FprEN 6042
(Main)Aerospace series - Organic compounds - Test method - Analysis by infrared spectroscopy
Aerospace series - Organic compounds - Test method - Analysis by infrared spectroscopy
This test method describes the principles applicable to infrared transmission spectrophotometric analysis of organic compounds (elastomers, basic resins, resin mixes or resin systems) used as the matrix in reinforced polymers, adhesives, bonding primers and, in general terms, all organic compounds.
The method could also be applied to some inorganic products.
It is intended to be used jointly with special test conditions specified in the materials specification invoking the test.
This document does not give any directions necessary to meet the health and safety requirements. It is the responsibility of the user of this document to adopt appropriate health and safety precautions.
Luft- und Raumfahrt - Organische Verbindungen - Prüfverfahren - Analyse durch lnfrarot-Spektroskopie
Série aérospatiale - Composés organiques - Méthode d'essai - Analyse par spectroscopie infrarouge
La présente méthode d’essai décrit les principes applicables à l’analyse spectrophotométrique par transmission infrarouge des composés organiques (élastomères, résines basiques, mélanges de résines ou systèmes de résines) utilisés comme matrice dans les adhésifs, les apprêts de liaison et les polymères renforcés et, de manière générale, dans tous les composés organiques.
Cette méthode est également susceptible d’être appliquée à certains produits inorganiques.
Elle doit être utilisée conjointement avec les conditions d’essai particulières définies dans la spécification des matériaux faisant appel à l’essai.
La présente norme ne donne pas les instructions nécessaires au respect des exigences en matière de santé et de sécurité. Il est de la responsabilité de l'utilisateur d'adopter les précautions appropriées liées à la santé et la sécurité.
Aeronavtika - Organske spojine - Preskusna metoda - Analiza z infrardečo spektroskopijo
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN 6042:2021
01-september-2021
Aeronavtika - Organske spojine - Preskusna metoda - Analiza z infrardečo
spektroskopijo
Aerospace series - Organic compounds - Test method - Analysis by infrared
spectroscopy
Luft- und Raumfahrt - Organische Verbindungen - Prüfverfahren - Analyse durch lnfrarot-
Spektroskopie
Série aérospatiale - Composés organiques - Méthode d'essai - Analyse par
spectroscopie infra-rouge
Ta slovenski standard je istoveten z: prEN 6042
ICS:
49.025.40 Guma in polimerni materiali Rubber and plastics
oSIST prEN 6042:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 6042:2021
DRAFT
EUROPEAN STANDARD
prEN 6042
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2021
ICS 49.025.40
English Version
Aerospace series - Organic compounds - Test method -
Analysis by infrared spectroscopy
Série aérospatiale - Composés organiques - Méthode Luft- und Raumfahrt - Organische Verbindungen -
d'essai - Analyse par spectroscopie infra-rouge Prüfverfahren - Analyse durch lnfrarot-Spektroskopie
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee ASD-
STAN.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 6042:2021 E
worldwide for CEN national Members.
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Contents Page
European foreword . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle of the method . 5
4.1 General. 5
4.2 The Beer-Lambert law (Method of tangents) . 6
5 Designation of the method . 6
6 Apparatus . 7
6.1 Spectrophotometer . 7
6.1.1 General. 7
6.1.2 Wavelength dispersion spectrophotometer . 7
6.1.3 Fourier Transform Infrared spectrophotometer (FTIR) . 7
6.1.4 Calibration . 7
6.2 Sampling method . 7
7 Test specimen . 7
7.1 Preparation . 7
7.2 Storage . 8
8 Procedure . 8
8.1 General. 8
8.2 Pelletization . 8
8.3 Deposit on a plate . 8
8.4 Deposit between two plates . 8
8.5 Dissolution and pelletization . 8
8.6 Total dissolution . 8
8.7 Liquid cell method . 9
8.8 Gas cell method . 9
9 Analysis and interpretation of spectra . 9
9.1 General. 9
9.2 Qualitative interpretation . 9
9.3 Semiquantitative interpretation . 9
9.3.1 General. 9
9.3.2 Calculation of the infrared index. 9
9.3.3 Validity of the interpretation . 10
9.4 Quantitative interpretation . 10
9.4.1 General. 10
9.4.2 Preliminary calibration . 10
9.4.3 Use of the spectrum . 11
10 Test report . 12
Annex A (normative) Pelletization (Method A) . 14
A.1 General. 14
A.2 Apparatus and reagents . 14
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A.3 Procedure . 14
A.3.1 Sampling . 14
A.3.2 Record the spectrum . 15
Annex B (normative) Deposit between on a plate (Method B) . 16
B.1 General . 16
B.2 Apparatus and reagents . 16
B.3 Procedure . 16
B.3.1 Sampling . 16
B.3.2 Record the spectrum . 17
Annex C (normative) Deposit between two plates (Method C) . 18
C.1 General . 18
C.2 Apparatus and reagents . 18
C.3 Procedure . 18
C.3.1 Sampling . 18
C.3.2 Record the spectrum . 19
Annex D (normative) Dissolution and pelletization (Dispas) (Method D) . 20
D.1 General . 20
D.2 Apparatus and reagents . 20
D.3 Procedure . 20
D.3.1 Sampling . 20
D.3.2 Record the spectrum . 21
Annex E (normative) Total dissolution (Distot) (Method E) . 22
E.1 General . 22
E.2 Apparatus and reagents . 22
E.3 Procedure . 22
E.3.1 Preparation of the solution . 22
E.3.2 Filtration . 23
E.3.3 Record the spectrum . 23
Annex F (normative) Liquid cell (Method F) . 24
F.1 General . 24
F.2 Apparatus and reagents . 24
F.3 Procedure . 24
Annex G (normative) Gas cell (Method G) . 25
G.1 General . 25
G.2 Apparatus and reagents . 25
G.3 Procedure . 25
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European foreword
This document (prEN 6042:2021) has been prepared by the Aerospace and Defence Industries
Association of Europe — Standardization (ASD-STAN).
After enquiries and votes carried out in accordance with the rules of this Association, this document has
received the approval of the National Associations and the Official Services of the member countries of
ASD-STAN, prior to its presentation to CEN.
This document is currently submitted to the CEN Enquiry.
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1 Scope
This test method describes the principles applicable to infrared transmission spectrophotometric
analysis of organic compounds (elastomers, basic resins, resin mixes or resin systems) used as the matrix
in reinforced polymers, adhesives, bonding primers and, in general terms, all organic compounds.
The method could also be applied to some inorganic products.
It is intended to be used jointly with special test conditions specified in the materials specification
invoking the test.
This document does not give any directions necessary to meet the health and safety requirements. It is
the responsibility of the user of this document to adopt appropriate health and safety precautions.
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.
EN 2743, Aerospace series - Fibre reinforced plastics - Standard procedures for conditioning prior to testing
unaged materials
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 https://www.electropedia.org/
3.1
base resin
main component of a resin system
3.2
resin mix
resin system
neat resin
resin
base resin + fillers + additive + catalytic systems + hardener + accelerator + thinner
3.3
prepreg resin
resin obtained from the prepreg
4 Principle of the method
4.1 General
Organic molecules consist of atoms bonded together. Many bonds vibrate at a characteristic frequency in
the infrared (IR) range.
If a monochromatic IR beam impinges on the molecule and its frequency corresponds to a natural
vibration frequency between functional groups, energy from the beam is absorbed.
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Varying the wavelength of the beam therefore generates a series of absorption lines corresponding to the
various molecular bonds. This set of lines forms a spectrum. The sample is subjected to a beam at all
frequencies of interest and a computer determines which wavelengths have been absorbed.
The preferred method is Fourier Transform Infrared (FTIR).
The IR absorption spectrum is reproducible and not greatly affected by the apparatus. It can be used to:
• identify the main organic functional groups of the molecule (carbonyl, ether, amine, epoxy, etc.),
• identify a material by comparison with reference spectra.
4.2 The Beer-Lambert law (Method of tangents)
For any absorption line in the JR spectrum (see Figure 1), a line can be drawn tangential to the
transmission maxima on either side of the band. The absorption Beer's law is then written:
I
o
A= log =ε××C L
I
where:
A is the absorbance,
I is the transmittance at the maximum absorption within the ban (see Figure 1),
I is the transmittance read from the tangent at the maximum absorption wavelength (see
O
Figure 1),
ε is the factor of absorption (characteristic of the bond generating the absorption),
C is the concentration,
L is the length of the optical path in the sample.
For a given absorption band, ε and L are constant and absorbance A is therefore directly proportional to
concentration C.
5 Designation of the method
The designation of the method used shall be drawn up according to the following example:
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6 Apparatus
6.1 Spectrophotometer
6.1.1 General
-1 -1
Two types of spectrophotometer are used covering the range 400 cm to 4 000 cm (2,5 µm to 25 µm).
These instruments give the same type of spectrum.
6.1.2 Wavelength dispersion spectrophotometer
An infrared polychromatic source generates a beam which is partially absorbed in the sample and then
enter a monochromator. The output from the monochromator is a monochromatic beam with
wavelength λ.
A detector measures the intensity of this beam and transmits the result to a recorder.
The monochromator scans the wavelength and the recorder thus produces the sample IR absorption
-1 -1 -1
spectrum. The spectral resolution at 3 000 cm shall be better than 5 cm and at 1 000 cm
-1
better than 3 cm .
6.1.3 Fourier Transform Infrared spectrophotometer (FTIR)
The Fourier transform is a basic mathematical operation which converts a time periodic function into a
frequency function.
In the FTIR spectrophotometer, the optical dispersion system is replaced by an interferometer. The
absorption spectrum A = f (λ) is the Fourier transform of the interference diagram obtained; this
operation is performed by a computer connected to the spectrophotometer. FTIR spectroscopy offers the
following advantages:
• faster,
-1
• better resolution (1-2) cm ,
• more sensitive since the energy loss is lower and the detectors used are more sensitive,
• more suitable for sensitive materials that change with time.
6.1.4 Calibration
The wavelength and absorption shall be calibrated with the standards recommended by the instrument
supplier (e.g. polystyrene film).
6.2 Sampling method
Sampling procedures together with method specific apparatus and reagents are defined in
Annexes A to G.
7 Test specimen
7.1 Preparation
In general terms, the sample analyzed shall be representative of the entire substance, i.e. the quantity of
each component it contains shall be reproducible.
With reinforced products, it is usually necessary to eliminate the support (fibres or fabric), any mineral
fillers and solvents using an appropriate process (extraction of the solvent, evaporation,
centrifuging, etc.) to isolate the resin system.
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Subsequently, take all precautions to obtain a homogeneous sample from a mixture of compounds, some
of which tend to segregate. A resin system can contain some insolubles, some partially solubles and some
entirely solubles.
7.2 Storage
The sample for analysis shall be stored under conditions such that it does not change between sampling
and analysis or between two analyses.
8 Procedure
8.1 General
The test shall be carried out at (23 ± 2) °C and (50 ± 5) % relative humidity (EN 2743 B conditions).
Several infrared spectrophotometry methods can be used. The differences lie in the preparation and
processing of the sample or the type of result expected.
The Annexes describe special features of each method.
8.2 Pelletization
This method is applicable to solid substances that are insoluble or difficult to dissolve, such as elastomers
and cured materials.
It is described in Annex A.
It offers qualitative and, possibly, semi-quantitative results.
8.3 Deposit on a plate
This is a method frequently used for pasty, viscous organic substances. The deposit may be
heterogeneous and difficult to reproduce.
The method is described in Annex B.
It will only give qualitative results.
8.4 Deposit between two plates
This is a method frequently used for pasty and viscous organic substances. The deposit takes the form of
a homogeneous, reproducible thin film.
The method is described in Annex C.
It provides qualitative and semi-quantitative results.
8.5 Dissolution and pelletization
This method can be applied to solid or pasty substances even if not totally soluble.
It is described in Annex D.
It provides qualitative and semi-quantitative results.
8.6 Total dissolution
This method can be used to determine the proportion of a component in a resin system by comparing the
absorbance with that obtained by previous calibration using a solution of known concentration.
The method is described in Annex E.
It provides qualitative, semi-quantitative and quantitative results.
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8.7 Liquid cell method
This method is applicable to liquid or dissolved substances.
It is described in Annex F.
It provides qualitative, semi-quantitative and quantitative results.
8.8 Gas cell method
This method is applicable to gaseous substances.
It is described in Annex G.
It provides qualitative results and can be used to determine the proportion of the various components in
the gaseous mixture by comparing the absorbance with that obtained by previous calibration using
mixture of known concentration (quantitative results).
9 Analysis and interpretation of spectra
9.1 Introduction
Figure 2 gives an example of a typical spectrum.
The results can be interpreted in several ways, depending on how the sample analyzed was prepared.
9.2 Qualitative interpretation
This method is used to check, within the limits imposed by the method, the product by comparison with
a reference spectrum given in the product specification or held on computer. The features checked are
the appearance, disappearance or changes to the absorption bands. It is also possible to identify
characteristic bands (functional groups) and thus usually identify, the major components.
9.3 Semi-quantitative interpretation
9.3.1 General
Semi-quantitative interpretation involves measuring the intensity of the bands and then calculating the
infrared indices.
9.3.2 Calculation of the infrared index
The infrared index expresses the concentration of one function relative to another. The index is
determined from the absorbance ratio.
• Let E be the absorption band to be determined quantitatively.
• A reference band R in the infrared spectrum is determined.
• This band shall be invariable: the bond shall be non-reactive and its intensity shall be
independent of changes to the system.
• This band shall possess an absorbance of the same magnitude that of band E.
The infrared index i corresponding to band E is then calculated as follows:
E
I
oE
• Calculate the absorbance A = (see Figure 1).
E
I
E
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I
OR
A = log
• Calculate the absorbance (see Figure 1).
R
I
R
A
E
I =
• The infrared index i is given by .
E E
A
R
This index i is independent of the sample quantity and proportional to the concentration of chemical
E
function E relative to that of chemical function R.
9.3.3 Validity of the interpretation
• After calibration using known standard solutions which give a relation i = f(C ), where C is the
E E E
concentration of the function or compound of which band E absorption is characteristic, it becomes
possible to determine:
• the proportion of certain functional groups, epoxy, amine, alcohol,
• the proportion of one compound relative to another.
• With no calibration, the infrared indices can still be used to highlight variations in composition and
the proportions of the functions.
The validity of the infrared index measurement depends on the sampling quality and that of the IR
spectrum.
On average, the absorbance in the bands measured shall be between 0,050 and 0,400.
9.4 Quantitative interpretation
9.4.1 General
In this method, the absorbance in a band characteristic of the component being measured is compared to
that obtained by calibration using a solution of known concentration.
To this end, the Beer-Lambert law (see 4.2) is applied to the result of calibration using known standard
solutions. Unlike the index method, this method can only be applied to liquid and gaseous mixtures and
materials which are totally soluble in a solvent.
9.4.2 Preliminary calibration
The operating conditions shall be identical to those for the measurement itself. The purpose of calibration
is:
• to determine the concentration range over which the Beer-Lambert law can be applied to determine
the ratio in which the sample to be analyzed, subsequently, shall be diluted,
• to determine the absorbance/concentration relationship in the selected dilution range. One of the
following two techniques can be used:
• a calibration solution, which brackets the values to be measured, is prepared from pure products,
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• the B factors in the Beer-Lambert law can be determined experimentally:
A A+ B× C A+ε× L× C
oo
where:
A is the absorbance,
C is the concentration to be measured,
B is ε x I,
ε is the absorption factor,
L is the length of the optical path.
9.4.3 Use of the spectrum
Figure 3 gives an example of a spectrum.
It is possible to determine:
• the concentration C of component x in the solution.
x
There are two possible methods:
• by plotting value A _ on the calibration curve (see 9.4.2)
x
• by calculation if the Beer-Lambert factor Bis known:
A
x
C =
x
B
where:
C is the concentration of component x, in mg / ml,
x
A is the absorbance of the component x,
x
B is ε x I,
ε is the absorption factor,
L is the length of the optical path.
• the mass M of component x, in milligrams, in the test sample:
x
M C× v
xx
where:
V is the volume of the solution, in millilitres.
11
=
= =
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• the percentage T of the compound, in %, in the mixture:
x
M
x
T × 100
x
M
where:
M is the mass of the sample, in milligrams.
NOTE 1 In case of resin and fibres or other carriers (e.g. prepreg, film adhesives).
M
x
T ×100
x
M
R
M MM−
RF
where:
M is the mass of resin, in milligrams,
R
M is the mass of fibres or carrier in the sample, in milligrams.
F
NOTE 2 When the resin is in solution (e.g. bonding primer).
M
x
T ×100
x
M× ES
where:
ES is the dry extract of the product analyzed.
10 Test report
The test report shall refer to this document and include the following:
10.1 The complete identification of the material tested, including ma
...
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