United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S2-88/003 Feb. 1988
Project Summary
Control Technology Overview
Report: CFC Emissions from
Rigid Foam Manufacturing
K. P. Wert, T. P. Nelson, and J. D. Quass
Depletion of stratospheric ozone
through the action of halocarbons,
particularly chlorofluorocarbons
(CFCs). has been the subject of exten-
sive study and wide debate. Although
many uncertainties remain, current
scientific evidence strongly suggests
that anthropogenic CFCs could con-
tribute to depletion of the stratospheric
ozone layer as was first postulated in
1974.
In the production of rigid cellular
foams, CFCs are used as physical
blowing agents to reduce foam density
and impart thermal insulating proper-
ties. Such rigid foams include polyure-
thane, polyisocyanurate, polystyrene,
polyethylene, polypropylene, polyvinyl
chloride, and phenolic foams. Uses of
these foams include building insula-
tion, packaging materials, and single
service dinnerware.
This report estimates total CFC
emissions from the various rigid foam
manufacturing processes and from the
foam products themselves, and exam-
ines potential methods for reducing
these emissions. Options studied
include replacement of CFC-blown
products with alternative products not
requiring CFCs, replacement of ozone-
depleting CFCs with other chemicals
less likely to destroy stratospheric
ozone, and recovery/recycle of CFCs
released during the manufacturing
processes.
This Project Summary was devel-
oped by EPA's Air and Energy Engi-
neering Research Laboratory, Research
Triangle Park, NC, 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
Halocarbons known as chlorofluoro-
carbons (CFCs) are the primary suspects
in the stratospheric ozone depletion
theory. Since they are chemically stable,
CFCs are not readily decomposed i/1 the
lower atmosphere and can survive the
longtime necessary f or transporting the
stratosphere. Once a CFC molecule has
reached the stratosphere, it can be acted
upon by the greater flux of short-
wavelength ultraviolet (UV) radiation
present in the stratosphere. This causes
the CFC molecule to release halogen
atoms which then become reactants in
the breakdown of ozone into diatomic
oxygen.
Such depletion of the earth's layer of
stratospheric ozone is predicted to result
in increased levels of biologically dam-
aging UV radiation reaching the earth's
surface. Related adverse environmental
and health effects include increased
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incidences of human skin cancer,
reduced yields of important food crops,
and disruption of the aquatic food chain.
CFCs are widely used in several indus-
tries including rigid foam manufacturing.
In that industry, CFC-11 (fluorotrichlo-
romethane), CFC-12 (dichlorodifluorome-
thane), CFC-113 (trichlorotrifluoroethane),
and CFC-114 (dichlorotetrafluoroethane)
are used as physical blowing agents to
lower foam density and to impart thermal
insulating properties. CFC-11 is the
primary blowing agent for rigid polyure-
thane and polyisocyanurate foams. The
exotherm from the polymerization reaction
causes volatilization of the CFC, and the
vapor is trapped within the cellular matrix
of the foamed polymer. The cellular
structure provides the foam with its
rigidity, and the CFC-11 vapor trapped
within the cells gives these foams their
exceptional thermal insulation value.
For nonpolyurethane foams such as
extruded polystyrene foam, CFCs are also
used as a primary blowing agent. CFC-
12 is the predominant blowing agent
used in production of extruded polysty-
rene foam. The main function of the CFC
blowing agent in this application is to
produce numerous small closed cells
which provide a lightweight, rigid mate-
rial that can be used in a variety of end
products ranging from building insula-
tion to disposable dinnerware. The
amount of blowing agent in a given
formulation depends on the property
specifications of the end-use product.
CFC-11 in rigid polyurethane and
polyisocyanurate foams is trapped within
the polymer matrix and is referred to as
"banked" CFC since the gas diffuses very
slowly from the foam over the lifetime
of the material. These foams are used
primarily as insulation for buildings,
tanks, refrigerated appliances, and
refrigerated transport vehicles. As the
use of these foams increases, the bank
of CFCs continues to grow, essentially
becoming an uncontrollable source of
emissions for decades in the future. The
half-life of CFC-11 in rigid polyurethane
and polyisocyanurate foams is estimated
at 100 years. Similarly, the CFC-12 used
to blow polystyrene boardstock is banked
with a half-life estimated at 40 years. In
addition, CFC-11 and CFC-113 are
banked in closed-cell phenolic foam for
the life of the foam.
Emissions of CFCs from the production
of extruded polystyrene foam sheet and
rigid polyethylene, polypropylene, poly-
vinyl chloride, and open-cell phenolic
foams are characterized as being prompt;
i.e., the CFC gas is released during, or
soon after, foam formation.
This study evaluated the technical
options to reduce emissions of CFCs
associated with rigid foams and their
manufacturing processes. It emphasized
the substitution of hydrocarbons for CFC-
12, the capture and recycle of CFC-12
in the production of extruded polystyrene
sheet, and alternative products for all
rigid cellular foams. The factors involved
in these priority areas were evaluated in
depth. For all control technologies,
engineering and economic aspects were
examined, as well as barriers to control
implementation. A profile of the rigid
foam industry (including the number and
location of active firms, process technol-
ogy, and projected growth) was also
prepared.
Accomplishments/Results
Rigid Polyurethane/
Polyisocyanurate (PU) Foam
Because rigid PU foam manufacturing
emissions are relatively small and in-use
product emissions occur slowly over an
extremely long time period, it is difficult
to effectively control these emissions.
However, one option which can reduce
future CFC emissions is to switch to
substitute products which contain either
smaller quantities of CFCs or none at all.
Most rigid PU foam is used as insulation
for commercial and residential buildings.
In this application, such foams are found
in a wide variety of installation config-
urations for roofs and walls. Because of
this, the applicability and selection of
substitutes is dependent upon the end
use with such considerations as insula-
tion value, fire retardancy, structural
rigidity, moisture resistance, and UV
radiation resistance playing an important
role.
Some possible substitute insulation
materials are: fiberglass batts, fiberglass
board, perlite, expanded polystyrene
bead board, extruded polystyrene board,
fiberboard, cellular glass, insulating
concrete, rock wool, and vermiculite. In
most cases, to match the insulation val ue
(R-value) of the PU foam, substitution of
these alternative insulation materials for
PU foam will necessitate the use of
greater thicknesses and/or modifica-
tions to the installation configuration.
However, except for extruded poly-
styrene board, all of these alternatives
offer 100% reduction in CFC-11 emis-
sions. Because extruded polystyrene
board does use some CFCs, it offers
approximately a 40% CFC-11 emission
reduction potential.
For insulation of refrigerated appli-
ances and transport vehicles, the use ol
alternative insulation materials such as
fiberglass is not considered to be a viable
control option. To replace the relatively
small amount of foam typically found in
a refrigerator would require a majoi
redesign of the cabinet with thicker walls
and thicker metal in the walls. Manu-
facturing labor costs would also increase
Currently, the PU foam is injected intc
the appliance cabinet cavity and allowec
to cure in place. The cured foam adhere:
to the inner and outer skins of the unit
providing structural rigidity. The use o
substitute insulation products woulc
require more intensive labor in which th<
insulation would be cut and placed int(
the wall cavities, and metal bracket:
would have to be used to attach the inne
and outer walls.
Instead of alternative insulation mate
rials one control option is to use mon
water in the foam formulation. The us<
of water to generate C02 as an auxiliar
blowing agent is a technology which i
well known and widely used in thi
industry. Typically about 15% of the CF(
blowing agent is replaced with CC>2, bu
it is possible to replace up to about 33%
CO2 has a higher thermal conductivit
than CFC-11, and to maintain the foam'
insulation efficiency, the density of th
foam can be increased. This contrc
option results in higher foam cost
because of increased raw materials use
In packaging applications, the therm;
insulating characteristics of polyui
ethane foams are usually not importan
and a variety of alternatives exis
Possible substitutes for these applice
tions are numerous and include non-CF
blown loose-fill expanded polystyreni
shredded and wadded paper, cellules
wadding, die-cut cardboard, wood sha\
ings, pre-formed expanded polystyren
packing blocks, and plastic film bubbl
wrap.
Use of new low ozone depleting CFC
as blowing agents is a longer-ten
possibility for reducing ozone-depletir
CFC emissions from rigid polyurethar
foams. For these foams, the identifie
CFC alternatives are CFC-123 and CF(
141b. These chemicals were selected c
the basis of having chemical and physic
properties similar to those of CFC-1
however, each has possible drawbacl
including substantially higher cost the
CFC-11 and the fact that neither
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commercially available at the present
time.
Rigid Polystyrene Foam
Polystyrene (PS) is extruded into both
sheet and board profiles. Extruded PS
sheet is a thermoformable material
which is used to make a variety of single
service and packaging Items such as
stock food and produce trays, egg car-
tons, hinged carry-out containers, plates,
cups, and bowls. Over 80% of extruded
PS foam is manufactured as sheets.
Extruded PS board is used as an insu-
lation material in much the same way
as foamed polyurethane insulation.
Because the blowing agent (CFC-12) is
able to permeate through the foam sheet
relatively quickly, the CFC from sheet
manufacture is emitted early in the
product's shelf life. On the other hand,
because PS board is much thicker than
the sheet, the CFC is retained for a longer
period of time (half-life approximately 40
years).
For PS foam sheet, the use of low
ozone depleting blowing agents can
reduce the emission of ozone depleting
CFC-12. Such alternative blowing agents
include non-fully halogenated CFCs,
hydrocarbons, and inert gases. Currently,
hydrocarbons such as n-pentane, iso-
pentane, and butane are viable candi-
dates. These hydrocarbons can eliminate
use of CFC-12 in this application, but the
resulting hydrocarbon emissions may be
subject to state and local VOC (volatile
organic compound) regulations in areas
where high levels of ground-level ozone
are an environmental concern. Also,
there are added costs associated with
increased fire protection necessary for
use of the flammable hydrocarbons in the
manufacturing process.
The use of carbon adsorption systems
for the recovery and recycle of CFC-12
for PS sheet manufacturing can also
reduce the emission of ozone depleting
CFC-12. Though the system would
require a substantial capital investment,
this cost could be partially offset if the
recovered CFC-12 could be reused.
The only other currently available
control technique for CFCs from PS foam
sheet is substitution with products which
do not contain CFCs. A host of alternative
materials are already used for the same
products made with CFC-blown PS sheet.
As one example, both PS and paper egg
cartons can be found alongside each
other in many food stores.
Since PS board is used as an insulation
material and the CFC-12 is essentially
trapped within the foam matrix for
several years, substitution of alternative
materials which do not contain CFCs is
one promising control option as was true
for rigid PU insulation materials.
Polyolefin and Phenolic Foams
The development of closed-cell
phenolic foam in 1981 has resulted in
an increase in the production of phenolic
foam in recent years. Improved fire
retardance, low smoke generation, high
temperature resistance, and good
thermal properties have promoted its use
as insulation material in the construction
industry. As in the case of rigid
polyurethane and rigid polystyrene
boardstock, most CFC-11 and CFC-113
used in the production of closed-cell
phenolic foam is stored, or banked, and
either diffuses out slowly during the
foam's lifetime, or is released when the
foam is destroyed after use.
Manufacturing controls can achieve a
maximum emissions reduction equal
only to the amount of CFC emitted during
manufacture. Quantitative emission data
are not available for the types of
emissions occurring during phenolic
foam manufacture. Again, the most
effective controls for CFCs from this type
of foam will be those which not only
reduce manufacturing emissions, but
will also reduce the CFC bank in the
products. Both chemical and product
substitutes therefore are attractive
control options. Currently, there are
many alternative products available
which are used as sheathing and roof
insulating materials as was noted in the
discussion of rigid polyurethane
insulation foam. Since phenolic foam
insulation is relatively new and currently
competes with the other non-CFC
containing alternatives, a change in the
availability or cost of phenolic foam
should not cause severe disruptions in
the building trade.
Like phenolic foam, polypropylene,
polyethylene, and polyvinyl chloride
foams are relative newcomers to the
marketplace. These foams find limited
use in specialty applications such as
padding for athletic equipment, deco-
rative wrapping, and packaging of
delicate electronic components. CFC
emissions for these foams may be best
characterized as prompt, with emissions
essentially equalling consumption for a
given year. Owing largely to the relatively
recent appearance of these foams on the
marketplace and to the fact that there
are few producers of these materials,
data on production, CFCs used and
emitted, and control opportunities are
very limited. However, it is expected that
a number of alternative non-CFC con-
taining products could be substituted for
these foams in some applications, and
this would be a likely market response
if the cost of the polyolefin foams were
to increase significantly due to a price
increase in currently used CFCs. How-
ever, because of the physical attributes
of polyolefin foams (e.g., multiple-drop
protection, strength, static discharge
protection), they are often the most cost
effective packaging materials. In these
instances, alternative products may not
be available.
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K. P. Wert, T. P. Nelson, and J. D. Quass are with Radian Corp., Austin, TX
78720.
N. Dean Smith is the EPA Project Officer (see below).
The complete report, entitled "Control Technology Overview Report: CFC
Emissions from Rigid Foam Manufacturing," (Order No. PB 88-16O 379/
AS; Cost: $19.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Officer can be contacted at:
Air and Energy Engineering Research Laboratory *
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
U.S.OFFICJALM
U.S.POSTA
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Official Business
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EPA/600/S2-88/003
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