EP A/600/A-97/005
Characterization of Emissions from Conversion Varnishes
Robert C. McCrillis and Elizabeth M. Howard
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
and
Roy Fortmann, Huei-Chen Lao, Zhishi Guo, and Kenneth A. Krebs
Acurex Environmental Corp.
4915 Prospectus Drive
Durham, NC 27709
ABSTRACT
Three commercially available conversion varnish coating "systems" (stain, sealer, and topcoat) were
selected for an initial scoping study. Total volatile content of the catalyzed varnishes, as determined by
EPA Method 24, ranged from 64 to 73 weight %. Uncombined (free) formaldehyde concentrations,
determined by a sodium sulfite titration method, ranged from 0.15 to 0.58 weight % of the resin. Each
resin was also analyzed by gas chromatography/mass spectrometry (EPA Method 311) to identify the
volatile components that may be emitted. The primary volatile organic constituents identified in the resin
formulations included 2-butanone, n-butanol, 4-methyl-2-pentanone, toluene, ethylbenzene, 1,2,4-
trimethylbenzene, and the xylenes.
Dynamic small chamber (53L stainless steel) tests were performed to identify and quantify emissions
following application to coupons of typical kitchen cabinet wood substrates and during curing and aging.
One of the objectives is to determine the relationship between the concentration of hazardous air
pollutants (HAPs), volatile organic compounds (VOCs), and formaldehyde in the resins and emissions
from the catalyzed varnish. The results to date show good mass balance for the HAPs and VOCs.
Formaldehyde emissions show 6-7 times the emission compared to the free formaldehyde content,
indicating that formaldehyde is formed during the curing process. Results of the formulation analyses and
emission tests completed to date are described in this paper.
INTRODUCTION
Wood and wood-veneered kitchen cabinets present a unique finishing challenge because the finish
must not only be attractive, but must also be resistant to water and the many different detergents and
foods which may be spilled onto the cabinets during their lifetime. Conversion varnishes are widely used
to provide a decorative and protective finish on kitchen cabinets. They form strong, water resistant,
attractive coatings by chemical reaction after they are applied. Also referred to as acid-catalyzed
varnishes, these coatings consist of amino cross-linking agents, such as melamine formaldehyde or urea
formaldehyde, that are "catalyzed" with a strong acid. Because these products may emit hazardous air
pollutants (HAPs), including formaldehyde, the U.S. Environmental Protection Agency is conducting
scoping analyses to gain a better understanding of emissions during curing and aging.
Because these coatings are reactive, they may release reaction byproducts during application and
curing, as well as during their use in the indoor environment. This contributes to chemical emissions from
the manufacturing facilities as well as emissions into the household indoor air. Although several
chemicals may be emitted from these coatings, the chemical of primary interest is formaldehyde, because
it is a HAP, a probable carcinogen, and an irritant. In addition, because the formaldehyde may be formed
by the reaction that occurs after the coating is applied, its emissions cannot be estimated from formulation
information.

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DISCUSSION
The overall objectives of this project are to:
1)	Develop methods to measure cure emissions from conversion varnishes;
2)	Measure cure emissions from several commonly used conversion varnishes to gain an understanding
of their amount and composition;
3)	Investigate alternative, lower-emitting coatings which can provide the water and chemical resistance
and appearance necessary for this application, including coatings currently in use commercially, and
promising emerging coatings, and
4)	Demonstrate the most promising alternatives, and measure emissions both in the manufacturing plant
and in the household indoor environment to evaluate their emissions compared to those of the
conversion varnishes.
This paper addresses steps 1 and 2; preliminary plans are being made to proceed, at least on a limited
basis, with step 3; and step 4 is planned for the future.
Emission Testing and Test Method Development
Because conversion varnishes cure by chemical reaction, no existing standard test method provides a
measure of their cure volatiles. There are, however, several test methods available for testing volatile
emissions from coatings. Work on this project began with an investigation of these existing methods, and
ways in which they could be modified to measure cure volatiles from conversion varnishes.
EPA Method 24 for VOCs EPA Method 24 is used to determine VOC content of coatings1. A
number of American Society for Testing and Materials (ASTM) standard methods are incorporated by
reference. For total volatile content2, a 0.5 g sample of the coating, in 3 ml of solvent, is placed in an
open aluminum weighing dish, heated to 110°C for 60 minutes, then cooled and re-weighed. The volatile
content of the sample, which includes VOCs, exempt solvents, and water, is determined by the difference
between the beginning and ending weights. Then the water content is measured3 and subtracted from the
total volatile matter to yield the total volatile organic content. Exempt solvents are determined4 and
subtracted from the total volatile organic content to arrive at the VOC content. The solids content is
determined from the manufacturer's formulation, and the VOC content is expressed as weight of VOCs
per weight of solids.
Recent changes to Method 24 (allowing an "induction period" at ambient temperature before placing
the sample in the oven) now make it possible to obtain a reasonable measure of the volatile organic
content of reactive coatings such as conversion varnishes. Method 24 is based primarily on simple
gravimetric methods so it does not provide for chemical speciation; emissions of any particular compound
(in this case, formaldehyde is of particular interest) cannot be measured.
EPA Method 311 for HAPs. Method 311 is a method for determining the HAPs in paints and
coatings used in the wood furniture industry5. It is an analysis of the bulk product, so it measures only
the organics contained in the product, not any that are formed during the curing process. In this method,
the coating is mixed with an appropriate solvent, then injected into a gas chromatograph (GC). The GC
results can be used to identify and quantify individual HAPs, but formaldehyde is not detectable by GC
analysis. In this project, Method 311 is being used to obtain an analysis of the bulk varnish.
Measurement of cure emissions is addressed below.
Determination of free formaldehyde in the varnish formulation. In order to find out if there is any
relationship between the formaldehyde content of the varnish and the formaldehyde contained in the cure
volatiles, a sodium sulfite titration method6 was used to measure the formaldehyde in the as-received
varnish.
Small Chamber Tests — Curing in small environmental chambers. To measure the cure volatiles under
realistic, but controlled conditions, small chamber tests are being conducted7. These tests are conducted
using 53L stainless steel chambers, which are commonly used for indoor air quality studies,. A substrate
(glass or wood in this case) is coated with a specified thickness of varnish, then placed in the chamber.
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Clean air, at a controlled temperature and humidity, flows through the chamber. Samples are taken on
sorbent tubes, and analyzed as appropriate, based on the compounds to be measured. The small chamber
setup is shown schematically in Figure 1. These tests are designed to provide a good approximation of
actual emissions from curing and aging of any coating, including conversion varnishes.
Small Chamber Tests — Measurement of cure emissions The substrate coupon, measuring 29.5 x 9.2
cm, is coated using a slit applicator and then placed immediately into the environmental chamber. The air
exiting the chamber is passed through adsorbent cartridges to collect the various compounds of interest.
Hydrocarbons are collected on charcoal (high concentrations) or Tenax® (low concentrations), while
aldehydes are collected on silica gel impregnated with dinitrophenylhydrazine (DNPH)8. The organics
caught on the charcoal and Tenax® cartridges are desorbed and analyzed on a gas chromatograph/mass
selective detector (GC/MSD) and/or a gas chromatograph/ion trap mass spectrometer. The DNPH-silica
gel tubes are extracted and the extract analyzed on a high performance liquid chromatograph (HPLC).
Test series
Three commercially available conversion varnish coating systems (hereafter referred to as A, B, and
C) were selected for analysis. A coating system includes liquids used for each step in the coating process.
For this project, short coating systems, consisting of stain, sealer, and topcoat, are being investigated in
this phase. Although all three systems selected included a stain step, it was decided to not include it in
the project, at least not at this time. None of the stains were conversion varnishes and thus contained
other solvents, which would increase the complexity of the analysis without adding appreciably to our
knowledge of conversion varnishes. The three coating systems (not including the stains) are described in
Table 1.
Results of Scouting Test. An initial scouting test was run on topcoat C to: determine the general
conditions, flow rates, and sampling rates appropriate for use with conversion varnishes; and identify the
compounds emitted during cure so that calibration standards for those compounds could be purchased for
use in the subsequent tests. The use of calibration standards allows for good quantification of the amount
of each chemical present. The VOCs for the scouting test were calculated as toluene, since the GC was
calibrated to toluene. A glass panel was used as the substrate, with 72% of its surface area coated with a
100 (j, m wet film thickness of varnish. Glass was selected for this scouting test to eliminate the possibility
of any confounding substrate effects.
The varnish was prepared by thinning it with xylene, as specified in the manufacturer's instructions.
The standard chamber conditions used for this test (and the subsequent test series) are shown in Table 2.
Emission sample analyses yielded chamber concentration versus time curves for each compound. The
total mass of formaldehyde emitted during this test was 25.3 mg, or 1% of the mass of varnish applied.
Although the formaldehyde emissions did not fit a theoretically based mass transfer model, they did fit a
second order decay model9 fairly well. (Note that this model is not useful beyond the time frame of this
test, because it allows for infinite emissions.) The model may be expressed as:
E(t) = E0/(l+ktEo)
where E(t) = the emission factor as a function of time,
Ec = 29.0 mg/m2 /hr is the initial emission factor;
k = 0.00361 m2/mg is the second-order decay rate constant; and
t = time after the beginning of the test.
The total mass of VOCs emitted during the test period (250 hr) was 41 mg, or 44% of the mass of
varnish applied, calculated as toluene. The predominant VOC compounds were xylene, at 34%, and
isobutanol, at 5% of the mass of varnish applied. These VOC emissions fit a mass transfer model10 very
well. In fact, the constants for the model could be calculated using physical constants for the formulation
and xylene, and mass transfer coefficients previously measured for this small chamber system.
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Based on the results of this scouting test, the following five compounds were selected for analysis
during the main test series: formaldehyde, isobutanol, m,p-xylene, o-xylene, and ethylbenzene.
Results to date from main test series. To date, tests have been completed on Coating System C,
cured at room temperature. Systems A and B require elevated temperature for a portion of the sealer and
topcoat drying cycles. Tests on C have been completed on two substrates, solid oak and oak veneer on
hardboard. Chamber conditions were the same as for the scouting test reported above. Test coupon
dimensions were also the same. Prior to applying the coating, the test coupons were placed in chambers
and background emissions measured over a period of 2 weeks. Results from the background tests (Tests
0, 1, and 2) are summarized in Table 3.
The coupons were conditioned for 48 hours in a chamber under the conditions shown in Table 2 prior
to coating. In Test 3, on solid oak substrate, the sealer was applied then the coupon was placed in the
chamber. The coupon was removed 23 hours later and the topcoat was applied, then it was returned
immediately to the chamber, where it remains. For Test 4, on oak veneer hardboard, the sealer was
applied and allowed to dry in the chamber for 1 hour. The test coupon was removed, the topcoat was
applied, then the coupon was returned to the chamber, where it remains.
Following application of the sealers and topcoats to these coupons, emission samples were taken
every 15 minutes during sealer cure (for the first hour only in Test 3) and every 15 minutes for the first
hour after topcoat application. Sampling rate tapered off from that point as the evolution rate of organics
slowed, to the point that biweekly samples are now being taken.
Results for the selected volatile organics from this first test series on Coating System C are
summarized in Tables 4 and 5.
One of the major objectives of this research is to measure the evolution of formaldehyde and look for
a relationship to the free formaldehyde content of the varnish. As shown in Table 1, the topcoat in
System C contained 0.21 % free formaldehyde. Tables 4 and 5 show that emissions of formaldehyde are
6-700 % of the amount of free formaldehyde applied in the coating. Plots of cumulative formaldehyde
emissions (in mg) versus time (Figures 2 and 3) show that formaldehyde is still being emitted 1500 hours
(about 9 weeks) after the coating was applied. Typically, a kitchen cabinet will be placed in a home
within 4 weeks after it is coated. Figure 4, a graph of chamber formaldehyde concentration as a function
of time (since the coating was applied), shows that formaldehyde concentration is about 0.3 mg/m3 at the
1500 hour mark. One possible explanation for the continued evolution of formaldehyde is that the
coating has not yet fully cured; polimerization is not complete. Biweekly samples will continue to be
taken for several more weeks.
Another objective of the tests on Coating System C was to determine the effect of substrate on
emissions, especially the emissions decay rate. Figure 5 shows that, indeed, there is a substrate effect for
m,p-xylene (a similar, but less pronounced effect was also seen for isobutanol). A possible explanation is
that the glue attaching the veneer to the hardboard acted as a barrier to the solvents. Thus they remained
very close to the surface and could desorb and diffuse more readily. The substrate effect is, however,
very minor when considered in terms of the mass applied compared to mass emitted during the test period
(mass balance).
Next Steps
The test series on the three conversion varnish coating systems will be completed over the next few
months. The plan is then to select several low-VOC/low-HAP coatings for testing in the chambers. The
coatings selected would have to meet the Kitchen Cabinet Manufacturers Association criteria. Beyond
this, the plan includes working with one or more furniture manufacturers to switch over to one of the
low-VOC/low-HAP coating systems.
ACKNOWLEDGMENTS
The authors would like to thank the following Acurex Environmental Inc., employees for their
assistance, without which this project would not have been possible:
4

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Nancy Roache, chamber testing and analytical support,
Mark Bero, analytical support and data processing and analysis, and
Steve Marfiak, analytical and test support.
References
1.	40 CFR Ch. 1, Part 60, Appendix A, "Method 24 - Determination of Volatile Matter
Content, Water Content, Density, Volume Solids, and Weight Solids of Surface
Coatings," July 1, 1994.
2.	ASTM D2369-93, "Standard Test Method for Volatile Content of Coatings," American
Society for Testing and Materials, 1916 Race Street, Philadelphia, PA.
3.	ASTM D3 792-79, "Standard Test Method for Water Content in Paints and Paint
Materials by the Karl Fisher Titration Method," American Society for Testing and
Materials, 1916 Race Street, Philadelphia, PA.
4.	ASTM D4457-85, "Standard Test Method for Determination of Dichloromethane and
1,1,1 -Trichloromethane in Paints and Coatings by Direct Injection into a Gas
Chromatograph," American Society for Testing and Materials, 1916 Race Street,
Philadelphia, PA.
5.	40 CFR Part 63, Appendix A, "Method 311 - Analysis of Hazardous Air Pollutant
Compounds in Paints and Coatings by Direct Injection into a Gas Chromatograph,"
promulgated December 7, 1995.
6.	Walker, J.F., Formaldehyde. Third Edition (1955), Robert E. Krieger Publishing Co.,
Huntington, NY, pp 251 and 486.
7.	ASTM D5116-90, "Standard Guide for Small-Scale Environmental Chamber
Determinations of Organic Emissions from Indoor Materials/Products," American Society
for Testing and Materials, 1916 Race Street, Philadelphia, PA.
8.	Method TO-11, Compendium of Methods for Determination of Toxic Organic
Compounds in Ambient Air, EPA-600/4-89-017 (NTIS PB90-116989), U.S.
Environmental Protection Agency, Research Triangle Park, NC, June 1988.
9.	Tichenor, B.A., Guo, Z., and Dorsey, J.A., "Emission Rates of Mercury from Latex
Paints," IAO 91: Healthy Buildings. American Society of Heating, Refrigerating and Air-
conditioning Engineers, Inc., 1991, pp 276-279.
10.	Tichenor, B.A., Guo, Z., and Sparks, L.E., "Fundamental Mass Transfer Model for Indoor
Air Emissions from Surface Coatings," Indoor Air. 1993, Vol. 3, pp 263-268.
R

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Table 1, Description of three conversion varnish coatings systems (excluding stains) selected for
evaluation.



Free


Formaldehyde
Volatiles
System Code
Description
(%wt)
f%wO
A sealer
Modified nitrocellulose (not a conversion
varnish).
ND
78.2
A topcoat
Acid cure allcyd urea.
0.15
66.1
A catalyst
Added to topcoat 2% by volume
immediately before application.

NA
B sealer
Modified alkyd amino.
0.49
73.0
B topcoat
Modified alkyd amino.
0.53
64.0
B catalyst
Added to sealer and topcoat 3% by volume
immediately before application.

NA
C sealer
C topcoat thinned with 25% xylol.
0.17
64.9
C topcoat
Tall oil alkyd resin with urea formaldehyde
resin as cross-linking agent
0.21
59.1
C catalyst
p-toluenesulfonic acid added 3% by
volume to topcoat and sealer immediately
before application.

NA
Table 2. Environmental chamber standard parameters.
Air exchange rate: 0.5 hr'1
23 °C
50%
-10 cm/s
0.5 m2/m3 (surface area of test coupon/volume of chamber)
Temperature:
Relative humidity:
Air speed:
Loading factor:
Table 3. Summary of chamber and substrate background emission tests.
Concentration, up/m3
Condition	TVOC	Hexanal	Decanal Acetic acid
2-Furaldehyde
Empty chamber	11,0	0.4	0.4	0.8	0.2
Solid oak	32,9	1.9	2.6	3.7	5.5
Oak veneer	15.8	2.3	2.5	1.0	NDb
a = total volatile organic compounds, including any exempt solvents, found in the sample; reported as
toluene,
b = not detected.
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Table 4. Mass balance for selected volatile organics and formaldehyde for Test 3,1514 hours after
coating application.
Compound	Emitted (rog)	Applied (mg)	Recovered (%)
Isobutanol	645	637	101
Ethylbenzene	253	317	80
m,p-Xylene	990	1261	78
o-Xylene	265	292	91
All Xylenes	1254	1553	81
Formaldehyde	67.4	10.5	642
Table 5. Mass balance for selected volatile organics and formaldehyde for Test 4,1157 hours after
coating application.
Compound	Emitted (mg)	Applied (mg)	Recovered (%)
Isobutanol	523	479	109
Ethylbenzene	193	243	79
m,p-Xylene	800	971	82
o-Xylene	175	226	77
All Xylenes	977	1197	81
Formaldehyde	56	7.9	709
MASS FLOW
CONTROLLER
COMPRESSOR
DRYER
CATALYTIC
OXIDIZERS
SORBENT
TRAP
MANIFOLD
;*** Flow Controll«r*
dry
dr' ¥ '•!
TEST CHAMBER
SAMPLING
MANIFOLD
•ource
ENVIRONMENTAL
CHAMBER CONTROL
COMPUTER
-C=L=D- Mixing Fan
TEST CHAMBER
WATER FILLED
IMPINGER6
SAMPLING
MANIFOLD
CONTROLLED
TEMPERATURE
WATER BATH
INCUBATOR
Figure 1. Schematic of small environmental test chambers.
7

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1000

f

	\

K
'-Test 3 -«
Test 4

CO
E
o>
E
•
o
c
o
O
0 200 400 600 800 1000 1200 1400 1600
Elapsed Time (h)
Figure 4 Comparison of formaldehyde concentrations in chamber exhaust for conversion varnish
system C, room temperature drying Test 3 = solid oak, Test 4 = oak veneer on hardboard.
CO
£
"to
E,
•
o
c
o
O
0 200 400 600 800 1000 1200 1400 1600
Elapsed Time (h)
Figure 5. Comparison between m-p-Xylene concentrations in chamber exhaust over time, room
temperature drying. Test 3 = solid oak substrate, Test 4 = oak veneer on hardboard substrate.
8

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80
CD
60
u
Emitted
Applied
0
400
800
Elapsed Time (h)
1200
1600
0
Figure 2. Cumulative formaldehyde (HCHO) emissions in Test 3, conversion varnish system C, room
temperature drying Total HCHO applied = 10.5 mg, total emitted = 67.4 mg
"U
"E 30
Emitted
Applied
O 20
0 200 400 600 800 1000 1200
Elapsed Time (h)
Figure 3 Cumulative formaldehyde (HCHO) emissions in Test 4, conversion varnish system C, room
temperature drying Total HCHO applied = 7.9 mg, total emitted = 56.0 mg.
9

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MDMDI DTt) T3 10C technical report data
iNxtlvirt J_»— ft I 1 r ~ iOU (Please read Instructions on the reverse before completin
' REP|RPTa7600/A-97/005
3. R
4. TITLE AND SUBTITLE
Characterization of Emissions from Conversion
Varnishes
5. REPORT DATE
6. PERFORMING ORGANIZATION COOE
7.author(s) R> Cf McCrillis and E. M.Howard (EPA); and
R. Fortmann, H-C Lao, Z. Guo, and K. A. Krebs
(A cur ex)
8. PERFORMING ORGANIZATION REPORT NO.
8, PERFORMING ORGANIZATION NAME AND ADDRESS
Acurex Environmental Corporation
4915 Prospectus Drive
Durham, North Carolina 27709
10, PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-D4-0005, Task 2-033
12. SPONSORING AGENCY NAME ANO ADDRESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13, TYPE OF REPORT ANO PERIOD COVERED
Published paper; 9/96
14. SPONSORING AGENCY CODE
EPA/600/13
is.supplementary notes appcd project officer is Robert C. McCrillis, Mail Drop 61,
919/541-2733. Presented at EPA/AWMA Emission Factors Conference, New
Orleans, LA, 9/4-6/96.
16, abstract paper discusses the characterization of emissions from conversion
varnishes. Three commercially available conversion varnish coating "systems"
(stain, sealer, and topcoat) were initially scoped. Total volatile content of the cata-
lyzed varnishes (determined by EPA Method 24) ranged from 64 to 73 weight %. Un-
combined (free) formaldehyde concentrations (determined by sodium sulfite titration)
ranged from 0.15 to 0. 58 weight % of the resin. Each resin was also analyzed by gas
chromatography/mass spectrometry (EPA Method 311) to identify the volatile compo-
nents that may be emitted. The primary volatile organic constituents identified in the
resin formulations were 2-butanone, no-butanol, 4 - me thyl- 2- p entanone, toluene,
ethylbenzene, 1, 2, 4-trimethylbenzene, and the xylenes. Dynamic small chamber
(53 L stainless steel) tests identified and quantified emissions following application
to coupons of typical kitchen cabinet wood substrates and during curing and aging.
An objective was to determine the relation between the concentration of hazardous
air pollutants (HAPs), volatile organic compounds (VOCs)>_ and formaldehyde in the
resins and emissions from the catalyzed varnish. Results to date show good mass
balance for the HAPs and VOCs. Formaldehyde emissions show 6-7 times the emis-
sion compared to the free formaldehyde content.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/OPEN ENOED TERMS
c. cosati Field/Group
Pollution Formaldehyde
Emission Polymers
Varnishes Test Chambers
Wood
Volatility
Catalysis
Pollution Control
Stationary Sources
Resins
13 B 07C
14G
11C 14 B
11L
20 M
07D
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Reportf
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page/
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)

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