[Pharmwaste] Formulating environmentally friendly flame retardants

DeBiasi,Deborah dldebiasi at deq.virginia.gov
Wed Sep 26 16:10:15 EDT 2007


http://pubs.acs.org/subscribe/journals/esthag-w/2007/sept/tech/kb_flamer
etard.html

Technology News -September 26, 2007

Formulating environmentally friendly flame retardants

Regulations, consumer demand, and innovation are inspiring manufacturers
to design more environmentally friendly flame retardants.

Polyurethane foam is so flammable that people in the insurance industry
sometimes call it "solid gasoline". Until a few years ago, manufacturers
of the inexpensive plastic combined it with brominated flame retardants,
typically a PBDE formulation known as Penta BDE, to ensure that it was
safe for use in products such as upholstered furniture, mattresses,
carpet padding, and automotive interiors. The situation changed
significantly in 2004, when Penta BDE and another PBDE formulation, Octa
BDE, were banned in Europe and discontinued in the U.S. because of
concerns related to their persistence, bioavailability, and toxicity.
Since then, the flame retardant industry has been under increasing
pressure to move away from the use of environmentally persistent
halogens, such as bromine and chlorine, according to the participants at
a conference on environmentally friendly flame retardants organized in
Baltimore by IntertechPira in July.

 
NIST

As this fire test carried out by NIST illustrates, the polyurethane foam
used in upholstered chairs is extremely flammable. Until 2004, PBDEs
were used to prevent such foam padding from catching fire. Now,
manufacturers are struggling to find a substitute that works as well-and
causes no environmental problems.The industry is responding with new
approaches for making flame retardants, and some design teams are
actively adopting the tenets of green chemistry. In the long run, the
work now under way could result in the development of materials that are
inherently resistant to fire.

Legislation is driving some of the move away from halogenated flame
retardants. The use of Deca BDE-the only PBDE formulation still used
widely-is being challenged in the EU. Deca BDE was also recently banned
in Washington and Maine, and legislatures in other states, including
California, are also considering bills to ban the compound.

Flame retardant formulators acknowledge that many of their customers are
also steering them toward halogen-free offerings. Ikea was one of the
first companies to announce that it would no longer use PBDEs in its
furniture; its products have been free of brominated flame retardants
since 2002. According to the nonprofit Environmental Working Group, at
least 10 other major manufacturers have also made similar announcements
about discontinuing or phasing out either PBDEs or all brominated flame
retardants; these include Apple, Dell, Ericsson, Hewlett-Packard, IBM,
Intel, Motorola, Panasonic, Philips, and Sony.

Computer manufacturers are now competing to be viewed as green, and
halogen-based flame retardants do not have a green image, explains Scott
O'Connell, the environmental program manager for Dell. Stephen Tisdale
of Intel agrees that his company wants halogen-free materials.

"One of the big issues with halogenated materials is the formation of
dioxins under poor burning conditions," such as when electronics
products are "recycled" via outdoor burning in the developing world,
explains Lauren Heine, a consultant and former director of applied
science at the Green Blue Institute, a nonprofit that focuses on
sustainable design. Some producers of flame retardants complain that it
is unfair for them to be pushed away from halogenated flame retardants
because of others' illegal activity, but the electronics manufacturers
"do think that you need to look at the less desirable scenarios, such as
open burning," points out Kathleen Vokes, project manager for the U.S.
EPA's Design for the Environment (DfE) program.

High demand in Asia

Although the demand for halogen-free flame retardants continues to grow,
most bromine used in the world today still goes into flame retardants,
according to the Bromine Science and Environmental Forum, an industry
group. Asia has the largest market for nonhalogenated flame retardants,
according to Tim Reilly, Sr., of Clariant, a company that makes
phosphorus-based flame retardants, which are now often used in place of
brominated ones. Clariant estimates that Japan's market for
nonhalogenated flame retardants is growing at 15% a year, Taiwan and
China's at more than 6%, and Korea's at 3-6%. In comparison, the EU's
market growth is stable at 3-5% a year, and demand is rising at less
than 1% a year in the U.S.

In the U.S., the efficacy of nonhalogenated flame retardants remains a
key issue, according to the research firm Frost & Sullivan.

"Halogenated flame retardants primarily work in the gas phase by
interfering with the complete combustion of carbon to CO2," says Jeffrey
Gilman, a chemist in the Fire Research Division at the National
Institute of Standards and Technology (NIST). Finding a replacement for
bromine in flame retardants is a real challenge because bromine-based
formulations have the advantage of working across a wide spectrum of
plastic products, says Susan Landry of Albemarle, one of the major
producers of flame retardants. "Brominated flame retardants provide the
best balance between performance, mechanical properties, process
ability, and cost in use," according to material accessible through
Albemarle's website. Albemarle's website.

Companies that make nonhalogenated flame retardants acknowledge that
brominated flame retardants' properties make them tough to compete with.
For example, the amount of brominated flame retardant that must be added
into plastic polymers to pass many flame-retardancy tests is relatively
low, at 10-20%, points out Tong Chen of Huber, a company that makes
metal hydroxide flame retardants. In comparison, three times as much
metal hydroxides must be added to achieve the same flame retardancy.
These high levels can interfere with plastic properties; as a result,
metal hydroxides cannot be used in all plastic polymers where brominated
retardants can, he says.

Even so, one of the metal hydroxides, magnesium hydroxide, "is the
fastest growing nonhalogen flame retardant in the market today," says
James Innes of Flame Retardants Associates, an independent U.S.
consulting firm.

Although flame retardant formulations are generally identified by the
chemical composition of their main constituents, most are actually
mixtures optimized to meet the flame-retardancy standards for different
classes of plastic polymers, says Gilman. In addition to bromine,
phosphorus, and metal hydroxides, these mixtures may include antimony
oxides, boron, melamine, melamine salts, silicon dioxide, and silicones
as well as a newer class of materials known as "nanoadditives," he says.

NIST is testing these nanoadditives in support of its mission to enhance
public safety and decrease fire deaths, Gilman says. Numerous layered
silicate clay minerals, many of which occur naturally, are now being
used in newer flame retardant formulations, he says. Introducing such
nanomaterials into these mixtures can render them more desirable for
plastics formulators, who generally prefer to add as little flame
retardant as possible to maintain the performance of the plastic
polymers, Gilman explains.

For example, Nanocor is developing nanoclay flame retardants. The
company found that it is quite efficient to combine nanoclay with
magnesium hydroxide flame retardants in polyolefin plastics, which are
used in a wide variety of consumer applications, according to Tie Lan,
general manager for Nanocor's U.S. operations. The materials burn "at a
noticeably reduced rate," he says. Adding 3% (by weight) of Nanocor's
"nanomer" formulation allows 10% less (by weight) of the magnesium
hydroxide formulation to be used, while improving the processing and
material properties of polyethylene, polypropylene, and other common
polyolefin plastic polymers.

Mark Buczek, vice president of advocacy and regulatory affairs for
Supresta, says that the company is looking at how to use nanoclays in
conjunction with its phosphorus-based flame retardants. "We've struggled
with ways to get equal dispersion over large quantities of material," he
says. Nanoclays do "offer a lot of potential, but we're not there yet."

Other nanomaterials being investigated for use as flame retardants
include carbon nanofibers and nanocomposites.

Orange to green

When it became clear that the Penta BDE and Octa BDE formulations would
be discontinued in the U.S., EPA's DfE program put together a Furniture
Flame Retardancy Partnership "to better understand fire safety options
for the furniture industry," according to the DfE website. "DfE
partnerships support informed substitution. We needed to look at the
alternatives and to make sure that they were in fact safer," explains
Heine, who was a member of the partnership's steering committee. DfE is
currently working with manufacturers of printed circuit boards to
evaluate the flame retardants used in those products, including
tetrabromobisphenol A, a widely used brominated flame retardant.

Heine says that DfE's efforts have led to some important advances, but
they also showed that none of the alternatives identified for use in
furniture at the time were perfectly green. "It wasn't obvious which
flame retardants were better from a health and environmental
perspective," she says.

To respond to such concerns, Heine collaborated with members of Clean
Production Action, a nonprofit that helps organizations design greener
products and manufacturing processes, to create the Green Screen for
Safer Chemicals. The Green Screen evaluates the environmental
preferability of chemicals and is based on the principles of green
chemistry and the work of the DfE program. It begins with the DfE
assessment's approach but also evaluates the chemicals' likelihood of
causing endocrine disruption and of being very persistent and
bioaccumulative (using criteria consistent with the EU's Registration,
Evaluation, Authorisation, and Restriction of Chemicals [REACH]
regulation) as well as the chemicals' degradation products. When the
Green Screen was used to evaluate three flame retardants currently being
used in television casings, including the Deca BDE formulation, it
showed that only one of them cleared the first hurdle and reached the
"orange" category, which means 'use, but search for safer
alternatives,'" says Mark Rossi, Clean Production Action's research
director.

One of the greenest approaches to creating products may be to design
materials that are inherently flame-resistant, Rossi says. Last year,
scientists at the University of Massachusetts Amherst announced that
they had synthesized such a plastic polymer. Richard Farris, Bryan
Coughlin, and Todd Emrick designed their polymer around
bishydroxydeoxybenzoin (BHDB), which releases water vapor when it breaks
down in a fire, rather than hazardous gases. The scientists believe that
the synthetic polymer has all the desired qualities of a flame-resistant
plastic. Emrick says it promises more flexibility and durability than
the high-temperature and heat-resistant plastics in current use. NIST is
now testing BHDB's suitability for use in less flammable polyurethane
foams, Gilman says.

The Amherst scientists were funded through a Federal Aviation
Administration (FAA) project with the goal of identifying new chemicals
and materials that burn slowly enough to provide passengers with 10
minutes of escape time. "This is an environmentally friendly solution
with a lot of economic potential," says Richard Lyon, manager of FAA's
fire research program. -KELLYN S. BETTS


Deborah L. DeBiasi
Email:   dldebiasi at deq.virginia.gov
WEB site address:  www.deq.virginia.gov
Virginia Department of Environmental Quality
Office of Water Permit Programs
Industrial Pretreatment/Toxics Management Program
Mail:          P.O. Box 1105, Richmond, VA  23218 (NEW!)
Location:  629 E. Main Street, Richmond, VA  23219
PH:         804-698-4028
FAX:      804-698-4032



More information about the Pharmwaste mailing list