ISO 11443:2021
(Main)Plastics — Determination of the fluidity of plastics using capillary and slit-die rheometers
Plastics — Determination of the fluidity of plastics using capillary and slit-die rheometers
This document specifies methods for determining the fluidity of plastics melts subjected to shear stresses at rates and temperatures approximating to those arising in plastics processing. Testing plastics melts in accordance with these methods is of great importance since the fluidity of plastics melts is generally not dependent solely on temperature, but also on other parameters; in particular shear rate and shear stress. The methods described in this document are useful for determining melt viscosities from 10 Pa∙s to 107 Pa∙s, depending on the measurement range of the pressure and/or force transducer and the mechanical and physical characteristics of the rheometer. The shear rates occurring in extrusion rheometers range from 1 s−1 to 106 s−1. Elongational effects at the die entrance cause extrudate swelling at the die exit. Methods for assessing extrudate swelling have also been included. The rheological techniques described are not limited to the characterization of wall-adhering thermoplastics melts only; for example, thermoplastics exhibiting "slip" effects[1][2] and thermosetting plastics can be included. However, the methods used for determining the shear rate and shear viscosity are invalid for materials which are not wall-adhering. Nevertheless, this document can be used to characterize the rheological behaviour of such fluids for a given geometry.
Plastiques — Détermination de la fluidité au moyen de rhéomètres équipés d'une filière capillaire ou plate
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 11443
Fourth edition
2021-02
Plastics — Determination of the
fluidity of plastics using capillary and
slit-die rheometers
Plastiques — Détermination de la fluidité au moyen de rhéomètres
équipés d'une filière capillaire ou plate
Reference number
©
ISO 2021
© ISO 2021
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Published in Switzerland
ii © ISO 2021 – All rights reserved
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General principles . 4
5 Apparatus . 4
5.1 Test device . 4
5.1.1 General. 4
5.1.2 Rheometer barrel . 5
5.1.3 Capillary dies (method A) . 5
5.1.4 Slit dies (method B) . 9
5.1.5 Piston . 9
5.2 Temperature control . 9
5.3 Measurement of temperature and calibration .10
5.3.1 Test temperature .10
5.3.2 Measurement of test temperature .10
5.3.3 Temperature calibration .10
5.4 Measurement of pressure and calibration .10
5.4.1 Test pressure .10
5.4.2 Pressure drop along the length of the slit die .11
5.4.3 Calibration .11
5.5 Measurement of the volume flow rate of the sample .11
6 Sampling .11
7 Procedure.11
7.1 Cleaning the test device .11
7.2 Selection of test temperatures .12
7.3 Preparation of samples .13
7.4 Preheating .13
7.5 Determination of the maximum permissible test duration .13
7.6 Determination of test pressure at constant volume flow rate: Method 2 .14
7.7 Determination of volume flow rate at constant test pressure: Method 1 .14
7.8 Waiting periods during measurement.14
7.9 Measurement of extrudate swelling .14
7.9.1 General.14
7.9.2 Measurement at room temperature .15
7.9.3 Measurement at the test temperature .15
8 Expression of results .15
8.1 Volume flow rate .15
8.2 Apparent shear rate .16
8.2.1 General.16
8.2.2 Method A: Capillary dies .16
8.2.3 Method B: Slit dies .16
8.3 Apparent shear stress .17
8.3.1 General.17
8.3.2 Method A: Capillary dies .17
8.3.3 Method B: Slit dies .17
8.4 True shear stress .17
8.4.1 General.17
8.4.2 Bagley correction for capillary dies (method A) .18
8.4.3 Bagley correction for slit dies (method B) .21
8.4.4 Direct determination using slit dies (method B) .22
8.5 True shear rate .22
8.5.1 General.22
8.5.2 Method A: Capillary dies .23
8.5.3 Method B: Slit dies .23
8.6 Viscosity .23
8.7 Determination of extrudate swelling .23
8.7.1 Measurement at room temperature .23
8.7.2 Measurement at the test temperature .24
9 Precision .24
10 Test report .25
10.1 General .25
10.2 Test conditions .25
10.3 Flow characteristics .26
10.3.1 General.26
10.3.2 Graphical representation .26
10.3.3 Individual values .27
10.4 Visual examination .27
Annex A (informative) Method of correcting for the influence of H/B on the apparent shear rate .28
Annex B (informative) Measurement errors .30
Annex C (informative) Uncertainties in the determination of shear viscosity by capillary
extrusion rheometry testing .31
Bibliography .36
iv © ISO 2021 – All rights reserved
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 5, Physical-
chemical properties.
This fourth edition cancels and replaces the third edition (ISO 11443:2014), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— the use of a zero length die has been added.
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.
INTERNATIONAL STANDARD ISO 11443:2021(E)
Plastics — Determination of the fluidity of plastics using
capillary and slit-die rheometers
1 Scope
This document specifies methods for determining the fluidity of plastics melts subjected to shear
stresses at rates and temperatures approximating to those arising in plastics processing. Testing
plastics melts in accordance with these methods is of great importance since the fluidity of plastics
melts is generally not dependent solely on temperature, but also on other parameters; in particular
shear rate and shear stress.
The methods described in this document are useful for determining melt viscosities from 10 Pa∙s
to 10 Pa∙s, depending on the measurement range of the pressure and/or force transducer and the
mechanical and physical characteristics of the rheometer. The shear rates occurring in extrusion
−1 6 −1
rheometers range from 1 s to 10 s .
Elongational effects at the die entrance cause extrudate swelling at the die exit. Methods for assessing
extrudate swelling have also been included.
The rheological techniques described are not limited to the characterization of wall-adhering
[1][2]
thermoplastics melts only; for example, thermoplastics exhibiting “slip” effects and thermosetting
plastics can be included. However, the methods used for determining the shear rate and shear viscosity
are invalid for materials which are not wall-adhering. Nevertheless, this document can be used to
characterize the rheological behaviour of such fluids for a given geometry.
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 1133-1, Plastics — Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR)
of thermoplastics — Part 1: Standard method
ISO 1133-2, Plastics — Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR)
of thermoplastics — Part 2: Method for materials sensitive to time-temperature history and/or moisture
ISO 4287, Geometrical Product Specifications (GPS) — Surface texture: Profile method — Terms, definitions
and surface texture parameters
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 11403-2, Plastics — Acquisition and presentation of comparable multipoint data — Part 2: Thermal
and processing properties
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
Newtonian fluid
fluid for which the viscosity is independent of the shear rate and of time
3.2
non-Newtonian fluid
fluid for which the viscosity varies with the shear rate and/or with time
Note 1 to entry: For the purposes of this document, this definition refers to fluids for which the viscosity varies
only with the shear rate.
3.3
apparent shear stress
τ
ap
fictive shear stress to which the melt in contact with the die wall is subjected, expressed in pascals (Pa)
Note 1 to entry: It is calculated as the product of test pressure and the ratio of die cross-sectional area to die
wall area.
3.4
apparent shear rate
γ
ap
fictive shear rate that the melt at the wall would experience at the observed volume flow rate if its
−1
behaviour were Newtonian, expressed in reciprocal seconds (s )
3.5
true shear stress
τ
actual shear stress to which the melt in contact with the die wall is subjected, expressed in pascals (Pa)
Note 1 to entry: It is estimated from the test pressure p by applying corrections for entrance and exit pressure
losses, or is directly determined from the melt-pressure gradient in the channel.
Note 2 to entry: For the purposes of notation, the absence of a subscript is used to denote true values.
3.6
true shear rate
γ
shear rate obtained from the apparent shear rate γ (3.4) by taking into account the deviations from
ap
Newtonian behaviour by appropriate correction algorithms (see Note in 8.2.2), expressed in reciprocal
−1
seconds (s )
Note 1 to entry: For the purposes of notation, the absence of a subscript is used to denote true values.
3.7
viscosity
η
viscosity in steady shear, defined as the ratio τγ/ of true shear stress τ (3.5) to true shear rate γ (3.6),
expressed in pascal seconds (Pa∙s)
3.8
apparent viscosity
η
ap
ratio τγ/ of apparent shear stress τ to apparent shear rate γ (3.4), expressed in pascal
ap
ap ap ap
seconds (Pa∙s)
3.9
Bagley corrected apparent viscosity
η
apB
ratio τγ/ of true shear stress τ (3.5) to apparent shear rate γ (3.4), expressed in pascal seconds (Pa∙s)
ap ap
2 © ISO 2021 – All rights reserved
3.10
Rabinowitsch corrected apparent viscosity
η
apR
ratio τγ/ of apparent shear stress τ to true shear rate γ (3.6), expressed in pascal seconds (Pa∙s)
ap
ap
Note 1 to entry: This term is appropriate for use when testing with a single die of large length-to-diameter aspect
ratio for which entrance effects are negligible.
3.11
volume flow rate
Q
volume of melt flowing through the die per unit time, expressed in cubic millimetres per second (mm /s)
3.12
swell ratio at room temperature
S
a
ratio of the diameter of the extrudate to the diameter of the capillary die, both measured at room
temperature
3.13
swell ratio at the test temperature
S
T
ratio of the diameter of the extrudate to the diameter of the capillary die, both measured at the test
temperature
3.14
percent swell at room temperature
s
a
difference between the diameter of the extruded strand and the diameter of the capillary die, expressed
as a percentage of the diameter of the capillary die, both measured at room temperature
3.15
percent swell at the test temperature
s
T
difference between the diameter of the extruded strand and the diameter of the capillary die, expressed
as a percentage of the diameter of the capillary die, both measured at the test temperature
Note 1 to entry: Equivalent slit-die extrudate swell terms can be derived based on the thickness of slit-die
extrudate with reference to the slit-die thickness.
3.16
preheating time
time interval between completion of charging of the barrel and the beginning of measurement
3.17
dwell time
time interval between the completion of charging of the barrel and the end of measurements
Note 1 to entry: In certain special cases, it can be necessary to note the dwell time at the end of each measurement
where more than one measurement per barrel filling is made.
3.18
extrusion time
time corresponding to the period of measurement for a given shear rate
3.19
critical shear stress
value of the shear stresses at the die wall at which any of the following occur:
— a discontinuity in the curve plotting shear stress against flow rate or shear rate;
— roughness (or waving) of the extrudate as it leaves the die
Note 1 to entry: It is expressed in pascals (Pa).
3.20
critical shear rate
−1
shear rate corresponding to the critical shear stress (3.19), expressed in reciprocal seconds (s )
3.21
zero length die
special designed die for an easy, quick and accurate entrance pressure loss correction by Bagley
correction, because only measurements with two different die lengths are necessary
4 General principles
The plastics melt is forced through a capillary or slit die of known dimensions. Two principal methods
can be used:
a) Method 1: for a specified constant test pressure p, the volume flow rate Q is measured, or
b) Method 2: for a specified constant volume flow rate Q, the test pressure p is measured.
These methods can be used with capillary dies (method A) and slit dies (method B). For full designation
of the test method options, see Table 1.
Table 1 — Designation of test methods
Preset parameter
Die cross section
Test pressure, p Volume flow rate, Q
Circular (capillary die) A1 A2
Rectangular (slit die) B1 B2
Measurements can be made using a range of values of the preset parameter (either applied test pressure
in method 1, or volume flow rate in method 2).
If a slit die with pressure transducers positioned along its length and also upstream of the die entry
is used, then entrance and exit pressure drop values can be determined. If capillary dies of the same
radius but of varying lengths are used, then the sum of the entrance and exit pressure drops can be
determined.
A slit die with pressure transducers positioned along its length is particularly suited for automated
measurements using online computer evaluation.
Recommended values for capillary die dimensions and for flow rates and temperatures to be used in
testing are presented either in the relevant clauses below or in ISO 11403-2.
In using a slit die, either the aspect ratio H/B between the thickness H and the width B of the slit is small
or else a correction for H/B (see Annex A) is necessary. In the latter case, the calculated quantities are
dependent on assumptions made in deriving the correction formulae used, notably that elastic effects
are irrelevant.
5 Apparatus
5.1 Test device
5.1.1 General
The test device shall consist of a heatable barrel, the bore of which is closed at the bottom end by an
interchangeable capillary or slit die. The test pressure shall be exerted on the melt contained in this
4 © ISO 2021 – All rights reserved
barrel by a piston, screw, or by the use of gas pressure. Figure 1 and Figure 2 show typical examples.
Other dimensions are permitted.
5.1.2 Rheometer barrel
The barrel shall consist of a material resistant to wear and corrosion up to the maximum temperature
of the heating system.
The barrel can have a lateral bore for the insertion of a melt-pressure transducer close to the die
entrance.
The permissible deviations in the mean bore diameter throughout the length of the barrel shall be less
than ±0,007 mm.
The barrel shall be manufactured using techniques and materials that produce a Vickers hardness
preferably of at least 800 HV 30 (according to ISO 6507-1 and Note 1) and a surface roughness of less
than R = 0,25 µm (average arithmetic discrepancy, according to ISO 4287).
a
NOTE 1 For temperatures up to 400 °C, nitrided steel has been found suitable. Materials of hardness values
lower than that specified but of sufficient corrosion and abrasion resistance have been found to be acceptable for
construction of the barrel and dies.
NOTE 2 An increase in barrel-bore diameter increases the number of measurements that can be made with a
single barrel filling and increases the shear rate range of the instrument. Disadvantages of using a larger barrel-
bore diameter are that larger sample masses are required and that the time necessary to reach temperature
equilibrium throughout the sample is greater. The barrel-bore diameters of commercially available rheometers
lie in the range between 6,35 mm and 30 mm.
5.1.3 Capillary dies (method A)
5.1.3.1 The entire length of the capillary die wall shall be machined to an accuracy of ±0,007 mm for
the diameter (D) and ±0,025 mm for the length (L) (see Figure 1).
The capillary shall be manufactured using techniques and materials that produce a Vickers hardness
preferably of at least 800 HV 30 (according to ISO 6507-1 and Note 1 in 5.1.2) and a surface roughness of
less than R = 0,25 µm (average arithmetic discrepancy, according to ISO 4287).
a
The capillary opening shall show no visible machining marks or perceptible eccentricity.
NOTE 1 Diameters of capillary dies typically used lie in the range between 0,5 mm and 2 mm, with various
lengths to obtain the desired L/D ratios. For testing of filled materials, larger diameters can be required.
NOTE 2 Hardened steel, tungsten carbide, stellite, and hardened stainless steel are the most common die
materials.
NOTE 3 The precision with which capillary dimensions can be measured is dependent upon both the capillary
radius and the capillary length. With capillaries of diameter smaller than 1,25 mm, the specified precision
(±0,007 mm) is difficult to obtain. Due to the extreme sensitivity of flow data to capillary dimensions, it is
important that the capillary dimensions, and the precision with which the dimensions are measured, are known
and reported. This also applies to the dimensions (thickness, width, and length) of slit dies (see 5.1.4).
Dimensions in millimetres
Key
1 applied force or constant velocity 7 capillary die
2 thermal insulation 8 die-retaining nut
3 piston 9 optical sensor
4 barrel 10 temperature-controlled air chamber
5 heating coil 11 thermometer
6 pressure transducer 12 inlet angle
Figure 1 — Typical example of an extrusion rheometer used with a capillary die
6 © ISO 2021 – All rights reserved
Dimensions in millimetres
Key
1 piston 5 channel
2 barrel 6 electrical heater
3 die P pressure transducers
i
4 exchangeable part T thermometers
i
Figure 2 — Typical example of an extrusion rheometer used with a slit die
5.1.3.2 To determine the apparent shear rate γ and the apparent shear stress τ with one capillary
ap
ap
die, the ratio L/D of the length L to the diameter D of the capillary die shall be at least 16 and its inlet
angle shall be 180°, unless otherwise specified by the referring standard. Only data obtained with
capillaries of the same inlet angle (±1°), length (±0,025 mm), and diameter (±0,007 mm) shall be
compared. The inlet angle is defined in Figure 1.
It is recommended that a die of length either 16 mm or 20 mm, diameter of 1 mm, and entry angle of
180° be used.
NOTE 1 Die lengths of 16 mm and 20 mm are most commonly used, the choice often being dependent on, and
limited by, the design of the instrument.
Options for other die diameters in the range of 0,1 mm to 6 mm are permitted when the recommended
value is not appropriate, for example for heavily filled or low viscous materials. For dies of diameter
other than 1 mm, the recommended ratio of length to diameter (L/D) shall be the same, where possible,
as that of the 1-mm-diameter die used in that instrument.
NOTE 2 For a given value of the apparent shear rate, the effect of shear heating of the melt is reduced by use of
smaller diameter capillary dies.
5.1.3.3 To determine the true shear rate γ and the true shear stress τ, capillary dies of the same
diameter (±0,007 mm) and inlet angle (±1°) and having at least two different L/D ratios selected from
the recommended series L/D = 0,25 to 1, 5, 10, 16, 20, 30, and 40 (see also 8.4.2) are required, provided
the following conditions are met.
The use of only two dies, of the same diameter (±0,007 mm) and inlet angle (±1°), of L/D ≤ 5 and L/D ≥ 20 is
permitted where the test conditions are such that the resultant Bagley plot is not significantly nonlinear,
i.e. these conditions having been established in advance for each class of sample, by using additional
dies (see 8.4). When using only two dies, the difference in the L/D ratios of the two dies shall be at least
15. Instead of using a short die having the same entrance angle as the long die, a zero length die with
a different entrance angle can be used for a two die Bagley correction in combination with a long die
especially if the measurement with the short die is not appropriate due to sticking of the material at the
outlet. The zero length die should have an absolute length between 0,2 mm and 0,25 mm and the same
diameter as the long die. The entrance angle of “zero length die” can be different from 180°.
It is recommended that, when using only two dies to determine shear viscosity corrected for entrance
pressure drop effects, a short die of length-to-diameter (L/D) ratio in the range 0,25 to 1, and a long die
of length-to-diameter (L/D) ratio in the range 5 to 20, both dies having a diameter of 1 mm and an entry
angle of 180°, be used. Alternative to the short die, a zero length die can be used. Options for other die
diameters, of 0,3 mm; 0,5 mm; 2 mm; 4 mm, shall be permitted when the recommended value of 1 mm
is not appropriate, for example for heavily filled or low viscous materials. For dies of diameter other
than 1 mm, the recommended ratios of length to diameter (L/D) shall be the same as that specified for
the 1-mm-diameter dies.
NOTE 1 The procedure for correction for entrance pressure drop effects (see 8.4) is based on an extrapolation
of data to a die length of zero by Bagley correction, rather than by making the approximation that the short die
yields the entrance pressure drop value.
NOTE 2 The reason for using a zero length die is that short dies create sticking of material at the outlet of the
capillary generating errors in too high pressure reading. The plot of pressure versus several die lengths from
the linear part of the Bagley plot (see also Figure 4) will then show that the pressure of the short die is not in line
with the pressure plot of the other dies. The use of a zero length die helps prevent this situation. A comparison
with different die lengths ≤ 20 mm can prove whether the use of the zero length die can give correct results. In
this case, the pressure drop of the zero length die matches the linear part of the plot pressure versus die length of
the Bagley correction (see also Figure 4).
8 © ISO 2021 – All rights reserved
5.1.4 Slit dies (method B)
5.1.4.1 The entire length of the slit die shall be machined to an accuracy of ±0,007 mm for the thickness,
±0,01 mm for the width, and ±0,025 mm for the length. As applicable, the distance between the centres
of the pressure transducers and the exit plane shall be determined to ±0,05 mm. (See Note 3 in 5.1.3.1.)
The die shall be manufactured using techniques and materials that produce a Vickers hardness
preferably of at least 800 HV 30 (according to ISO 6507-1 and NOTE 1 in 5.1.2) and a surface roughness
of less than R = 0,25 µm (average arithmetic discrepancy, according to ISO 4287.)
a
NOTE For slit die materials, see NOTE 1 in 5.1.2 and NOTE 2 in 5.1.3.1.
5.1.4.2 To determine the apparent shear rate γ and the apparent shear stress τ , unless otherwise
ap
ap
specified by the referring standard, the slit die shall have a ratio H/B of the thickness H to the width B of
at most 0,1 and shall have an inlet angle of 180°. Only data obtained with slit dies of the same inlet angle
(±1°), thickness (±0,007 mm), width (±0,01 mm), and length (±0,025 mm) shall be compared.
5.1.4.3 To determine the true values of shear rate γ and shear stress τ, slit dies conforming to the
specification given in 5.1.4.1 and 5.1.4.2 can be used in exactly the same way as capillary dies, i.e. using
the Bagley correction method modified accordingly (see 8.4). Alternatively, a slit die with pressure
transducers positioned along the length of its channel can be used to determine true shear stress values.
5.1.5 Piston
If a piston is used, its diameter shall be 0,040 mm ± 0,005 mm smaller than the barrel-bore diameter.
It can be equipped with split or whole sealing rings in order to reduce melt backflow past the land of
the piston. The hardness of the piston shall be less than that of the barrel, but not less than 375 HV 30
(according to ISO 6507-1).
5.2 Temperature control
For all temperatures that can be set, the barrel temperature control shall be designed such that, within
the range of the capillary die or slit die, as applicable, and the permissible filling height of the barrel, the
temperature differences and variations measured at the wall do not exceed those given in Table 2 for
the duration of the test.
Table 2 — Maximum allowable temperature differences as a function of distance and as a
function of time
Temperature difference from the set tem- Temperature variation as a
Test temperature, θ
a a
perature as a function of distance function of time
°C °C °C
≤200 ±1,0 ±0,5
200 < θ ≤ 300 ±1,5 ±1,0
>300 ±2,0 ±1,5
a
For all positions within the range of the capillary die or slit die, as applicable, and the permissible filling height of the
barrel, for the duration of the test.
The test device shall be designed so that the test temperature can be set in steps of 1 °C or less.
5.3 Measurement of temperature and calibration
5.3.1 Test temperature
5.3.1.1 Method A: Capillary dies
When capillary dies are used, the test temperature shall be either the temperature of the melt in the
barrel near the capillary inlet or, if this is not possible, the temperature of the barrel wall near the
capillary inlet. It is preferable that the test temperature is measured at a position not more than 10 mm
above the capillary inlet. (See also 5.3.2.)
5.3.1.2 Method B: Slit dies
When slit dies are used the die wall temperature shall be measured and taken as the test temperature.
This temperature shall be equal to the test temperature measured in the barrel to within the distance-
related and time-related temperature tolerances given in Table 2. (See also 5.3.1.1 and 5.3.2.)
5.3.2 Measurement of test temperature
The tip of the temperature-measuring device shall be either in contact with the melt or, if this is not
possible, in contact with the metal of the barrel or die wall, as close as possible to the melt channel, if it
is feasible not more than 1,5 mm. Thermally conductive fluids can be used in the thermometer well to
improve conduction. Thermometers, preferably thermocouples or platinum resistance sensors, can be
placed as shown in Figure 1 and Figure 2.
5.3.3 Temperature calibration
The temperature-measuring device used during the test shall read to within 0,1 °C and be calibrated
by means of a standard thermometer, with error limits of ±0,1 °C, while complying with the depth of
immersion prescribed for the thermometer concerned. For this purpose, the barrel can be filled to the
top with a low-viscosity melt.
No liquids that can contaminate the die or barrel or influence the ensuing measurements, such as
silicone oil, shall be used as heat transfer media during calibration.
5.4 Measurement of pressure and calibration
5.4.1 Test pressure
The test pressure shall be the pressure drop in the melt, measured as the difference between
the pressure in the melt before the capillary-die or slit-die inlet and the pressure at the die exit, as
applicable. If possible, the test pressure shall be measured by a melt-pressure transducer located near
the entrance of the die, in which case the distance from the pressure transducer to the die entry face
shall be kept constant for all tests and should preferably be not more than 20 mm (see Note). Otherwise,
the test pressure shall be determined by the force exerted on the melt, for example by the piston, that
force being measured by a load cell above the piston (see Annex B).
NOTE It is important that the distance from the die entry face to the pressure transducer is kept constant
for all tests as this otherwise affects the pressure drop measured. The use of pressure transducers at a distance
equivalent to that of the barrel diameter from the die entry face can reduce fluctuations in the pressure being
measured that can arise due to recirculating flow above the die entry.
If testing is to be carried out by extruding to a channel or vessel pressurized to a pressure above
atmospheric pressure, then the pressure at the die exit shall also be measured, preferably using a
pressure transducer located immediately below the exit of the die.
The force- or pressure-measuring devices shall be operated in the range between 1 % and 95 % of their
nominal capacity.
10 © ISO 2021 – All rights reserved
5.4.2 Pressure drop along the length of the slit die
When using slit dies, the pressure profile along the length of the die shall be measured by flush-mounted
melt-pressure transducers positioned along the die wall.
Alternatively, when slit dies not equipped with melt-pressure transducers are used, the sum of entrance
and exit pressure losses can be taken into account by employing the Bagley correction modified for slit
dies (see 8.4.3).
5.4.3 Calibration
External hydraulic test equipment can be used for the calibration of melt-pressure transducers. Load
cells shall be calibrated in accordance with manufacturer’s specifications. The maximum permissible
error in the reading of the melt-pressure transducers or load cells shall be both less than or equal to
1 % of the full scale value and less than or equal to 5 % of the absolute value. The calibration of melt-
pressure transducers should preferably be performed at the test temperature.
5.5 Measurement of the volume flow rate of the sample
The volume flow rate shall be determined either from the feed rate of the piston or by weighing the
mass of the sample extruded during a measured period of time.
If weighing is performed, the conversion to the volume flow rate shall be made by using the density of
the melt at the prevailing test temperature, the influence of the hydrostatic pressure on the density
being ignored.
The volume flow rate shall be determined to within 1 %.
It is recommended that, for purposes of providing comparable data, the apparent shear rates and hence
flow rates used for testing are such that data at the true shear rates specified in ISO 11403-2 can be
determined by interpolation. The apparent shear rates should be set at equispaced intervals, when
plotted logarithmically, and there should be at least two data points per decade of apparent shear rate.
NOTE The specified maximum permissible error for determining the volume flow rate via the feed rate of
the piston can only be conformed to if, among other things, the leakage rate between the piston and barrel is
sufficiently small. Experience indicates that this can be achieved if the clearance between piston and barrel does
not exceed 0,045 mm (see 5.1.5).
6 Sampling
From the material to be tested, a representative sample shall be taken for use as the test sample. The
number of determinations per single barrel filling depends on the moulding material under test and
shall therefore be agreed upon between the interested parties. The temperature during test sample
preparation shall be less than that during the subsequent test.
7 Procedure
7.1 Cleaning the test device
Before each measurement, ensure that the barrel, transducer bores, where applicable, piston,
and capillary or slit die are free of adherent foreign matter. Make a visual examination to check for
cleanliness.
If solvents are used for cleaning, ensure th
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