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FRT
- (Flame Retardant
wood Treatments) |
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What
is FRT? |
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| In
New York City, in
the earlier part of
the twentieth century,
fire officials began
to required the use
of flame retardant
wood treatments for
trim wood on structures
exceeding twelve stories.
Fire, code, and insurance
organizations later
recognized that applications
of this technology
might also be useful
in preventing flame
spread, via the roof,
on townhouse and condominium
structures. The use
of FRT materials became
common practice and
is now required by
model codes, largely
adopted, with local
modifications by county
and municipal agencies.
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It
should be noted that
manufacturers of plywood
and dimensional lumber
do not treat their
products with FRT
chemicals. This is
done by roughly 60
companies in the U.S.
and others in Canada
and Europe. These
treatment companies
are licensed by firms
which develop proprietary
processes for FRT. |
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How
FRT is Made and Distributed |
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Process
companies have developed
methods and formulations
for the treatment
of wood and then licensed
treatment companies
to process the wood
using the methods
and formulations.
The treatment companies
would purchase the
wood on the open market
from firms which produce
plywood or dimensional
(structural) lumber.
In some cases, truss
manufacturers purchased
FRT material from
treatment companies
to incorporate into
their products (this
is typically the plywood
"I" type
floor trusses more
often than pre-engineered
ceiling trusses).
Treatment companies
and those truss manufacturers
then would sell their
materials to building
supply firms or, perhaps
in some cases, directly
to large builders.
IT IS IMPORTANT TO
NOTE THAT STAMPS FROM
THE PRODUCTION COMPANIES
DO NOT IDENTIFY THE
MATERIAL AS A FRT
OR NOT A FRT. LABELING
OR NON-LABELING OCCURS
AFTER THE WOOD IS
SHIPPED, THEREBY CREATING
AN IDENTIFCATION PROBLEM.
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How
FRT is Stamped for
Identification |
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| Stamping
of material for identification
as FRT is done by
the company that performs
the FRT treatment,
a licensee of the
firm that developed
and sold rights to
the use of the process.
Conventionally, either
the name of the process
company or the class
established by an
association or laboratory,
or a trade name of
a specific process
developed by a process
company could appear
to identify the material
as FRT.
Note:
Since dozens of individual
processors have entered
and left the market,
it is unlikely that
anyone can predict
with any certainty
how all processors
through time have
selected stamps to
indicate FRT. Be alert
for any of the following
possibilities.
Through
time, as standards
have changed, as new
processes were developed,
and as new process
companies entered
the market, new stamps
appeared and older
ones were no longer
used. |
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General
Problems Associated
with FRT Wood Products |
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1.
Oxidizing Metal Fasteners
- Older FRT materials
were often associated
with corroding the
nails or screws used
to fasten it to structural
framing elements,
to the effect that
the fasteners could
snap, destabilizing
the FRT elements.
Through time, newer
formulations of FRT
offering lower hygroscopicity
(lower moisture retention)
were developed to
attempt to improve
upon this problem.
Some of the chemicals
in FRT processes are
salts that retain
water, exposing ferrous
metals to corrosive
tendencies. |
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2.
Loss of Strength
- The chemicals
used in FRT will,
in the presence of
elevated temperatures,
cause chemical changes
in the wood that will
weaken the wood, causing
it to sag, tear away
from its fasteners
in the wind, or collapse
under a load. Attics
build up heat. Many
heat up to 130 degrres
F, some up to 170-200
degrees F. Significant
deterioration of FRT
can occur at 130 degrees
F and almost always
occurs at higher temperatures.
Other variables, such
as moisture content
of the wood at the
time of elevated temperatures,
the duration and frequency
of variable temperatures.
Even variations of
the chemical concentrations
from one batch to
the next in FRTs can
influence the degree
of degradation. |
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3.
Delamination of Plywood
- This almost always
appears to be a result
of process problems
such as drying the
product after impregnation
at too high a temperature
for the current moisture
content. As the wood
dries after processing,
higher temperatures
may be better tolerated
in the drying process.
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