1、AEROSPACERECOMMENDED PRACTICEARP1610 REV. A Issued 1981-10Revised 1985-04Reaffirmed 2014-08Superseding ARP1610Physical-Chemical Characterization Techniques,Epoxy Adhesive and Prepreg Resin SystemsRATIONALEARP1610A has been reaffirmed to comply with the SAE five-year review policy.1. SCOPE;1.1 This r
2、ecommended practice describes the physical and chemicalcharacterization techniques for identification of epoxy adhesive and prepregresin systems in order to verify the chemical formulation, resin B-staging(See 8.1), cure reaction rates, adhesive moisture content, and resincomponent mix ratios, as ne
3、cessary to achieve manufacturing and qualityproducibility and engineering performance.1.2 Application: While these techniques have been developed and validated forepoxy adhesive and prepreg resin systems, they are expected to be applicableto other thermoset materials, such as phenolics, polyimides,
4、or polyesters.It is the responsibility of the user of the materials to establish limits onthe acceptable variations of compositional parameters from the standard orbaseline values of the original formulations qualified for use. Whenestablished, these variations should be included in applicable mater
5、ialspecifications.1.3 Limitations; These techniques have been developed to detect chemicalformulation variations in epoxy systems. Chemical formulation variationshave not been quantitatively related to changes in mechanical properties,long-term durabilities, or moisture sensitivities of the material
6、. Thesetechniques should not be considered all-inclusive. The equipment usedherein is generally applicable to the quantitative and qualitative analysisof epoxy resins; however, specific materials, other than those discussedherein, may require modified techniques.1.4 Justification: The procedures des
7、cribed herein are the result of extensiveevaluations of structural epoxy adhesive and resin formulations applicableto aerospace applications.SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this
8、report isentirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.“SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized,
9、 or cancelled. SAE invites your written comments andsuggestions.Copyright 2014 SAE InternationalAll rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical,photocopying, recording, or otherwise,
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11、omerServicesae.org |_SAE WEB ADDRESS: http:/www.sae.orgSAE INTERNATIONAL ARP1610A Page 2 of 312. DESCRIPTION OF THE METHOD:2.1 Objective: The use of structural adhesives and epoxy composite materialsrequires that the composition of these materials be reproducible withinprescribed limits established
12、by the user of the materials throughapplicable procurement specifications. This document describes physical andchemical techniques to identify the constituents in the formulations and toaid in detection of qualitative and quantitative changes or variations ofthe constituents.2.2 Summary: This docume
13、nt outlines a standard method to chemically andphysically analyze and control epoxy adhesive and composite matrixformulations.2.3 Processing Steps: In order to achieve the high reliability and consistencynecessary in structural applications using epoxy adhesives and compositematerials, the following
14、 primary steps must be followed:Chemically characterize selected epoxy formulations,Establish minimum and maximum formulation standards,Provide quality control methods for purchased formulations,Develop manufacturing cure cycles and controls.3. ANALYTICAL METHODS:3.1 Chemical Analysis and Quality Co
15、ntrol Methods: Quality control foraerospace structural applications requires that epoxy adhesive or prepregmaterials selected for a specific design be controlled. This control canonly be achieved by knowing the chemical composition of the particularadhesive or composite matrix formulation. The use o
16、f the methods describedherein, spectroscopy, elemental and wet chemical analysis, chromatography,differential scanning calorimetry and dynamic dielectric analysis, serve notonly to identify and confirm the chemical constituents of a formulation butalso to establish the basis for ensuring that the pu
17、rchased products arechemically identical and have been processed to the proper degree ofB-staging. A schematic on how the analytical techniques can be used toidentify the formulations is given in Fig. 1. The techniques required touse these methods to characterize and ensure the consistency and quali
18、ty ofmaterial are described in the individual methods. Selection of whichprocedures are required for quality assurance testing is based on thecomponents of a given formulation.3.2 Spectroscopy: Spectroscopy is a valuable tool for the identification ofspecific components of a prepreg or adhesive resi
19、n. It is used primarily inthe qualitative identification of formulative components. It can be used inspecial cases for quantitative estimation of formulation constituents asdemonstrated herein. The primary areas of spectroscopy useful for epoxymaterials are infrared, ultraviolet, and emission spectr
20、oscopy.SAE INTERNATIONAL ARP1610A Page 3 of 313.2.1 Infrared Spectroscopy: Infrared absorption spectroscopy (IR) is extremelyuseful for ascertaining the absence or presence of a variety oforganofunctional groups.3.2.1.1 General Infrared Spectroscopy Methods:(1) Extract the prepreg or adhesive resin
21、in acetone, tetrahydrofuran(THF), or chloroform.(2) Filter the solution, saving the filtrate.(3) Apply the filtrate to an infrared plate (KBr or NaCl) and allowsolvent to evaporate.(4) Place the plate in the spectrometer.(5) Run the spectrum from 4000 cm“- t o 400 cm-*- using a slow scanand transmis
22、sion mode.(6) Compare epoxy spectra to known epoxy reference standards.3.2.1.2“ Quantitative Estimation of the Sulfone Group, Diaminodiphenyl Sulfone(DPS) by Infrared Spectroscopy:Step 1. Weigh (to the nearest 0.1 mg) 30, 40, 50, 60, 75, and 200-mg(if the IR absorbs in this range) samples of DDS plu
23、s resincomponent into 50-mL volumetric flasks. Dilute to volume withacetonitrile.Step 2. Place two 1.0 mm KBr precision path length, matched liquidcells filled with acetonitrile in both the sample andreference beams of the spectrophotometer. Scan the regionfrom 1200 to 1100 cm“-1- to ensure a clean
24、baseline free ofextraneous absorptions.Step 3. Replace the acetonitrile in the sample cell with a standardsample solution. Flush 2-3 times with the solution to beanalyzed. Record the spectrum from 1200 to 1100 cm“- f o reach standard solution.Step 4. Construct a calibration curve on linear graph pap
25、er forpercent DDS by plotting the negative logarithms of the percenttransmittance (T) values for thdissolve in 20 mL of acetonitrile. Filter on a tared glasscrucible, decant liquid into a 50-mL volumetric flask, diluteto volume.SAE INTERNATIONAL ARP1610A Page 4 of 313.2.1.2 (Continued):Step 6. Dry t
26、he reinforcement to constant weight at 100C (212F).Determine the amount of resin by subtracting the dryreinforcement weight from the prepreg weight and divide by 50to give the sample concentration in g/litre.Step 7. Analyze the sample in accordance with steps 3 and 4 above.Step 8. Take the negative
27、log (%T/100%T) of the sample from the IRspectra and determine the amount DDS from the calibrationcurve.Step 9. Record the DDS value (mg/mL).Step 10. Calculate percent DDS (by weight) as follows:DDS concentration g/L% DDS = : rrr2TT * 100Sample concentration g/L3.2,1,3 Quantitative Estimation of Dicy
28、andiamide (DICY) by Infrared Spectroscopy:Step 1. Weigh (to the nearest 0.1 mg) 10, 25, 37.5, and 50-mg samplesof DICY into 50-mL volumetric flasks. Dilute to volume with a mixture of 80/20 tetrahydrofuran/methanol. DICY is extremelysensitive to moisture; i t should be stored with a desiccantand wei
29、ghed in a dry atmosphere.Step 2, Place two 1.0-mm KBr precision path length matched liquidcells filled with 80/20 tetrahydrofuran/methanol in both thesample and reference beams of the infrared spectrophotometer.Scan the region from 2300 t o 2100 cm“- t o verify a cleanbaseline.Step 3. Replace the 80
30、/20 THF/CH3OH in the sample cell with a standard sample solution. The cell should be flushed 2-3times with the solution to be analyzed. Record the spectrumfrom 2300 t o 2100 cm“-1-. DICY exhibits a transmittanceminimum at 2190 cm“-. A calibration curve for determiningDICY, percent, in resin samples
31、is constructed by plotting thenegative logarithm of the percent transmission (%T) values forthe standard solutions divided by the baseline transmittance(100%T) versus their concentration in g/L on linear graphpaper.Step 4. Weigh between 0.8 and 0.9 g (to the nearest 0.1 mg) of prepregand transfer to
32、 a 50-mL beaker. Add 20 mL of 80/20tetrahydrofuran/methanol. Thoroughly agitate the solution toensure resin dissolution.SAE INTERNATIONAL ARP1610A Page 5 of 313.2.1.3 (Continued)Step 5. Decant solvent into a 50-mL volumetric flask and collectreinforcement in a preweighed fritted glass crucible. Wash
33、fibers with 80/20 tetrahydrofuran/methanol to ensure completesolution of resin and combine the wash solvent with the 20 mLin the volumetric flask. Dilute to volume and shake untiladequately mixed.Step 6. Dry the glass crucible containing the reinforcement toconstant weight at 100C (212F). Determine
34、the amount ofresin by subtracting the reinforcement weight from the prepregweight and divide this value by 50 to give the sampleconcentration in g/litre.Step 7. Analyze the liquid portion of the sample as described in step3.Step 8. Take the %T value of the sample and calculate -log/100%.Determine th
35、e amount of DICY by constructing a parallel lineto the X-axis from this value to the calibration curve anddropping a perpendicular line to the X-axis. Record the valueof DICY in mg/mL.Step 9. Calculate the percent of DICY (by weight) in the resin asfollows:DICY Concentration, g/LSample Concentration
36、, g/Lx 1003.2.2 Ultraviolet Spectroscopy: Ultraviolet spectroscopy (UV) i s similar toinfrared spectroscopy- except that wavelength is in the 190 - 400 nm rangeand is rarely used by itself for chemical characterization. UV i s usefulin conjunction with liquid chromatography where the separated solut
37、ion ispassed through a UV beam, absorbs the UV light and a spectrophotometerdetects and quantifies the change in transmittance. An analysis can bebased on a fixed wavelength or a scan of the entire spectrum.3.2.2.1 Ultraviolet Spectroscopy Methods: Ultraviolet spectroscopy chemicalcharacterization t
38、echniques are explained under chromatography (See 3,3)3.2.3 Emission Spectroscopy: Emission spectroscopy is useful to determine theelements and the relative percentages present in the filler materials,resins, or accelerators. The emission method makes use of prisms anddiffraction gratings to dispers
39、e the radiant energy emitted by excitedatoms, ions, or molecules when a sample is excited by an electric arc orspark discharge across electrodes. The energy is recordedphotographically and measured for wavelength and intensity.SAE INTERNATIONAL ARP1610A Page 6 of 313.2.3.1 Emission Spectroscopy Meth
40、od:Step 1. Prepare a suitable size sample of the material by ashing atnot lower than 425C (800F) or by extraction with solvent.Step 2. Place sample on holder in spectrometer.Step 3. Spark the sample.Step 4. Determine the elements present from the wavelengths on thephotographic plate.Step 5. Record t
41、he elements.3.3 Chromatography:3.3.1 Chromatography Parameters:3.3.1.1 Chromatography is a technique that can be used for separating epoxyformulations based on either the polarity or molecular size of theparticular constituents. The adhesive or prepreg formulation isextracted with a solvent. Tetrahy
42、drofuran (THF), acetonitrile, acetone,or chloroform are commonly used. The extracts are passed throughvarious columns which separate the formulative components depending onthe molecular size or polarity of the particular constituent. Highmolecular weight (large) and low polarity compounds pass throu
43、gh thecolumn in question more rapidly, thus effecting the separation. Thepresence of a particular compound in the effluent stream is detected byeither refractive index or ultraviolet light. The component i sidentified by the time required to elute from the column. The areaunder the IR- or UV-peak i
44、s used to obtain a quantitative measure of theconcentration. Resin/curing agent reaction product peaks are alsoseparated in the process giving a measure of the degree of B-stage.3.3.1.2 The eluent fractions can also be collected separately for IR scans todetermine the structure for chemical identifi
45、cation.3.3.1.3 Three commonly used chromatographic techniques are described herein:Thin layer chromatography (TLC), reverse phase liquid chromatography(RPLC) and gel permeation chromatography (GPC). The RPLC methodseparates the components by polarity. GPC analysis is based on the useof molecular sie
46、ves. TLC makes use of an adsorbent on a glass plate forits separation.SAE INTERNATIONAL ARP1610A Page 7 of 313.3.2 Thin Layer Chromatography (TLC); Thin layer chromatography is a simple,low cost, qualitative tool for separating an epoxy formulation into itscomponents, i.e., resin, diluent, additives
47、, and curing agents. Theseparation is achieved by applying a solution of the mixture near thelower edge of a glass plate coated with an adsorbent, normally a silica.The plate is placed vertically in a closed container containing a smallamount of the elution solvent on the bottom. The solvent migrate
48、s up theplate by capillary action carrying the components of the formulation whichseparate out at specific distances depending on the adsorptioncoefficients of the compound from the base. The components are locatedand scraped off the plate for solvent extraction and subsequent IRanalysis to identify
49、 the chemical structure (See Pig. 2).3.3.2.1 Thin Layer Chromatography Procedure;Step 1. Use silica gel coated glass plates (50 x 200 mm) which containa fluorescent dye (See 8.2).Step 2. Extract the resin with acetone and filter as necessary.Step 3. Spot the plate 20 mm from the bottom with extract to form a continuous line of sample using a streaking pipette.Step 4. Evaporate the acetone.Step 5. Develop the plate 40 - 60 min. in a vertical position byimmersing the lower edge approximately 10 mm in the selectedsolvent.Step 6. Locate
