United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-85/127 Jan. 1986
Project Summary
M'
Resistance of Flexible
Membrane Liners to
Chemicals and Wastes
Arthur D. Schwope, Peter P. Costas, and Warren J. Lyman
Qualitative and quantitative informa-
tion on the chemical resistance of
flexible membrane liners (FMLs) has
been collected from vendors and tech-
nical publications. This information has
been compiled in a computer data base
comprising about 3.000 data fields on
23 liner materials and 549 chemicals. A
printout of the information is included
in the full report.
Criteria for assessing the information
on a common basis were developed.
Based on these criteria, normalized
ratings of chemical resistance were
developed for each chemical/material
pair for which there were data. In all,
1,300 ratings were developed and have
been summarized in a chemical resis-
tance matrix. These ratings are intended
to provide guidance to FML users, but
they are not appropriate by themselves
as a basis for selecting or rejecting a
liner. Furthermore the pertinence of the
criteria on which the ratings are based
has not been substantiated by field
experience.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research 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
Concern about the long-term integrity
of waste containment systems (impound-
ments and landfills) has resulted in more
stringent containment regulations. These
regulations focus on the materials used
to line and cap waste sites to prevent
liquid escape and water entry. The mate-
rials used are principally clays and syn-
thetic polymers. The latter include flexible
membrane liners (FMLs), which are the
subject of the full report.
FMLs are installed in the form of
sheeting that is typically several feet wide
and 0.02 to 0.1 in. (20 to 100 mils) thick.
Sheets are seamed together at the site.
Sheeting is presently fabricated from one
of four primary or one of several second-
ary base polymeric materials, some of
which are used alone and some of which
are reinforced with fabric.
Selecting a liner for a given application
involves defining the site requirements,
the length of storage, and the waste to be
contained. Leaks may occur from tears,
punctures, cracking, faulty seams, or
other physical occurrences, but they may
also result from chemical attack of the
liner. The resistance of a liner material to
chemical attack and permeation are vital
considerations in liner selection.
Liner materials vary widely in their
resistance to any given chemical. Thus
chemical resistance testing is conducted
by the liner industry, by those contem-
plating installation of a waste impound-
ment facility, and by various government
agencies. Though these groups have
conducted considerable testing, their
results have been difficult to compare
because there have been no standard
procedures for testing and reporting the
results. Furthermore, the findings are
scattered throughout the technical litera-
ture, government reports, vendors' bro-
chures, and proprietary literature.
The objective of this study was to
gather, analyze, and report all available
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existing data on the resistance of poly-
meric FMLs to waste chemicals that may
be stored in hazardous waste landfills
and surface impoundments. The purpose
of this compilation is to help liner manu-
facturers, vendors, purchasers, and re-
viewers of permit applications to select
the most chemically resistant FML for a
given waste site.
Materials
FMLs are compounded from mixtures
of one or more base polymers with
additives to improve processing, physical
properties, and resistance to weather and
soil exposure. Except for highly com-
pounded FMLs such as polyvinyl chloride,
the base polymer is the main determinant
of the liner's ultimate chemical resis-
tance. The chemical resistance of any
polymer is principally a function of its
chemical structure, molecular weight,
crystallinity, and degree of crosslinking.
The base polymers most commonly used
for FMLs are as follows:
• Chlorinated polyethylene (CPE)
• Chlorosulfonatedpolyethylene(CSPE)
• High-density polyethylene (HOPE)
• Polyvinyl chloride (PVC)
Most of the chemical resistance data
presented in the full report are for these
materials. Another group of base poly-
mers is less widely used and has limited
data available. They are also included in
the full report.
Methods for Assessing
Chemical Resistance
The chemical resistance of any material
is related to its ability to perform any
intended functions during and/or after
contact with a chemical. If no change
occurs in a liner's ability to function as
designed after chemical exposure, it is
said to be resistant to the chemical.
Chemical resistance of an FML should be
rated on the liner's ability to prevent the
passage of waste and leachate or certain
components of these liquids. The barrier
can be breached by chemical interactions
that reduce the physical properties of the
FML to the point of failure, or it can be
breached by permeation of the waste or
its components through the FML. The
latter may occur with little noticeable
effect on the liner's physical properties.
Though no consensus yet exists on
what characterizes a nonresistant liner,
changes in the following physical charac-
teristics generally indicate a lack of
chemical resistance: weight, dimensions,
tear strength, tensile strength, percent
elongation at break, modulus of elonga-
tion, and hardness. In addition, semicrys-
talline polymers may also exhibit stress
cracking as a sign of poor chemical
resistance. Correlations between changes
in these physical properties and changes
in the barrier effectiveness of the FML
have not been developed.
Information Sources
Chemical resistance information was
solicited from the FML industry and from
university and independent researchers.
In addition, an extensive literature search
was conducted. The principal sources of
information were the vendors of liners
and liner materials (who provide chemical
resistance tables as part of their product
literature) and government-sponsored
research. The vendors' tables typically
contain qualitative ratings of resistance
upon exposure to neat chemicals. The
criteria for these ratings were not usually
available from the vendors, and test data
were supplied in only a few cases. Most
test data for liners exposed to neat
chemicals and waste mixtures came from
government-funded studies.
Computer Data Base
The information gathered was compiled
in a computer data base comprising about
3,000 data fields on 23 liner materials
and 549 chemicals.
The information in the data base con-
sists of two types: quantitative and quali-
tative. The quantitative data consisted of
specific test results. The qualitative in-
formation was provided by vendors and
technical literature that described chem-
ical resistance in subjective terms such
as "excellent," "fair," or "poor." Since
these terms are not -onsistent or com-
parable between sources, the ratings
have been normalized to a common 5-
grade scale of a, b, be, c, and d, where "a"
is the most chemically resistant liner and
"d" is the least.
All essential information of the data
base has been tabulated and is included
as an appendix to the full report for those
who may want to independently assess
chemical resistance or for those who may
be involved in research using chemical
resistance data.
Chemical Resistance Matrix
After the data were compiled and
entered into the data base, the data
needed to be summarized on a common
basis in a form that would serve various
groups interested in the use of FMLs for
waste containment. The format selected
was a matrix in which chemical resistance
was reducedto resistant and nonresistant
ratings and could be shown on a chemical-
by-chemical basis for each generic class
(base polymer) of liner material. A scheme
was devised to indicate chemical resis-
tance as derived from either the qualita-
tive ratings and/or from an evaluation of
laboratory results.
The ratings in the chemical resistance
matrix are intended to be used only as a
general guide in assessing the potential
performance of a liner. A favorable rating
is no guarantee that the liner will perform
successfully. Nor should an unfavorable
rating be taken as an absolute indicator
that the liner is unsuitable for a particular
application. No known correlations have
been made between the liner material
performance in short-term laboratory
tests and likely performance over decades
in the field. Nevertheless, compiling and
assessing available information will help
users reach intelligent decisions regard-
ing the installation of FMLs.
Information Handling
To facilitate the generation of the
chemical resistance matrix for FML mate-
rials, the information was organized by
means of a commercially available and
widely used computer data base system
known as FOCUS (Information Builders,
Inc., New York, New York).*
The key field for each record was the
Chemical Abstracts registry number for
the chemical of concern. Mixtures of
wastes were assigned numbers. The
chemicals were also assigned to a chem-
ical class (inorganic acids, amines, ke-
tones, etc.), and each class was given a
code number. Depending on the type of
information available, the record also
contained the type of liner, vendor's
resistance rating, temperature for the
rating, type of test performed, exposure
conditions and time, test results, and
fields for referencing information sources.
Thus, once the data were compiled, they
could be retrieved on the basis of the
chemical, chemical class, liner material,
test type, etc. The types of liner materials
and tests for which published data were
found are listed in Tables 1 and 2.
As described earlier, the qualitative
ratings of chemical resistance were nor-
malized to a common 5-grade scale from
most to least resistant.
•Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use.
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Table 1. Liner Materials
Table 2.
Chemical Resistance Tests
Code*
Description
HDPE/EPDM High-density polyethylene/
EPDM alloy
HOPE High-density polyethylene
LDPE (Copol) L ow-density polyethylene
copolymer
EVA (Copol) Ethylene vinyl acetate
copolymer
CSPE Chlorosulfonated
polyethylene
CR Polychloroprene
EPDM Ethylene-propylene-diene
terpolymer
IIP Isobutene-isoprene copolymer
(butyl rubber)
CO Polyepichlorohydrin
ECO Epichlorohydrin-ethylene
oxide copolymer
CPE Chlorinated polyethylene
PVC Polyvinyl chloride
Polyester Polyester elastomer
AC Asphalt concrete
HAC Hydraulic asphalt concrete
SC Soil cement—95 parts soil,
5 parts clay, 10 parts cement,
9 parts water
SA Soil asphalt— 7 parts asphalt,
100 parts soil
ASPH Asphalt
ECB Ethylene-bitumen copolymer
PVC-CPE Polyvinyl chloride-chlorinated
polyethylene blend
CPE/PE/CPE Laminate of CPE and PE
XR-5 XR-5® (Seaman Corporation)
"As used in the chemical resistance matrix.
Data Limitations
The organization and consolidation of
chemical resistance information required
grouping liner materials by generic type.
All information for a given base polymer
was thus categorized together, regardless
of liner formulation or supplier. This
approach facilitated data handling, but it
could also lead to false conclusions about
the performance of a given brand of liner
material. This problem may be particularly
significant when only one source of
information has been found for a single
liner/chemical pair. If that information
applies to a liner that was specially
formulated for the specific waste or
chemical, it may lead to false conclusions
Description
Permeation
Immersion followed by dimensional
measurements
Data Reported As
g/m*/hr
% swelling
Test
Code"
1
2
Immersion followed by measurement
of elongation at break
Immersion followed by weighing
Immersion followed by determination
of tensile strength at break
Immersion followed by determination
of stress at 100% elongation
Hardness
Immersion followed by determination
of stress at 20O% elongation
Soil permeability
% change in elongation at break
% weight change
% change in maximum strength
% change in 100% modulus
Hardness points change
% change in 200% modulus
cm/s
5
7
9
10
11
"As used in the appendix to the full report.
about other liners in the same generic
class. But if the information indicated
poor performance, it could wrongly deter
the user from investigating the use of a
generic material in an upgraded formu-
lation.
Conclusions
The criteria for assessing the compiled
data and developing chemical resistance
ratings for the matrix are based on
technical judgment and generally concur
with similar attempts by other investi-
gators. However, the criteria have not
been proposed or adopted as standards by
the U.S. Environmental Protection Agency
(EPA) or any independent organization.
The criteria represent a starting point for
developing chemical resistance standards
for liner materials. All information on
which the ratings are based is presented
in the appendix to the full report to
facilitate other interpretations. As more
information from the laboratory and field
becomes available, the data base can be
expanded and the criteria modified to
reflect experience.
The full report was submitted in fulfill-
ment of Contract No. 68-01-6160 by
Arthur D. Little, Inc., under the sponsor-
ship of the U.S. Environmental Protection
Agency.
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Arthur D. Schwope, Peter P. Costas, and Warren J. Lyman are with Arthur D.
Little, Inc., Acorn Park, Cambridge, MA 02140.
Robert P. Hartley is the EPA Project Officer (see below).
The complete report, entitled "Resistance of Flexible Membrane Liners to
Chemicals and Wastes, "fOrder No. PB 86-119 955/AS; Cost: $22.95, 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 Project Officer can be contacted at:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S2-85/127
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