United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-87/067 Nov. 1987
Project Summary
Development of Chemical
Compatibility Criteria for Assessing
Flexible Membrane Liners
Gordon Bellen, Rebecca Corry, and Mae Lynn Thomas
A laboratory testing of flexible mem-
brane liner (FML) materials was con-
ducted to develop chemical resistance
data using immersion tests. Six FML
materials (polyvinylchloride, chlorinated
polyethylene, chlorosulfonated polye-
thylene, high density polyethylene,
epichlorohydrin and ethylene propylene
diene terpolymer) were tested. Twenty
chemical solutions providing a range of
chemical challengers; acid and base,
polar and non-polar, organic and in-
organic, and increasing chemical con-
centration, were used. Duration of im-
mersions were 1, 7, 14, 28. and 56
days, and four month increments for up
to two years. All immersion tests were
conducted at two temperatures, 23°
and 50°C. Liners were evaluated for
changes in appearance, weight, dimen-
sions, and tensile properties.
Procedures and criteria for evaluating
immersion test results were developed
using data from this study and com-
paring them with comparable data from
other studies, published reports and
criteria, and liner manufacturer recom-
mendations. The criteria for chemical
resistance include the need for a liner
response to have stabilized, retention
of minimum physical properties, and
maximum percent change of physical
properties.
A mathematical curve fitting method
is proposed for evaluating immersion
data as a function of time. The method
assumes the liner approaches a limit of
physical property change (stability)
asymptotically. The method can be used
to predict the ultimate end point of
physical property change and sampling
time intervals for continued immersion
testing.
This Pro/ecf Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH, to
announce key findings of the research
prelect that Is fully documented In a
separate report of the same title (see
Project Report ordering Information at
back).
Scope
Flexible membrane liners (FMLs) are
used increasingly as lining materials for
hazardous waste containment, in landfills
and surface impoundments. A double-
liner system, including at least one
synthetic liner, is required in all new
installations. The FML used in a waste
containment application must show long-
term chemical resistance to the waste
stream.
Waste streams are mixtures of chemical
substances, with some chemical com-
ponents present in small or trace quanti-
ties. The presence of some trace
components may be unknown at the time
a liner is being selected. Published
chemical resistance tables generally list
only pure components, or mixtures of
one component in water. A small amount
of a substance deleterious to the liner
could be present in a mixture whose
major component has no effect. Looking
only at the effect of the major component
in tables, the liner would appear to be
resistant. The presence of the incompat-
ible chemical could mean the difference
between success and failure of the in-
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stallation. As an example of the effect of
a small amount of an incompatible
chemical. Figure 1 compares the change
in weight of the PVC liner used in this
study in two solutions of very different
concentrations. Percent weight change
is shown as a function of immersion
time. While a saturated brine solution
(approximately 35% by weight) causes
very minor changes in FML weight, a
0.5% solution of 1,2-dichloroethane (DCE)
results in much greater weight gain. A
waste containing both components might
be classified as a brine waste, and
chemical resistance predicted. For these
reasons, the EPA requires that FML selec-
tion be based on evaluation of changes in
physical properties resulting from im-
mersion in the actual waste to be
contained.
More guidance information is needed
by FML users, who must select the most
appropriate lining material and demon-
strate its resistance to the waste.
Theoretical methods of predicting chemi-
cal resistance such as Hansen solubility
parameters and cohesive energy density
numbers are not yet well developed for
FMLs, and expert systems for data inter-
pretation are not currently refined and
available. Acceptable changes in a physi-
cal property such as tensile strength at a
given temperature and immersion time
may be different for different FML mate-
rials. This project was initiated by the
EPA to help develop chemical resistance
selection guidance information for FML
users.
In this project, immersion testing of six
FMLs was conducted at two temperatures
(23°C and 50°C) with a broad range of
chemical exposures. FML property
changes were measured for exposure
periods from one day to two years. Results
were studied to determine the basic FML
responses to combinations of chemical
challenge, concentration, temperature,
and time. The focus in data interpretation
was on the types of degradation en-
countered, stabilization of the material
response, the extent of property change,
and indicators of non-resistance. The
method of interpretation can then be
generalized to provide guidance to FML
users testing FMLs with specific waste
streams.
Conclusions
• The stabilization of a material's
response to a chemical challenge,
when considered in conjunction with
the magnitude of that response, is
an important parameter in the evalu-
ation of chemical resistance.
• Increasing the immersion tempera-
ture may be used to accelerate the
FML response to determine chemical
resistance. For some chemical/
material combinations, however, in-
creasing the immersion temperature
to 50°C produced a different
response from the FML, instead of
an accelerated response. An elevated
temperature may provide a test that
is too aggressive for some FMLs to
60-
SO-'
40- •
30- '
20- -
10--
• = Weight change (%) .5% DCE
• = Weight change (%) Sard NaCI
•m •
2 5 W 20 50 tOO 200 500 1000
Log Days Immersion
Figure 1. PVC in brine and 0.5 percent DCE.
2
simulate anticipated use (e.g.,
elastomers).
• Not all materials are suitable for
service at 50°C. Heat degradation is
an important consideration in con-
junction with chemical resistance.
• Water is sometimes an aggressive
medium in itself, especially in con-
junction with an elevated tempera-
ture. The effect of water alone on an
FML must be evaluated when evalu-
ating chemical resistance.
• Increasing the concentration of
organic solvents in water solution in
general increased the magnitude of
the FML response (physical changes).
• Weight change is a valuable indicator
of material change for all FMLs
tested.
• The proposed criteria for chemical
resistance of the FMLs tested in this
project generally agree with ratings
given in existing chemical resistance
tables. The criteria may possibly be
expanded to evaluate immersion data
for USEPA Method 9090.
• Chemical resistance criteria for the
six materials tested are shown in
Table 1.
Recommendations
• Immersion testing of a liner in the
waste it is intended to contain is
essential for determining chemical
resistance. Low concentrations of
some chemicals can cause more
significant change in FML physical
properties than higher concentra-
tions of othr chemicals. Testing only
with major constituents would not
be satisfactory.
• The proposed method of determining
stability may be useful in determining
longevity of service based on chemi-
cal resistance, and also for com-
paring FMLs for relative suitability
for waste containment.
• Minimum as-received property
values listed in NSF Standard 54 for
Flexible Membrane Liners can be
useful as benchmarks in evaluating
chemical resistance test results.
• Compatibility tables can best be used
to screen FMLs to identify possibly
incompatible combinations. However,
compatibility tables are limited be-
cause materials are usually rated
qualitatively: (good, fair, poor) and
the test conditions used to determine
resistance are not always detailed.
• Generalizations about the criteria
and chemical immersion responses
of the FMLs tested in the project
-------
Tab/0 1. Criteria for Determining FML Chemical Resistance
Criteria Material Type Material Type Material Type
Material Type
Material Type
Material Type
Stability
Weight gain
Stability
Breaking
Factor
% Elongation
at Break
Yield
Strength
% Elongation
at Yield
Tear
Resistance
Modulus of
Elasticity
S-100
Modulus
PVC
(Plasticized
Thermoplastic)
Yes
-1O%< Wt. change
<5%
> 50% of initial
and > NSF Std. 54
> 70% of initial
and > NSF Std. 54
60% < S-100
Modulus < J4O%
CPE*
(Thermoplastic)
Yes
<25%
> 75% of initial
and > NSF Std. 54
>: 70% of initial
and > NSF Std. 54
> 70% of initial
and > NSF Std. 54
HOPE
(Partially
Crystalline)
Yes
<3%
> 80% of initial
and > NSF Std. 54
>8O% of initial
and > NSF Std. 54
> 8O% of initial
and > NSF Std. 54
> 80% of initial
and > NSF Std. 54
> 8O% of initial
and > NSF Std. 54
> 70% of initial
and > NSF Std. 54
EPDM
("Non-polar"
Cross-linked
Rubber)
Yes
<30%
> 80% of initial
and > NSF Std. 54
> 75% of initial
and 2: NSF Std. 54
EPI-CO
("Polar"
Cross-Linked
Rubber)
Yes
<20%
> 80% of initial
and > NSF Std. 54
> 70% of initial
and > NSF Std. 54
CSPE-LW
(Vulcanized
Rubber)
Yes
<5%
> 80% of initial
> 125% of initial
> 80% of Initial
> 70% of Initial
* All criteria for 23 C immersion tests
must be made with caution. Similar
liner materials (such as two polar
elastomers) may be expected to
respond similarly, but the degree of
the response (amount of property
change) may change with different
formulation and fabrication tech-
niques.
Gordon Bel ten, Rebecca Corry, and Mae Lynn Thomas are with National
Sanitation Foundation, Ann Arbor. Ml 48106.
Mary Ann Curran is the EPA Project Officer (see below).
The complete report, entitled "Development of Chemical Compatibility Criteria
for Assessing Flexible Membrane Liners," (Order No. PB 87-227 310/AS;
Cost: $42.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Officer can be contacted at:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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Agency
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