ISO 16565:2002

INTERNATIONAL ISO
STANDARD 16565
First edition
2002-03-15

Rubber — Determination of
5-ethylidenenorbornene (ENB) or
dicyclopentadiene (DCPD) in ethylene-
propylene-diene (EPDM) terpolymers
Caoutchouc — Détermination du 5-éthylidènenorbornène (ENB) ou du
dicyclopentadiène (DCPD) dans les terpolymers d'éthylène-propylène-
diène (EPDM)




Reference number
ISO 16565:2002(E)
©
ISO 2002

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ISO 16565:2002(E)
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ISO 16565:2002(E)
Contents Page
Foreword.iv
1 Scope .1
2 Principle.1
3 Apparatus .1
4 Test specimen preparation.2
5 Acquisition of spectra.3
6 Calibration of the spectrophotometer .3
7 Diene determination .4
8 Precision and bias.8
9 Test report .10
Annex A (normative) Procedure for spectral subtraction of water vapour.11
Bibliography.13

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ISO 16565:2002(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.
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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 16565 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 2,
Testing and analyses.
Annex A forms a normative part of this International Standard.

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INTERNATIONAL STANDARD ISO 16565:2002(E)

Rubber — Determination of 5-ethylidenenorbornene (ENB) or
dicyclopentadiene (DCPD) in ethylene-propylene-diene (EPDM)
terpolymers
WARNING — Persons using this International Standard should be familiar with normal laboratory practice.
This standard 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 standard to establish appropriate safety and health practices and to
ensure compliance with any national regulatory conditions.
1 Scope
This International Standard specifies the methods to be used to determine the content of 5-ethylidenenorbornene
(ENB) or dicyclopentadiene (DCPD) in ethylene-propylene-diene (EPDM) terpolymers in the 0,1 % to 15 % range.
ENB and DCPD are dienes introduced into ethylene-propylene rubbers to generate specific cure properties. Since
high precision for diene content determination is important, a Fourier transform infrared spectroscopic (FT-IR)
method is utilized.
NOTE The procedures for mass fraction of ENB and mass fraction of DCPD differ only in the location in the infrared (IR)
peak being quantified.
2 Principle
A test specimen is moulded between two PTFE-coated aluminium or mylar sheets. The ENB content is determined
−1 −1
from its infrared absorbance at 1 681 cm to 1 690 cm , a measure of the exocyclic double bond in ENB. The
−1 −1
DCPD content is determined from its infrared absorbance at 1 605 cm to 1 610 cm , a measure of the
monocyclic double bond in DCPD.
The second derivative of the absorbance is calculated and ratioed to an internal standard. For ENB, the resulting
−1
second-derivative peak near 1 690 cm is related to the ENB mass fraction by calibrating the instrument with
−1
known EPDM standards. For DCPD, the resulting second-derivative peak near 1 610 cm is related to the DCPD
mass fraction in the same way.
For oil-extended polymers, the oil must be extracted before the diene content is determined.
3 Apparatus
3.1 Carver-type press, capable of compressing films at 150 °C and 10 MPa.
3.2 Mould
3.2.1 The mould primarily used is made of stainless-steel strip 400 µm thick with an opening which will give a
specimen of the appropriate size for the specimen-film holder described in 3.4 (2 cm by 2 cm). The mould shall
have approximately the same dimensions as the press platens.
3.2.2 Alternatively, a thinner mould plate may be used. However, precision can be adversely affected at low
diene levels. The precision of the method shall be determined when thinner films are utilized. For example,
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ISO 16565:2002(E)
127-µm-thick stainless-steel foil with a 15 mm by 35 mm opening may be used for the simultaneous determination
of ethylene and diene.
3.2.3 For liquid EPDMs, a ring washer of 22 mm outer diameter by 16 mm inner diameter and 400 µm thick is
used as a spacer between salt plates (NaBr, NaCl) to set a fixed path length. The spacer is sized to cover only the
outer edge of the salt plates.
3.3 PTFE-coated aluminium moulding sheets, type A, 36 µm thick, or silicone release sheeting.
3.4 Specimen-film holders: Films may be moulded, cut out and transferred to a film holder. Magnetic-film
holders are ideal. Alternatively, a mould sized to fit in the spectrophotometer specimen compartment, with an
appropriate-size opening, may be used to support the film without removal after compressing. A standard salt plate
support is used for liquid samples prepared between salt plates.
3.5 Infrared Fourier transform spectrophotometer, capable of measuring absorbances in the range
−1 −1
4 000 cm to 600 cm with a transmittance specification (accuracy) of ± 1 % T or better. The instrument shall be
−1
capable of spectral resolution of 2 cm . A deuterated triglycerine sulfate (DTGS) or, as an alternative, a mercury
cadmium telluride (MCT) detector shall be used.
NOTE A specification for the evaluation of the analysis of infrared spectra is given in reference [1].
The instrument shall be capable of spectral accumulation, averaging and subtracting. Water is the primary source
of interference in this method. Methods, physical and electronic, that minimize the moisture level and moisture-level
variation are required to obtain the highest precision. The preferred method is to use an instrument equipped with a
dry-gas purge and specimen shuttle, which permits alternating and repetitive collection of single-beam specimen
and background spectra (see clause 5). Alternatively, should a specimen shuttle be unavailable, careful purging of
the specimen compartment with dry nitrogen can yield satisfactory results. High precision of calibration-standard
data is indicative of adequate purging. When moisture interference is not removed by purging, spectral subtraction
of water vapour can be used. A procedure for further development of the method is described in annex A.
4 Test specimen preparation
4.1 Primary method
Place 0,20 g ± 0,05 g of the material to be analysed between two sheets (see 3.3) in the mould (see 3.2.1). Place
the mould between the press platens heated to 125 °C ± 5 °C and apply 4 MPa pressure for 60 s ± 10 s.
Should the material be highly viscous, the mould may be heated to 175 °C ± 5 °C.
Cool the material to ambient temperature. Cut out a piece of film approximately 15 mm by 50 mm. Detach the
specimen film from the sheets (see 3.3) and position it on the spectrophotometer specimen compartment window.
4.2 Alternative method
When using the thinner mould described in 3.2.2, place a small piece (0,04 g to 0,06 g) of the material to be
analysed in the mould opening between two sheets (see 3.3) and compress as in 4.1. Remove the mould from the
press, turn it over and compress it again. Then remove the mould from the press and allow it to cool to ambient
temperature. When cool, carefully remove the sheets (see 3.3), allowing the specimen film to remain attached to
the mould.
4.3 Alternative method for liquid polymer film preparation
Place a washer (see 3.2.3) on top of a salt plate. Place a small amount (about 0,3 g) of the liquid EPDM polymer to
be analysed in the centre of the washer, filling the hole completely. Place a second salt plate on top of the filled
washer. Gently place a 1 kg weight on top of the salt plate/washer assembly and allow the weighted assembly to sit
for 2 min to 3 min. (For viscous samples, it may be necessary to warm the sample prior to compressing.) Remove
the 1 kg weight and, if necessary, allow to cool. Wipe off any excess material that may have been pressed out of
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ISO 16565:2002(E)
the assembly. Hold the assembly up to the light and inspect for bubbles and/or voids. Should there be
imperfections, repeat the preparation with a larger amount of material.
5 Acquisition of spectra
5.1 With a specimen shuttle
5.1.1 The data-acquisition parameters shall be:
−1
 resolution: 2 cm ;
 scans/scan time: total scan time, split between specimen scans and background scans, about 90 s.
5.1.2 Place the test specimen in the specimen compartment, allow purge to re-establish and, in alternating
fashion, collect single-beam specimen and empty specimen compartment spectra. Eight passes of the shuttle shall
be made (eight specimen and eight empty-compartment collections), collecting four scans at each position.
5.1.3 Calculate the specimen absorbance spectrum as minus log of the ratio of the accumulated single-beam
10
specimen to the empty-compartment spectrum:
A = −log (P/P )
10 0
where
A is the absorbance of the specimen at a given wavelength;
P is the empty specimen compartment light-beam intensity at that wavelength;
0
P is the single-beam specimen light-beam intensity at that wavelength.
5.2 Without a specimen shuttle
5.2.1 The data-acquisition parameters shall be:
−1
 resolution: 2 cm ;
 scans/scan time: background scans: 32 scans, 120 s total; specimen scans: 32 scans, 120 s total.
5.2.2 Establish a dry atmosphere inside the empty specimen compartment and collect the empty specimen
compartment spectra.
5.2.3 Place the test specimen in the specimen compartment and re-establish a dry atmosphere inside the
compartment. Collect the single-beam specimen spectra and calculate the specimen absorption spectrum as
described in 5.1.3.
6 Calibration of the spectrophotometer
6.1 Obtain a series of known standards covering the diene content range 0 % to 10 %. Calibration may be based
on secondary standards qualified by other laboratories using this method or, more generally, by primary standards
whose diene content is well known. Primary standards may be established via use of hydrogen nuclear magnetic
1)
resonance (H-NMR), in conjunction with other techniques. The ENB calibration standards employed in the

1) The sole source of supply of the ENB standards is Exxon
...