ISO 8130-15:2023

INTERNATIONAL ISO
STANDARD 8130-15
First edition
2023-01
Coating powders —
Part 15:
Rheology
Poudres pour revêtement —
Partie 15: Rhéologie
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 Powder . 1
4.2 Melt . 1
5 Apparatus . 2
6 Sampling . 2
7 Experimental . 2
7.1 Powder measurements . 2
7.1.1 Fluidization measurements . 2
7.1.2 Fluidized bed rheology measurements . 3
7.1.3 Deaeration measurements . 3
7.1.4 Cohesion strength measurements . 3
7.2 Melt rheology measurements . 3
8 Expression of results . 3
9 Precision . 3
10 Test report . 4
Annex A (informative) Interpretation of results . 5
Bibliography .11
iii
Foreword
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This document was prepared by Technical Committee ISO/TC 35, Paints and varnishes, Subcommittee
SC 9, General test methods for paints and varnishes.
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iv
Introduction
The powder coating process is dependent on several material variables, whose presence within the
powder mixture is critical for ensuring smooth operation. A precise understanding of the fluidization
behaviour is important for optimal processing parameters in the fluidized bed, during pneumatic
conveyance and the spraying process. In addition, understanding the long-term stability during storage
or behavioural change during processing can also help to improve the reuse of powder coatings.
Furthermore, melt rheology is introduced to understand the melt flow properties of a given powder
coating system, to provide information after spraying, on the powder melt viscosity and gel point. The
methods in this document can be used for quality-control and detailed studies.
v
INTERNATIONAL STANDARD ISO 8130-15:2023(E)
Coating powders —
Part 15:
Rheology
1 Scope
This document specifies methods for the determination of the rheological behaviour of a coating
powder both in particulate and molten form.
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 3219-1, Rheology — Part 1: Vocabulary and symbols for rotational and oscillatory rheometry
ISO 3219-2, Rheology — Part 2: General principles of rotational and oscillatory rheometry
ISO 8130-14, Coating powders — Part 14: Vocabulary
ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 3219-1, ISO 8130-14 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
apparent viscosity
flow resistance of the fluidized powder bed
4 Principle
4.1 Powder
The different fluidization properties are determined in a rheometer. In addition to rotational speed
and torque, the airflow rate through the powder bed can be precisely controlled and the pressure drop
determined. This allows complete analysis of all fluidization parameters that influence the powder
coating process.
4.2 Melt
In order to characterize the powder in its molten form, a rheometer in accordance with ISO 3219-2 shall
be used to determine the melt and polymerization properties.
5 Apparatus
Use ordinary laboratory apparatus, together with the following.
5.1 Rheometer, in accordance with ISO 3219-2, equipped with a cylindrical measurement cell with
a minimum diameter of 50 mm and a minimum height of 100 mm, ideally transparent and coated with
conductive material to prevent electrostatic charging to maintain visibility. As a measurement system,
a rectangular stirrer of minimum of 10 mm × 30 mm measurement surface is recommended unless
otherwise specified.
For particulate measurements, a mass flow controller capable of generating an airflow from 0,05 l/min
to at least 5 l/min is connected to ensure a uniform fluidization. A pressure transducer is required if
pressure drop measurements shall be gathered.
For molten measurements, a disposable plate-plate geometry in a rheometer according to ISO 3219-2
with a heated plate and hood is advised.
5.2 Measurement geometry
For fluidization, deaeration and apparent viscosity measurements, use a profiled cylinder. Alternatively,
measure in an undisturbed bed, without any measurement system inserted.
For cohesion strength measurements, a rectangular stirrer with a minimum measurement surface of
10 mm × 30 mm is recommended.
Use of a disposable plate of at least 25 mm diameter is advised in molten measurements.
NOTE A plate of smaller diameter can give spurious results.
6 Sampling
Take a representative sample of the product under test as specified in ISO 15528.
A minimum sample volume for powder particulate rheology measurements of 80 ml is recommended.
For further measurements of the same powder, it is recommended to keep a consistent mass.
For melt rheology measurement, it is advised to fill the plate-plate gap with the excess particulate
powder, e.g. × 15 the volume, and then compress it prior to melting.
7 Experimental
7.1 Powder measurements
7.1.1 Fluidization measurements
Carry out the fluidization measurement using the profiled cylinder and perform it in two modes, i.e.
-1
unstirred and stirred, e.g. rotational speed 8 min . First, decrease the air flow from 5 l/min to 0 l/min
continuously, within a minimum of 30 s and then increase again from 0 l/min to 5 l/min.
This measurement is carried out to find the volumetric flow rate i.e. the volume of gas per time
necessary for subsequent testing, as well as the volumetric flow rates for incipient and full fluidization
of the sample.
NOTE For explanations of transitions such as incipient and full fluidization, see A.1.
The measurements shall be performed first unstirred, then stirred.
A pressure transducer is required for pressure drop measurements by taking a baseline measurement
with the same parameters in the empty cell immediately prior to measurement giving absolute results.
7.1.2 Fluidized bed rheology measurements
Carry out fluidized bed rheology measurements with a profiled cylinder system. The rotational speed
-1 -1
shall be increased from 0,1 min to 1 200 min , corresponding to an applied shear rate increase from
-1 -1
0,02 s to 320 s .
Calculate the powder’s apparent viscosity in a manner analogous to that of a non-Newtonian fluid. To
this end, the dimensions of the measuring chamber (e.g. 50 mm diameter) and the profiled cylinder (e.g.
17 mm diameter, no cone at the bottom) shall be measured in accordance with ISO 3219-2. Set the data
gathered so that each data point is equivalent to at least one full revolution of the cylinder.
7.1.3 Deaeration measurements
Measure bed deaeration by first stirring and fluidizing the powders with an airflow of 5 l/min for 5 min
-1
at 8 min , then stop the airflow and obtain the pressure data under the powder bed.
7.1.4 Cohesion strength measurements
Cohesion strength describes the internal resistance of the powder to flow, and thereby a measure of
powder flowability. It is defined as a measure for the strength of the bonding forces between
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