United States
Environmental Protection
Agency
Municipal Environmental Researc
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-138 Aug. 1981
Project Summary
Securing Containerized
Hazardous Wastes with
Polyethylene Resins and
Fiberglass Encapsulates
H. R. Lubowitz and R. W. Telles
This study investigates the fabrica-
tion and use of polyethylene resin and
fiberglass to encapsulate and secure
containerized hazardous wastes. Lab-
oratory-scale encapsulates of com-
posite structure were made from
powdered, high-density polyethylene
(HOPE) and epoxy-resin-wetted fiber-
glass. Methods are described for
fabricating encapsulates with seamless
polyethylene walls backed by fiber-
glass, and a demonstration is given of
their high performance under severe
leaching and mechanical stresses.
The objective of the study was to
develop a method for securing hazard-
ous wastes held either in small,
corroding containers or in large ones
such as 208-L (55-gal) drums. The
drums would be encapsulated without
emptying their contents. Encapsulation
would make them safe to transport
and to deposit within a final disposal
site such as a landfill.
This study is a companion to two
other documents investigating the use
of plastics for the encapsulation of
corroding containers of hazardous
wastes: "Securing Containerized
Hazardous Wastes with Welded Poly-
ethylene Encapsulates" (EPA-600/2-
81-139) and "Securing Containerized
Hazardous Wastes by Encapsulation
with Spray-on/Brush-on Resins"
(EPA-600/2-81-140).
This Project Summary was devel-
oped by EPA's Municipal Environmen-
tal Research Laboratory, Cincinnati,
OH, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Contaminants leaking from corroding
drums of hazardous wastes may harm
man and his environment. This study
investigates methods for securing such
containers through the use of water-
tight encapsulates made of powdered,
high-density polyethylene (HOPE) and
fiberglass-reinforced epoxy resin. Con-
tents of the drums were to remain in
place. The encapsulates were fabricated
with seamless polyethylene outer walls
backed by fiberglass casings. These
features (particularly the homogeneity
of the outer wall material) resulted in
high performance under mechanical
and chemical stresses.
Securing hazardous waste containers
means to make them safe for trans-
porting to and sequestering within a
direct disposal site such as a landfill.
Several approaches to securing con-
tainerized wastes are possible, including
reinforcement of containers with spray-
on/brush-on materials and removing
contents to manage them by other
means. This project uses an approach
that places containers of hazardous
waste in receptacles and seals them
with contents intact. This simple
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approach to waste management has
been used previously in commercial
operations, but the receptacles used did
not satisfy Department of Transportation
(DOT) regulations, and/or they could
not adequately safeguard hazardous
consignments under landfill conditions.
These receptacles were steel containers
and thus were subject to corrosion.
The size and construction of commer-
cial plastic receptacles that exhibit
corrosion resistance (such as 208-L
(55-gal) polyethylene drums) were not
suitable for securing 208-L (55-gal)
metal drums. The largest commercial
plastic vessels that could be transported
with compliance to DOT regulations
were 208-L (55-gal) drums fined with
bung holes. Available wide-mouth
drums did not qualify, anti larger plastic
vessels were not fitted with the means
to effect secure closure.
Because suitable commercial recep-
tacles were not available, this work
establishes technical expertise for
making such containers a viable option
for managing corroding 208-L (55-gal)
drums of hazardous consignments. This
study sets forth a new type of drum
receiver of composite construction with
seamless, HDPE outer walls reinforced
by fiberglass casing. The container
encases wastes within a chemically
stable encapsulate having high me-
chanical performance, and it was
geared to overcome the deficiencies in
state-of-the-art plastic containers
created largely by the use of lids,
gaskets, sealants, threading, and hoops
for the making of closures.
The technique for making such
encapsulates was based on the results
of previous work performed by TRW for
EPA under Contract No. 68-03-2037.
The previous work is described in EPA-
600/2-77-045 (August 1977), "Devel-
opment of Polymeric Cementing and
Encapsulating Process for Managing
Hazardous Wastes." This project con-
cerned management of unconfined
waste particulates by fashioning them
into agglomerates and fitting them with
seamless jackets of 6.35-mm-thick(1/4
in.) HDPE. The resulting agglomerates
stiffened the flexible plastic outer walls
of the encapsulates, and thereby
enabled the encapsulates to maintain
their dimensional integrity under ap-
preciable compression. In the present
project, the stiffening role is carried out
by fiberglass casings.
This report describes the technique
for encapsulate fabrication on a labora-
tory scale and outlines the product
performance. Though this technique
may appear to be essentially the same
as that developed previously for manag-
ing unconfined, participated wastes, it
is not. The technique described here
was found to be preferable after
investigations of a number of other
options.
Materials
Candidate Outer Wall Materials
Polyolef ins (particularly polyethylenes)
were selected as the materials for the
outer walls. On a price/performance
basis, polyolefins were unique. Bitumens
and asphaltics, though lower in cost, did
not exhibit the engineering properties
required in containers. Engineering
resins such as the thermoplastic poly-
esters were appreciably more expensive
than the polyolefins.
Many types of polyethylenes are on
the market, but the types preferred for
this project were those used in the
commercial rotomolding of polyethylene
containers. All of these types were
satisfactory for making the containers
needed for this project. Other types
used in extrusion and blow molding
were also applicable, because the
successful in-place fusion of polyethylene
particulates carried out here was found
to be relatively insensitive to resin
viscosity. Low-pressure, linear poly-
ethylenes, which are becoming available
commercially and claim to exhibit
advanced performance, were also
suitable candidates. Particulated scrap
polyethylene was also considered to
reduce costs.
Candidate Inner Wall Materials
Fiberglass was selected for the inner
walls because it is lightweight, rigid,
and low-cost. Concrete was considered
for its potentially lower costs, but this
advantage was mitigated by the addi-
tional weight needed to obtain tough
structures. Various types of fiberglass
exist, and the least expensive varieties
(such as chopped glass fiber used in the
spray-up of shower stalls, tubs, etc.)
were preferable. Cloth, mat, and roving
were eliminated because of their
greater costs. Nevertheless, mat and
roving were viable candidates in situa-
tions that needed processing advan-
tages. Cloth was used to prepare
laboratory-scale encapsulates because
it facilitated fabrication.
Procedures
Laboratory-Scale Encapsulates
Cylindrical encapsulates 76.2 mm (3
in.) in diameter and 102 mm (4 in.) high
were fabricated using heated, matched
die molds. They were produced by
fabricating 0.5-mm-thick (1/50 in.)
fiberglass-reinforced epoxy resin casings
(Figure 1) and fusing powdered HDPE
onto the casings. The resulting water-
tight encapsulates (Figure 2) were
characterized by seamless 6.35-mm-
thick (1 /4 in.) HDPE walls backed by the
reinforced casing. The fiberglass pro-
vided stiff, regular surfaces that facili-
tated fabrication of HDPE walls and (in
full-scale encapsulates) would also
reinforce them suitably for manipula-
tion, stacking, transportation, and final
charging into a-Jandfill.
Some specimens were filled with
sand, and some were kept hollow. The
sand-filled specimens were charged
with aqueous solutions of heavy metats
to simulate the loss of container
contents within encapsulates. They
were then examined with respect to
their ability to secure metal contaminants
under harsh aqueous leaching condM
tions. Sand and soil were contemplated
for filling voids between containers and
container/encapsulate walls, even
though compaction of containerized
wastes was considered to be a more
effective use of encapsulating materials
and product manipulation methods.
Compaction would have required con-
siderable pollution control procedures.
Thus the containers were initially
tailored to manage hazardous waste
containers as they were received.
The hollow specimens were used
mainly to evaluate the mechanical
performance of encapsulates, since
Figure 1. Fiberglass encased material.
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Figure 2. Fiberglass-reinforced
polyethylene encapsulate.
they would yield a clearer picture of
encapsulate wall performance than
would filled specimens.
Commercial-Scale
Encapsulates
A commercial-scale encapsulate was
envisioned to hold about 284 L (75 gal).
, The walls would consist of 6.35-mm-
' thick (1 /4 in.) polyolefin jacket backed
by a 1.58- to 3.17-mm-thick (1/16 to
1 /8 in.) chopped fiberglass casing. The
jacket and the casing 'make up about
3.5% and 1.8% of the encapsulate
volume, respectively. The exact thick-
ness and nature of the fiberglass moiety
needed for commercial-scale containers
must be determined in future work.
Results
Evaluations indicated that fiberglass-
backed HOPE encapsulates assured
high-performance retention of contam-
inants. Encapsulates exhibited stability
in chemically aggressive waters, and
they showed unusual resistance to
rupture when compressed appreciably.
The encapsulates examined held water
soluble compounds of the following
toxic metals: Ni, Cd, Hg, Cr, Zn, Cu, Sb,
As, Se, and Pb. In aqueous hydrochloric
acid (an excellent solvent for metals),
the hazardous consignments remained
secure. When severely distorted verti-
cally and lateraJiy«the encapsulates not
only withstood rapture, but uncon-
strained, they exhibited appreciable
recovery of their original dimensions.
The high performance of laboratory-
scale encapsulates indicated that full-
scale encapsulates holding corroding
55-gal drums with hazardous wastes
would keep their consignments secure
when manipulated, transported, and
sequestered within a landfill. Full-scale
encapsulates with 6.35-mm (1/4-in.)
polyethylene jackets backed by fiberglass
fabricated according to this work are
expected to satisfy DOT requirements
for containers used to transport hazard-
ous wastes.
Conclusions
Watertight, laboratory-scale encap-
sulates of hazardous wastes can be
readily fabricated from powdered poly-
ethylene and fiberglass. Seamless
polyethylene plastic walls backed by
fiberglass casings were the structural
features of the encapsulates. Their high
performance under applied chemical
and mechanical stresses was because
of the material homogeneity of their
outer walls and to their composite
structure.
As containers, the encapsulates were
unique, and their performance was
estimated to be significantly better than
that of state-of-the-art containers
fabricated from low-cost materials.
Such encapsulates scaled to encase
corroding 208-L (55-gal) drums of
hazardous wastes are expected to
comply with DOT criteria governing
such containers and to keep their
contents secure under landfill condi-
tions.
Specifically, the work gave rise to the
following observations and suppositions:
• Laboratory-scale encapsulates
consisting of 6.35-mm-thick (1/4
in.), HOPE seamless jackets backed
by 1/50-in. fiberglass casings
snowed high performance reten-
tion of enclosed wastes when
subjected to severe aqueous leach-
ing and mechanical stresses.
• The fiberglass casings and the
tough, flexible jackets yielded
tough encapsulates. The casings
facilitated fabrication of encapsu-
lates by providing suitable sub-
strates for polyethylene fusion, and
they preserved their dimensional
integrity under mechanical stress.
The flexible jackets sealed the
casings and prevented contact of
the hazardous consignments with
environmental leaching waters.
When encapsulates were distorted
by mechanical stresses such as
impact and compression, wastes
were safeguarded by jackets, even
though flaws occurred in the
casings.
• Fusion of powdered polyethylene
in matched die molds under minimal
mechanical pressures yielded con-
solidated polyethylene jackets with
a full compliment of expected
properties, including flexibility and
toughness. The high elongation-
to-break of the jackets prevented
rupture even when the jackets
were severely distorted.
• The method of heating used hereto
make laboratory-scale jackets
would not be appropriate for full
scale. Convenience and simplicity
dictated this method for the task at
hand, but it required appreciable
time to form the jackets because of
the slow heat exchange rate. With
commercial rotomolding. practice
as a guideline, it should be possible
to fuse the resin in several minutes.
• The appreciable amounts of un-
confined volatile liquid present did
not preclude sealing of the encap-
sulates. Thus liquids accumulating
from a leaking 208-L (55-gal) drum
in a full-scale encapsulate under
fabrication should not interrupt the
operation. Sealing the hazardous
consignments required fusing
resin only at the extremity of the
encapsulate. Thus no heating of
the encapsulate consignment was
anticipated under these conditions.
• The fabrication of full-scale encap-
sulates does not require heavy-
duty equipment, since powder
rather than molten resin is used to
charge the molds. (In injection and
extrusion molding, the movement
of molten resin makes heavy-duty
equipment necessary for managing
the required resin displacement
pressures.) Full-scale encapsulates
could therefore be fabricated by
readily transportable equipment.
• The work indicated that corroding
208-L (55-gal) drums holding
hazardous wastes can be managed
as follows:
1. Transport equipment and mate-
rials (materials can also be in
the form of partially fabricated
encapsulates) to the site where
drums reside.
2. Secure drums in fiberglass-
backed polyethylene encapsu-
lates and transfer them to a
landfill (encapsulates secure
contents in case of mishaps in
transportation).
3. Charge encapsulates into a
landfill according to accepted
» U.S. GOVERNMENT PRINTING OFFICE 1»1 -757-012/72?!
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practice for disposing of con-
tainerized wastes.
Recommendations
Work should proceed on the fabrica-
tion of full-scale encapsulates of about
246- to 321 -L (65- to 85-gal) capacity.
This range is most applicable for
managing both standard sizes and
distorted 208-L(55-gal) drums. Fabrica-
tion would consist of:
1. Forming receivers from fiberglass
casings by commercial techniques
of spray-up or hand lay-up of
fiberglass.
2. Fusing powdered polyethylene
onto the walls of the receivers to
obtain a jacketed, open-mouth
receiver for 208-L (55-gal) drum.
3. Sealing the jacketed receiver with
additional fiberglass and then
fusing additional polyethylene
onto the uncoated casing.
The product would be a double-walled
encapsulate with a 6.35-mm-thick (1 /4
in.) polyethylene seamless outer wall
backed by a reinforcing fiberglass
casing approximately 3.17-mm (1/8-
in.) thick. The outer wall thickness will
be the same as that used and evaluated
in this project. The casing thickness is
an estimated value; a more exact value
would stem from detailed analysis of
stresses an encapsulate would en-
counter in manipulation, stacking,
transportation, and sequestering in a
landfill.
An apparatus should be constructed
for making fulUscale encapsulates.
Such equipment would carry out in-
place fusion and solidification of
powdered polyethylene. Sophisticated
mechanical equipment would be un-
necessary because the resin is charged
into the apparatus in powdered form at
atmospheric temperatures. The process
would be analogous to commercial
rotomolding. The apparatus should be
similar to the one used here for
laboratory-scale encapsulates, but it
should have more -facile heating ar-
rangements. Nonetheless, it will be a
simple device compared with those
used for fabricating commercial plastic
products. The encapsulating device
would be similar to those used for
rotomolding, but it would require no
provisions for rotating and tumbling.
Like the laboratory models, full-scali
encapsulates must demonstrate satis
factory resistance to leaching and higl
mechanical performance to resis
stresses stemming from fabrication
manipulation, stacking, and locatior
within a final disposal site.
The full report was submitted ir
fulfillment of Contract No. 68-03-2482
by the Environmental Protection Poly
mers, Inc., under sponsorship of th<
U.S. Environmental Protection Agency
H. R. Lubowitz and R. W. Telles are with Environmental Protection Polymers,
Inc., Hawthorne, CA 90250.
Carlton C. Wiles is the EPA Project Officer (see below).
The complete report, entitled "Securing Containerized Hazardous Wastes with
Polyethylene Resin and Fiberglass Encapsulates," (Order No. PB81 -232 449;
Cost: $9.50, 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:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
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