United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati. OH 45268
Research and Development
EPA/600/SR-92/049 April 1992
EPA Project Summary
Permeation of Multifunctional
Acrylates through Three
Protective Clothing Materials
Rosemary Goydan and Thomas Stolki
Permeation tests were conducted
with trimethylolpropane triacrylate
(TMPTA), 1,6-hexanedioI diacrylate
(HDDA), arid two mixtures of 1,6-
hexanediol diacrylate with 2-ethylhexyl
acrylate (EHA) to better understand the
permeation behavior of multifunctional
acrylate compounds. The tests were
conducted using the ASTM F739-85 per-
meation method with a silicone rubber
sheeting material as the collection me-
dium because of the low vapor pres-
sure and low water solubility of the
acrylate compounds. Permeation tests
were performed at 20°C with butyl, ni-
trile, and natural rubber glove materi-
als. None of the acrylate compounds
nor mixtures was detected to permeate
the butyl or nitrile rubber at the condi-
tions and sensitivity of the method. Per-
meation of the natural rubber was de-
tected in tests with pure HDDA, a 50%
HDDA/50% EHA mixture, and a 25%
HDDA/75% EHA mixture. TMPTA per-
meation through the natural rubber was
also detected but only in one of the
triplicate tests after the 360-480 min
sampling interval. For pure HDDA, the
breakthrough detection time was 30-60
min and the steady-state permeation
rate was 0.92 jig/cm2-mih. For the
HDDA/EHA mixtures, permeation of
both mixture components was detected
at the same time in each test. The break-
through detection time was 30-60 min
for the 50% HDDA/50% EHA mixture
and was from 15-30 to 30-60 min for
the 25% HDDA/75% EHA mixture. The
HDDA steady-state permeation rates
from the mixtures were somewhat
higher than that measured for pure
HDDA: 1.02 ng/cm2-min for the 50%
HDDA/50% EHA mixture and 1.35 jig/
cmz-min for the 25% HDDA/75% EHA
mixture. The slight increase in perme-
ation rate is attributed to the presence
of the more rapidly permeating EHA
carrier solvent, which has a permeation
rate of 11.7 uxj/cntf-min from the 50%
HDDA/50% EHA mixture and 20.0 ng/
cm2-min from the 25% HDDA/75% EHA
mixture. Permeation tests with pure
EHA, however, were not performed.
This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
Introduction
Section 5 of the Toxic Substances Con-
trol Act requires prospective manufactur-
ers or importers of new chemicals to sub-
mit Premanufacture Notifications (PMNs),
which are reviewed by the EPA Office of
Toxic Substances (OTS) before their
manufacture or import. One objective of
the review is to assess the potential risks
to human health that could result from
dermal or inhalation exposures during the
manufacture, processing, and end use of
the PMN chemical. In those cases in which
the PMN submitter recommends protec-
tive'clothing as a way to minimize dermal
contacts, OTS evaluates the ability of the
protective clothing to act as a barrier to
the PMN chemical. Since 1985, the EPA
Office of Research and Development, in
support of OTS, has explored approaches
to developing predictive models, test meth-
Printed on Recycled Paper
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ods, and data review procedures for esti-
mating protective clothing barrier proper-
ties. Chemical permeation of clothing ma-
terials has been the focus because it is an
important mechanism by which chemicals
can move through protective clothing. OTS
can, when available, use permeation data
for the PMN substance or for a similar
compound to judge permeation resistance.
The PMN submitter, however, is not re-
quired to provide data that demonstrate
acceptable clothing permeation resistance.
For most PMN substances, therefore, suit-
able permeation data are not available to
judge permeation resistance.
OTS identified a specific need for per-
meation data for the general class of com-
pounds known as multifunctional acrylates.
Several recent PMN submissions have in-
volved such compounds, and a search of
the literature and databases uncovered
essentially no permeation data for these
compounds. Consequently, OTS selected
several representative multifunctional ac-
rylates and requested that permeation tests
be performed to establish a better basis
for estimating the permeation behavior of
such compounds. Performing these tests
is not routine, however, because of the
solubility and physical properties of the
compounds. Similar to many organophos-
phorus pesticides, multifunctional acrylates
nave low vapor pressure and low water
solubility. Thus, a collection medium other
than those now specified by ASTM F739—•
water or an inert gas—must be used to
perform permeation tests. A silicone rub-
ber sheeting material has been used suc-
cessfully as an alternative collection me-
dium and was used here.
In this study we measured the perme-
ation of TMPTA, HDDA, and mixtures of
HDDA with EHA, an acrylate carrier sol-
vent, through 3 protective clothing materi-
als: butyl rubber, natural rubber, and ni-
trile rubber. The laboratory program re-
quired a methods development task be-
fore performing the permeation tests:
• to establish the collection capacity and
efficiency of the silicone sheeting for
the acrylate compounds, and
• to validate the methods for extracting
and quantifying the amounts of the
acrylate compounds that permeate
and are collected by the silicone
sheeting. •
The data generated in this study are in-
tended for use by OTS to better under-
stand the permeation of multifunctional
acrylates through protective clothing ma-
terials.
Experimental Methods and
Procedures
Materials
Permeation tests were conducted with
two multifunctional acrylates, TMPTA and
HDDA, as pure chemicals. Tests were
also conducted with two mixtures of HDDA
with EHA: 50% HDDA/50% EHA and 25%
HDDA/75% EHA. The mixtures were pre-
pared on a percent volume basis. Proper-
ties of these compounds are given in Table
1. The permeation tests were conducted
with 3 protective clothing materials: butyl
rubber, natural rubber, and nitrile rubber.
Descriptions and sources of these cloth-
ing materials are provided in Table2.
Permeation Test Procedure
The permeation tests were conducted
according to ASTM Method F739-85 with
a modification for collecting low water solu-
bility, low vapor pressure permeants. In a
previous EPA study, several candidate
media were evaluated for the efficient col-
lection of the low water solubility, low vola-
tility pesticides. These studies found that
a commercially available, 0.051-cm (0.02-
in.) silicone rubber sheet material
(Silastic®, Dow Corning Corporation') was
more efficient at collecting the permeating
materials than were the other collection
media evaluated: aqueous solutions con-
taining surfactants or other solubilizing
compounds, filter paper, and synthetic
gauze.
The ASTM permeation test cell was
modified by replacing the standard collec-
tion chamber of the cell with a 7.62-cm (3-
in.) long section of flanged 5.08-cm (2-in.)
ID glass pipe. Thus, the standard ASTM
F739 clothing material surface area for
chemical contact was maintained at 20.3
cm2. The silicone rubber sheeting material
used as the collection medium was cut to
the size of the pipe ID and placed on the
collection side of the protective clothing
material to be tested. A tight-fitting, 2.54-
cm (1-in) long Teflon® piston was placed
in the glass pipe to ensure good contact
of the silicone rubber disc with the cloth-
ing material and to minimize evaporation
of the permeant collected. The challenge
side of the test cell was also modified to
minimize the handling of large challenge
chemical volumes.The standard challenge
chamber was replaced with a stainless
1 Mention of trade names or commercial products does
not constitute endorsement or recommendation for
use.
steel plate machined to hold 10 mL of
challenge solution. The challenge cham-
ber is connected through an overflow line
to a vial containing additional challenge
solution to ensure both a continuous chal-
lenge and a closed system. A schematic
of the modified test cell is shown in Figure
1.
The collection medium was sampled by
using stainless steel forceps to remove
the silicone rubber disc after a predeter-
mined sampling period. In these tests, the
silicone rubber discs were removed and
replaced with fresh discs at 0, 15, 30, 60,
120, 180, 240, 360, and 480 min. After
removal, each collection disc was trans-
ferred to a screw cap vial for extraction
and analysis. Each test was conducted in
triplicate and concluded after 480 min.
The permeation tests were performed at
20°C in a controlled temperature and hu-
midity laboratory.
Collection Medium Extraction
and Analysis Sequence
The collection medium samples re-
moved from the permeation test cell were
placed in individual vials and extracted
with 10 mL of isopropanol (Fisher Scien-
tific ACS grade). The samples were ex-
tracted for 30 min with sonication. An ali-
quot of the isopropanol extract was then
analyzed, without concentration, to deter-
mine the concentration of the permeant.
For each permeation test set (i.e., each
set of triplicate samples at the 9 sampling
intervals over the 480 min test duration),
the 240 min samples were first extracted
and analyzed to determine if permeation
was detected. If measurable quantities of
permeant(s) were detected in any of the
three replicates, all remaining samples for
that set were analyzed. If no measurable
quantities of permeant were detected in
the 240 min samples, only the 180, 360,
and 480 min samples were analyzed. At
this point, if permeant was detected in
any of the 180 min samples, the remain-
ing samples (0, 15, 30, 60, and 120 min)
were also analyzed.
Analytical Methods
Gas chromatographic/FID methods were
validated and used to determine TMPTA,
HDDA, and EHA concentrations in the
collection medium extracts.
Quality Assurance and Control
Procedures
To determine the method detection limit
(MDL), we analyzed seven replicates of
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Table 1. Chemical Properties*
Chemical name/
CAS Registry No.
TMPTA
CAS No. 1S62S-89-5
HDDA
Molecular
weight
(daltons)
296.32
226.28
Liquid
density f
(g/mL)
1.11
1.01
Vapor
pressure *
(mm Hg)
0.01
0.05
Solubility
in water*
Insoluble
Insoluble
CAS No. 13048-33-4
EHA
CAS No. 103-11-7
184.28
0.89
0.1
Insoluble
' Chemical source: Aldrich Chemical Company, Milwaukee, Wl.
* At20PC.
Table 2. Glove Materials Tested
Thickness
Generic material
Butyl rubber
Natural rubber
Nitrite rubber
Manufacturer
North
Pioneer
Edmont
Model
Butyl
Ivory White L-1 18
Solvex37-155 '•
. Nominal
(cm)
0.041
0.046
0.038
Actual
(cm)
0.046
0.048
0.037
the spiked silicone rubber matrix at or
near an estimated detection limit. The stan-
dard deviation of the concentration values
for the seven spiked samples was used to
calculate the MDL The precision and ac-
curacy of the analytical method were es-
tablished by analyzing four spiked silicone
rubber samples each at three concentra-
tion levels: 2 x MDL, 5 x MDL, and 10 x
MDL. These samples were analyzed over
2 consecutive days. From the spiked sili-
cone results, the average percent recov-
ery (P), the standard deviation of the av-
erage percent recovery (Sp), and the rela-
tive standard deviation (RSD) were calcu-
lated. The accuracy of the method was
defined as a percent recovery interval from
P - 2Sp to P + 2Sp. The RSD was used to
assess the precision of the method. The
results of the method validation effort are
summarized in Table 3. These results met
the quality assurance objectives estab-
lished for this laboratory program.
Quality assurance and control proce-
dures followed throughout the test pro-
gram included daily analysis of calibration
standards and a spiked silicone standard,
analysis of replicate samples, and the mea-
surement of permeant "absorbance." In
addition to characterizing the average
permeant recovery in spiking tests, we
attempted to measure the absorbance or
the mass of chemical absorbed by the
silicone rubber versus the total mass of
chemical that permeates through the cloth-
ing material during each permeation test.
At the end of the 360-480 min sampling
period, we rinsed the collection medium
side of the clothing material sample with
chilled isopropanol and analyzed the rinse
for the permeant. The absorbance was
calculated as:
ua
Absorbance-(%) = 100 x.
TMPTA
The results of the TMPTA permeation
tests with natural rubber, reported in Table
5, show that TMPTA permeation was de-
tected in one of the 3 replicate tests in the
360-480 min sample. No TMPTA was de-
tected in any of the isopropanol rinses of
the natural rubber samples at the conclu-
sion of the permeation tests (i.e., absor-
bance equalled 100%).
HDDA
The results of the permeation tests with
pure HDDA, also reported in Table 5, show
that in two of the replicates the HDDA
was first detected in the 30-60 min sample.
In the third replicate, the HDDA was de-
tected first in the 60-120 min sample. In
the subsequent samples, the cumulative
permeation increased and approached a
linear permeation rate by the 360-480 min
sample interval. The slope of the cumula-
tive permeation curve from the 240-360
min sample to the 360-480 min sample
was used to calculate the average steady-
state permeation rate of 0.92 u-g/crr^-min.
As reported in Table 5, the average ab-
sorbance of the HDDA was 87.6%, indi-
cating that the amount of HDDA found in
the isopropanol rinses of the natural rub-
ber samples was small relative to the
amount collected during the permeation
test. This result appears to further confirm
that the silicone rubber sheeting is a suit-
able collection medium for HDDA.
Mixtures of HDDA and EHA
No permeation of either HDDA or EHA
from the mixtures was detected in tests
with the butyl and nitrile rubber materials.
Results of the permeation tests with the
mixtures and natural rubber are summa-
absorbed by silicone
u.g in rinse + ug absorbed by silicone
Compound detected in the rinse may rep-
resent compound available on the surface
of clothing material or compound extracted
from the material. Our objective for the
mean absorbance of the permeant was s
80% with a coefficient of variation of ±
20%.
Results
The results of the permeation tests, sum-
marized in Table 4, indicate that none of
the acrylate compounds or mixtures was
detected to permeate the butyl rubber or
nitrile rubber materials. Permeation through
the natural rubber material was detected
for each challenge compound or mixture
and these results are discussed below.
rized in Table 6. The results indicate that,
for the 50% HDDA/50% EHA mixture, per-
meation of both the HDDA and the EHA
was first detected at the 30-60 min sam-
pling interval in all three replicates. Both
permeants reached a steady-state perme-
ation rate after the 120-180 min sample.
The permeation rate of the EHA was much
higher than that of HDDA from the mix-
ture: 11.7 (ig/cm2-min versus 1.02 jig/cm2-
min. The permeation rate of the HDDA
from the 50% mixture is essentially equal
to that measured in the pure HDDA ex-
periments. Thus, the decrease in concen-
tration of the HDDA does not appear to
affect the permeation rate. It is important
to note, however, that the absorbance
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Piston Holder
Teflon Piston
Bolts
Bolt I
Teflon
Gasket.
Test Material
Centering
Groove
Silicone Rubber
Clamp
Glass Pipe
\
Challenge
Chemical
Chamber
Overflow Tubing and
Containment
1 1 "
1 1 "
^l
1 1
1 1
J 1
\v "^':
:B,;
,_
1— ,
J-* Cl/f I/O/I/O 0
Tubing
Figaro 1. Permeation cell used with silicone rubber collection medium.
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Table 3. Method Validation Results
TMPTA
HDD A
EHA
Method Detection Limit
Concentration in extract 0.74 0.22
fag/mL)
Cumulative amount 0.36 0.11
permeated per sampling
interval fog/cnf )*
Precision and Accuracy *
Average recovery (%) 98.0 102.2
Standard deviation (%) 2.4 12.0
Accuracy 93.2- 102.8 78.2- 126.2
Precision (RSD%) 2.5 11.7
0.20
0.099
92.2
5.0
82.3-102.1
5.4
* Calculated from minimum detectable extract concentration fag/mL), 10 mL total extraction
volume, and 20.3 cm * exposed surface area.
f Based on analysis of spiked samples at2x MDL, 5 x MDL, and 10 x MDL on 2 consecutive
days.
value for the HDDA in these experiments
was low, only 40.1% on average. This
value is low compared with the average
value for the EHA absorbance in the same
test, 86.9%, and the average value in the
pure HDDA permeation tests, 87.6%.
Some puckering of the natural rubber ma-
terials was noted after the 15-30 min
sample. Possibly this puckering prevented
intimate contact of the natural rubber with
the silicone rubber collection medium so
that the absorbance was reduced for
HDDA, which has a low vapor pressure
relative to that of EHA (see Table 1).
Higher absorbance may have resulted in
higher permeation values for the HDDA
from the mixture.
Similar results were found in the per-
meation tests with the 25% HDDA/75%
EHA mixture and the natural rubber mate-
rial. Permeation of both the HDDA and
EHA was first detected in the 15-30 min
samples as reported in Table 6. As shown
in Figure 2, the permeation of the HDDA
from this mixture (and the 50% mixture)
was similar, although somewhat higher,
than that measured for pure HDDA. The
slight increase in the HDDA permeation
rates from the mixtures relative to that for
pure HDDA could possibly result from the
presence of the more rapjdly permeating
EHA carrier solvent. In comparison, the
EHA permeation rate from the 25% HDDA/
75% EHA mixture was much higher than.
that for EHA permeating from the 50%
HDDA/50% EHA mixture. The EHA per-
meation rate is strongly dependent on its
concentration in the mixture; however, we
did not perform experiments with pure EHA
so that quantitative comparisons are not
possible.
Conclusions and
Recommendations
The permeation of multifunctional aery-
late compounds and mixtures can be mea-
sured successfully using the ASTM F739
permeation method employing a silicone
rubber collection medium. The silicone rub-
ber sheeting was suitable as a collection
medium for TMPTA, HDDA, and EHA. In
general, the collection capacity and effi-
ciency were good; however, in the perme-
ation tests with HDDA and EHA mixtures,
the absorbance for the HDDA was low.
Use of the permeation method with
permeants that swell or pucker the protec-
tive clothing material being tested needs
further investigation.
The butyl rubber and nitrile rubber ma-
terials at the material thicknesses tested
were more effective barriers to perme-
ation by the multifunctional acrylate com-
pounds than was natural rubber under the
conditions and sensitivity of the test
Table 4. Summary of Permeation Test Results*
Temperature = 2CPC
Chemical/Mixture Butyl rubber , Natural rubber
Nitrile rubber
TMPTA
HDDA
50% HDDA/50% EHA
25% HDDA/75% EHA
No permeation detected
No permeation detected
No permeation detected
No permeation detected
Permeation detected at 360-48O min
(only 1of3 replicates)
Permeation detected at 30-60 to
60-120 min;
Steady-state rate: 0.92 ^g/cnf-mm
Permeation detected at 30-60 min;
Steady-state rates:
HDDA: 1.02ng/cml-min
EHA: 11.7 i3.g/cm*-min
Permeation detected at
15-30 to 30-60 min;
Steady-state rates:
HDDA: 1.35 \igfcnf-min
EHA: 20.0 \Lgfcm2-min
No permeation detected
No permeation detected
No permeation detected
No permeation detected
* Detection limits (per sampling interval): TMPTA: 0.36 pa/cm2
HDDA: 0.1 lug/err?
EHA: 0.099 \ig/cmz
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0.045
0.050
Tabto 5. Results for Permeation of TMPTA and HDDA through Natural Rubber
Temperature = 20°C
TMPTA HDDA
Thickness (cm)
Cumulative Permeation
Time (min)
0
15
30
60
120
180
240
360
480
Rinse
Breakthrough detection time (min)
Steady-state permeation rate
fog/cm '-min)1
Absorbance (%)*
nd
nd
nd
0.51*
nd
360-480, >480,
>480
N/A
100.0
nd'
nd
nd
0.18*
3.9
23.0
57.2
147.2
257.5
33.4
30-60, 30-60,
60-120
0.92
87.6
method. Comparison of these results with
those reported by other researchers shows
that the multifunctional acrylates perme-
ate the glove materials (in this case natu-
ral rubber) at much lower rates than those
measured for simple acrylate compounds.
The full report was submitted in fulfill-
ment of Contract No. 68-C9-0037, Work
Assignment 0-10, by Arthur D. Little, Inc.,
under sponsorship of the U.S. Environ-
mental Protection Agency.
* Values reported are averages of 3 replicates. (-) indicates samples were not
analyzed, (nd) Indicates that no permeant was detected in the collection medium
extract for that sampling interval. Detection limits: TMPTA, 0.36 iig/cm2;
HDDA, 0.11 \ig/cm*.
* Permeant detected in 2 of the 3 replicates: 0.15 \s.g/cnf,0.21 ng/cm2, nd.
* Permeant detected in only 1 of the 3 replicates: 0.51 ^.g/crtf, nd, nd.
i Values reported are averages of 3 replicates. (N/A) indicates not applicable.
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Table 6. Permeation Test Results for HDDA and EHA Mixtures through Natural Rubber
Temperature =2CPC
50% HDDA/50% EHA
25% HDDAJ75% EHA
HDDA
EHA
HDDA
EHA
Thickness (cm)
Cumulative Permeation fag/cm2)*:
Time (mm)
0.050
0.048
0
15
30
60
120
180
240
360
480
Rinse
Breakthrough detection time (mm)
Steady-state permeation rate
fag/cnf-min) *
Absorbance (%)*
nd'
nd
nd
2.6
36.2
97.0
153.9
275.9
405.8
605.0
30-60
1.02
40.1
nd
nd
nd
19.0
492.1
1254.6
1994.6
3411.3
4697.9
706.2
30-60
11,7
86.9
nd
nd
. 0.14 *
2.6
26.1
54.8
90.2
196..1
357.8
415.6
15-30, 30-60, 30-60
1.35
46.3
nd
nd
6.28* . . .
88.5
1129.4
2335.6
3525.3
5689.7
8331.3
1235.2
15-30,15-30,30-60
20.0
87.1
Values reported are averages of 3 replicates, (nd) indicates no permeantwas detected in the collection medium extract for that
sampling interval. Detection limits: HDDA, 0.11 pg/cm2; EHA, 0.099 ng/cm*.
HDDA: Permeant detected in 1 of 3 replicates: 0.14 v.g/crrf, nd, nd; EHA: Permeant detected in 2 of 3 replicates-
0.72 \ng/cm2, 0.55 us/cm* nd.
Values reported are averages of 3 replicates.
10000
O EHA (25% HDD A/75% EHA)
HDDA (25% HDDA/75% EHA)
0 EHA (50% HDDA/50% EHA)
HDDA (50% HDDA/50% EHA)
HDDA (100%)
100
200 300
Time (minutes)
400
500
Figure 2. Permeation of HDDA and EHA from mixtures through natural rubber glove material (Average of 3 replicates, error baris± standard deviation.)
irU.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40251
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FL GoydanandT. Stolkiare with Arthur D. Little, Inc., Cambridge, MA 02140-2390.
Esperanza P. Renard is the EPA Project Officer (see below).
The complete report, entitled "Permeation ofMultifunctionalAcrylates through Three
Protective Clothing Materials," (Order No. PB92-164 797/AS; Cost: $26.00,
subject to change) wilt be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Edison, NJ 08837-3679
United States
Environmental Protection
Agency
Center for Environmental
Research Information "
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/SR-92/049
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