ISO 16790:2021

INTERNATIONAL ISO
STANDARD 16790
Second edition
2021-02
Plastics — Determination of drawing
characteristics of thermoplastics in
the molten state
Plastiques — Détermination des caractéristiques d'étirage des
thermoplastiques à l'état fondu
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Apparatus . 3
5.1 Apparatus for heating the polymer and forming the extrudate . 3
5.1.1 General. 3
5.1.2 Capillary extrusion rheometer. 3
5.1.3 Extruder . 4
5.2 Apparatus for drawing the polymer extrudate . 5
5.2.1 Drawing unit . 5
5.2.2 Drawing unit design . 5
5.3 Data-acquisition system . 7
6 Calibration . 7
6.1 General . 7
6.2 Test temperature . 7
6.3 Capillary or rod die . 7
6.4 Drawing-force transducer . 7
6.5 Drawing velocity and drawing acceleration . 7
6.6 Drawing length . 7
7 Sampling . 8
8 Procedure. 8
8.1 Cleaning the apparatus . 8
8.2 Rheometer or extruder preparation . 8
8.3 Loading the capillary rheometer barrel . 9
8.4 Preheating . 9
8.5 Running the extruder .10
8.6 Preliminary checks of the extrudates .10
8.6.1 Absence of defects .10
8.6.2 Check on drawing down under gravity .10
8.7 Determination of the extrudate behaviour .12
8.7.1 Determination of the mean velocity .12
8.7.2 Determination of the drawing force as a function of the drawing velocity .12
8.7.3 Measurement of melt strength .13
9 Calculation and expression of results .14
9.1 Initial cross-sectional area of the extrudate .14
9.2 Initial velocity .14
9.3 Drawing velocities .14
9.4 Drawing forces .15
9.5 Draw ratio.15
10 Precision .15
11 Test report .15
Bibliography .17
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
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electrotechnical standardization.
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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).
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iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-
chemical properties.
This second edition cancels and replaces the first edition (ISO 16790:2005), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— the normative references have been updated;
— the figure keys have been completed;
— the test procedure and parameters have been revised.
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 © ISO 2021 – All rights reserved

INTERNATIONAL STANDARD ISO 16790:2021(E)
Plastics — Determination of drawing characteristics of
thermoplastics in the molten state
1 Scope
This document specifies a method for determining the drawing and break characteristics of molten
plastics. The method involves the measurement of the force generated in deforming a molten filament
under defined extrusion temperature and drawing conditions.
Data is generated under non-isothermal and non-homogeneous deformation conditions. However, it is
useful for the interpretation of polymer behaviour in extensional flow.
The method is suitable for thermoplastics moulding and extrusion materials that can be extruded using
a capillary extrusion rheometer, or an extruder with capillary rod die or other extrusion devices and
have sufficient melt strength to be handled without difficulty.
The method is applicable to chemically stable materials that produce a uniform extrudate free from
heterogeneities, bubbles, unmelted impurities, etc.
This method can provide information on
— processability for all extrusion techniques,
— the effect of mechanical and thermal history, and
— the effect of chemical structure, such as branching, entanglements and molecular mass.
This technique is one of a number of techniques that can be used to measure the extensional flow
behaviour of a material. This method of measurement does not necessarily reproduce the drawing
conditions to which thermoplastics are subjected to during their processing.
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 291, Plastics — Standard atmospheres for conditioning and testing
ISO 11443, Plastics — Determination of the fluidity of plastics using capillary and slit-die rheometers
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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/
3.1
drawing
process of stretching a filament of polymer melt that is being continuously formed by a capillary
extrusion rheometer or extruder or other extrusion device
3.2
melt strength
F
b
...