ISO 19252:2008
(Main)Plastics — Determination of scratch properties
Plastics — Determination of scratch properties
ISO 19252:2008 specifies a method for determining the scratch properties of plastics under defined conditions. The method involves making a scratch by moving a hard instrument (scratch tip) of specified geometry under specified conditions of load and speed across the surface of a test specimen and then assessing the result. The method is used to investigate the behaviour of specified types of specimen under the scratch conditions defined and for classifying the type of scratch of specimens within the limitations inherent in the test conditions. It can also be used to determine comparative data for different types of material by means of a so‑called scratch map in which the types of scratch behaviour for each set of test conditions of test load and test speed are determined using the basic method of constant-load testing, and also by means of the so‑called critical normal load determined using an alternative method of linearly increasing load testing. The method is suitable for use with uncoated and unlacquered thermoplastic moulding materials and thermosetting moulding materials. The method specifies the preferred dimensions for the test specimen and the preferred scratch-tip geometry.
Plastiques — Détermination du comportement à la rayure
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INTERNATIONAL ISO
STANDARD 19252
First edition
2008-12-15
Plastics — Determination of scratch
properties
Plastiques — Détermination du comportement à la rayure
Reference number
ISO 19252:2008(E)
©
ISO 2008
---------------------- Page: 1 ----------------------
ISO 19252:2008(E)
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INTERNATIONAL ISO
STANDARD 19252
First edition
2008-12-15
Plastics — Determination of scratch
properties
Plastiques — Détermination du comportement à la rayure
Reference number
ISO 19252:2008(E)
©
ISO 2008
---------------------- Page: 1 ----------------------
ISO 19252:2008(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
COPYRIGHT PROTECTED DOCUMENT
© ISO 2008
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
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ii © ISO 2008 – All rights reserved
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ISO 19252:2008(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Principle. 4
5 Apparatus . 4
6 Test specimens . 6
7 Procedure . 7
8 Expression of results . 10
9 Test report . 14
Annex A (informative) Photographic illustrations of different types of scratch behaviour . 16
Annex B (informative) Test machine . 17
Bibliography . 18
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ISO 19252:2008(E)
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 19252 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 2, Mechanical
properties.
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INTERNATIONAL STANDARD ISO 19252:2008(E)
Plastics — Determination of scratch properties
IMPORTANT — The electronic file of this document contains colours which are considered to be
useful for the correct understanding of the document. Users should therefore consider printing this
document using a colour printer.
1 Scope
1.1 This International Standard specifies a method for determining the scratch properties of plastics under
defined conditions. The method involves making a scratch by moving a hard instrument (scratch tip) of
specified geometry under specified conditions of load and speed across the surface of a test specimen and
then assessing the result.
1.2 The method is used to investigate the behaviour of specified types of specimen under the scratch
conditions defined and for classifying the type of scratch of specimens within the limitations inherent in the test
conditions. It can also be used to determine comparative data for different types of material by means of a
so-called scratch map in which the types of scratch behaviour for each set of test conditions of test load and
test speed are determined using the basic method of constant-load testing, and also by means of the
so-called critical normal load (see 3.8) determined using an alternative method of linearly increasing load
testing.
1.3 The method is suitable for use with uncoated and unlacquered thermoplastic moulding materials and
thermosetting moulding materials.
1.4 The method specifies the preferred dimensions for the test specimen and the preferred scratch-tip
geometry.
2 Normative references
The following referenced documents are indispensable for the application 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 294-1, Plastics — Injection moulding of test specimens of thermoplastic materials — Part 1: General
principles, and moulding of multipurpose and bar test specimens
ISO 3167:2002, Plastics — Multipurpose test specimens
ISO 10724-1:1998, Plastics — Injection moulding of test specimens of thermosetting powder moulding
compounds (PMCs) — Part 1: General principles and moulding of multipurpose test specimens
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R
ISO 19252:2008(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
scratch
damage made by a hard instrument (scratch tip) when moved across a test specimen surface under specified
conditions of tip geometry, test load and test speed (see Figure 1)
NOTE The term “surface”, as used in this definition, applies to the macroscopic surface and not the microscopic
surface.
2
1
Key
1 test specimen
2 scratch tip
P test load
v test speed
Figure 1 — Schematic representation of a scratch (see 3.1)
3.2
test load
P
load applied by the scratch tip perpendicularly to the test specimen during the test
NOTE It is expressed in newtons.
3.3
test speed
v
relative rate of displacement between the scratch tip and the test specimen during the test
NOTE It is expressed in millimetres per second.
3.4
scratch force
F
s
horizontal force between the scratch tip and the test specimen at any given moment during the test
NOTE It is expressed in newtons.
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ISO 19252:2008(E)
3.5
scratch-tip displacement
d
vertical displacement of the scratch tip relative to the test specimen surface at any given moment during the
test
NOTE It is expressed in micrometres.
3.6
scratch distance
s
horizontal distance travelled by the scratch tip relative to the test specimen at any given moment during the
test
NOTE It is expressed in millimetres.
3.7
scratch behaviour
type of deformation of the material under the action of the scratch tip
NOTE Scratch behaviour is classified into three types: ploughing (p), wedge formation (w) and cutting (c), as defined
in 3.7.1 to 3.7.3.
3.7.1
ploughing
p
scratch behaviour in which the scratch force and scratch-tip displacement are constant over the scratch
distance during the test (see Figure 2)
NOTE 1 The surface of the scratch is smooth along its whole length rather than rough.
NOTE 2 A small, inherent level of episodic signal oscillation (of amplitude less than 3 N in the scratch force and 10 µm
in the tip displacement) is acceptable.
3.7.2
wedge formation
w
scratch behaviour in which the scratch force and/or scratch-tip displacement oscillate, resulting in a
corresponding increase in the actual distance travelled by the scratch tip during the test (see Figure 2)
NOTE The surface of the scratch exhibits a continuous serrated or wedge-like pattern, and stick-slip occurs.
3.7.3
cutting
c
scratch behaviour in which the scratch force and/or scratch-tip displacement vary randomly, resulting in a
corresponding increase in the actual distance travelled by the scratch tip during the test (see Figure 2)
NOTE During the test, chips are cut from the surface.
3.8
critical normal load
P
c
minimum normal load at which wedge formation or cutting, whichever occurs first, takes place at a given test
speed
NOTE It is expressed in newtons.
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ISO 19252:2008(E)
4 Principle
A standard test specimen is scratched by a hard tip which applies a load perpendicular to the test specimen
and moves lengthwise across the surface at a constant speed along the centreline of the test specimen.
During the scratch, the horizontal force between the scratch tip and the test specimen (the scratch force), the
vertical displacement of the scratch tip (tip displacement) and the scratch distance are each measured
continuously and recorded. The scratch force/scratch distance and tip displacement/scratch distance
diagrams thus produced describe the scratch behaviour of the test specimen. Using the basic method of
constant-load testing, the type of scratch behaviour can be determined for a series of test conditions (load and
speed) and expressed as a so-called scratch map. Using an alternative method of linearly increasing load
testing, the critical normal load can be determined at a given test speed (see Table 1). Changes in slope
and/or spikes in the scratch force/scratch distance curve indicate transitions from one type of scratch
behaviour to another (e.g. from ploughing to wedge formation or to cutting).
5 Apparatus
5.1 Test machine
5.1.1 General
The test machine shall consist essentially of a frame with a specimen support, a scratch tip with its associated
fittings, and a device for applying the load (see Annex B), and shall meet the specifications given in 5.1.2 to
5.1.8.
5.1.2 Frame
The frame of the machine shall be capable of being levelled and shall not be deformed by more than 3 µm
under the maximum load.
5.1.3 Scratch tip
The scratch tip shall be hardened to at least Rockwell HRC 64 hardness, shall be polished to a roughness of
less than 0,20 µm and shall not show any deformation or damage after a test.
The scratch tip shall be hemispherical in shape, with an outside radius R of 0,5 mm ± 0,025 mm.
NOTE Tips made from hardened and polished steel or tungsten carbide have been found to be satisfactory.
5.1.4 Test load
The machine shall be capable of maintaining the test load within a tolerance of ± 1 %, for any test load chosen
as specified in 7.2.3, and shall be capable of applying the load perpendicular to the test specimen within a
tolerance of ± 5°.
5.1.5 Test speed
The machine shall be capable of maintaining the test speed within a tolerance of ± 1 %, except over the first
and the last 10 mm of the scratch distance, for any test speed chosen as specified in 7.2.4 and shall be
capable of reaching the test speed within 10 mm and stopping within 10 mm.
5.1.6 Test specimen support
The test specimen support shall be flat, smooth and free of holes in the area where the test specimen will be
placed.
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ISO 19252:2008(E)
The clamping system for holding the test specimen on the support shall be attached to the test machine so
that the longitudinal axis of the test specimen coincides with the line of scratch.
The clamping system shall not cause any premature fracture of the test specimen, and the test specimen shall
be held in such a way that it cannot slip relative to the specimen support.
5.1.7 Load indicator
The load indicator shall incorporate a mechanism capable of showing the horizontal force between the scratch
tip and the test specimen continuously during the test. The mechanism shall be essentially free from inertia
lag at the specified test speeds and shall indicate the load with an accuracy equal to or within ± 1 % of the
actual value.
5.1.8 Scratch tip displacement gauge
A mechanical or, preferably, an electronic device shall be used which incorporates a mechanism capable of
indicating the vertical displacement of the scratch tip to an accuracy of ± 1 µm or better under static conditions.
The mechanism shall be essentially free from inertia lag at the specified test speeds and shall be capable of
indicating the vertical displacement of the scratch tip to an accuracy of ± 10 µm or better continuously during
the test.
5.2 Instruments for measuring the test specimen dimensions
The width b of the test specimen shall be measured using a micrometer or gauge with an accuracy of
± 0,01 mm or better. For measuring the thickness h of the test specimen, a micrometer with a flat circular foot
reading to ± 0,01 mm or less shall be used.
5.3 Monitoring and inspection devices (optional)
5.3.1 Monitoring device
A monitoring device, such as a video camera equipped with a recording system and a magnifying mechanism,
is useful for monitoring the area around the scratch tip during the test (see 7.2.9, 8.2 and 8.4).
The device shall not have any thermal effect on the specimen.
5.3.2 Scratch inspection device
In addition to inspection with the naked eye, a device such as a magnifying glass, microscope, flatbed scanner
or interferometer is useful for observing the appearance of the surface of the scratch after the test (see 7.2.9,
8.2 and 8.4).
The device shall not have any thermal effect on the specimen.
NOTE When testing using a linearly increasing load (the alternative method), an image of the surface of the scratch
at the critical normal load can be generated with the aid of computer software using, for instance, a “grey-level threshold”
programme (see Figure 4).
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ISO 19252:2008(E)
6 Test specimens
6.1 Shape and dimensions
Type A multipurpose test specimens as specified in ISO 3167:2002 shall be used.
6.2 Preparation
6.2.1 Moulding
Test specimens shall be directly injection-moulded in accordance with ISO 294-1 or ISO 10724-1, as
appropriate, under conditions defined in the relevant standard for the material under examination.
The specimens shall be suitably marked outside the test area to indicate the melt-flow direction, the particular
cavity from which the specimen came (when using a multi-cavity mould) as well as the side of the mould
(cavity-plate side or fixed-plate side) on which a particular specimen face was formed (see e.g.
ISO 10724-1:1998, Annex B).
NOTE Certain types of material may show different scratch behaviour depending on the face of the specimen which
is tested and/or the melt-flow direction.
Strict control of all conditions during specimen preparation is essential to ensure that all test specimens are in
the same state.
6.2.2 Inspection of specimens and measurement of specimen dimensions
Test specimens shall be free of twist. The faces and edges shall be free from scratches, pits, sink marks, flash
and other imperfections.
Test specimens shall be checked for conformity with these requirements by visual observation, using straight
edges, squares and flat plates, and by measuring the dimensions (thickness and width) of the parallel-sided
section to the nearest 0,01 mm with instruments as specified in 5.2.
Specimens showing measurable or observable departure from any of these requirements shall be rejected.
With injection-moulded specimens, it is not necessary to measure the dimensions of each specimen. It is
sufficient to measure one specimen from each set. When using multi-cavity moulds, measure the dimensions
of a specimen from each cavity. If the difference in dimensions between mould cavities is greater than
0,02 mm, the specimens from each cavity shall be treated as different batches.
6.3 Number of test specimens
For determining the type of scratch behaviour as specified in 8.2, a single specimen is required for each set of
test conditions if only one type of scratch behaviour occurs during a single test. Three specimens are required
for each set of test conditions when several types of scratch behaviour occur during a single test.
In order to obtain a scratch map as specified in 8.3, it is recommended that at least 25 different sets of test
conditions (for example, five different constant test loads and five different test speeds), and hence a total of
at least 25 specimens, be used.
To
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