1、 AECMA PRENxb042 95 1012311 0010035 442 Edition approved for publication 1995-1 1-30 AECMA STANDARD prEN 6042 NORME AECMA Edition P1 AECMA NORM November 1995 PUBLISHED BY THE EUROPEAN ASSOCIATION OF AEROSPACE INDUSTRIES (AECMA) Gulledelle 94 - B-1200 BRUXELLES - Tel. (32) 2 775 81 10 - Fax. 132) 2 7
2、75 81 11 Comments should be sent within six months after the date of publication to AECMA Gulledelle 94 B-1200 BRUXELLES ICs : Descriptors : ENGLISH VERSION Aerospace series Organic compounds Test method Analysis by infrared spectroscopy Srie arospatiale Composs organiques Mthode dessai Analyse par
3、spectroscopie infra-rouge Luft- und Raumfahrt Organische Verbindungen Prfverfahren Analyse durch Infrarot-Spektroskopie This “Aerospace Series“ Prestandard has been drawn up under the responsibility of AECMA (The European Association of Aerospace Industries). It is published on green paper for the n
4、eeds of AECMA-Members. It has been technically approved by the experts of the concerned Technical Committee following comment by the Member countries. Subsequent to the publication of this Prestandard, the technical content shall not be changed to an extent that interchangeability is affected, physi
5、cally or functionally, without re-identification of the standard. After examination and signature of the AECMA Standard Checking Centre (NPSI and formal agreement of the Official Services of the Member countries it will be submitted as a draft European Standard to CEN (European Committee for Standar
6、dization) for formal vote. Nota - Extra copies can be supplied by B.N.A.E. - Technopolis 54 - 199, rue Jean-Jacques Rousseau - 921 38 ISSY-LES-MOULINEAUX CEDEX AIBITFG Chairman Mr K. Schneider aecma 199! AECIA PRENxb042 95 W LOI12311 001003b 389 W Page 2 prEN 6042 : 1995 Contents list 1 Scope 2 Norm
7、ative references 3 Definitions 4 Principle of the method 5 Designation of the method 6 Apparatus 7 Test specimen 8 Procedure 9 Presentation of the results 10 Test report Annex A Pellititation Annex B Annex C Annex D Annex E Total dissolution (Distot) Annex F Liquid cell Annex G Gas cell Deposit on a
8、 plate Deposit between two plates Dissolution and pellititation (Dispas) AECMA PRENxb042 95 10123Ll 0010037 215 Page 3 prEN 6042 : 1995 1 Scope This test method describes the principles applicable to infrared transmission spectrophotometric analysis of organic compounds (elastomers, basic resins, re
9、sin 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 shall be used jointly with special test conditions specified in the materials specification
10、invoking the test. This standard does not give any directions necessary to meet the health and safety requirements. It is the responsibility of the user of this standard to adopt appropriate health and safety precautions. 2 Normative references This European Standard incorporates by dated or undated
11、 reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when inc
12、orporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. EN 2743 Aerospace series Reinforced plastics Standard procedures for conditioning prior to testing 3 Definitions 3.1 Base resin The main component of a resin system. 3.2 Resin
13、mix, resin system, neat resin, resin The base resin + fillers + additive + catalytic systems + hardener + accelerator + thinner. 3.3 Prepreg resin The 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 ch
14、aracteristic 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. Varying the wavelength of the beam therefore generates a series of absorp
15、tion 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). AECMA PRENlilb042 9
16、5 m 1012311 0010038 151 m Page 4 prEN 6042 : 1995 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 refe
17、rence spectra. 4.2 The Beer-Lambert law (Method of tangents) For any absorption line in the IR spectrum (see figure 11, a line can be drawn tangential to the transmission maxima on either side of the band. The absorption Beers law is then written: where: A is the absorbance I Io E C is the concentra
18、tion L is the transmittance at the maximum absorption within the band (see figure 1) is the transmittance read from the tangent at the maximum absorption wavelength (see figure li is the factor of absorption (characteristic of the bond generating the absorption) is the length of the optical path in
19、the sample For a given absorption band, E 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 : Description block Identity block Analysis of orga
20、nic compounds by Infrared Spectroscopy (IR) Method used (see Annex A-G) Number of this standard 6 Apparatus 6.1 Spectrophotometer Two types of spectrophotometer are used covering the range 400 cm- to 4000 cm- (2,5 ,um to 25 ,um). These instruments give the same type of spectrum. 6.1.1 Wavelength dis
21、persion spectrophotometer An infrared polychromatic source generates a beam which is partially absorbed in the sample and then enters a monochromator. The output from the monochromator is a monochromatic beam with wavelength A. A detector measures the intensity of this beam and transmits the result
22、to a recorder. The monochromator scans the wavelength and the recorder thus produces the sample IR absorption spectrum. The spectral resolution at 3000 cm- shall be better than 5 cm- and at 1 O00 cm- better than 3 cm- . AECMA PRENx6042 95 = LOL23LL OOL0037 O98 Page 5 prEN 6042 : 1995 6.1.2 Fourier T
23、ransform 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 (A) is the
24、 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 - better resolution (1 -2) cm? - more sensitive since the energy loss is lower and the detectors used are
25、 more sensitive - more suitable for sensitive materials that change with time. 6.1.3 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
26、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, .e. the quantity of each component it contains shall be reproducible. With reinforced products, it is usually necessary to elim
27、inate 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. Subsequently, take all precautions to obtain a homogeneous sample from a mixture of compounds, some of which ten
28、d 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 The test shall be carri
29、ed out at (23+2I0C and (50151% 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. AECMA PREN*b042 9
30、5 LOL23LL OOLO040 80T Page 6 prEN 6042 : 1995 8.1 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. 8.2 Deposit o
31、n 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. 8.3 Deposit between two plates This is a method frequently used for pasty and visc
32、ous 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. 8.4 Dissolution and pelletization This method can be applied to solid or pasty substances even if not totally solubl
33、e. It is described in Annex D. It provides qualitative and semi-quantitative results. 8.5 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 concentrat
34、ion. The method is described in Annex E. It provides qualitative, semi-quantitative and quantitative results. 8.6 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. 8.7 Gas c
35、ell 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
36、 known concentration (quantitative results). AECMA PREN*b042 95 LOL23LL 00LOYl1 746 Page 7 prEN 6042 : 1995 9 Analysis and interpretation of spectra Figure 2 gives an example of a typical spectrum. The results can be interpretated in several ways, depending on how the sample analyzed was prepared. 9
37、.1 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.
38、It is also possible to identiy characteristic bands (functional groups) and thus usually identify, the major components. 9.2 Semi-quantitative interpretation Semi-quantitative interpretation involves measuring the intensity of the bands and then calculating the infrared indices. 9.2.1 Calculation of
39、 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
40、 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: OE - calculate the absorbance A E- -
41、log - IE OR - calculate the absorbance A R- - log - IR A AR - the infrared index iE is given by E = - (see figure 1) (see figure 1 ) This index i, is independent of the sample quantity and proportional to the concentration of chemical function E relative to that of chemical function R. AECMA PRENtb0
42、42 95 W IIOIIIIII 0010042 682 = Page 8 prEN 6042 : 1995 9.2.2 Validity of the interpretation - after calibration using known standard solutions which give a relation i, = f(C, 1, where CE is the concentration of the function or compound of which band E absorption is characteristic, it becomes possib
43、le 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
44、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. 9.3 Quantitative interpretation In this method, the absorbance in a band characteristic of the component being measured is compar
45、ed 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
46、are totally soluble in a solvent. 9.3.1 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 sa
47、mple to be analyzed, subsequently, shall be diluted. - to determine the absorbancekoncentration 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, - the 8 fa
48、ctors in the Beer-Lambert law can be determined experimentally: A =A, + BxC = A, + ExLxC where: A is the absorbance C B SEXI this absorption shall be between 15 and 30 % of transmission. apply additional deposit if the spectrum intensity is too low, prepare a completely new deposit if the spectrum i
49、ntensity is too high. If the spectrum is not satisfactory: 2.2 Record the spectrum Record the IR spectrum using a scan speed which gives good peak definition, .e. approximately 150 cm-/min. For FTIR use the mean of 16 scans in order to obtain a good signalhoise ratio. Recording range (4000 - 400) cm- if possible. Note : Carry out at least two tests giving satisfactory IR spectra - AECMA PRENxb042 95 m 1012311 0010047 164 m Page 13 prEN 6042 : 1995 Annex C : Deposit between two plates (Method Cl This annex describes the method of qualitativ
