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Significance and Use
This test method measures the amount of formaldehyde that 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 melamine-formaldehyde resins. Cure formaldehyde is evolved in the final bake or cure oven, when the coating temperature is high enough to initiate cross-linking. Formaldehyde can be released from a coating during application, solvent flash-off and cure. Free formaldehyde is primarily evolved during coating application and solvent flash-off. Test Method D1979 measures “free formaldehyde” in amino resins and Test Method D6191 measures formaldehyde evolved from coatings at ambient temperature. This method measures only the formaldehyde released during heat cure, which is primarily “cure formaldehyde.”
This test method is not intended to duplicate the evolved formaldehyde from an industrial process, but serves as a reproducible comparative laboratory evaluation.
This test method has not been evaluated with catalyzed coating systems that cure at or below 40°C, such as those used by the wood-finishing industry, and would likely require special adaptation for this application.
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 determine the “cure formaldehyde” evolved from a sample under controlled laboratory conditions.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 This test method is capable of measuring from 500 μg/g to 22 000 μg formaldehyde/g dry coating under the test conditions specified (3 000 ml/min total flow, 50 ml/min DNPH tube flow). The ratio of total flow to DNPH tube flow could be adjusted to extend the range of the method.
1.4 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.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D362 Specification for Industrial Grade Toluene
D1979 Test Method for Free Formaldehyde Content of Amino Resins
D6191 Test Method for Measurement of Evolved Formaldehyde from Water Reducible Air-Dry Coatings
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
ICS Number Code 83.080.10 (Thermosetting materials)