1、Designation: D 6902 04e1Standard Test Method forLaboratory Measurement of Formaldehyde Evolved Duringthe Curing of Melamine-Formaldehyde-Based Coatings1This standard is issued under the fixed designation D 6902; the number immediately following the designation indicates the year oforiginal adoption
2、or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEParagraph 5.1 was corrected editorially in August 2004.1. Scope1.1 This test metho
3、d is for the determination of formalde-hyde evolved from melamine-formaldehyde-based coatingsduring the cure step. The results may be used to determine the“cure formaldehyde” evolved from a sample under controlledlaboratory conditions.1.2 The values stated in SI units are to be regarded as thestanda
4、rd. The values given in parentheses are for informationonly.1.3 This test method is capable of measuring from 500 g/gto 22 000 g formaldehyde/g dry coating under the testconditions specified (3 000 ml/min total flow, 50 ml/minDNPH tube flow). The ratio of total flow to DNPH tube flowcould be adjuste
5、d to extend the range of the method.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limi
6、tations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 362 Specification for Industrial Grade Toluene3D 1979 Test Method for Free Formaldehyde Content ofAmino ResinsD 6191 Test Method for Measurement of Evolved Formal-dehyde from Water Reducible Air-Dry CoatingsE 691 Practice for Conducti
7、ng an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 cure formaldehyde, nthe formaldehyde generated asthe result of a chemical reaction during coating curing.3.1.2 free formaldehyde, nthe residual formaldehyde in
8、 acoating due to the raw materials.4. Summary of Test Method4.1 Approximately 0.2 g of coating formulation is placed inan aluminum foil pan, dried in a vacuum oven at 40C (toremove free formaldehyde and solvents) and then baked at theoptimum process cure temperature for 30 min. Formaldehydeemissions
9、 are collected from the cure chamber on a DNPH/Silica tube, which is then extracted and the extract analyzed byHPLC/UV. The amount of formaldehyde evolved from thecoating during the cure step is calculated on both a wet-weightand dry-weight basis. The test is run in triplicate plus a blankand system
10、 standard.5. Significance and Use5.1 This test method measures the amount of formaldehydethat is evolved from a coating containing melamine-formaldehyde resin(s) during cure at elevated temperature.Cure formaldehyde results from a side-reaction during cross-linking of functionalized polymers with me
11、lamine-formaldehyde resins. Cure formaldehyde is evolved in the finalbake or cure oven, when the coating temperature is highenough to initiate cross-linking. Formaldehyde can be releasedfrom a coating during application, solvent flash-off and cure.Free formaldehyde is primarily evolved during coatin
12、g appli-cation and solvent flash-off. Test Method D 1979 measures“free formaldehyde” in amino resins and Test Method D 6191measures formaldehyde evolved from coatings at ambienttemperature. This method measures only the formaldehydereleased during heat cure, which is primarily “cure formalde-hyde.”5
13、.2 This test method is not intended to duplicate the evolvedformaldehyde from an industrial process, but serves as areproducible comparative laboratory evaluation.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the di
14、rect responsibility ofSubcommittee D01.21 on Chemical Analysis of Paints and Paint Materials.Current edition approved July 1, 2004. Published July 2004. Originally approvedin 2003. Last previous edition approved in 2003 as D 6902 03.2For referenced ASTM standards, visit the ASTM website, www.astm.or
15、g, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.
16、3 This test method has not been evaluated with catalyzedcoating systems that cure at or below 40C, such as those usedby the wood-finishing industry, and would likely requirespecial adaptation for this application.6. Apparatus6.1 High Pressure Liquid Chromatograph (HPLC), either agradient or isocrati
17、c system. A gradient system is preferredwhen other aldehydes or ketones are present.NOTE 1The system shall be equipped with a temperature-controlledcolumn oven. A liquid autosampler is optional.6.2 Column,aC18ODS packed with 5-m pellicular beadswith the dimensions of approximately 4 mm by 75 or 150
18、mm.A 2-cm guard column packed with the same material isrecommended to protect the analytical column.6.3 Detector, UV/VIS detector capable of measuring absor-bance at 360 nm.6.4 Integrator, peak integration system.6.5 Air Sampling Pump, an air sampling pump with thecapability of maintaining a constan
19、t flow rate between 3 and 4L/min. Both an inlet and outlet port must be available formeasuring flow. An SKC AirCheck Sampler Model 224-PCXR8 has been found suitable.6.6 Flow MetersAn in-line mass flow meter or flowsensor capable of measuring 30 to 120 mL/min with at least3 % accuracy. A flow meter o
20、r bubble meter capable ofmeasuring 3 to 4 L/min with at least 5 % accuracy.6.7 Glass Purge ChamberA glass purge chamber with amouth at least 60 mm wide and a lid with an air-tight gasketseal. One liter reaction flask, reaction flask head with twothreads, two 5029 tetrafluorethylene polymer bushings
21、andFETFE O-Ring and 124 mm anodized 2 piece clamp, AceGlass part numbers 6511-53, 6513-SP, and 6508-6.6.8 Valves Two metering valves to adjust split flow rate.One valve must be constructed of stainless steel. A Swagelok506-1-316 has been found suitable.6.9 Aluminum Foil Dishes, 58 mm in diameter by
22、18 mmhigh with a smooth (planar) bottom surface.6.10 Forced Draft Oven, oven, capable of maintaining160C (320F), of adequate size to accommodate one or morepurge chambers.6.11 Vacuum Oven, capable of maintaining 40C and avacuum of 0.1 to 0.2 Barr (100 mm Hg).6.12 Volumetric Glassware, various volume
23、tric flasks andpipettes for preparation of calibration standards. Also, 5-mLvolumetric flasks for sample elution.6.13 Analytical BalanceFour-place analytical balance ca-pable of measuring to 60.1mg (0.0001 g).6.14 Sherer Impinger Diffuser, A 25 mm dia, 275 mL withimpinger stopper, Ace Glass part num
24、ber 7538-29 has beenfound suitable.6.15 Water Trap, 1000 mL vacuum flask with stopper.6.16 Thermometer, thermocouple with temperature readoutcalibrated in range of 50F to 400F.7. Reagents and Materials7.1 Purity of ReagentsUse reagent grade chemicals in alltests, unless otherwise specified. Other gr
25、ades may be used,provided it is first ascertained that the reagent is sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.7.2 Toluene, technical grade, Specification D 362.7.3 Tetrahydrofuran, HPLC Grade.7.4 Water, HPLC Grade.7.5 Acetonitrile, HPLC Grade.7.6
26、DNPH-Silica Cartridge, Waters Sep-Pak Cartridges,Part # WAT037500.7.7 Formaldehyde/2,4-dinitrophenylhydrazone (DNPH)Complex, may be purchased or prepared in the laboratory.7.8 Calcium Nitrate Tetrahydrate, reagent grade.7.9 Paraformaldehyde, reagent grade.8. Hazards8.1 Check the suppliers Material S
27、afety Data Sheet(MSDS) on all chemicals before use.9. Preparation of Apparatus9.1 Install the column in the chromatograph following themanufacturers directions and establish the operating condi-tions required to give the desired separation (see Table 1).Allow sufficient time for the instrument to re
28、ach equilibrium asindicated by a stable baseline.9.2 Purge Chamber Set Up:9.2.1 Assemble apparatus (empty purge chamber, impinger,pump, flow meters and valving) as shown in Fig. 1 with aDNPH cartridge in line (use two DNPH cartridges for water-borne coatings and paraformaldehyde calibration check).9
29、.2.2 Add 500 g of calcium nitrate tetrahydrate to 250 mL ofreagent grade water to form a near saturated solution. Place thismixture in the constant humidity Insert the Sherer Impinger sothat the solution is 8 in. above the bottom of the impinger tip.Mark the solution level on the impinger.NOTE 2This
30、 calcium nitrate tetrahydrate solution ensures a constanthumidity of 55 %. Add water when the solution level falls below the mark.9.2.3 Adjust the forced draft oven so that the pan tempera-ture is set at the coating manufacturers recommended optimumprocess cure temperature 6 2F (usually with the ran
31、ge of 260to 310F for automotive coatings). Use a thermocouple tapedto the bottom of the pan to measure pan temperature.9.2.4 Adjust pump flow rate to 3.0 to 3.5 L/min.9.2.5 Adjust valves A and B until the DNPH Cartridge hasa flow of 50 mL/min.TABLE 1 Instrument ConditionsDetector UV/VIS Absorbance 3
32、60 nmColumn (Isocratic) C18ODS4by75mmMobile Phase (Isocratic) Water/Acetonitrile/Tetrahydrofuran65/30/5 volume/volumeColumn (Gradient) C18ODS 4 by 150 mmMobile Phase (Gradient) Water/Acetonitrile/TetrahydrofuranA: 65/30/10 volume/volumeB: 40/60/0 volume/volume100 % A for 1 min then linear gradientto
33、 100 % B in 10 minFlow Rate 1.5 mL/minColumn Temperature 40CRun Time (Isocratic) 10 minRun Time (Gradient) 15 minInjection Volume 10 to 20 LD690204e129.2.6 Check pump flow rate to ensure it is still in the properrange. Recommended starting flows; Pump 3.0 L/min, DNPHCartridge 50 mL/min (1:60 split).
34、10. Calibration10.1 Use the information in Table 1 as a guide to select theconditions that give the necessary resolution of formaldehyde-DNPH derivative from interferences in the samples.10.2 Determination of Relative Response FactorsThe re-sponse factor relative to the standard is determined by mea
35、ns ofthe following procedure. It is good practice to determine therelative retention time daily or with each series of determina-tions.10.2.1 Prepare a minimum four-point standard curve ofFormaldehyde-DNPH derivative in acetonitrile, ranging from0.1 to 10 g/mL as formaldehyde. Recommended curve 0.1,
36、1.0, 5.0 and 10 g/mL.10.2.2 Inject a 10 to 20 L aliquot of the standard mixtureinto the HPLC. At the end of the chromatographic run,calibrate the integrator by following the manufacturers proce-dure for external standard calibration. If this capability is notavailable, refer to the following calcula
37、tions. See Figs. 2 and 3for typical chromatograms using the three listed columns.10.2.3 The response factor of each analyte is calculated asfollows:Ranalyte5AanalyteCanalyte(1)where:Ranalyte= response factor for the analyte being calibrated,Canalyte= concentration of formaldehyde in mg/mL, andAanaly
38、te= peak area for the analyte being calibrated.10.2.4 Calculate the average response factor for all concen-trations and the correlation coefficient for calibration curve. Ifthe correlation coefficient is not 0.9999 or greater, repeatcalibration process.10.3 System Integrity:10.3.1 System BlankFollow
39、 procedure (Section 11) belowonly using a blank aluminum foil dish. Result should be belowdetection for formaldehyde.10.3.2 System StandardFollow procedure beginning at10.2, using two DNPH cartridges and an oven temperature ofFIG. 1 Page Chamber Set-UpD690204e13150C. Add 4.0 6 0.5 mg of paraformalde
40、hyde to a cool emptypan and record weight to nearest 0.1 mg. Total formaldehydemeasured should be equal to the amount of paraformaldehydeused 65 %, with less than a 1 % breakthrough to the secondcartridge. Analyze system standard on a minimum daily basis.11. Procedure11.1 Prepare Coating Specimens:1
41、1.1.1 Mix the coating sample, preferably on a mechanicalshaker or roller for solventborne and by hand for waterbornecoatings, until homogeneous. If air bubbles become entrapped,stir by hand until air has been removed.11.1.2 Rinse aluminum foil dishes (6.9) with toluene, wipedry with a lint-free clot
42、h then bake at cure temperature andtime. Place dishes in a desiccator to cool after baking.FIG. 2 Isocratic Separation of C1-C3Aldehyde and Ketone DerivativesFIG. 3 Gradient Separation of C1-C9Aldehyde and Ketone DerivativesD690204e1411.1.3 Record the weight of three dry aluminum foil dishes.11.1.4
43、Measure 0.2 6 0.05 g of coating formulation into atared aluminum foil dish using a syringe by measuring theweight of the syringe before and after dispensing the coating.Record weight of the dispensed coating on Bench Data Sheet(Fig. 4).11.1.4.1 For solventborne coatings add 1.5 mL of toluene todispe
44、rse the coating evenly on the bottom of the dish.11.1.4.2 For waterborne coatings add one mL of distilledwater, swirling pan until the coating formulation is fullywetted. Add one mL of ethanol again swirling the pan until thecoating is fully dispersed.11.1.5 Place dish immediately into a level vacuu
45、m oven setat 40C.11.1.6 Repeat steps 11.1.3-11.1.5 two more times. Thenevacuate the oven to 0.1 to 0.2 Barr (100 mm Hg).11.1.7 Allow specimens to dry in vacuum oven for1hat40C.11.1.8 Remove the dishes from the vacuum oven and placein a covered container at room temperature. Specimens shouldnot stand
46、 for more than 72 h between solvent evaporation andcuring.NOTE 3For applications where a clearcoat is applied on top of abasecoat, it is recommended that the procedure be followed through step11.1.8 for the basecoat then return to step 11.1.4 and apply the clearcoat.11.2 Cure Coating Specimens:FIG.
47、4 Bench Data SheetD690204e1511.2.1 Assemble apparatus as described in 9.2 with a freshDNPH Cartridge (two cartridges for waterborne coatings).11.2.2 Place one dish containing specimen in a cool (roomtemp) purge chamber.11.2.3 Replace hot empty purge chamber (using insulatedgloves) with chamber conta
48、ining specimen, attaching the coveras quickly as possible.11.2.4 Record initial flows (Total Flow and Tube Flow) andstart time on Bench Data Sheet.11.2.5 Allow coating to cure for 30 min then record finalflows (Total Flow and Tube Flow) and end time on Bench DataSheet.11.2.6 Disconnect, cap and labe
49、l the DNPH Cartridge(s).11.2.7 Remove purge chamber from oven (using insulatedgloves), remove aluminum foil dish from purge chamber withtongs and place into a desiccator to cool.11.2.8 Repeat steps 11.2.1-11.2.7 for other two replicatesand one blank run with empty foil dish.NOTE 4An alternative to running a purge chamber blank would be toattach a DNPH cartridge at the inlet to the purge chamber (outside of theoven) and analyze this cartridge every 20 runs to demonstrate thatformaldehyde has not broken through (75 g formaldehyde/cartridge).11.
