Fire-retardant and smoke-suppressant performance of an intumescent waterborne amino-resin fire-retardant coating for wood


Wang, F.Q.; Zhang, Z.J.; Wang, Q.W.; Tang, J.Y.

Frontiers of Forestry in China 3(4): 487-492

2008


An intumescent waterborne amino-resin fire-retardant coating for wood (C) was synthesized and its fire-retardant and smoke-suppressant properties were investigated. The main film-builder of C was urea-formaldehyde resin blended with polyvinyl acetate resin. The intumescent fire-retardant system of C consisted of guanylurea phosphate (GUP), ammonium polyphosphate (APP), pentaerythritol (PER) and melamine (MEL). Specimens of plywood painted, respectively, with a commercial intumescent fire-retardant coating (A), a synthesized coating (C), and the main film-builder of coating C (B), as well as an unpainted plywood (S-JHB), were analyzed by cone calorimetry (CONE). The results show a marked decrease in the heat release rate (HRR) and the total heat release (THR), an increased mass of residual char (Mass), a marked postponement in time to ignition (TTI) and a reduced carbon monoxide production rate (PCO). The smoke production rate (SPR) and total smoke production (TSP) of the plywood painted with coating C were observed with the CONE test. The overall fire-retardant and smoke-suppressant performance of the synthesized coating C was much better than that of the commercial coating A. The thermo-gravimetric analysis (TGA) results of coating C and its film-builder B indicated that the thermal degradation process of B was slowed down by the addition of the intumescent fire-retardant system; the increase in the amount of charring of coating C was considerable.

Front.
For.
China
2008,
3(4):
487-492
DOI
10.1007/s11461-008-0075-y
RESEARCH
ARTICLE
Fengqiang
WANG,
Zhijun
ZHANG,
Qingwen
WANG,
Jiayin
TANG
Fire-retardant
and
smoke-suppressant
performance
of
an
intumescent
waterborne
amino-resin
fire-retardant
coating
for
wood
©
Higher
Education
Press
and
Springer-Verlag
2008
Abstract
An
intumescent
waterborne
amino-resin
fire-
retardant
coating
for
wood
(C)
was
synthesized
and
its
fire-retardant
and
smoke-suppressant
properties
were
investigated.
The
main
film-builder
of
C
was
urea-form-
aldehyde
resin
blended
with
polyvinyl
acetate
resin.
The
intumescent
fire-retardant
system
of
C
consisted
of
guany-
lurea
phosphate
(GUP),
ammonium
polyphosphate
(APP),
pentaerythritol
(PER)
and
melamine
(MEL).
Specimens
of
plywood
painted,
respectively,
with
a
commercial
intumes-
cent
fire-retardant
coating
(A),
a
synthesized
coating
(C),
and
the
main
film-builder
of
coating
C
(B),
as
well
as
an
unpainted
plywood
(S-JHB),
were
analyzed
by
cone
calori-
metry
(CONE).
The
results
show
a
marked
decrease
in
the
heat
release
rate
(HRR)
and
the
total
heat
release
(THR),
an
increased
mass
of
residual
char
(Mass),
a
marked
post-
ponement
in
time
to
ignition
(TTI)
and
a
reduced
carbon
monoxide
production
rate
(P
co
).
The
smoke
production
rate
(SPR)
and
total
smoke
production
(TSP)
of
the
ply-
wood
painted
with
coating
C
were
observed
with
the
CONE
test.
The
overall
fire-retardant
and
smoke-suppres-
sant
performance
of
the
synthesized
coating
C
was
much
better
than
that
of
the
commercial
coating
A.
The
thermo-
gravimetric
analysis
(TGA)
results
of
coating
C
and
its
film-
builder
B
indicated
that
the
thermal
degradation
process
of
B
was
slowed
down
by
the
addition
of
the intumescent
fire-
retardant
system;
the
increase
in
the
amount
of
charring
of
coating
C
was
considerable.
Keywords
waterborne
wood
coatings,
intumescent
fire-
retardant
coatings,
amino-resin,
cone
calorimeter,
thermo-
gravimetric
analysis,
smoke
suppression
Translated
from
Scientia
Silvae
Sinicae,
2007,43(12):
117-121
[
-
if
:
wk
4
,3
-1-*]
Fengqiang
WANG,
Zhijun
ZHANG,
Qingwen
WANG
(n),
Jiayin
TANG
Key
Laboratory
of
Bio-based
Material
Science
and
Technology
of
Ministry
of
Education,
Northeast
Forestry
University,
Harbin
150040,
China
E-mail:
1
Introduction
With
the
increase
in
living
standards
and
growing
con-
cerns
about
environmental
protection
for
people,
wood
is
attracting
gradually
more
attention
for
its
particular
characteristics
and
excellent
environmental
properties.
However,
its
marked
combustibility
may
cause
unexpec-
ted
potential
fire
hazards.
Therefore,
some
wood
should
be
treated
with
fire-retardants
when
they
are
used
in
den-
sely
populated
sites.
Intumescent
fire
retardant
coatings
can
expand
and
form
a
thick
porous
charred
layer
to
insulate
the
substrate
from
the
action
of
heat,
and
protect
substrates
against
high
temperatures
and
exposure
to
oxy-
gen
over
a
certain
period
of
time.
These
coatings
have
a
wide
application
in
the
efficient
protection
of
flammable
materials
against
fire.
They
have
received
considerable
attention
and
have
been
rapidly
developed
in
recent
years.
Generally,
intumescent
coatings
contain
natural
or
syn-
thesized
polymers
as
film-builders,
and
from
acid,
carbon
and
gas
sources
an
active
intumescent
fire-retardant
sys-
tem
is
formed,
usually
with
some
fillers
and
auxiliary
agents.
Many
instruments
are
used
to
investigate
the
fire-
retardant
and
smoke-suppressant
performance
and
pyro-
lytic
behavior
of
materials,
such
as
the
cone
calorimeter
(Xu
et
al.,
2005),
TGA
(Jimenez
et
al.,
2006),
DTA,
DSC
(Gu
et
al.,
2007),
TG-DSC,
TG-MS
and
TG-FTIR
(Kunze
et
al.,
2002;
Li
et
al.,
2007).
Because
a
cone
cal-
orimeter
can
synthetically
characterize
fire-retardant
and
smoke-suppressant
performance
and
reveal
the
fire-
retardant
mechanism
of
the
fire-retardant
material,
it
has
been
widely
used
by
researchers
to
simulate
real
fires.
In
our
study,
we
have
also
used
a
cone
calorimeter
to
evaluate
the
properties
of
fire
retardation
and
smoke
sup-
pression
by
measuring
HRR,
THR,
Mass,
TTI,
P
ao
,
SPR
and
TSP
of
the
different
coatings.
A
thermo-gravimetric
analysis
was
carried
out
to
investigate
pyrolysis
and
the
charring
process
of
the
synthesized
waterborne
intumes-
cent
amino-resin
fire-retardant
coatings.
488
Fengqiang
WANG,
et
al.
2
Experiment
2.1
Materials
The
binder
used
was
a
mixture
of
urea-formaldehyde
resin
(UF)
and
polyvinyl
acetate
(PVAc)
resin.
The
film-builder
was
cured
at
ambient
temperatures.
The
fire
retardant
system
that
was
chosen
was
guany-
lurea
phosphate
(GUP),
ammonium
polyphosphate
(APP),
pentaerythritol
(PER)
and
melamine
(MEL).
GUP
was
made
at
Northeast
Forestry
University,
China;
APP
(its
polymerization
degree
exceeds
1000)
was
supplied
by
Xinye
Chemical
Raw
Material
Company,
Changsha;
PER
was
purchased
from
Bazhou
Chemical
Industry
Branch
Factory,
Tianjin;
and,
MEL
was
supplied
by
Taixing
Refined
Chemical
Industry
Company,
Jinan.
A
few
auxiliary
agents
for
coatings
were
purchased
from
the
local
coatings
market.
A
five-layer
plywood
was
supplied
by
the
Huatai
Wood-Industry
Company,
China.
2.2
Equipment
An
ND6
type
of
frequency
conversion
planetary
ball
mill
was
supplied
by
Nanjing
Nanda
Tianzun
Electron
Company.
A
standard
type
cone
calorimeter
was
supplied
by
Fire
Test
Technology
Company
in
the
U.K,
and
a
Pyris
6
thermo-gravimetric
analytical
instrument
came
from
Perkin
Elmer
Company,
USA.
2.3
Preparation
The
technical
processing
of
the
waterborne
fire-retardant
coatings
is
as
follows:
Component
a:
APP-GUP-MEL-PER
was
ground
and
mixed
well
with
some
water,
then
sifted
out;
Component
b:
auxiliary
coating
agents
were
mixed
equally
with
some
water;
Component
c:
color
filler
and
other
materials
were
mixed
equally
with
some
water.
The
mixture
of
UF
and
PVAc
was
stirred
with
compon-
ent
a,
then
placed
in
the
ball
mill
for
about
1.5
h.
Components
b
and
c
were
added
to
this
mixture,
and
the
intumescent
fire-retardant
coating
was
prepared
by
the
pro-
cesses
of
mixing,
sifting
and
canning.
The
solid
content
was
about
35%
of
the
synthesized
intumescent
coating,
of
which
the
content
of
the
film-builder
(UF
and
PVAc)
was
50%.
The
fineness
of
the
intumescent
coating
was
tested
by
carrying
out
the
test
in
a
coating
barrel.
The
intumescent
coating
was
painted
on
the
prepared
plywood
surface
(painted
twice,
spaced
more
than
24
h
apart)
at
least
48
h
after
canning,
at
a
temperature
of
23
±
2°C
and
a
relative
humidity
of
50
±
5%.
2.4
Cone
calorimetry
analysis
(CONE)
Cone
calorimetry
analysis
was
carried
out
according
to
ISO
5660-1,
with
a
heat
flux
of
50
kW/m
2
and
a
gas
flow
rate
of
24
L/s.
The
samples,
with
dimensions
of
100
mm
x
100
mm
x
4
mm,
were
placed
under
the
con-
ical-shaped
heater
that
provided
uniform
irradiance
on
the
sample
surfaces.
2.5
Thermo-gravimetric
analysis
(TGA)
Thermo-gravimetric
analysis
was
carried
out
at
10°C/min
in
a
nitrogen
atmosphere
with
a
flow
rate
of
50
mlJmin,
using
the
Pyris
6
TGA.
The
samples
(approx
10
mg)
in
powder
form
were
placed
in
open
vitreous
silica
pans.
The
measure-
ment
temperatures
ranged
from
50
to
800°C
and
the
TGA
curves
were
processed
using
Microsoft
Excel
software.
3
Results
and
discussion
3.1
Heat
release
rate
(HRR)
The
HRR
provides
a
relative
fire
hazard
assessment
for
materials.
The
HRR,
especially
its
peak
value
(pk-HRR),
is
the
primary
characteristic
determining
the
size,
growth
and
suppression
requirements
in
a
fire
environment
(Charles,
2004).
In
general,
material
with
a
low
heat
release
rate
per
unit
weight
or
volume
will
do
less
damage
to
the
surroundings
than
material
with
a
high
release
rate.
The
HRR
profiles
for
different
painted
plywood
A,
B,
C
and
S-JHB
are
shown
in
Fig.
1.
Compared
with
S-JHB,
the
HRR
of
B
decreased
and
its
flaming
period
was
delayed
slightly;
the
pk-HRR
of
B
decreased
by
22%
com-
pared
with
S-JHB
and
the
corresponding
peak
time
was
deferred
by
about
0.7
min.
For
the
coating-painted
ply-
wood,
their
HRRs
were
far
more
subtle
and
decreased
markedly:
the
pk-HRRs
of
plywood
A
and
C
were
respectively
lowered
to
8.2%
and
12.4%,
and
the
time
of
occurrence
was
delayed
2.7
and
5.9
times,
respectively,
compared
with
S-JHB.
400
300
g
200
100
3
6
9
12
time/min
S-J1-1B
-
A
Fig.
1
HRR
profiles
for
different
painted
plywood
0
489
Fire-retardant
and
smoke-suppressant
performance
of
a
waterborne
amino-resin
fire-retardant
coating
for
wood
For
the
plywood
painted
with
fire-retardant
coatings,
the
flame
retardant
effect
was
very
evident.
The
produc-
tion
rate
of
flammable
volatiles
from
fire-retardant
coat-
ings
and
plywood
decreased
markedly;
the
release
time
was
considerably
slower
and
later
than
that
of
S-JHB.
The
rate
of
heat
transfer
to
plywood
was
decreased,
and
the
spread
of
fire
was
deferred
effectively
once
the
fire
occurred.
Once
the
material
catches
fire,
it
is
an
advant-
age
for
the
heat
release
peak
to
appear
later,
for
the
later
the
conflagration
occurs,
the
more
time
is
provided
for
personnel
to
evacuate
the
fire
site
and
to
implement
fire-
fighting.
It
is
generally
agreed
that
the
fire
retardant
property
of
materials
for
buildings
and
decorations
should
ensure
an
evacuation
time
of
at
least
3.5
min
after
the
fire
starts
(Wang,
2000).
The
heat
release
peak
of
plywood
C
was
a
little
higher
than
that
of
plywood
A,
but
the
occurrence
of
the
peak
time
was
considerably
prolonged.
3.2
Total
heat
release
(THR)
The
total
heat
release
(THR
for
short)
is
defined
as
the
total
heat
released
by
a
material
per
unit
area
in
a
fire.
Material
with
a
high
THR
value
will
release
more
heat
and,
in
general,
the
fire
danger
will
be
greater.
Figure
2
shows
the
THR
curves
of
the
differently
painted
plywood
A,
B,
C
and
S-JHB.
With
time,
the
THRs
of
S-JHB
and
B
rapidly
increased
and
reached
maximum
values
of
16.8
and
19.7
MJ/m
2
,
respectively,
which
meant
that
the
samples
ignited
quickly
and
burned
acutely.
The
THR
of
B
was
higher
than
that
of
S-JHB,
resulting
from
the
heat
released
from
the
com-
bustion
of
the
film-forming
resin
painted
on
the
surface
of
B.
However,
for
the
plywood
painted
with
fire-retard-
ant
coatings
A
and
C,
their
THRs
were
greatly
reduced
to
7.2
and
2.8
MJ/m
2
,
respectively,
and
the
heat
release
process
was
considerably
delayed.
Especially
for
coating
C,
it
did
not
release
heat
during
the
first
6
min.
Contrasting
Figs.
1
and
2,
it
can
be
seen
that
most
of
the
heat
released
from
the
material
took
place
at
the
stage
of
flaming
combustion.
The
fire-retardant
coatings
(both
A
and
C)
decreased
the
fire
intensity
and
effec-
tively
inhibited
fire
combustion.
3.3
Mass
Mass
refers
to
the
amount
of
burning
residue
of
material
which
varies
over
time.
It
is
commonly
expressed
in
terms
of
relative
amounts,
i.e.,
in
per
cent
(instantaneous
mass/
initial
mass)
for
a
better
comparison
of
samples
with
dif-
ferent
initial
masses.
The
mass
curves
of
the
different
coated
plywood
are
shown
in
Fig.
3.
The
mass
curve
of
S-JHB
is
similar
to
that
of
plywood
B
on
the
steeper
gradient,
which
means
that
they
both
had
a
large
mass
loss
rate
and
were
burned
out
in
a
short
time.
Compared
with
S-JHB
and
20
15
10
5
0
0
9
12
3
6
time/min
S-JHB
A
13
C
Fig.
2
THR
profiles
for
different
painted
plywood
B
(plywood
painted
with
film-builder),
A
(plywood
painted
with
commercial
intumescent
coating)
had
a
much
greater
final
mass
and
a
slightly
longer
burning-
out
time.
However,
the
mass
curve
of
the
plywood
painted
with
coating
C
was
considerably
different
from
that
of
the
other
three
types
of
plywood;
it
had
a
flatter
gradient,
implying
a
lower
mass
loss
rate.
One
point
especially
worth
mentioning,
is
that
the
main
mass
loss
of
C
took
place
6.9
min
after
its
exposure
to
the
heat
source,
i.e.,
during
this
time
combustion
did
not
start
in
C;
in
contrast,
it
was
precisely
during
these
first
six
min-
utes
that
the
other
samples
had
already
been
burnt
out;
in
fact,
all
of
them
were
completely
burnt
in
less
than
5
min.
Further,
coating
C
had
the
largest
amount
of
ash
(about
40%
of
its
initial
mass),
mainly
owing
to
the
honeycomb
structure
formed
in
the
process,
which
plays
an
important
role
in
fire
prevention
and
heat
insulation.
1.0
0.8
e.
0.6
I
0.4
0.2
0
0
3
6
9
12
time/min
S-.11-113
A
Fig.
3
Mass
curves
of
different
painted
plywood
490
Fengqiang
WANG,
et
al.
3.4
Time-to-ignition
(TTI)
Time-to-ignition
is
defined
as
the
duration
of
time
for
fire
to
ignite
on
the
surface
of
material.
The
TTI
is
an
import-
ant
parameter
for
describing
fire
hazards
of
materials
(Li,
2000).
Materials
with
a
long
TTI
will
ignite
with
greater
difficulty
under
the
same
conditions
and
will
have
better
fire-retardant
properties.
The
TTI
histograms
of
different
painted
plywood
A,
B,
C
and
S-JHB
are
shown
in
Fig.
4.
We
can
clearly
see
that
the
TTI
of
S-JHB
is
lower
than
that
of
the
other
plywood.
The
TTI
of
C,
the
longest
of
the
four,
is
about
7
min,
or
1.5
times
longer
than
that
of
the
commercial
intumescent
fire-retardant
coating
painted
on
plywood
A.
It
indicates
that
the
intumescent
fire-retardant
system
of
C
fully
exploited
the
property
of
thermal
expansion,
obstructing
the
heat
source
and
deferring
ignition
during
the
heating
period,
consequently
gaining
enough
time
for
people
to
escape
and
for
fire
suppression
to
be
initiated.
5
min,
a
time
longer
than
the
3.5
min
required
for
evacu-
ation,
thereby
decreasing
the
danger
of
fire.
3
6
9
12
time/min
A
0.012
0.006
0.003
(
0
S-JHB
8
Fig.
5
Pco
curves
of
different
painted
plywood
6
2
4
2
S-JHB
A
types
of
plywood
Fig.
4
TTI
histogram
for
different
painted
plywood
3.5
CO
release
rate
(Pco)
According
to
statistics,
80%
of
deaths
in
fires
are
attrib-
uted
to
smoke
inhalation
(Zhang,
2007).
In
natural
fires,
people
often
are
first
knocked
out
by
smoke,
dust
and
toxic
gases
and
then
burn
to
death.
Especially,
carbon
monoxide
(CO),
the
major
toxic
gas
released
from
partial
combustion
of
wood,
is
regarded
as
the
chief
offender.
P
co
is
defined
as
the
amount
of
CO
released
per
unit
time,
which
represents
an
instantaneous
concentration
of
CO
(g/s).
The
curves
of
P
co
of
different
coated
plywood
are
illustrated
in
Fig.
5.
Compared
with
S-JHB,
the
amount
of
CO
release
from
B
was
not
significantly
differ-
ent,
but
the
release
was
delayed
entirely.
The
rate
of
CO
release
from
A
increased
markedly
with
a
peak
more
than
twice
as
high
as
that
of
S-JHB.
For
coating
C,
not
only
was
the
CO
release
delayed
significantly,
but
the
rate
of
CO
production
was
also
kept
at
a
very
low
level
for
at
least
Carbonaceous
organic
materials
can
generate
a
large
amount
of
gaseous
volatiles
and
form
diffusion
flames
dur-
ing
violent
combustion
processes.
Both
can
dilute
the
oxy-
gen
of
the
combustion
atmosphere
and
obstruct
the
oxygen
supply
from
the
surroundings.
Under
such
conditions
and
as
a
consequence,
this
will
lead
to
oxygen
deficiency
of
the
combustion
atmosphere
and
the
carbonaceous
pyrolysates
would
burn
incompletely
and
quickly
generate
much
CO
gas
(Wang
et
al.,
2006).
For
fire-retardant
coating
C,
at
the
flaming
combustion
stage,
its
carbon
source
produced
a
large
amount
of
char,
which,
along
with
some
carbonaceous
pyrolysates,
gener-
ated
much
CO
gas
quickly
due
to
incomplete
combustion
under
the
condition
of
oxygen
deficiency
formed
in
a
viol-
ent
combustion
process.
3.6
Smoke
producing
rate
(SPR)
The
smoke
producing
rate
(SPR,
m
2
/s)
refers
to
the
amount
of
dense
smoke
released
per
unit
time
that
can
be
calculated
from
the
division
of
a
specific
extinction
area
(SEA)
by
the
mass
loss
rate
(MLR).
Figure
6
shows
the
SPR
profiles
of
different
painted
plywood.
It
can
be
seen
that
all
four
tested
samples
have
a
similar
release
process.
The
profile
can
be
split
arti-
ficially
into
three
stages:
in
the
first
stage
(before
ignition
occurs)
a
small
amount
of
smoke
is
released,
in
the
second
stage
(flaming
combustion
period)
heavy
smoke
is
released,
and
in
the
third
stage
(after-glow
combustion
period)
a
small
amount
of
smoke
is
released.
In
our
experiment,
it
was
found
that
the
main
source
of
dense
smoke
release
was
the
second
stage (flaming
combustion
period);
a
small
amount
of
dense
smoke
was
produced
in
the
first
stage
and
hardly
any
dense
smoke
was
released
in
Fire-retardant
and
smoke-suppressant
performance
of
a
waterborne
amino-resin
fire-retardant
coating
for
wood
491
the
third
stage.
The
SPR
of
the
plywood
coated
with
intu-
mescent
fire-retardant
coating
C
was
clearly
reduced
because
the
guanylurea
phosphate
in
coating
C,
which
has
a
decomposition
temperature
of
about
200°C,
decom-
posed
before
the
plywood
did
during
the
first
stage,
to
avoid
or
lessen
the
decomposition
of
the
plywood,
in
turn
further
suppressing
the
release
of
volatile
pyrolysates,
i.e.,
the
release
of
smoke
was
suppressed
in
an
efficient
man-
ner.
In
contrast,
the
commercial
intumescent
coatings
A
and
B
increased
the
SPR
of
plywood
markedly,
especially
plywood
A.
Its
pk-SPR
was
almost
the
highest
among
the
specimens,
about
the
same
level
as
the
pk-SPR
of
S-JHB,
and
13
times
higher
than
plywood
C.
3
6
9
12
time/min
S-JHB
A
Fig.
7
TSP
profiles
of
different
painted
plywood
3.8
Thermo-gravimetric
analysis
(TGA)
5
4
3
C.
VI
2
0.12
0.09
;E
.
0.06
0.03
0
0
A
—B
C
Fig.
6
SPR
profiles
of
different
painted
plywood
3.7
Total
smoke
product
(TSP)
The
total
smoke
product
(TSP,
m
2
)
is
defined
as
the
total
amount
of
smoke
released
by
material
in
the
process
of
burning
and
pyrolysis.
It
can
be
calculated
by
a
process
of
integration
of
SPR
over
time;
it
is
also
called
the
cumu-
lative
smoke
release
product.
From
a
comprehensive
analysis
of
Figs.
1,
6
and
7,
it
is
seen
that
the
TSP
of
the
samples
can
be
largely
attributed
to
the
smoke
released
during
the
initial
smol-
dering
and
flaming
combustion
stages.
The
TSPs
of
the
plywood
painted
with
film-builder
B
and
commercial
intumescent
coating
A
were
very
high,
respectively
about
2
and
3.3
times
that
of
S-JHB.
However,
for
the
plywood
painted
with
intumescent
coating
C,
its
TSP
was
about
54.9%
that
of
S-JHB.
In
other
words,
the
intumescent
fire-retardant
coating
C
not
only
reduced
the
SPR
and
TSP
effectively,
but
also
delayed
the
entire
smoke
release
process
for
more
than
5
min,
so
that
it
decreased
the
instantaneous
degree
of
damage
from
smoke
and
could
save
enough
time
for
people
to
evacuate
and
for
fire
to
be
suppressed.
TGA
is
a
thermal
analysis
technique
used
to
measure
qual-
itative
changes
in
material
as
a
function
of
temperature.
TGA
is
commonly
used
for
evaluating
the
combustibility
and
combustion
stability
of
materials
(Hu,
1999).
During
the
degradation
process,
the
weight
loss
curve
(TG
curve)
is
recorded
and
its
first
derivative
(DTG
curve)
is
obtained
to
show
the
rate
of
change
as
the
apparent
weight
loss.
Both
the
TG
and
DTG
curves,
typical
parameters
of
TGA
(Wang,
2000;
Li,
2003),
can
reveal
the
thermal
degradation
process
of
materials
and
provide
the
value
of
the
residual
mass,
used
as
a
standard
for
assessing
the
fire-retardant
effect
of
materials
(Zhang,
2001).
TG
and
DTG
curves
of
samples
B
(film-builder)
and
C
(the
synthetic
intumescent
coating)
are
shown
in
Fig.
8.
It
can
be
seen
from
Fig.
8
that
the
rate
of
thermal
weight
loss
relaxed,
and
the
thermal
decomposition
process
became
more
gentle
because
of
the
use
of
the
intumescent
fire-
retardant
system.
Further,
the
initial
thermal
decomposi-
tion
temperature
was
advanced
to
about
101°C,
lower
than
that
of
the
film-builder,
and
is
attributed
to
the
release
of
free
water
and
some
small
molecular
additives
with
a
low
boiling
point,
largely
emitted
from
the
coat-
ings,
by
which
the
combustion
atmospheric
concentration
was
effectively
diluted
and
the
ignition
time
prolonged.
GUP
in
the
intumescent
fire-retardant
system
began
to
decompose
at
about
185°C.
With
increasing
temperature,
the
decomposition
of
other
fire
retardants
accelerated.
When
the
temperature
increased
to
250°C,
PVAc
started
to
decompose
and
emitted
acetic
acid.
Rapid
decomposi-
tion
of
coating
C
began
at
354°C
and
tended
to
remain
mild
until
450°C.
At
760°C,
the
temperature
that
we
arbit-
rarily
regarded
as
the
end-point,
the
residual
masses
of
B
and
C
were,
respectively,
10.3%
and
26.8%
of
their
initial
masses.
This
indicated
that
the
charring
effect
of
the
intu-
mescent
fire-retardant
system
was
excellent,
owing
mainly
3
6
time/min
9
12
sJHB
M
R
492
100
80
60
ti
-8
40
-12
20
0
16
200
400
600
temperature!°C
800
--B
TG
C
TO
B
TG
C
TG
Fig.
8
TG
and
DTG
curves
of
sample
B
and
C
to
the
combined
action
of
the
composite
sources
of
acid
(GUP
&
APP),
gas
(MEL)
and
carbon
(PER)
mixed
in
proper
proportions
in
the
intumescent
fire-retardant
sys-
tem,
as
well
as
to
the
catalytic
charring
action
on
the
film-
builder
of
the
protonic
acid,
formed
by
the
decomposition
of
APP
and
GUP
under
different
temperature
ranges.
4
Conclusions
An
intumescent
waterborne
fire-retardant
coating
for
wood
was
synthesized
in
which
the
main
film-builder
was
urea-formaldehyde
resin
blended
with
polyvinyl
acet-
ate
resin;
the
intumescent
fire-retardant
system
consisted
of
guanyl-urea
phosphate
(GUP),
ammonium
polypho-
sphate
(APP),
pentaerythritol
(PER)
and
melamine
(MEL).
1)
CONE
and
TGA
tests
proved
that
coating
C
could
give
rise
to
much
char
and
suppress
after-glowing
effectively
and
markedly.
When
the
coating
thickness
was
about
0.3
mm,
the
pk-HRR
value
was
reduced
to
just
12.4%
that
of
S-JHB;
the
TTI
was
10
times
longer
than
that
of
S-JHB
and
1.5
times
longer
than
that
of
commercial
coating
A.
The
THR
value
was
16.8
MJ/m
2
,
about
42.9%
that
of
S-
JHB.
The
heat
released
by
the
burning
material
and
the
fire
intensity
were
decreased
by
using
coating
C.
2)
Our
experiment
shows
that
the
smoke
suppression
effect
of
coating
C
was
well
demonstrated,
for
the
CO
release
was
clearly
delayed
and
SPR
and
TSP
obviously
reduced,
implying
that
the
fire
hazard
was
effectively
Fengqiang
WANG,
et
al.
weakened
by
coating
C,
gaining
enough
time
for
saving
lives
and
property
from
the
emerging
fire.
Acknowledgements
This
work
was
supported
by
the
National
Natural
Science
Foundation
of
China
for
the
Mechanism
of
Smoke
Suppression
on
Wood
Fire
Retardant
(No.
30371127)
and
the
Foundation
for
the
Author
of
National
Excellent
Doctoral
Dissertation
of
PR
China
(FANEDD)
for
support
of
"Applied
Fundamental
Research
of
N-P-B
Fire-retardant
System
for
Lignocellulosic
Materials
(No.200457)".
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