict specification work.
Clause 10 requires the report to identify the method, solvent, temperature, sample treatment, whether the solution was filtered, the result values, deviations, and unusual observations. In practice, this is what makes the test traceable and repeatable.
What terms does prEN ISO 1628-3 define?
- Reduced viscosity - the main calculated flow property from the test, reported in millilitres per gram and also called viscosity number.
- Intrinsic viscosity - the derived viscosity value used to characterize the polymer solution at low concentration.
- Efflux time method - the manual method based on measuring solvent and solution flow times in an Ubbelohde viscometer.
- Differential pressure method - the alternative method based on pressure difference across solvent and solution capillaries.
- Ubbelohde viscometer - the capillary viscometer recommended for the efflux time method.
- Decahydronaphthalene - the reference solvent named for the manual method, with antioxidant added before use.
- PE-UHMW / PP-UHMW - ultra-high molecular weight polyethylene and polypropylene, which may need larger capillaries and more careful dissolution.
Who uses prEN ISO 1628-3?
prEN ISO 1628-3 is used by polymer testing laboratories, quality control teams, and material developers working with polyethylene and polypropylene. It is relevant for producers checking batch consistency, laboratories comparing material grades, and buyers or specifiers who need a standardized viscosity test for incoming or outgoing material control. It also supports work on manufactured articles, especially when surface and core material may need separate assessment.
What changed in prEN ISO 1628-3 from the previous edition?
prEN ISO 1628-3 is the fourth edition and replaces the third edition. The main stated change is the addition of an alternative differential pressure method, aligned with the same change made in ISO 1628-1:2024.
Which standards are used with prEN ISO 1628-3?
- ISO 1628-1:2024 - provides the general principles for dilute-solution viscosity testing and supports the calculation and instrument framework used here.
- ISO 3105:1994 - gives specifications and operating instructions for the glass capillary kinematic viscometers referenced for the efflux time method.
What does the prEN ISO 1628-3 document contain?
The document contains the solvent guidance, apparatus descriptions, sample preparation rules, and step-by-step procedures for both the efflux time method and the differential pressure method. Table 1 lists recommended Ubbelohde viscometer sizes, Table 2 and Table 3 guide solution concentration selection for the two methods, and Clause 9 gives the formulas used to calculate reduced viscosity and intrinsic viscosity. It also includes the report content required to document the test in a traceable way.
Relations
- Effective Date
- 18-Dec-2024
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Frequently Asked Questions
prEN ISO 1628-3 is a draft published by the European Committee for Standardization (CEN). 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.
prEN ISO 1628-3 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.
prEN ISO 1628-3 has the following relationships with other standards: It is inter standard links to EN ISO 1628-3:2010. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
prEN ISO 1628-3 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
PUBLISHED AS SUCH.
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
...