United States
                                Environmental Protection
                                Industrial Environmental Research 1.
                                Cincinnati OH 45268           ~,w .\
                                Research and Development
                                EPA-600/S2-82-038  August 1982
Project Summary
                                Carbon  Fiber Data  Base:
                                Review and Assessment  of
                                Carbon  Fiber Release  Into the
                                  The investigation described in this
                                report was conducted as part of the
                                carbon fiber disposal research effort
                                undertaken by the Environmental
                                Protection Agency. The purposes of
                                this investigation  were  (1) to
                                determine, from a literature search,
                                the sources, extent, and frequency of
                                carbon  fiber releases to the
                                environment, the risks related to these
                                releases,  and means  of coping with
                                the resulting problems, and (2) to
                                assess future requirements and
                                methodologies for minimum-risk
                                disposal of carbon fiber materials.
                                  This Project Summary was
                                developed by EPA's Industrial
                                Environmental Research Laboratory,
                                Cincinnati. Ohio, 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).

                                  Carbon fibers are used in combination
                                with polymers to form lightweight, high-
                                strength composite materials that will
                                find  increasing use in automobiles,
                                sports equipment, and aircraft parts.
                                During the manufacture of such
                                composites or during the production of
                                items made from them, some of their
                                carbon fiber content may be accidently
                                released to the environment. When
                                items containing the  composites are
                                disposed  of in municipal  waste
                                treatment systems employing
                                conventional incinerators, significant
                                amounts of the carbon fibers may be
                                released to the environment with the
                                flue gases from the incinerator. The
                                freed carbon fibers, which are
                                electrically conductive, can cause
                                shorting out of electrical and electronic
                                equipment. The potential health effects
                                of short, small-diameter airborne fibers
                                are presently under investigation.
                                  This Project Summary presents
                                results from an EPA-sponsored study on
                                problems related to the production and
                                use of carbon fiber materials. The final
                                report upon which this summary is
                                based identifies and evaluates potential
                                environmental and health  impacts of
                                carbon fibers,  and examines methods
                                for controlling their release to the
                                environment,  in light of the increasing
                                prevalence of carbon fiber composites
                                in consumer goods and transportation
                                  The study evaluates overall  systems
                                for disposal of carbon fiber materials.
                                The  evaluation identifies major
                                potential  sources of fibrous carbon
                                expected  to  enter  municipal waste
                                streams, assesses the capabilities of
                                solid waste disposal techniques
                                applicable to carbon fiber materials,
                                estimates the quantities of carbon fibers
                                that will be released from municipal
                                incinerators under various  degrees of
                                control, and estimates the  number of
                                electrical equipment failures expected
                                to result from such releases.
                                  The report reviews the carbon fiber
                                programs  being conducted  by various
                                Federal organizations. These programs

 focus  on accidents that cause fires,
 effects of airborne  fibers, and
 development of measurement
 techniques for airborne fibers.
  The report also presents the results of
 a survey of current  literature, which
 reveals  that the following types of
 information are available: the effects of
 combustion of carbon fiber composites;
 the impacts of  airborne  carbon fibers,
 including incidents involving electrical
 failure; the  present and projected future
 applications of  composites; trends in
 current research into materials,
 processes, use, and environmental
 impacts; and the present manufacturers
 and users of fiber and of carbon fiber
 composites. Selected  items from a
 research bibliography of  some 600
 pertinent publications and data sources
 are provided.
  The study was performed by Bionetics
 Corporation under EPAContract No. 68-
 03-2848. The work was completed in
 September, 1980.

Survey of Existing
  A major endeavor in the carbon fiber
project was to  identify, acquire, and
summarize data relevant to carbon
fibers and composites in general and
specific information on evaluations of
projected risks of carbon fiber releases
into the environment.  This program
involved  an extensive  survey  of  the
literature. Informational areas included
the  determination  of means of
producing carbon fiber materials and
their resultant properties, identification
of principal uses  of  carbon fiber
 materials,  identification of available
 reports on  composites evaluations,
investigations  of fiber incineration
 hazards, and  results of current
assessments related to  carbon fibers
and composites utilized in specified

Properties and Production of
 Carbon Fiber Materials
  The  physical properties  of carbon
fiber materials  hinge on the type and
 proportion of fiber, as well as the type of
 resin  matrix   employed.  The first
 production  stage forms long strands of
 spun, multifilament fiber on spools. The
 spooled material, called  tow, is either
 shipped to the ultimate parts fabricators
 or utilized directly for weaving into cloth
 or for chopping into  matting/molding
 elements. Particular applications (cloth
 or tape formation) benefit from
 prepregging —  an impregnation of the
fiber tow with resin prior to layup. The
parts manufacturer then forms and
cures  the layups  or moldings in
fabrication  of the  carbon fiber
composite article. The degree of carbon
fiber graphitization (affected by curing
temperature, pressure, and time)
determines tensile strengths  and
material stiffness characteristics. Step-
by-step flows of the materials  and
processes in the production of carbon
fiber composites are presented in the
report. Important material properties
are numerically tabulated. Names and
locations of U.S. producers and users of
carbon fiber materials are listed in the
report.  A listing of 138 users of such
materials, nationwide, is given.

Principal Applications of
Carbon Fiber Materials;
Anticipated Increases
  Major uses foreseen for carbon fiber
composites  include consumer pro-
ducts/sporting goods, surface transport
vehicles, industrial equipment/hard-
ware, medical equipment (orthopedic
implants, furniture), aircraft, and space-
  The authors of the final report found
that the greatest potential growth area
for carbon  fiber composites  is in
highway vehicles.*  In  aircraft
applications,  a nominal fleet  of 3,000
commercial  aircraft will  probably
require about 3,000  metric  tons of
carbon fiber composites, or about one
metric ton per aircraft. Some production
models of next-generation military
aircraft  are  expected to  utilize
cumulatively in excess of 450 metric
tons of carbon fiber materials.

Reporting of Composites
  Both U.S.  and foreign publications
emphasized aerospace applications of
carbon  fiber  composites,  principally
documenting the physical/mechanical
properties,  analytical techniques,
design and fabrication methods, and
component testing.  Somewhat  less
research has been  conducted in the
properties and production of fibers and
resins. About 400 U.S. documents and
more than 200 foreign documents were
reviewed  in  the literature search. A
selected research bibliography is
included in the report.
 •Author's note. Since the final report was written, a
 shift in potential carbon fiber use has occurred,
 with automobile usage decreased and aerospace
 industry usage increased
  To  facilitate interchange of
information, a "Directory and Locator
for the  National  Graphite Fiber
Program" is presented. Included in the
Interagency Data Exchange are Federal
offices, agencies, departments, and
support operations. Interagency
generators of data as well as potentially
interested recipients  of data are
tabulated,  and  likely major subject
categories are cross-referenced.

Fiber Incineration Hazards

  Categories of optically distinguishable
types of materials released from carbon
fiber composite fires are shown in Table
1. All categories except the single fibers
have settling rates generally sufficient
for  their capture within the flow
passages of an incinerator. Low free fall
rates of single fibers contribute to their
remaining in the gas stream,  thence
lofted  from  the stack to drift downwind
in the plume.
  Test results of carbon fibers released
from   burning  of composites are
presented in Figure  1. Shown are the
typical distributions of free carbon
fibers, fire residue (multiple-fiber
constituents remaining after  test
combustion) and completely oxidized
fiber (release of COz) to effect a mass
balance based on the initial preburned
weight of fiber  in the composite. The
fraction  of escaping  single fibers
accompanying  incineration  tends to
increase  with  increased  stirring  or
agitation  of the  burning material.
  Estimated releases of  carbon fibers
from  the  fire  zones of  municipal
incinerators with low agitation are as
• Up to one percent  by weight of the
  input fibers -would appear  in  the
  exhaust as single fibers greater than
  1 mm long. These longer fibers vary in
  length  essentially  within an
  exponential distribution with a mean
  of about 1.8  mm.  Oxidation during
  burning would reduce the diameters
  of up to 80 percent of this population
  of fibers from an as-produced
  diameter of 8 micrometers to around
  4 micrometers.
• Up to four percent of the incinerator
  input fibers  would appear  in  the
  exhaust stream as discrete fibers less
  than 1  mm long and with an average
  length  of about 0.25 mm. Oxidation
  effects would again be  expected to
  reduce about 80 percent  of  the
  population to diameters of the order of
  4 micrometers.

 Table 1.    Fire-Release Fiber Categories

       Category                  Description
                             Free Fall Rate In Air
 1. Single Fibers

 2. Lint

 3. Brush/Clump

 4. Fragments

 5. Strips
Single fibers up to Sum
in diameter, and up to
10mm in length

A group of fibers loosely
bound, randomly aligned

A group of fibers, bound
together with well defined

Pieces of burned compo-
site with dimensions
ranging from 2 mm to

Elements of composite
having lengths comparable
to the dimensions of the
item being burned
0.032 m/sec (max)

0.22 m/sec

0.88 m/sec

1.5 to 1.9 m/sec

2.0 to 10.0 m/sec
 (1) Lieberman, P.. Chovit, A.R.. Sussholz. B.. andKorman, H.F.. "Data Reduction and
    Analysis of Graphite Fiber Release Experiments." NASA CR-159032. 1979.
 (2) Bell.  V.L.. "Releases  of Carbon Fibers from Burning Composites," NASA
    Conference Publication 2119. December 4-5, 1979. pp. 29-57.
0.05% maximum
single fibers of
diameters less
than 4 micrometers
and less than
50 micrometers
Single fibers
longer than
1 millimeter
Single fibers
shorter than
1 millimeter
1 I Fire residue '
II *' Completely
J / x oxidized fiber
1 /
) 20 40 60 80 IOC
                                 Percent of initial weight of fiber

Figure 1.  Mass balance for carbon fibers from burned composites.

  Bell, V.L, "Release of carbon fibers from burning composites," NASA Conference
  Publication 2119. December 4-5. 1979, pp. 29-57.
• At the extreme short end of the short-
  fiber population (the short dashed line
  at the upper left edge of the curves in
  Figure 1), about 0.05 percent of the
  input fibers would appear as emitted
  particles shorter than 50 micrometers,
  with as-incinerated diameters
  reduced below 4 micrometers.
  In these three portions of the fiber
population  emitted during  burning at
low agitation, the longer fiber segment
is principally responsible for electrical
hazards and resultant system failures.
The shorter fibers fall into the category
which is currently under investigation
for health-related effects.
  The tendency for  airborne carbon
fibers to create electrical  failures is
defined in terms of the exposure of
electrical equipment to time-integrated
fiber concentrations.  Repeated tests of
specific items of electrical equipment at
established levels of airborne  fiber
concentrations for extended times have
yielded an average value of exposure
that  produces an electrical  failure.
Based on actual operational exposures
compared with average test specimen
exposures to produce equipment
failure,  probabilities of equipment
failure levels have been modeled.
  Electrical equipment degradation that
causes electrical shock hazards to the
user appears to occur rarely. Downwind
dispersion  of airborne carbon fibers is
generally adequate to dilute the plume
concentrations to the point where such
hazards appear to be random, i.e., not
readily distinguishable from insulation-
related failures from  other causes.
  As produced, carbon fibers  have
diameters larger than the air passages
leading to the alveoli within the lungs.
Studies of animals exposed to chopped
fiber have produced no conclusive
results. Partial  oxidation of fibers
reduces their  diameters, making them
more respirable. At the present  time,
the mechanism for human  interaction
with respirable size fibers has not been
defined and  studies  in this area  are

Current Assessments

  Assessments of incremental risks
from releases of carbon fibers conduct-
ed under governmental sponsorship as
well as by governmental laboratories
are reviewed and summarized. Losses
in terms of economic impact (malfunc-
tioning of electrical and electronic com-
ponents) have been  investigated by
NASA, based on carbon fiber releases

from accidents and fires involving com-
mercial aircraft; a counterpart study has
been conducted by the Department of
Transportation for fire-releases likely to
result from  surface vehicle accidents.
The Department of Energy has  evalu-
ated the economic losses of power sys-
tem outages due to carbon fiber short-
  The Department of Health and Human
Services/NIOSH  is conducting
experiments in which  laboratory test
animals were exposed  to fibers in the
respirable range (diameters less than
3.5 /urn and length-to-diameter ratios in
the range, 3:1  to 10:10). The Depart-
ment of Labor/OSHA is monitoring the
results toward establishing regulatory
needs, if they are deemed necessary.
  The  Department of Defense has
examined the effects of  carbon fiber
fallout on the operation and availability
of electronics and electrical components,
vital for national defense.
  Department of Commerce investiga-
tions (completed) have addressed
present and future production of carbon
fiber materials.
  The President's Office of Science and
Technology  Policy (OSTP) designated
other Federal organizations to perform
other  research  related  to carbon fiber
utilization. In the EPA, the Environmental
Sciences Research Laboratory at
Research Triangle Park, North Carolina,
has the responsibility for conducting the
Carbon Fiber Monitoring Research
Program. The program  focuses on the
development of instrumentation and
monitoring  techniques for measuring
airborne emissions of carbon fibers.
Also, the Municipal Environmental
Research Laboratory  in Cincinnati,
Ohio*, is overseeing studies in disposal
technology for carbon fiber materials.
  The Federal Emergency Management
Agency  is  engaged  in  identifying,
analyzing, and reporting civil incidents
involving carbon fibers.  The Federal
Aviation  Administration  is  to
summarize identifying  information  on
aircraft incorporating the composites
and  to report accidents related to
aircraft which contain carbon fiber
Assessment of Release
Mechanisms and Disposal
  Once a level of anticipated usage of
carbon fiber composites is determined,

"Disposal research responsibility has recently been
shifted within EPA to the Industrial Environmental
Research Laboratory, Cincinnati, OH
assessments  of carbon fiber  disposal
and damage hinge on factors such as
handling procedures thoroughout the
life cycle of the commercial products,
the characteristics of the disposal
techniques, and carbon fiber emission
  The  likelihood of controlled  or
uncontrolled  releases of disposed
carbon fiber materials is expected to
depend on the type of application of the
material, whether in transport aircraft,
automobiles, sporting goods, or medical
devices..Any industries that dispose of
production scrap without control could
be expected to contribute to the overall
fiber release problem.
  The potential releases of airborne
carbon fibers from waste composites in
disposal systems are evaluated. The two
major disposal methodsare/>t//fr(landfill-
ing and recycling) and combustion/'ox/da
tion. Adverse impacts associated with
carbon fiber material disposal aredeter-
ined by:
• the probability  of fibers becoming
  airborne, which in turn is a function of
  fiber release from the  matrix, fiber
  destruction, and process retention of
  the fibers (e.g., filtration and removal
  in the exhaust)
• the released fiber characteristics
  (e.g., dimensional, electrical)
• duration  and  magnitude of the
  The report evaluates three categories
of carbon  fiber composite disposal
methods: (1) municipal disposal tech-
niques in current use; (2) potentially ap-
plicable techniques; and (3) special-pur-
pose disposal techniques that require
further development. Among the vari-
ous disposal  techniques single-step,
mass  burning  and refuse-derived fuel
processes are considered "good" based
on potential for fiber oxidation, but are
expected to require particle control. The
mass-fired  two-step burn  process is
rated  "good"  and  probably will not  re-
quire downstream particle  control.
Pyrolitic  processing is similarly  rated
"good" but may require a precipitatoror
scrubber to remove particles from the
exhaust stream. Molten salt and wet air
oxidation are two techniques which are
believed to possess an "excellent"
potential for fiber oxidation, and need no
downstream particle removal.
  No  obvious  large-volume source of
carbon-fiber-type wastes currently
exists. Although automotive applications
and sporting  goods  scrap rates are
expected in the future to generate large
volumes of waste materials, projections
indicate that carbon fiber composites
will comprise  only about 1.15 x 10~3
percent of the total  mass  of waste
handled in municipal waste streams,
with an assumed 5.2 percent of that
material being incinerated, or about 110
metric tons per year.
  The report presents  order  of
magnitude calculations of the potential
effects of  carbon  fiber incineration in
the 1990's. By application of Bureau of
Census demographic projections and a
simplified  plume dispersion model, the
resulting total release of incinerated
fibers, nationwide number of sources,
and prevalent depositions of fibers  for
sizes  of electrical and  of  respirable
concern are  estimated.  Only a small
number  of  household electrical
appliances are likely to fail annually as a
result of  shorting  by carbon fibers.
Correspondingly, individuals receiving
the maximum calculated exposure to
respirable  carbon fibers downwind of
incinerators would require an estimated
7400 years  of  exposure to even
accumulate  the  equivalent  of  the
current NIOSH workplace limit  on
asbestos fiber exposure.

Conclusions and

  Projections  of  increasing usage of
carbon fiber  composites  indicate that
electrical electronic shorting problems
are a small  but  definable  risk with
uncontrolled releases of unburned
fibers during incineration of expended
products or of scrap materials.
  Manufacturing  processes  also may
release  concentrations of fibrous air-
borne particles which require protective
measures for nearby production per-
sonnel;  in production areas, exhaust
filtering/collection systems are con-
ventionally installed, and production
workers are customarily required to use
protective  breathing  apparatus. Also,
the diameters and  lengths of the air-
borne raw fibers,  prior to reduction by
combustion,  generally exceed  the
dimensions which can be carried into
the air cells of the lungs. Ongoing re-
search is  focused on  investigating  the
potential for production  of  respirable
particulates during manufacturing.
  While incinerators may  produce
significant concentrations of released
carbon fibers, the emission of respirable
fibers has been  observed  to be low.
Health hazards of exposure to respir-
able  carbon  fibers  are still  under

  The report authors anticipate that
properly designed  and controlled
incinerators may  be capable of
completely destroying most free carbon
fibers—to the point of even nullifying
any need for fiber  entrapment.
Nevertheless, limited quantities of
uncontrolled carbon  fiber composites
still would be expected to find their way
into the municipal waste streams that
feed conventional  incinerators.  Since
conventional incinerators may not be
designed exclusively for destruction of
carbon  or  graphite  substances, the
flame temperatures and retention times
may be inadequate  for complete
combustion of carbon fibers.
  Carbon fiber  composites  will have
extensive use in aerospace structures
as well as in medical applications and
industrial hardware, but the major
sources of uncontrolled disposal are
likely to be  consumer  sporting goods
and automotive products (discarded
mainly  by  body shops or backyard
mechanics).  Controlled disposal, as in
the case of wastes from manufacturers,
is  expected to be directed to  suitable
facilities such as dedicated incinerators
or secure landfills.
  The  following recommended  re-
search activities should be accorded
prompt attention:
• Evaluation of  particle control
  technology, namely, the effectiveness
  of electrostatic  precipitators, wet
  scrubbers, and baghouses in cleaning
  up incinerator exhaust gases during
  operations with carbon fibers of
  various diameters  and  lengths and
  mixed with other exhaust products.
• Estimation of  possible  levels of
  airborne fibers produced from front-
  end, pre-incineration operations
  including  refuse shredding,
  screening, crushing,  air classifying,
• Determination of the efficiency of
  mass-fired two-stage incinerators for
  handling carbon fiber composites,
  especially designs  of  units and
  operational  means  to reduce
  uncertainties in production of carbon
  fiber emissions.
• In the longer term, it is recommended
  that  EPA evaluate  the  need for
  dedicated facilities for disposal of
  carbon fiber  materials, especially
  landfilling operations resulting  in the
  release of the loose carbon fibers.
The authors are staff of the Carbon Fiber Data Base Project  Group.  The
  Bionetics Corporation, Hampton. VA 23666.
R. A. Carries is the EPA Project Officer (see below for contact).
The complete report, entitled "Carbon Fiber Data Base: Review and Assessment
  of Carbon Fiber Release Into the Environment." (Order No. PB 82-236 027;
  Cost: $19.50, subject to change) will be available only from:
        National Technical Information Service
        5285 Port Royal Road
        Springfield, VA 22161
        Telephone: 703-487-4650
For information contact B. L. Blaney at:
        Industrial Environmental Research Laboratory
        U.S. Environmental Protection Agency
        Cincinnati, OH 45268
                                                                                        OUSGPO: 1982 — 599-092/0475

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