United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-85/029 July 1985
&EPA Project Summary
Test Methods for Determining
the Chemical Waste Compatibil-
ity of Synthetic Liners
Joseph Tratnyek, Peter Costas, and Warren Lyman
Flexible membrane liners (geomem-
branes) used to contain liquid chemi-
cals and leachate at waste containment
sites are required to be chemically re-
sistant (compatible) to the liquid. In
order to select a liner for use as well as
judge its long-term reliability, its chem-
ical resistance against the liquid(s) to be
contained must be known. The mea-
surement of compatibility is a complex
matter, because a variety of physical
and chemical interactions can occur,
and compatibility failure of a mem-
brane has never been adequately
defined for this application.
A search was made for test methods
that would ascertain the compatibility
performance of liners. Disclosed
methods and procedures were exam-
ined and compared. Two tests being
promoted for general acceptance are
NSF Standard No. 54 (a voluntary
industry-generated test) and the pro-
posed EPA Test Method 9090. Several
other tests developed by liner manufac-
turers and researchers were found, as
well as those methods generally applied
to pipes, bottles, film, plastics, rubber
sheeting and the like.
Although details of tests vary, all are
laboratory tests in which selected phys-
ical properties of the membrane are
compared and evaluated after contact
with the liquid for specified periods of
time. All are tedious, time-consuming,
and potentially costly. Useful data for
product specification and application
are derived from these tests, but none
adequately addresses all issues and
questions raised, especially with regard
to liner life-time prediction. Nor is any
one test universally accepted for use. A
combination of compatibility tests
(e.g., immersion, stress-crack, and per-
meation) may be necessary to fully
characterize chemical resistance in
specific cases. A superior test(s) based
on a comprehensive understanding of
liner compatibility remains to be
developed.
Two levels of effort (immediately prac-
tical, and long-term) directed at evalu-
ating membrane compatibility are
proposed. In the first, a test methodol-
ogy based on current protocols and
methods would be developed to provide
three kinds of required infor-
mation: short-term (testing up to 30
days' exposure), intermediate (testing
up to 4 months' exposure), and long-
term (greater than 4 months' exposure).
In the second, research and test method
development would be pursued with the
purpose of exploring new methods,
techniques, apparatus, etc., for better
compatibility characterization.
This Project Summary was devel-
oped by EPA's Hazardous Waste Engi-
neering Research Laboratory,
Cincinnati. OH, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back}.
Introduction
Liners fabricated from synthetic poly-
mer materials (often referred to as flexi-
ble membrane liners, - FML*) will be used
at a large number of the waste sites to
contain leachate and other waste liquids.
Since the primary function of a liner is to
contain waste liquids, a priori, a liner
must be resistant to the liquid. A key
issue in the use of an FML is its compati-
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bility (chemical resistance)* with the
waste liquid it will hold. The criteria for
evaluating chemical resistance and the
choice of test methods are part of that
issue.
Field test information is preferred
because it reflects "real" exposure. Ade-
quate field data have not been generated
because the use of FML for waste con-
tainment is too new a technology (in the
order of 20 years of experience).
Although field information is currently
being generated, field testing is a slow
process. To expedite the evaluation and
selection of an FML, data are obtained
from laboratory tests in which an FML is
exposed to a chemical challenge under
set conditions, and then properties- usu-
ally physical - of the exposed FML are
measured. Laboratory tests serve as the
primary screening approach to FML
chemical compatibility evaluation.
There are problems with current
methodology. Most tests produce only
indirect indication of FML chemical re-
sistance, and important parameters are
neglected or minimized in FML product
evaluation. No actual determination of
chemical change is made in routine test-
ing. In the absence of true long-term data
from field or laboratory (the FMLtechnol-
ogy is too new), current compatibility
data, in conjunction with industrial expe-
rience, must be used to judge future
behavior of FML. Lack of correlation with
field performance remains a present
issue.
For the benefit of regulators, planners,
and designers, the current test methodol-
ogy requires review and assessment so
that uncertainties about data can be min-
imized. Chemical resistance data are
needed for FML product development,
screening purposes, site liner-waste
matching, and liner life prediction.
The purpose of this projectwasto com-
pile, review, and evaluate available test
methods for measuring and/or estimat-
ing the chemical compatibility of poly-
meric flexible membrane liners with
liquid wastes for use at hazardous waste
treatment, storage, and disposal facili-
ties. The intention was not to write a test
method for FML/waste compatibility, but
to assess the current state of affairs and
direct the thinking of all those concerned
toward routes that might lead to a satis-
factory, comprehensive, and reliable
*The currently used term "geomembrane" includes
FML. In FML technology, a "compatible" liner is gen-
erally accepted as one that is "resistant" to chemical
attack as judged by its changes in physical properties
upon exposure to liquid waste
chemical compatibility measurement
technique.
General Technical
Considerations
General technical considerations rele-
vant to FML compatibility testing include
the nature of liner products, the nature of
chemical and leachate which a liner is to
contain, the nature of chemical compati-
bility, the compatibility measurement
features and test requirements.
Although the behavior of an FML prod-
uct will depend upon its total composi-
tion, the fundamental behavioral
element will be the polymer phase.
Therefore, the polymer has to be selected
for its chemical resistance in a specific
application. Chemical resistance will
depend not only upon the chemical
makeup of the polymer, but also on other
factors, such as degree of polymerization
or molecular weight, degree of crosslink-
ing, crystallinity, morphology, and the
like.
The nature and composition of the
waste liquid challenging the liner may be
infinite in variation. While water and
selected organic liquids can be chosen to
challenge the membrane alone, combi-
nations of liquids and other waste mate-
rial may also be used. Dissolved salts and
other materials may be found in the chal-
lenge liquid. In the field, actual leachate/
waste at a site is usually a complex mix-
ture of many components. It may be diffi-
cult to analyze and characterize because
of multiphase components or immiscible
material. In any case, mixtures frequently
do not behave in a manner predicted from
components.
Within the FML industry,^! "compati-
ble" FML material is generally accepted
as one that is resistant to chemical attack
as judged by its changes in physical prop-
erties after exposure to the waste. How-
ever, the chemical attack can take place
via several routes, all of which can be
mutually interactive. They are'
• Chemical reaction,
• Hydrolysis,
• Solvation/plasticization, and
• Environmental response (heat,
light, ozone, bio-organism, etc.).
It is important to remember that
although we are dealing specifically with
tests for chemical compatibility, FML
chemical resistance is influenced or
altered by all factors capable of producing
polymer degradation.
A variety of properties has been pro-
posed and used for evaluating mem-
branes. Chemical resistance or
compatibility is usually based on physical
test data gathered after exposure to a
chemical or leachate. Physical test data
may include tensile properties such as
tensile strength, yield strength, elonga-
tion at break, elongation at yield, and
some others. These are one-dimen-
sional, short-term, simple tests that are
easily accomplished in the laboratory,
and that are preferred by the industry as
service indicators. Additional physical
tests may include tear and puncture re-
sistance of the membrane, hardness,
and, in the case of a reinforced mem-
brane, ply adhesion tests. Stress-
cracking is measured in testing
polyethylene-type plastics, and permea-
tion is presently being considered as a
property to be measured for FMLs.
Present Compatibility Tests
The search for compatibility test
methods included not only tests strictly
intended to determine the chemical re-
sistance of rubber and plastic mem-
branes such as FMLs, but also allied tests
(e.g., for pipe, packaging, and film). All
types of tests that were relevant to chem-
ical resistance and the transfer of liquids
through membranes were considered
and reviewed.
Levels of information sources are
categorized as follows:
I. International standards and
tests;
II. National standards and tests;
III. Industrial standards and tests;
IV. Project tests; and
V. Academic/literature tests.
Tests (27) applicable to the subject are
described and discussed in detail. Infor-
mation is presented in tabular form, in
descriptive text, and in schematic
diagrams.
A general feature of the tests is com-
monality of approach. This is evidenced
by the cross-referencing of key tests (e.g.,
ASTM D543, ASTM 471, ISO 175, ISO
1817, DIN 53 521, BS 4618). The
approach to testing appears to be based
on assimilating test methods for rubber
sheet and plastic sheet into a test useful
for FMLs. It is worth noting that a
"caveat" is generally found in each
method, warning that the test may not
correspond with the service condition
and that data are only comparative in
nature. Absolute values or criteria for
compatibility are not established in the
tests.
At the present time, two specific test
methods for evaluating FML perfor-
mance in a chemical environment have
evolved - NSF Standard No. 54 and EPA
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Method 9090. The latter was designed
specifically as a compatibility test for
membrane liners in the presence of
waste. In the NSF standard, chemical
compatibility testing is described in the
document which deals with other
aspects of FML specifications. The NSF
method is a voluntary approach to indus-
try standardization; the EPA method may
be promulgated as a national standard
having regulatory authority. The NSF test
is primarily short-term, although provi-
sion is made for longer testing.
Both tests rely on measurement of sim-
ilar physical property changes. Criteria
for failure are not specified by the NSF
test, nor the EPA test, although the EPA
test refers to RCRA guidance documents
for evaluation of data. The NSF document
deals with stress-cracking phenomena in
a separate test; the EPA test does not at
all. Both employ similar test tempera-
tures (23°C and 50°C). Importantly, in
Method 9090 samples are subjected to
one-side exposure; in NSF 54, individual
test specimens are immersed in a rea-
gent. Both recommend FML contact with
actual waste liquid or leachate.
Other FML industry test methods
depend primarily upon immersion in
fluid, although one-side contact in a sim-
ulated ponding arrangement (heated dish
or tub) is sometimes used. Attempts are
made to simulate real experience, but the
merit of the exposure methods is still
being debated. Physical and mechanical
features are generally monitored for
change. Information on industry test
results is scarce because results tend to
be proprietary. Industry does retain its
own concept as to what constitutes fail-
ure in products. Tests are static in nature
and single property measurements (e.g.,
tensile strength, elongation, hardness,
and tear strength) suffice for
characterization.
In summary, the test reviewed exhibit
the following characteristic features:
• Test by immersion or one-side
exposure;
• Test without stress, except for
the polyethylene-type plastics,
which are a special case;
• Test at ambient temperature and
some elevated temperature;
• Test with varying time (short to
long), or to equilibrium;
• Test in laboratory;
• Test with reagents or waste; and
• Measurement of mechanical
properties and evaluation of
appearance as the preferred indi-
cators of compatibility.
No one test satisfies all needs for a
chemical compatibility test, and test pro-
tocols and experimental details are sub-
jects for discussion and re-evaluation.
Consensus Meeting
As part of the need to elucidate and
understand compatibility test methods
and FML requirements, a meeting with
experts in FML technology and applica-
tions was held at Arthur D. Little, Inc.,
Cambridge, Massachusetts, in January
1984. In attendance were several manu-
facturers' representatives, an independ-
ent FML researcher, EPA representatives,
and members of the Arthur D. Little staff.
This meeting provided an opportunity to
discuss the current test methodology and
recommendations for improvements in
tests for FML compatibility. The discus-
sions identified areas of concern, issues,
and means for resolution. This meeting
was most useful in bringing to light practi-
cal aspects of testing not dealt with in the
published test methods.
General Approach to Compati-
bility Testing
Compatibility testing of FML is made
complex by a number of factors and inter-
actions. Although apparatus and protocol
may differ, current test methods apply
simple, familiar technological tests to
evaluate those FML materials being used
in a demanding, new application. Each of
the tests described appears to be useful
for screening and evaluation, but all are
inadequate for predicting behavior patt-
erns on a truly long-term basis. Evalua-
tion of test results is based on limited
experience, mostly from membrane
manufacturers. Because of a recognized
need for better information, the subject f
FML compatibility testing requires
further development. Test methodology
must be matched to performance
requirements. The scope of compatibility
testing, FML material versus liquid chal-
lenge, test parameters, measurement
and observation, and test details are sub-
jects that require rethinking. New
methods, which include stress-
relaxation measurement and dynamic
mechanical analysis, are described and
suggested for further study and
development.
Aside from refining present test
methodology to meet immediate
demands, and for building a technologi-
cal and historical baseline, research is
required in several areas if chemical
compatibility is to be fully understood and
measured. The result of current and
future investigations into FML perfor-
mance in a chemical environment will be
a better understanding and a test(s) satis-
factory to all.
Conclusions
1. Presently there is no generally
accepted test method that fully
meets the needs of industry or
regulatory agency for the chemi-
cal compatibility assessment of
FML in the presence of waste
liquid.
2. Two general test methods specifi-
cally promoted for compatibility
testing of FMLs are NSF Standard
54 and EPA Method 9090. Sev-
eral manufacturers' tests are
used for evaluating liners; and
some standard material tests
have been applied to liners.
3. Chemical compatibility testing is
conducted primarily in the labora-
tory with actual leachate, waste,
or reagent. Field data are scarce
because liner technology for
waste containment is too new.
Reagent testing is preferred for
screening, but all current
methods specify exposing the test
specimen to actual waste sam-
ples or leachate. Exposing test
specimens in an actual waste
containment facility is recom-
mended, and provision for inclu-
sion of membrane coupons at the
site for periodic examination for
compatibility appears to be an
obvious prerequisite for obtaining
real data over the long term.
Chemical class lists versus the
FML type developed by industry
and investigators for tests appear
to be adequate for the initial
stages of selecting an FML for a
specific site.
4. FML chemical compatibility test-
ing is made complex because of a
large variety of possible interac-
tions among components of the
process.
5. Compatibility testing is tedious,
time-consuming, costly, and
potentially dangerous due to the
need for handling toxic substan-
ces. The ideal route to testing has
not yet been established, and
long-term prediction is tenuous
because of incomplete knowledge.
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6. Current tests, including those dis-
cussed, deal with only part of the
compatibility problem. Broader
issues include questions about
practicability, cost, time span, sig-
nificance, and reliability.
7. It appears that there will be no
immediate and ideal resolution of
the FML chemical compatibility
test issue. It is obvious that NSF 54
and Method 9090 are the current
contenders for a standard test
method, since other tests have not
been developed sufficiently for
FML evaluation. However,
whether NSF 54 is followed.
Method 9090 is imposed, other
methods surface, or industry goes
its own way, the problems are too
diffuse and complex to rely on a
simple set of rules as presently
conceived. The crux of the problem
is related to the need for good long-
term data in what is essentially a
new industry, and the fact that
chemical compatibility indicators
remain undefined. Truly reliable
compatibility data will be gener-
ated with time, but continuous
action is required by industry, regu-
latory agencies, and the research
community to define the requisite
parameters for evaluation, and
then to develop the appropriate
tests.
Recommendations
Effort on two levels is needed to evalu-
ate FMLs for waste liquid containment.
The first level of effort deals with the
immediate practical issue of ascertaining
FML compatibility for a particular appli-
cation. The second - of long-term nature
-focuseson understanding FMLcompat-
ibility in the chemical/physical context,
and then devising test methods for meas-
uring the identified parameters. The first
relies on maximizing application of cur-
rent tests. The second explores new or
untested methods.
For the first approach, it is recom-
mended that test protocol be developed
that would provide three kinds of infor-
mation which might satisfy industry and
regulatory body needs to the different
degrees required:
I. Short-term tests (up to 30 days'
exposure),
II. Intermediate tests (up to 4
months' exposure), and
III. Long-term tests (greater than £
months' exposure).
In the second approach to establishing
the chemical resistance of FML, an
exploratory course is called for in which
FML properties are evaluated with tech-
niques not now employed for compatibil-
ity measurement. Information about
visco-elastic behavior and permeability
obviously should be included. Methods
for measurement of dynamic stress-
strain properties, dynamic mechanical
analysis, torsional stress, and thermal
properties, especially under stress or
load, are examples of techniques that
might be explored further.
^~
Joseph Tratnyek, Peter Costas, and Warren Lyman are with Arthur D. Little, Inc.,
Cambridge. MA 02140.
Robert Hartley is the EPA Project Officer (see below).
The complete report, entitled "Test Methods for Determining the Chemical Waste
Compatibility of Synthetic Liners," (Order No. PB 85-182 970/AS; Cost $73.00,
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 Project Officer can be contacted at:
Hazardous Waste Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
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