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-------
APPENDIX B
INITIAL DRAFT ASTM METHOD
PROPOSED TEST METHODS FOR DETERMINING VOC OF RADIATION CURABLE
MATERIALS
-------
-------
PROPOSED TEST METHODS FOR DETERMINING VOC OF RADIATION CURABLE MATERIALS
Method A:
Scope: Only materials containing less than 3X non-reactive solvent.
1. Weigh a preconditioned Al panel or appropriate size Al foil to
0.1 mg (W,). Panels or foil pieces are preconditioned by
drying for 30 minutes at 110* C and storing in a
desiccator. Size of Al substrate must allow a minimum of
0.2 gm of total material to be applied at the supplier's
recommended film thickness. Standard 4" x 12" Al panels
may be used when appropriate. Use rubber gloves and/or
tongs to handle samples.
2. Apply a minimum of 0.2 gm of material to the Al substrate
and reweigh to 0.1 mg (Wj). (See Note 1)
3. Cure the material by exposure to UV or EB as prescribed by
the supplier of the material.
4. Allow the sample to cool 5 minutes at room temperature and
reweigh to 0.1 mg (W3).
5. Heat sample in a forced draft oven for 60 minutes at
110+5' C.
6. Allow sample to cool to room temperature in a desiccator
and reweigh to 0.1 mg (W4).
Calculations:
X Processing VOC s 100 [(Wj - Wj)/(W2 -W,)]
X Potential VOC = 100 ((Wj - W4)/(Wj -W,)]
x Total VOC = X Processing VOC + X Potential VOC
VOC (Wt/Vol basis: = (X VOC/100) x Density
Method B:
•
•Scope: All materials including those containing more than 3X
non-reactive solvent.
1. Weigh a preconditioned (see step 1 of Method A) Al dish with
a minimum diameter of 2 inches to 0.1 mg (W,). Use rubber
gloves and/or tongs to handle samples.
2. Add 3i1 ml of acetone (see note 2) to the Al dish and,
using a 1 ml syringe or eye dropper, weigh, by difference,
-------
to 0,1 mg (Wj) 0.3+0.1 gm of material into the dish. Swirl
the disK to disperse the material in the acetone and
uniformly cover the bottom of the dish.
3. Dry the sample for 30 minutes at 50' C (See Note 3).
Be sure that oven shelves are level.
4. Cure the material by exposure to UV or EB as prescribed by
the supplier of the material.
5. Allow sample to cool for 5 minutes at room temperature and
reweigh (Wj).
6. Heat the sample in a forced draft oven for 60 minutes at
110+5* C.
7. Allow sample to cool to room temperature in a desiccator
and reweigh (Wt).
Calculations:
X Processing VOC = 100 [(Wj - (Wj -W,
X Potential VOC = 100 t(Wj - wt)/W2)
X Total VOC = X Processing VOC •»• X Potential VOC
VOC (Wt/Vol basis) = (X VOC/100) x Density
Note 1 -
Note 2
Note 3
If the material to be tested contains any non-reactive
solvent, the elapsed time between application and
weighing should be no greater than 30 seconds. If the
material to be tested contains any reactive diluent
with a vapor pressure at room temperature greater than
1 mm Hg (e.g. styrene), the elapsed time between
material application and weighing must be no more than
15 seconds.
If the material is not compatible with acetone,
a blend of acetone and THF may be substituted.
THF or
If the material contains only very fast solvents, a
lower temperature/shorter time may be substituted if
it can be demonstrated that. the conditions are
adequate to remove at least 90x of the original
solvent in the composition. Any remaining solvent
will be removed during the subsequent cure and/or
bake steps.
-------
APPENDIX C
INITIAL DRAFT EPA METHOD
DETERMINATION OF VOLATILE ORGANIC CONTENT FOR ULTRAVIOLET
RADIATION-CURED COATINGS
-------
-------
DETERMINATION OF VOLATILE ORGANIC CONTENT FOR
ULTRAVIOLET RADIATION-CURED COATINGS
L Applicability and Principle
1.1 Applicability. This method applies to the determination of the volatile
organic content of ultraviolet radiation-cured coatings (UV-cured coatings).
This method has been tested with commercial UV-cured coating formulations,
including acrylic-based formulations, cationic epoxies, polyester/styrene, and
thiol-poiyene based coatings.
1.2 Principle. UV-cured coatings are a class of coatings that contain
unreacted monomers that are polymerized by exposure to ultraviolet light. This
method measures the weight loss from UV-cured coatings in each of three
steps:
• sitting at room temperature to simulate product handling,
• after UV exposure to produce a cured coating, and
• after 1 hour in a 110°C oven to simulate the final life of the product.
The procedure includes a test for cure, which involves comparison of total
weight loss of a sample cured at multiple exposures.
2. Precision
Based on studies performed on laboratory samples having 0 to 11% total
volatiles (Vto,, see Section 6.5), the intralaboratory absolute standard deviation
for total volatiles using this method averaged 0.9 percent.
3. Apparatus
3.1 UV-Exposure Apparatus. A conveyor-fed ultraviolet curing apparatus.
The ultraviolet light shall be provided by one or more medium-pressure
mercury vapor lamps with quartz housings, capable of providing light with a
wavelength of between 200 and 400 nm. The lamp and conveyor system must
be capable of providing sufficient exposure for the materials being tested (see
Section 4). Other apparatus may be used if approved by the Administrator.
3.2 Oven. A forced-draft oven capable of maintaining a temperature of
110 ± 2°C for 1 hour.
-------
3.3 Thermometer. A thermometer capable of measuring oven temperature:
to ± 1°C.
3.4 Balance. A balance capable of weighing to ± 0.0001 g.
3.5 Sample Dishes. Circular flat-bottomed aluminum foil weighing
dishes, approximately 58 mm in diameter by 18 mm high.
3.6 Desiccator. An airtight container, with desiccant, large enough to
contain samples dishes.
3.7 Desiccant. Calcium sulfate (e.g., indicating Drierite") or equivalent
desiccant.
3.8 Disposable Pipettes. Disposable 5-ml polyethylene transfer pipettes.
3.9 Acetone. ACS reagent grade or equivalent.
NOTE: If acetone is not an adequate solvent for the material being tested,
another solvent with a sufficiently low boiling point (< 60°Q may be used.
Solvent must be tested to determine if it evaporates completely from the
coating at room temperature; i.e., the evaporative loss (LJ should be greater
than or equal to zero (see Section 6.2).
4. Procedure
NOTE:. All items that are weighed (e.g., sample dish, pipettes) must be
handled with gloves or sample tongs.
4.1 Initial Analysis
4.1.1 Condition the aluminum sample dishes by heating them in a
forced-draft oven at 110 ± 2°C for at least 1 hour. Remove the dishes and
allow them to cool in a desiccator. Store the conditioned dishes in a
desiccator.
4.1.2 Weigh an aluminum dish to ± 0.0001 g and record this weight as
Wj. Mix the coating thoroughly and fill a disposable pipette with enough
coating to deliver 0.2 ± 0.1 g of coating. Weigh the coating-filled pipette to
± 0.0001 g and record this weight as W2. Place 3 ± 1 mL qf acetone in the
aluminum dish and carefully add the coating into the dish. Gently swirl the
" Mention of trade names or specific products does not constitute endorsement by
the Environmental Protection Agency.
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dish to disperse the coating, talcing care not to spill any material. Weigh the
pipette after the sample has been dispensed to ± 0.0001 g and record this
weight as Wv
NOTE: It may be difficult to accurately dispense viscous samples from a
pipette. In order to achieve more uniform amounts (i.e. ±0.1 g), it may be
helpful to add the sample to the dish while on a balance. The acetone may
then be added to the sample and the dish swirled to disperse the sample
uniformly. Because of the possibility that volatiles might be lost during
weighing, the sample weight W7 should be calculated as described in
Section 6.2. An alternative procedure for viscous samples would be to use a
syringe in place of the disposable Pipette.
4.1.3 Place the sample dish on a level surface at room temperature in a
laboratory fume hood for 30 minutes to allow the acetone to evaporate, then
weigh the sample dish to ± 0.0001 g and record this weight as W4.
4.1.4 Cure the coating by exposing it to UV light at twice the exposure
specified by the manufacturer (i.e., double the number of passes through the
exposure apparatus at the manufacturer's suggested rate and intensity). Allow
the sample to cool to room temperature (approximately 30 seconds) between
passes. After all the passes have been completed weigh the sample to
± 0.0001 g and record this weight as Ws.
4.1.5 After UV exposure and weighing, place the sample dish in a
110 ± 2°C oven for 1 hour. Remove the sample dish and allow it to cool to
room temperature in a desiccator. Weigh the sample dish to ± 0.0001 g and
record this weight as W6, then calculate Vw (percent) as in Section 6.5.
4.1.6_ Analyze samples in triplicate and calculate an average total organic
content, Vw (percent) as in Section 6.6.
4.2 Subsequent Analysis
4.2.1 Using fresh samples of the material from the same lot as the sample
in Section 4.1, repeat Sections 4.1 using four times the manufacturer's
recommended exposure time (i.e., four times the number of passes at the
manufacturer's suggested curing conditions). Calculate Vm as in Section 6.5.
4.2.2 ^Analyze samples in triplicate and calculate an average total organic
content, V,,,, (percent) as in Section 6.6.
4.3 If the average total volatile organic content, V,,,, (percent) calculated in
Section 4.1 does not agree to ± 1 percent (absolute) with the one calculated in
Section 4.2, repeat Section 4.2 doubling the last exposure. Compare to the
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prior exposure'results until the average total organic content, VM (percent) of -
two consecutive exposures tested at the same feed rate and intensity agree to
± 1 percent (absolute).
NOTE: If the criterion has not been met by the second time that
Section 4.2 is repeated, the tester may want to consider changing curing
conditions (i.e., feed rate and intensity) and repeat Sections 4.1 through 4.3
beginning at twice the manufacturer's exposure with the modified curing
conditions.
4.4 Perform analyses in triplicate for each coating until the criterion in
Section 4.3 is met. Record the V— values used to meet the criteria in
Section 4.3 with the corresponding curing conditions and exposure. Report the
higher of the two values obtained as VM from the sample being tested.
NOTE: Underexposed UV-cured coatings may show excessively high
levels of total volatile organic content, Vw (Section 6.5). This may be
corrected by adjusting the exposure level as described in Section 4.2.
Overexposed coatings may show charring, discoloration, and bubbling. This is
often due to thermal overexposure rather than UV overexposure. To reduce
thermal effects, lower intensity or increase the feed rate and increase the
number of passes through the apparatus. Allow the samples to cool to room
temperature (approximately 30 seconds) between passes.
5. Calibration and Audits
5.1 Analytical Balance. Calibrate against standard weights.
52 Thermometer. Calibrate against a National Institute of Standards and
Technology (NIST)-traceable thermometer.
5.4 Audit Procedure. Analyze the performance audit sample, if available.
The same analyst, analytical reagents, and analytical system shall be used both
for compliance samples and the EPA audit samples. If this condition is met,
auditing of subsequent compliance analyses for the same enforcement agency
within 30 days is not required. An audit sample set may not be used to
validate different sets of compliance samples under the jurisdiction of different
enforcement agencies, unless prior arrangements are made with both
enforcement agencies.
5.5 Audit Samples. Audit samples will be supplied only to enforcement
agencies for compliance tests. The availability of audit samples may be
obtained by writing: Source test Audit Coordinator (MD-778), Quality
Assurance Division, Atmospheric Research and Exposure Assessment
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park,
NC 27711 or by calling the Source Test Audit Coordinator (STAC) at
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(919) 541-7834. The request for the audit sample must be made at least
30 days prior to {he scheduled compliance sample analysis.
5.6 Audit Results. Calculate the audit sample concentration according to
the calculation procedure described in the audit instructions included with the
audit sample. Fill in the audit sample concentration and the analyst's name on
the audit response form included with the audit instructions. Send one copy to
the EPA Regional Office or the appropriate enforcement agency and a second
copy to the STAC The EPA Regional Office or the appropriate enforcement
agency will report the results of the audit to the laboratory being audited.
Include this response with the results of the compliance samples in relevant
reports to the EPA Regional Office or the appropriate enforcement agency.
6. Calculations
6.1 Nomenclature.
L, « Evaporative loss, percent
L^ » UV loss, percent.
VM • Total volatile organic content,
Total volatile organic content of first sample, percent
g. • Total volatile organic content, of g^rH sample, percent
f - Total volatile organic content of third sample, percent
UXj
Vgg • Average total volatile organic
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6.3 Evaporative Loss. The evaporative loss (LJ is calculated as:
(W. + W. - WJ
L » V l 7 y x 100
W7
6.4 UV Processing Loss. The UV processing loss (LO is calculated as
6.5 Total Volatiles. The total volatile organic content is calculated as:
„ W * w7 - w«)
W7
x 100
6.6 Average Total Volatiles. The average of the total volatiles Vw is
calculated for triplicate samples as:
V + V + V
T Y Y
Report the average of the triplicate analyses rounded to ±0.1 percent.
7, Bibliography
1. U.S. Environmental Protection Agency, Method 24 - Determination of
Volatile Matter Content. Water Content. Density. Volume Solids, and Weight
Solids of Surface Coatings. 40 CFR 60, Appendix A.
2. American Society of Testing and Materials, ASTM D2369-87. Standard
Test Method For Volatile Content of Coatings. Philadelphia, PA, 1987.
3. American Society for Testing and Materials. Revised Test Methods for
Determining VOC of Radiation Curable Materials. ASTM proposed test method
for UV/EB curable materials (unpublished communications), October 1991.
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APPENDIX 0
RESPONSES TO COMMENTS ON DRAFT EPA METHOD
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APPENDIX D
RESPONSES TO COMMENTS ON EPA DRAFT METHOD
Commenter: 1
1.1 Comment: The method may have difficulties with skin formation.
Response: The current procedure is acceptable (even if some coatings have L. < 0)
for a regulation based on total voiatiles (i.e., V,Jt since measurement for VM involves
heating at 110 °C, which will drive off any remaining solvent.
Skin formation may affect Le and LW. since they have no heating step to drive off
solvent. If future regulations are to use LUV, then the method may require modification. This
could be done by allowing the solvent to evaporate at a higher temperature, such as the 50 °C
oven proposed by ASTM in revisions to D2369. Unfortunately, the use of a higher
temperature to evaporate the solvent would increase the risk of evaporating reactive
monomers that would normally be incorporated in the coating. This could lead to excessive
values of volatile loss as measured by the method (i.e., as compared to actual usage). This
could be a problem for polyester/styrene based coatings due to the volatility of styrene.
Laboratory tests with an acrylic based coating showed no difference between solvent
evaporation at 50 °C and at room temperature. Any method to measure the processing loss
will necessarily be a compromise between driving off the dispersing agent and driving off
reactive monomers.
Commenter: 2
2.1 Comment: This method only measures the VOC content of a completely cured
coating. It does not address facility emissions due to poor cure or overspray.
Response: This comment was noted by several reviewers. This method measures
properties of a coating, rather than properties of a coating process or facility. A coating test
method should be capable of giving results that are identical (i.e., within a reproducibility
error) when a sample of coating is tested by different laboratories. For a reproducible test, it
is necessary that the coating be fully cured and that no overspray be considered.
Commenter: 3
3.1 Comment: Does the method work with materials with more than 11% VOC?
Response: It is felt that this method should work as well, if not better, with higher
D 1
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VOC materials, since they will form thinner films that will be more easily cured. Additional
testing performed after the Draft Method was circulated showed good precision (i.e., less than
1% absolute statdard deviation within triplicate samples) for a coating with 30% total
volatiles.
3.2 Comment: The description of exposure apparatus does not include provisions for
use of inert atmospheres during exposure.
Response: In general, inert atmospheres are used only for electron-beam cured
coatings, which are not specifically addressed in this method.
3.3 Comment: Why should the evaporative loss (LJ be greater than or equal to zero?
What would happen if it isn't?
Response: For measurement of total volatile loss CO, it makes little difference
whether the L. is positive, i.e., whether all the solvent has evaporated before curing, since any
remaining solvent will be evaporated either in the curing step or upon heating. (This assumes
that the solvent does not interfere with curing.) The UV exposure loss (Luv) would be
affected (i.e., would be lower) if any solvent that remains after curing.
3.4 Comment: The note under Section 4.1.2 does not clearly explain the purpose for
weighing the samples on a balance. In particular, the word accurately is poorly chosen.
Response: The word accurately should be dropped from the first sentence of the note
and the note revised for clarity. The revised note would read as follows:
NOTE: It may be difficult to dispense viscous samples from a pipette. To
achieve uniform sample weights (i.e., ± 0.1 g), it may be helpful to place the sample
dish on a balance and add the required amount of sample. The acetone (or other
solvent) would then be added to the sample and the dish swiried to disperse the
sample uniformly. Because of the possibility that volatiles might be lost during
weighing, the sample weight W? should still be calculated as described in Section 6.2.
An alternate procedure for viscous samples would be to use a syringe in place of the
disposable pipette.
3.5 Comment: The exposure is referred to in several different ways. A standard
wording should be used to reduce confusion.
Response: This subject was also discussed by others who had seen the Draft Method.
Confusion can easily arise when the word rate is used to indicate the total exposure, the lamp
0 2
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intensity, and the conveyor belt feed rate (which is inverse with exposure). To reduce ~~
confusion, the method should be modified so that the word rate is used only for the conveyor
belt feed rate. The phrase exposure should be used to indicate the total exposure and the
"manufacturer's suggested curing conditions" in Section 4.2.1 and the "manufacturer's
suggested rate and intensity" in Section 4.1.5 should be replaced with "manufacturer's
suggested lamp intensity and conveyor feed rate".
3.6 Comment: Why is the procedure done twice at two different exposures?
Response: Due to different lamp and reflector designs, the actual emissions obtained
at a specified lamp intensity (given in watts of input power per length of lamp) may vary
widely between exposure facilities. Experimental work has shown that coatings may show
high total volatile emissions (V^) if adequate cure is not obtained. To obtain values of total
emissions (V^) that could be consistent between laboratories (note that interlaboratory testing
of the Method has not yet been performed) it is necessary to provide at test for adequate cure.
Most commercial UV-cured coatings are somewhat resistant to ovcrexposure. A simple test
for adequate cure is to repeat the method at double the original exposure. If the results at
double the exposure agree with the results at the original exposure to within 1%, absolute,
then the cure is adequate.
3.7 Comment: Why is two passes at the manufacturer's suggested lamp intensity and
conveyor feed rate used for the first attempt?
Response: In laboratory studies, the manufacturer's suggested lamp intensities and
conveyor feed rates did not always provide adequate curing. For this reason, the test method
is done at least two exposures • one at twice the manufacturer's suggested lamp intensity and
feed rate and again at four times the manufacturers suggested lamp intensity and feed rate.
Agreement at these two exposures indicates proper cure.
3.8 Comment: The requirements for auditing the method are unclear.
Response: At the current time, no audit materials for this method have been
developed. The need for and frequency of audits has not been determined. Sections 5.4 and
5.5 were included in the Draft Method to permit auditing to be performed in the future (i.e.,
after development of suitable audit materials) without revising the Draft Method in the '
Federal Register.
3.9 Comment: The UV processing loss (L^, equation 6.4) is not used. It should be
removed from the method.
D 3
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Response: At the current time, it has not been decided whether future regulations
should consider the processing losses. If future regulations are to use only the total volatile
loss (Vyy) then ail reference to L^y and Ws should be removed.
3.10 Comment: The method measures the volatiles per unit mass of coating. The
value should be multiplied by the density of the coating to get the volatiles per unit volume
of coating, for example, pounds per gallon of coating.
Response: The current method is for weight percent volatiles. The conversion to
mass of volatiles per unit volume could be easily incorporated, if needed.
Commenter 4
4.1 Comment: Use of the term "Volatile Organic Content" may be misleading since
the method actually measures total volatiles.
Response: The compounds tested did not have water present and, for these
compounds, the total volatiles are the Volatile Organic Content. The method should be
revised to more clearly state that total volatiles (as opposed to volatile organics) are
measured. We are not aware of any commercially available water-based UV curable coatings.
If it appears likely that such coatings are to be available commercially, then the draft method
should be modified to include a correction for water content (as in EPA Method 24).
Commenter 5
5.1 Comment: Repeatability and reproducability are not stated for the method.
Response: Estimation of reproducability would require an interlaboratory study of the
method, which has not been performed.
5.2 Comment: Use of a transfer pipette may permit low-viscosity samples to drip out
of the pipette. Disposable syringes should be used.
Response: The coatings tested during the development of this method did not drip out
of the pipette. If low-viscosity causes problems, then disposable syringes could be used.
53 Comment: The disposable gloves should be free of talc.
Response: The method should be revised to specify talc-free gloves.
D 4
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5.4 Comment: Weighing on a moving pan (see note in Section 4.1.2) presents a
moving target due to evaporation. Results will give lower VOC.
Response: The weighing of the sample in the pan (note on Section 4.1.2) is only to
achieve a more uniform sample size (i.e. ±0.1 g). This sample weight is not used in the VOC
calculations. The calculated sample weight is the weight of the pipette before and after
dispensing the sample.
5.5 Comment: Triplicate samples add little to method precision (compared to
duplicates), but require extra effort. Duplicates should be used instead of triplicates.
Response: The uncertainty associated with the sample mean should decrease with the
square root of the number of samples used to calculate the mean. Thus going from 2
samples to 3 samples should decrease the uncertainty of the mean by:
1 - ,/± - 18 %
Commenter 6
6.1 Comment: Method will not accommodate materials containing solvent, pigment,
or styrene.
Response: Solvent containing materials should work well with the EPA draft method,
as it does not weigh the sample on an open balance. Pigmented materials may be a problem
due to excessive film thickness. The use of larger weighing dishes (for more surface area and
thus thinner films) may be useful if problems are seen with* heavily pigmented coatings.
Styrene is a problem that is likely to exist for all volatile methods.
D 5
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APPENDIX E
REVISED DRAFT ASTM METHOD
PROPOSED TEST METHODS FOR DETERMINING VOC OF RADIATION CURABLE
MATERIALS
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This document is part of the Draft No. 4
ASTM standards process and is for August 6, 1992
ASTM committee use only. It shall
not be reproduced or circulated
or quoted, in whole or in part,
outside of ASTM committee
activities except with the
approval of the chairman of the
committee having jurisdiction or
the President of the Society.
ASTM Designation: D
Standard Test Methods for
VOLATILE CONTENT OF RADIATION CURABLE MATERIALS
1. - Scope
1§1 These test methods describe procedures for the determination
of weight percent volatile content of coatings, inks, and adhesives designed to
be cured by exposure to ultraviolet light or to a beam of accelerated electrons.
1,2 Test method A is applicable to radiation curable materials which
are essentially 100X reactive but may contain traces (no more than 3X) of volatile
materials as impurities or introduced by the inclusion of various additives.
1.3 Te8t method B is applicable to all radiation curable materials
but must be used for materials which contain volatile solvents intentionally
introduced to control application viscosity and which are intended to be removed
from the material prior to cure.
1,4 These test methods may not be applicable to radiation curable
materials wherein the volatile solvent is water, and other procedures may be
substituted by mutual consent of the producer and user.
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1.5 This standard may involve hazardous materials, operations, and
Equipment. This standard does nor purport tc address all of the safety problems
associated with its use. It is the responsibility of the user of this practice to
establish appropriate safety and health practices and determine the applicability
of regulatory limitations prior to use. A specific hazard statement is given in
Note 8.
2. Referenced Documents
2.1 ASTM Standards
D 2369 Test Method for Volatile Content of Coatings1
E 145 Specification for Gravity Convection and Forced Ventilation
Ovens
E 177 Practice for Use of the terms Precision and Bias in ASTM
Methods
E 691 Practice for Conducting an Intel-laboratory Study to Determine
the Precision of a Test Method*
3. Terminology
3.1 Definitions
3.1.1 pure - the condition of a coating after conversion to the final
state of cure as measured by tests generally related to end use performance and
mutually agreeable to supplier and purchaser.
3.1.2 yitraviolet (UV) Curing - conversion of a coating from its
application state to its final use state by means of a mechanism initiated by
ultraviolet radiation generated by equipment designed for that purpose.
3.1.3 Electron Beam (EB) Curing - conversion of a coating from ita
application state to its final use state by means of a mechanism initiated by
electron beam radiation generated by equipment designed for that purpose.
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3.1.4 Processing Volatiles - loss in specimen weight under test
conditions which are designed to simulate actual industrial cure processing
conditions.
3.1.5 Potential Volatiles - loss in specimen weight upon heating at
110* C for 60 minutes. This is an estimation of volatile loss which may occur
during aging or under extreme storage conditions. Potential Volatiles may also
be referred to as residual volatiles.
3.1.6 Total Volatiles - sum of the Processing Volatiles and the
Potential Volatiles.
4. Summary of Test Method
4.1 A designated quantity of material is weighed before and after
a cure step which simulates normal industrial processing. The test specimen is
weighed again after heating at 110±5*C for 60 minutes. The percent volatile is
calculated from the losses in weight.
5. Significance and Use
5.1 These test methods are the procedures of choice for
determining volatile content of materials designed to be cured by exposure to
ultraviolet light or electron beam irradiation. These types of "materials contain
liquid reactants which react to become part of the film during cure, but, which
under the test conditions of Test Method D 2369, will be erroneously measured
as volatiles. The conditions of these test methods are similar to Test Method
D 2369 with the inclusion of a step to cure the material prior to weight loss
determination. Volatile content is determined as two separate components -
processing volatiles and potential volatiles. Processing volatiles is a measure of
volatile loss during the actual cure process. Potential volatiles is a measure of
volatile loss which might occur during aging or under extreme storage conditions.
-------
These volatile content measurements are useful to the producer and user of a
material and to environmental interests for determining emissions.
6. Interferences
6,1 The degree to which the results of these procedures accurately
measure the volatiles emitted during actual use is absolutely dependent upon
proper cure during the test procedure. Although overcure will have little or no
effect upon measured volatiles, undercure may lead to erroneously high values.
Since various pieces of cure equipment may vary widely in efficiency, it is
essential that dialogue between material manufacturer and testing lab establish
a cure schedule appropriate both to the material to be tested and to the cure
equipment to be used in the procedure. See Note 2.
TEST METHOD A
7. Scope
T.I This method is applicable to radiation curable materials with
solvent content less than or equal to 3X.
8. Apparatus
8.1 Aluminum Substrate, standard test panels (102mm x 305mm) or
heavy gauge (0.05 mm min.) foil. Test panels are most convenient and may be
cut into smaller pieces for ease of weighing. Precondition the substrate for 30
minutes at 11045*C and store in a desiccator prior to use.
8.2 Forced Draft Oven. Type IIA or Type IIB as specified in
Specification E 145.
8.3 Ultraviolet Light or Electron Beam Curing Equipment - there
are several commercial suppliers of laboratory scale equipment which simulates
industrial curing processes. A list of such suppliers may obtained by contacting
RadTech International N.A., 60 Revere Drive, Suite 500, Northbrook, IL 60062.
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9. Procedure •
9.1 Mix the sample, if necessary, to ensure uniformity. Hand
stirring is recommended to avoid the entrapment of air bubbles.
9.2 Weigh the preconditioned Al substrate (8.1) to 0.1 rag (A). The
size of the Al substrate must allow a minimum of 0.2 gm of material to be applied
at the supplier's recommended film thickness. Use rubber gloves and/or tongs
to handle samples.
9.3 Apply a minimum of 0.2 gm of test specimen to the Al substrate
and reweigh to 0.1 mg (B). Prepare a total of three test specimens
Note 1 - The elapsed time between application and weighing should be no
greater than 30 seconds. If the sample to be tested contains any reactive
diluent with a vapor pressure at room temperature greater than 1.0 mm Hg (e.g.
styrene), the elapsed time between specimen application and weighing must be no
greater than 15 seconds.
9.4 Cure the test specimen by exposure to UV or EB as prescribed
by the supplier of the material. }
i
Note 2 - If there is 'any doubt as to the adequacy of the exposure for
affecting proper cure (6.1), an additional sample can be tested utilizing SOX
additional exposure and the volatile content results compared. If the original
i
exposure was adequate, there should be no difference in the results within the
i
precision of the test method. If the results are different, the supplier of the
material must be contacted and a revised cure schedule established.
^9.5 Allow the test specimen to cool 15 minutes at room temperature
and reweigh to 0.1 mg (C).
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9.6 Heat the test specimen in a forced draft oven (8.2) for 60
minutes at 110+5'C.
Note 3 - Materials which can react with atmospheric moisture during post
cure, i.e. UV cationic curable epoxy materials, may exhibit a weight gain during
step 9.6. If this ocurs, the sample should be retested and allowed to post cure
at room temperature for 48 hours after step 9.5, and then reweighed prior to
step 9.6. The weight after post cure should then be used as weight C in the
calculation of X Potential Volatiles in step 10.1.
9.7 Allow the test specimen to cool to room temperature in a
desiccator and reweigh to 0.1 mg (D).
10. Calculations
10.1 Calculate the weight percent volatiles as follows:
X Processing Volatiles = 100 [(B - C)/(B - A)]
X Potential Volatiles - 100 t(C - D)/(B - A)]
X Total volatiles = X Processing Volatiles + X Potential Volatiles
where:
A = weight of Al substrate
B = weight of Al substrate plus test specimen
C = weight of Al substrate plus test specimen after cure
D = weight of Al substrate plus cured test specimen after heating
11. Precision and Bias
11.1 Interlaboratory Test Prograq - An interlaboratory study*
of volatile content of radiation cured materials (Test Method A) was conducted in
accordance with Practice E 691 in nine laboratories with three materials, with
each laboratory obtaining three test results for each material.
6
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11%2 Test Result - The precision information given below for
volatile content in weight percent is for the comparison of two test results, each
of which is the average of three test determinations
11.3 Precision
Processing Volatiles
95X repeatability limit (within laboratory) 0.9X
95X reproducibility limit (between laboratories) 1.6X
Potential Volatiles
95X repeatability limit (within laboratory) 2.2X
95X reproducibility limit (between laboratories) 4.2X
Total Volatiles
95 X repeatibility limit (within laboratory) 2.3X
95X reproducibility limit (between laboratories) 3.9X
The terms repeatability limit and reproducibility limit are used as specified in
Practice E 177. The respective standard deviations among test results may be
obtained by dividing the above limit values by 2.8. The form of this precision
statement is in accordance with Practice E 177, section 31.1.
11.4 Bias - Since there is no accepted reference material,
method, or laboratory suitable for determining the bias for the procedure in this
test method for measuring the volatile content of radiation cured materials, no
statement of bias is being made.
TEST METHOD B
•
12. Scope
12.1 This method is applicable to all radiation curable
materials which will cure properly at the designated specimen weight, which
corresponds to a film thickness of 50 to 75 microns depending upon solvent
-------
content. Method B is the method'of choice for all radiation curable materials with
»
solvent content greater than 3X.
12.2 This method is not applicable to materials containing
styrene due to its volatility at 50 *C.
13. Apparatus
13.1 Aluminum Foil Dish. 58 mm in diameter by 18 mm height
with a smooth (planar) bottom surface. Precondition the dishes for 30 minutes
in an oven at 110±5*C and store in a desiccator prior to use.
13.2 Forced Draft Oven. Type IIA or Type IIB as specified in
Specification E 145.
Note 4 - The shelves of the Oven must be level.
13.3 Syringe. 1 ml, capable of properly dispensing the
material under test at sufficient rate that the specimen can be dissolved in the
solvent. Disposable syringes are recommended.
13.4 Ultraviolet Light or Electron Beam Curing Equipment -
there are several- commercial suppliers of laboratory scale equipment which
simulates industrial curing processes. A list of such suppliers may be obtained
by contacting RadTech International N.A., 60 Revere Drive, Suite 500, Northbrook,
IL 60062.
14. Reagents
14.1 Purity of Reagents - Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that all reagents
shall conform the specifications of the Committee on Analytical Reagents of the
American Chemical Society, where such specifications are available . Other grades
may be used, provided it is first ascertained that the reagent is of sufficiently
high purity to permit its use without lessening the accuracy of the determination.'
8
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15. " Procedure
15.1 Mix the sample, if necessary, to ensure uniformity. Hand
stirring is recommended to avoid the entrapment of air bubbles.
15.2 Weigh a preconditioned Al dish (13.1) to 0.1 mg (A).
•
Use rubber gloves and/or tongs to handle sample dishes.
15.3 Using the syringe (13.3) weigh to 0.1 mg (B), by
difference, 0.310.1 gm of test specimen into the foil dish to which has been added
3±1 ml of acetone. Add the material dropwise, swirling the dish to disperse it
completely in the acetone. If the material forms a lump that cannot be dispersed,
discard the test specimen and prepare a new one. Prepare a total of three
samples.
Note 5 - Be sure to wipe the outer surface of the syringe clean after
obtaining the test specimen. Pull the syringe plunger up 1/4 of an inch to pull
the material away from the neck of the syringe. Cap and weigh the syringe.
After dispensing the test specimen, do not wipe the tip of the syringe. Remove
the material from the neck of the syringe by pulling up the plunger. Cap and
reweigh the syringe. Note that sample weight (B) = initial weight syringe - final
weight syringe.
Note 6 - Use disposable rubber gloves or polyethylene to handle the
syringe.
Note 7 - If the material is not compatible with acetone,
tetrahydrofuran (THF) or a blend of acetone and THF may be substituted.
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15.4 Heat the samples in the forced draft oven (13.2) for 30
*
minutes at 50±2*C.
Note 8 - This step is critical since a large amount of solvent present
in the sample during cure will interfere with the cure process and an inadequate
degree of cure may result, which could produce erroneous volatile results (6.1).
If the material contains only very fast solvents, a lower temperature/shorter time
•
may b« substituted if it can be demonstrated that the conditions are adequate
to remove at least 90% of the original solvent in the composition. Any remaining
solvent will be removed during the subsequent cure and heating st.eps. In the
case of samples which contain volatile solvents for control of application
viscosityi this step also simulates the industrial processing stage necessary to
remove the solvent prior cure.
15.5 Cure the test specimen by exposure to UV or EB as
prescribed by the supplier of the material. See Note 2.
15.6 Allow test specimen to cool for 5 minutes at room
temperature and reweigh (C).
15.7 Heat the test specimen in the forced draft oven (13.2)
for 60 minutes at HOtS'C.
Note 9 - Precaution: In addition to other precautions, provide
adequate ventilation, consistent with accepted laboratory practice, to prevent
solvent vapors from accumulating to a dangerous level.
15.8 Allow test specimen to cool to room temperature in a
desiccator and reweigh (D).
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16. Calculations
16.1 Calculate the weight percent volatiles as follows:
% Processing Volatiles s 100 [B - (C - A)]/B
X Potential volatiles s 100 ((C - DJ/BJ
% Total Volatiles = X Processing Volatiles +
X Potential Volatiles
where:
A = weight of Al dish
B = weight of test specimen
C = weight of Al dish plus test specimen after initial heating and* cure
D = weight of Al dish plus cured test specimen after final heating
17. Precision and Bias
17.1 Interlaboratory Test Program - An
interlaboratory study of volatile content of radiation cured materials (Test
Method B) was conducted in accordance with Practice E 691 in eleven laboratories
with three materials, with each laboratory obtaining three test results for each
material.
17.2 Test Result - The precision information given below for
volatile content in weight percent is for the comparison of two test results, each
of which is the average of three test determinations.
17.3 Precision
Processing Volatiles
95X repeatability limit (within laboratory) 2.0X
95X reproducibility limit (between laboratories) 3.4X
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Potential Volatiles
95X repeatability limit (within laboratory) 1.1X
95X reproducibility limit (between laboratories) 4.7X
Total Volatiles
95X repeatability limit (within laboratory) 2.OX
95X reproducibility limit (between laboratories) 5.IX
The terms repeatability limit and reproducibility limit are used as specified in
Practice E 177. The respective standard deviations among test results may be
obtained by dividing the above limit values by 2.8. The form of this precision
statement is in accordance with Practice E 177, section 31.1.
17.4 Bias - Since there is no accepted reference material,
method, or laboratory for determining the bias for the procedure in this test
method for measuring volatile content of radiation cured materials, no statement
on bias is being made.
18 Key Words
18.1 Volatile content; radiation curing; ultraviolet
curing; electron beam curing; radiation curable material.
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FOOTNOTES
lThis test method is under the jurisdiction of ASTM Committee D-l on Paint and
Related Coatings and Materials and is the direct responsibility of Subcommittee
D01.55 on Factory Applied Coatings of Preformed Products.
Current edition approved . Published .
Annual Book of ASTM Standards. Vol. 06.01
Annual Book of ASTM Standards. Vol. 10.01
^Annual Book of ASTM Standards. Vol. 06.03
"Reagent Chemicals, American Chemical Society Specifications," Am. Chemical Soc.,
Washington, DC. For suggestions on the testing of reagents not listed by the
American Chemical Society, see "Reagent Chemicals and Standards," by Joseph
Rosin, D. Van Nostrand., Inc., New York, and the "United States Pharmacopeia."
Supporting data are available from ASTM headquarters. Request RR: DOl-xxxx.
13
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APPENDIX F
REVISED DRAFT EPA METHOD
DETERMINATION OF VOLATILE ORGANIC CONTENT FOR ULTRAVIOLET
RADIATION-CURED COATINGS
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REVISED . . DRAFT
DETERMINATION OF VOLATILE ORGANIC CONTENT FOR
ULTRAVIOLET RADIATION-CURED COATINGS
EPA Project No. 6SD10009
Work Assignment 1-132
February 1993
Project Officer
Lourdes L. Morales
Emissions Measurement Branch
Office of Air Quality Planning and Standards
Research Triangle Park, NC 27711
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DETERMINATION OP VOLATILE ORGANIC CONTENT FOR
ULTRAVIOLET RADIATION-CURED COATINGS
1. Applicability and Principle
1.1 Applicability. This method applies to the
determination of the volatile organic content of
ultraviolet radiation-cured coatings (UV-cured
coatings). This method has been tested with
commercial UV-cured coating formulations, including
acrylic-based formulations, cationic epoxies, and
thiol-polyene based coatings. This method has been
tested on UV-cured coatings with total volatiles
between 0 and 30 percent, as determined by the method.
The method is not applicable to coatings containing
styrene.
1.2 Principle. UV-cured coatings are a class of
coatings that contain unreacted monomers that are "
polymerized by exposure to ultraviolet light. This
method measures the weight loss from UV-cured coatings
in each of three steps:
• sitting at room temperature to simulate product
handling,
• after UV exposure to produce a cured coating, and
• after 1 hour in a 110°C oven to simulate the
final life of the product.
The procedure includes a test for cure, which involves
comparison of total weight loss of a sample cured at
different length of exposure.
2. Precision
Based on studies performed on laboratory samples
having 0 to 30% total volatiles (Vtot ," see
Section 6.5), the intralaboratory absolute standard
deviation for total volatiles using this method
averaged 0.7 percent. The interlaboratory precision
has not been determined.
3. Apparatus
3.1 UV-Exposure Apparatus. A conveyor-fed
ultraviolet curing apparatus. The ultraviolet light
shall be provided by one or more medium-pressure
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mercury vapor lamps with quartz housings, capable of
providing light with a wavelength of between 200 and
400 ran. The lamp and conveyor system must be capable
of providing sufficient exposure for the materials
being tested (see Section 4). Other apparatus may be
used if approved by the Administrator.
3.2 Oven. A forced-draft oven capable of
maintaining a temperature of 110 ± 5°C for 1 hour.
3.3 Thermometer. A thermometer capable of
measuring oven temperature to ± 1°C.
3.4 Balance. A balance capable of weighing to
± 0.0001 g.
3.5 Sample Dishes. Circular flat-bottomed aluminum
foil weighing dishes, approximately 58 mm in diameter
by 18 mm high.
3.6 Desiccator. An airtight container, with
desiccant, large enough to contain samples dishes.
3.7 Desiccant. Calcium sulfate (e.g., indicating
Drierite* ) or equivalent desiccant.
3.8 Disposable Pipettes. Disposable 5-ml
polyethylene transfer pipettes.
3.9 Acetone. ACS reagent grade or equivalent.
NOTE: If acetone is not an adequate solvent for the
material being tested, another solvent with a
sufficiently low boiling point (< 60°C) may be used.
Solvent must be tested to determine if it evaporates
completely from the coating at room temperature; i.e.,
the evaporative loss (L_) should be greater than or
equal to zero (see Section 6.2).
3.10 Gloves. Talc-free disposable gloves.
4. Procedure
NOTE: 1) All items that are weighed (e.g., sample
dish, pipettes) must be handled with gloves
or sample tongs.
Mention of trade names or specific products does not
constitute endorsement by the Environmental Protection
Agency.
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2.) Although many coatings can be handled in
room lighting, highly sensitive coatings may
exhibit curing with normal laboratory
lighting. The manufacturer should be
consulted on handling precautions for such
coatings.
4.1 Initial Analysis
4.1.1 Condition the aluminum sample dishes by
heating them in a forced-draft oven at 110 ± 5°C for
at least 1 hour. Remove the dishes and allow them to
cool in a desiccator. Store the conditioned dishes in
a desiccator.
4.1.2 Weigh an aluminum dish to ± 0.0001 g and
record this weight as W,. Mix the coating thoroughly
and fill a disposable pipette with enough coating to
deliver 0.2 ± 0.1 g of coating. Weigh the coating-
filled pipette to ± 0.0001 g and record this weight as
W2. Place 3 ± 1 mL of acetone in the aluminum dish and
carefully add the coating into the dish. Gently swirl
the dish to disperse the coating, taking care not to
spill any material. Weigh the pipette after the sample
has been dispensed to ± 0.0001 g and record this weight
as W3.
NOTE: It may be difficult to dispense viscous
samples from a pipette. To achieve uniform sample
weights (i.e., ± 0.1 g), it may be helpful to place
the sample dish on a balance and add the required
amount of sample. The acetone (or other solvent)
would then be added to the sample and the dish
swirled to disperse the sample uniformly. Because
of the possibility that volatiles might be lost
during weighing, the sample weight W7 should still
be calculated as described in Section 6.2. An
alternate procedure for viscous samples would be to
use a syringe in place of the disposable pipette.
4.1.3 Place the sample dish on a level surface at
room temperature in a laboratory fume hood for
30 minutes to allow the acetone to evaporate, then
weigh the sample dish to ± 0.0001 g and record this
weight as W4. The evaporative loss (Le , Section 6.3)
should be greater than or equal to zero.
NOTE: Some coatings, notably certain epoxy coatings,
may pick-up moisture during standing at room
temperature and thus show weight gain (i.e., negative
values of Le).
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>
S -, *•
'
4.1.4 Cure the coating by exposing it to UV light
doubling the length of exposure specified by the
manufacturer (i.e., doubling the number of passes
through the exposure apparatus at the manufacturer's
suggested conveyor-belt feed rate and lamp intensity).
Allow the sample to cool to room temperature
(approximately 30 seconds) between passes. After all
the passes have been completed weigh the sample to
± 0.0001 g and record this weight as W5.
4.1.5 After UV exposure and weighing, place the
sample dish in a 110 ± 5°C oven for 1 hour. Remove the
sample dish and allow it to cool to room temperature in
a desiccator. Weigh the sample dish to ± 0.0001 g and
record this weight as W6/ then calculate Vtot (percent)
as in Section 6.5.
4.1.6 Analyze samples in triplicate and calculate
an average total organic content, Vtot (percent) as in
Section 6.6.
4.2 Subsequent Analysis
4.2.1 Using fresh samples of the material from the
same lot as the sample in Section 4.1, repeat Section
4.1 using four times the manufacturer's recommended
length of exposure (i.e., four times the number of
passes at the manufacturer's suggested curing
conditions). Calculate Vtot as in Section 6.5.
4.2.2 Analyze samples in triplicate and calculate
an average total organic content, Vt0t (percent) as
in Section 6.6.
_ 4.3 If the average total volatile organic content,
Vtot (percent) calculated in Section 4.1 does not agree
to ± 1 percent (absolute) with the one calculated in
Section 4.2, repeat Section 4.2 doubling the last
length of exposure. Compare to the prior exposure
results until the average total organic content,
Vtot (percent) of two consecutive exposures tested at
the same conveyor belt feed rate and lamp intensity
agree to ± 1 percent (absolute).
NOTE: If the criterion has not been met by the
second time that Section 4.2 is repeated, the tester
may want to consider changing curing conditions (i.e.,
conveyor belt feed rate and lamp intensity) and repeat
Sections 4.1 through 4.3 beginning at twice the
manufacturer's recommended length of exposure with the
modified curing conditions.
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4.4 Perform analyses in triplicate for each coating
until the criterion in Section 4.3 is met. Record the
Vtot values used to meet the criteria in Section 4.3
with the corresponding light intensity, conveyor-belt
feed rate, and number of passes. Report the higher of
the two values obtained as Vtot from the sample being
tested.
NOTE: Underexposed UV-cured coatings may show
excessively high levels of total volatile organic
content, Vtot (Section 6.5). This may be corrected by
adjusting the exposure level as described in Section
4.2. Overexposed coatings may show charring,
discoloration, and bubbling. This is often due to
thermal overexposure rather than UV overexposure. To
reduce thermal effects, lower intensity or increase the
conveyor belt feed rate, and increase the number of
passes through the apparatus. Allow the samples to
cool to room temperature (approximately 30 seconds)
between passes.
5. Calibration and Audits
5.1 Analytical Balance. Calibrate against standard
weights.
5.2 Thermometer. Calibrate against a National
Institute of Standards and Technology (NIST)-traceable
thermometer.
5.4 Audit Procedure. Analyze the performance audit
sample, if available. The same analyst, analytical
reagents, and analytical system shall be used both for
compliance samples and the EPA audit samples. If this
condition is met, auditing of subsequent compliance
analyses for the same enforcement agency within 30 days
is not required. An audit sample set may not be used
to validate different sets of compliance samples under
the jurisdiction of different enforcement agencies,
unless prior arrangements are made with both
enforcement agencies.
5.5 Audit Samples. Audit samples will be supplied
only to enforcement agencies for compliance tests. The
availability of audit samples may be obtained by
writing: Source test Audit Coordinator (MD-778),
Quality Assurance Division, Atmospheric Research and
Exposure Assessment Laboratory, U.S. Environmental
Protection Agency, Research Triangle Park, NC 27711 or
by calling the Source Test Audit Coordinator (STAC) at
(919) 541-7834. The request for the audit sample must
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be made at least 30 days prior to the scheduled
compliance sample analysis."
5.6 Audit Results. Calculate the audit sample
concentration according to the calculation procedure
described in the audit instructions included with the
audit sample. Fill in the audit sample concentration
and the analyst's name on the audit response form
included with the audit instructions. Send one copy to
the EPA Regional Office or the appropriate enforcement
agency and a second copy to the STAC. The EPA Regional
Office or the appropriate enforcement agency will
report the results of the audit to the laboratory being
audited. Include this response with the results of the
compliance samples in relevant reports to the EPA
Regional Office or the appropriate enforcement agency^
6. Calculations
6.1 Nomenclature.
Le = Evaporative loss, percent.
LyV = UV loss, percent.
Vtot = Total volatile organic content, percent.
Vtotl = Total volatile organic content of first
sample, g.
Vtot2 = Total volatile organic content of second
sample, g.
Vtot3 = Total volatile organic content of third
_ sample, g.
Vtot = Average total volatile organic content,
percent.
Wj^ = Weight of empty aluminum sample dish, g.
W2 = Weight of pipette and sample, g.
W3 = Weight of pipette after sample has been
dispensed, g.
W5 = Weight of sample dish and sample after
acetone has evaporated, g.
W6 = Weight of sample dish and sample after UV
exposure.
W7 = Sample weight, g.
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SL> a
6.2 Sample Weight (W7). The sample weight is
calculated as the difference in the weight of the
pipette before and after the sample has been delivered,
i.e.:
w7 * wz - w,
6.3 Evaporative Loss. The evaporative loss (Le) is
calculated as:
(W, + W, - W,)
Le - 1J 2 r x 100
c \\f
6.4 UV Processing Loss. The UV processing loss
(Luv) is calculated as:
6.5 Total Volatiles. The total volatile organic
content is calculated as:
6.6 Average Total Volatiles. The average of the
total volatiles Vtot is calculated for triplicate
samples as:
Report the average of the triplicate analyses rounded
to +0.1 percent.
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7. Bibliography
1. U.S. Environmental "Protection Agency, Method 24
Determination of Volatile Matter Content. Water
Content, Density. Volume Solids, and Weight Solids of
Surface Coatings. 40 CFR 60, Appendix A.
2. American Society of Testing and Materials, ASTM
D2369-87. Standard Test Method for Volatile Content of
Coatings. Philadelphia, PA, 1987.
3. American Society for Testing and Materials.
Revised Test Methods for Determining VOC of Radiation
Curable Materials. ASTM proposed test method for UV/EB
curable materials (unpublished communications),
October 1991.
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