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

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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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