ASTM D6902-03
(Test Method)Standard Test Method for Laboratory Measurement of Formaldehyde Evolved During the Curing of Melamine-Formaldehyde-Based Coatings
Standard Test Method for Laboratory Measurement of Formaldehyde Evolved During the Curing of Melamine-Formaldehyde-Based Coatings
SCOPE
1.1 This test method is for the determination of formaldehyde evolved from melamine-formaldehyde-based coatings during the cure step. The results may be used to define the "cure formaldehyde" evolved from a sample under controlled laboratory conditions.
1.2 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 determine the applicability of regulatory limitations prior to use.
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Designation: D 6902 – 03
Standard Test Method for
Laboratory Measurement of Formaldehyde Evolved During
the Curing of Melamine-Formaldehyde-Based Coatings
This standard is issued under the fixed designation D 6902; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope coating during the cure step is calculated on both a wet-weight
and dry-weight basis. The test is run in triplicate plus a blank
1.1 This test method is for the determination of formalde-
and system standard.
hyde evolved from melamine-formaldehyde-based coatings
during the cure step. The results may be used to define the
5. Significance and Use
“cure formaldehyde” evolved from a sample under controlled
5.1 This test method measures the amount of formaldehyde
laboratory conditions.
that is evolved from a coating during curing. This “cure
1.2 This standard does not purport to address all of the
formaldehyde” is a reaction byproduct from the polymer
safety concerns, if any, associated with its use. It is the
cross-linking of substituted amino-formaldehyde groups (ami-
responsibility of the user of this standard to establish appro-
noplasts) with other functional melamine polymer groups such
priate safety and health practices and determine the applica-
as hydroxyl, carboxyl or amide. Cure formaldehyde is evolved
bility of regulatory limitations prior to use.
in the final bake or cure oven after the coating temperature is
2. Referenced Documents high enough to initiate cross-linking. The total amount of
formaldehyde that can be released from a coating is a combi-
2.1 ASTM Standards:
2 nation of “free formaldehyde” (Test Methods D 6191 or
D 362 Specification for Industrial Strength Toluene
D 1979) and “cure formaldehyde.” The majority of “free
D 1979 Test Method for Free Formaldehyde Content of
3 formaldehyde” is released during the coating application and
Amino Resins
solvent flash-off steps.
D 2369 Test Method for Volatile Content of Coatings
5.2 The method is capable of measuring from 30 μg/g to
D 6191 Test Method for Measurement of Evolved Formal-
22 000 μg formaldehyde/g dry coating under the test conditions
dehyde from Water Reducible Air-Dry Coatings
specified (3 000 mL/min total flow, 50 mL/min DNPH tube
3. Terminology
flow). The ratio of total flow to DNPH tube flow could be
adjusted to extend the range of the method.
3.1 Definitions:
5.3 This test method is not intended to duplicate the evolved
3.1.1 cure formaldehyde, n—the formaldehyde generated as
formaldehyde from an industrial process, but serves as a
the result of a chemical reaction during coating curing.
reproducible comparative laboratory evaluation.
3.1.2 free formaldehyde, n—the residual formaldehyde in a
5.4 This test method has not been evaluated with catalyzed
coating due to the raw materials.
coating systems that cure at or below 40°C, such as those used
4. Summary of Test Method
by the wood-finishing industry, and would likely require
special adaptation for this application.
4.1 Approximately 0.2 g of coating formulation is placed in
an aluminum foil pan, dried in a vacuum oven at 40°C (to
6. Apparatus
remove free formaldehyde and solvents) and then baked at the
6.1 High Pressure Liquid Chromatograph (HPLC), either a
optimum process cure temperature for 30 min. Formaldehyde
gradient or isocratic system. A gradient system is preferred
emissions are collected from the cure chamber on a DNPH/
when other aldehydes or ketones are present.
Silica tube, which is then extracted and the extract analyzed by
HPLC/UV. The amount of formaldehyde evolved from the
NOTE 1—The system shall be equipped with a temperature-controlled
column oven. A liquid autosampler is optional.
1 6.2 Column,aC ODS packed with 5-μm pellicular beads
This test method is under the jurisdiction of ASTM Committee D01 on Paint
with the dimensions of approximately 4 mm by 75 or 150 mm.
and Related Coatings, Materials, and Applications and is the direct responsibility of
Subcommittee D01.21 on Chemical Analysis of Paints and Paint Materials.
A 2-cm guard column packed with the same material is
Current edition approved July 10, 2003. Published August 2003.
recommended to protect the analytical column.
Annual Book of ASTM Standards, Vol 06.04.
6.3 Detector, UV/VIS detector capable of measuring absor-
Annual Book of ASTM Standards, Vol 06.01.
Annual Book of ASTM Standards, Vol 06.03. bance at 360 nm.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6902–03
6.4 Integrator, peak integration system. 9. Preparation of Apparatus
6.5 Air Sampling Pump, an air sampling pump with the
9.1 Install the column in the chromatograph following the
capability of maintaining a constant flow rate between 3 and 4
manufacturer’s directions and establish the operating condi-
L/min. Both an inlet and outlet port must be available for
tions required to give the desired separation (see Table 1).
measuring flow. An SKC AirCheck Sampler Model 224-
Allow sufficient time for the instrument to reach equilibrium as
PCXR8 has been found suitable.
indicated by a stable baseline.
6.6 Flow Meters—An in-line mass flow meter or flow
9.2 Purge Chamber Set Up:
sensor capable of measuring 30 to 120 mL/min with at least
9.2.1 Assemble apparatus (empty purge chamber, impinger,
3 % accuracy. A flow meter or bubble meter capable of
pump, flow meters and valving) as shown in Fig. 1 with a
measuring 3 to 4 L/min with at least 5 % accuracy.
DNPH cartridge in line (use two DNPH cartridges for water-
6.7 Glass Purge Chamber—A glass purge chamber with a
borne coatings and paraformaldehyde calibration check).
mouth at least 60 mm wide and a lid with an air-tight gasket
9.2.2 Add 500 g of calcium nitrate tetrahydrate to 250 mL of
seal. One liter reaction flask, reaction flask head with two
reagent grade water to form a near saturated solution. Place this
threads, two 5029 tetrafluorethylene polymer bushings and
mixture in the constant humidity Insert the Sherer Impinger so
FETFE O-Ring and 124 mm anodized 2 piece clamp, Ace
that the solution is 8 in. above the bottom of the impinger tip.
Glass part numbers 6511-53, 6513-SP, and 6508-6.
Mark the solution level on the impinger.
6.8 Valves —Two metering valves to adjust split flow rate.
NOTE 2—This calcium nitrate tetrahydrate solution ensures a constant
One valve must be constructed of stainless steel. A Swagelok
humidity of 55 %. Add water when the solution level falls below the mark.
506-1-316 has been found suitable.
9.2.3 Adjust the forced draft oven so that the pan tempera-
6.9 Aluminum Foil Dishes, 58 mm in diameter by 18 mm
ture is set at the coating manufacturers recommended optimum
high with a smooth (planar) bottom surface.
process cure temperature 6 2°F (usually with the range of 260
6.10 Forced Draft Oven, oven, capable of maintaining
to 310°F for automotive coatings). Use a thermocouple taped
160°C (320°F), of adequate size to accommodate one or more
to the bottom of the pan to measure pan temperature.
purge chambers.
9.2.4 Adjust pump flow rate to 3.0 to 3.5 L/min.
6.11 Vacuum Oven, capable of maintaining 40°C and a
9.2.5 Adjust valves A and B until the DNPH Cartridge has
vacuum of 0.1 to 0.2 Barr (~100 mm Hg).
a flow of 50 mL/min.
6.12 Volumetric Glassware, various volumetric flasks and
9.2.6 Check pump flow rate to ensure it is still in the proper
pipettes for preparation of calibration standards. Also, 5-mL
range. Recommended starting flows; Pump 3.0 L/min, DNPH
volumetric flasks for sample elution.
Cartridge 50 mL/min (1:60 split).
6.13 Analytical Balance—Four-place analytical balance ca-
pable of measuring to 60.1mg (0.0001 g).
10. Calibration
6.14 Sherer Impinger Diffuser, A 25 mm dia, 275 mL with
10.1 Use the information in Table 1 as a guide to select the
impinger stopper, Ace Glass part number 7538-29 has been
conditions that give the necessary resolution of formaldehyde-
found suitable.
DNPH derivative from interferences in the samples.
6.15 Water Trap, 1000 mL vacuum flask with stopper.
10.2 Determination of Relative Response Factors—The re-
6.16 Thermometer, thermocouple with temperature readout
sponse factor relative to the standard is determined by means of
calibrated in range of 50°F to 400°F.
the following procedure. It is good practice to determine the
relative retention time daily or with each series of determina-
7. Reagents and Materials
tions.
7.1 Purity of Reagents—Use reagent grade chemicals in all
10.2.1 Prepare a minimum four-point standard curve of
tests, unless otherwise specified. Other grades may be used,
Formaldehyde-DNPH derivative in acetonitrile, ranging from
provided it is first ascertained that the reagent is sufficiently
0.1 to 10 μg/mL as formaldehyde. Recommended curve 0.1,
high purity to permit its use without lessening the accuracy of
1.0, 5.0 and 10 μg/mL.
the determination.
7.2 Toluene, technical grade, Specification D 362.
7.3 Tetrahydrofuran, HPLC Grade.
TABLE 1 Instrument Conditions
7.4 Water, HPLC Grade.
Detector UV/VIS Absorbance 360 nm
Column (Isocratic) C ODS4by75mm
7.5 Acetonitrile, HPLC Grade.
Mobile Phase (Isocratic) Water/Acetonitrile/Tetrahydrofuran
7.6 DNPH-Silica Cartridge, Waters Sep-Pak Cartridges,
65/30/5 volume/volume
Part # WAT037500.
Column (Gradient) C ODS 4 by 150 mm
Mobile Phase (Gradient) Water/Acetonitrile/Tetrahydrofuran
7.7 Formaldehyde/2,4-dinitrophenylhydrazone (DNPH)
A: 65/30/10 volume/volume
Complex, may be purchased or prepared in the laboratory.
B: 40/60/0 volume/volume
7.8 Calcium Nitrate Tetrahydrate, reagent grade.
100 % A
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