ISO 11357-6:2002
(Main)Plastics — Differential scanning calorimetry (DSC) — Part 6: Determination of oxidation induction time
Plastics — Differential scanning calorimetry (DSC) — Part 6: Determination of oxidation induction time
This part of ISO 11357 specifies a method for the determination of the oxidation-induction time (OIT) of polymeric materials by differential scanning calorimetry (DSC). It is applicable to polyolefin resins that are in a fully stabilized/compounded form, either as raw materials or as finished products. It may be applicable to other plastics.
Plastiques — Analyse calorimétrique différentielle (DSC) — Partie 6: Détermination du temps d'induction à l'oxydation
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 11357-6
First edition
2002-05-01
Plastics — Differential scanning calorimetry
(DSC) —
Part 6:
Determination of oxidation induction time
Plastiques — Analyse calorimétrique différentielle (DSC) —
Partie 6: Détermination du temps d'induction à l'oxydation
Reference number
ISO 11357-6:2002(E)
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ISO 2002
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ISO 11357-6:2002(E)
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ISO 11357-6:2002(E)
Contents Page
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus and materials . 2
6 Test specimens . 3
7 Test conditions and specimen conditioning . 3
8 Temperature calibration . 3
9 Procedure . 3
10 Expression of results . 5
11 Test report . 6
Annexes
A Alternative OIT determination . 7
B Sample homogenization . 8
C Precision and bias. 9
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ISO 11357-6:2002(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 3.
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 part of ISO 11357 may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 11357-6 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee
SC 5, Physical-chemical properties.
ISO 11357 consists of the following parts, under the general title Plastics — Differential scanning calorimetry (DSC):
— Part 1: General principles
— Part 2: Determination of glass transition temperature
— Part 3: Determination of temperature and enthalpy of melting and crystallization
— Part 4: Determination of specific heat capacity
— Part 5: Determination of characteristic reaction-curve temperatures and times, enthalpy of reaction and degree of
conversion
— Part 6: Determination of oxidation induction time
— Part 7: Determination of crystallization kinetics
— Part 8: Determination of amount of absorbed water
Annex A forms a normative part of this part of ISO 11357. Annexes B and C are for information only.
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INTERNATIONAL STANDARD ISO 11357-6:2002(E)
Plastics — Differential scanning calorimetry (DSC) —
Part 6:
Determination of oxidation induction time
WARNING — The use of this part of ISO 11357 may involve hazardous materials, operations or equipment.
This part of ISO 11357 does not purport to address all of the safety concerns, if any, associated with its use.
It is the responsibility of the user of this part of ISO 11357 to establish appropriate safety and health
practices and determine the applicability of regulatory limitations prior to use. Specific hazard information is
given in subclause 5.3.
1 Scope
This part of ISO 11357 specifies a method for the determination of the oxidation-induction time (OIT) of polymeric
materials by differential scanning calorimetry (DSC). It is applicable to polyolefin resins that are in a fully
stabilized/compounded form, either as raw materials or as finished products. It may be applicable to other plastics.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 11357. For dated references, subsequent amendments to, or revisions of, any of these publications
do not apply. However, parties to agreements based on this part of ISO 11357 are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated below. For undated references,
the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of
currently valid International Standards.
ISO 291, Plastics — Standard atmospheres for conditioning and testing
ISO 293, Plastics — Compression moulding test specimens of thermoplastic materials
ISO 11357-1:1997, Plastics — Differential scanning calorimetry (DSC) — Part 1: General principles
3 Terms and definitions
For the purposes of this part of ISO 11357, the terms and definitions given in ISO 11357-1 plus the following term
and definition apply.
3.1
oxidation induction time
OIT
a relative measure of a stabilized material's resistance to oxidative decomposition
NOTE It is determined by the calorimetric measurement of the time interval to the onset of exothermic oxidation of a material at
a specified temperature in an oxygen atmosphere, under atmospheric pressure.
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ISO 11357-6:2002(E)
4Principle
The time for which the antioxidant stabilizer system present in a test specimen inhibits oxidation is measured while
the specimen is held isothermally at a specified temperature in a stream of oxygen. The OIT is an assessment of the
level (or degree) of stabilization of the material tested. It is dependent on the surface area of specimen available for
oxidation.
The specimen and a reference material are heated at a constant rate in an inert gaseous environment (a flow of
nitrogen). When the specified temperature has been reached, the atmosphere is changed to oxygen maintained at
the same flow rate. The specimen is then held at constant temperature until the oxidative reaction is displayed on the
thermal curve. The OIT is the time interval between the initiation of oxygen flow and the onset of the oxidative
reaction. The onset of oxidation is signalled by an abrupt increase in the specimen's evolved heat or temperature and
may be observed by a differential scanning calorimeter (DSC). The OIT is determined from the data recorded during
the isothermal test.
NOTE The OIT can be indicative of the effective antioxidant level present in the test specimen. Caution should be exercised in
data interpretation, however, since oxidation reaction kinetics are a function of temperature and the inherent properties of the
additives contained in the sample. For example, OIT results are often used to select optimum resin formulations. Volatile
antioxidants or differences in activation energies of oxidation reactions may generate poor OIT results even though they may
perform adequately at the intended use temperature of the finished product. It should also be noted that, since the test is carried
out in pure oxygen, the OIT under normal atmospheric conditions will be longer.
5 Apparatus and materials
See ISO 11357-1:1997, clause 5.
◦
5.1 The DSC instrument used shall be capable of maintaining stability within ± 0,1 C at the test temperature over
◦
the duration of the test, typically 60 min. It shall be able to achieve a maximum temperature of at least 600 C.
With some instruments, there may be modes of operation that promote precise isothermal temperature control. If
available, they shall be used. If not, the test shall be conducted at two different isothermal temperatures, with each
having been ascertained as accurately as possible. The data is then interpolated or extrapolated to the specified test
temperature (see annex A). Alternatively, the specimen temperature can be monitored and adjusted continually, as
required. Instruments incapable of automatic operation will additionally require a timer to monitor elapsed time.
5.2 The pans should preferably be open aluminium pans or closed ventilated pans. Other pans may be used by
agreement between the interested parties.
NOTE The material composition of the pan can influence the OIT test result significantly (that is, including any associated
catalytic effects). The type of containment system used depends on the intended application of the material being tested.
Polyolefins used in the wire and cable industry typically require copper or aluminium pans, whereas polyolefins used in
geomembrane and vapour-barrier film applications exclusively use aluminium pans.
5.3 Oxygen, 99,5 % ultra-high-purity grade (extra dry).
WARNING — The use of pressurized gas requires safe and proper handling. Further, oxygen is a strong
oxidizer that accelerates combustion vigorously. Keep oil and grease away from equipment using or
containing oxygen.
5.4 Nitrogen, 99,99 % ultra-high-purity grade (extra dry).
5.5 Gas-selector switch and regulators, needed to switch between nitrogen and oxygen. The distance between
the gas-switching point and the instrument cell shall be kept small, with a dead time of less than one minute, to
minimize the switching volume. Accordingly, for a flow rate of 50 ml/min, the dead volume shall be less than 50 ml.
NOTE Increased precision can be obtained if the dead time is known. One possible means of determining dead time is to carry
out a test using a non-stabilized material which will oxidize immediately in the presence of oxygen. The induction time from this
test will provide a correction for subsequent OIT determinations.
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ISO 11357-6:2002(E)
5.6 Flowmeter, of the rotameter or soap-film flowmeter type, for oxygen gas-flow calibration. Rotameters shall be
calibrated against a positive-displacement device.
6 Test specimens
See ISO 11357-1:1997, clause 6, also taking into account the following recommendations/requirements:
a) The following sample preparation procedures are recommended: following ISO293, the test sample is
compression-moulded into sheet of thickness 250µm± 15µm prior to analysis to yield consistent sample
morphology and mass. Limit heating to 2min at the moulding temperature. Use a bore-hole cutter to punch out a
disc from the sheet. Specimen discs small enough to lay flat in the pan, cut from the sheet, will have a mass of
approximately 5mg to 20mg, depending on sample density. Do not stack spec
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