Effects of retention and distribution of fire retardant chemical on performance of fire retardant treated China fir (Cunninghamia lanceolata) wood


Chuang H.B.; Wang, S.Y.

Holzforschung 56(2): 209-214

2002


This study investigates the effect of fire-retardant (FR) chemical retention and distributive percentage of FR chemical (DP) on FR performance of FR treated China fir (Cunninghamia lanceolata) wood. The specimens were treated with various concentrations of FR chemical solutions using a vacuum or full-cell process in order to obtain six different DP levels of FR treated woods with DP levels of 34, 48, 62, 76, 90 and 100%. FR treated woods were tested in accordance with the third grade of surface FR performance as specified by the CNS 6532 standard. Results indicated that the minimum FR chemical retention for meeting the requirement of the third grade standard was 49.2 and 56.6 kg/m3 for 100 and 90% of DP level specimens, respectively. However, when the specimens exhibited 62-34% of DP level and a FR chemical retention up to 100.5-115.8 kg/m3 they did not qualify for the third grade standard. The factors of surface FR performance were influenced significantly by the DP level of specimens, the factor of tl (flame lingering time index of material) of FR treated wood could be considered the most sensitive indicator for meeting the requirement of the third grade standard in this study.

H.-R
Chuang
and
S.
Y.
Wang:
Fire-Retardant
'Heated
China
Fir
Wood
209
Holzforschung
56
(2002)
209-214
Effects
of
Retention
and
Distribution
of
Fire
Retardant
Chemical
on
Performance
of
Fire
Retardant
Treated
China
Fir
(Cunninghamia
lanceolata)
Wood
By
Horng-Bin
Chuang
l
and
Song-Yung
Wang
2
1
Department
of
Botany,
National
Taiwan
University,
Taipei,
Taiwan,
R.
0.
C.
2
Department
of
Forestry,
National
Taiwan
University,
Taipei,
Taiwan,
R.
0.
C.
Keywords
Fire-retardant
treated
wood
Surface
fire-retardant
performance
Fire-retardant
chemical
retention
Distributive
percentage
of
fire-retardant
chemical
China
fir
wood
(Cunnighamia
lanceolata)
Summary
This
study
investigates
the
effect
of
fire-retardant
(FR)
chemical
retention
and
distributive
percentage
of
FR
chemical
(DP)
on
FR
performance
of
FR
treated
China
fir
(Cunninghamia
lanceolata)
wood.
The
specimens
were
treated
with
various
concentrations
of
FR
chemical
solutions
using
a
vacuum
or
full-cell
process
in
order
to
obtain
six
different
DP
levels
of
FR
treated
woods
with
DP
levels
of
34
%,
48
%,
62
%,
76
%,
90
%
and
100
%.
FR
treated
woods
were
tested
in
accordance
with
the
third
grade
of
surface
FR
performance
as
specified
by
the
CNS
6532
standard.
Results
indicated
that
the
minimum
FR
chemical
retention
for
meeting
the
requirement
of
the
third
grade
standard
was
49.2
kg/m
3
and
56.6
kg/m
3
for
100
%
and
90
%
of
DP
level
specimens,
respectively.
However,
when
the
specimens
exhibited
62
%—
34
%
of
DP
level
and
a
FR
chemical
retention
up
to
100.5-115.8
kg/m
3
they
did
not
qualify
for
the
third
grade
standard.
The
factors
of
surface
FR
performance
were
influenced
signifi-
cantly
by
the
DP
level
of
specimens,
the
factor
of
tl
(flame
lingering
time
index
of
material)
of
FR
treated
wood
could
be
considered
the
most
sensitive
indicator
for
meeting
the
requirement
of
the
third
grade
standard
in
this
study.
Introduction
Wood
is
a
porous
organic
material
and
due
to
the
variation
in
structures
and
constitutions,
its
permeability
may
be
influenced
by
habitat,
heartwood-sapwood
sections
and
chemical
constituents
(Rice
1996).
Absorption
varies
sig-
nificantly
among
samples
taken
from
different
trees
within
a
single
species
treated
by
the
same
method
(Chuang
et
al.
1999).
The
fire-retardant
(FR)
performance
of
FR
treated
wood
may
be
influenced
by
chemicals
(Brenden
1975;
Handa
et
al.
1979;
Hirata
et
al.
1981;
Lei
1992;
Lee
1995;
Wang
and
Rao
1999),
retention
(Alexiou
et
al.
1986;
Su
1992;
Lee
1995;
Chuang
and
Wang
1999),
wood
species
(Lei
and
Tsai
1992),
thickness
(Su
1992;
Lei
and
Tsai
1992;
Chuang
2000),
specific
gravity
(Lei
and
Tsai
1992),
knot
(Chuang
and
Wang
1998)
and
others.
Chemical
retention
is
considered
the
major
influencing
factor.
Almost
all
FR
performance
increased
with
an
increase
in
chemical
reten-
tion
(Alexiou
eta/.
1986;
Su
1992;
Chuang
and
Wang
1999).
However,
most
studies
failed
to
consider
the
distribution
factors
that
may
contribute
to
the
variation
in
FR
perfor-
mance.
In
particular,
the
distributive
percentage
and
dis-
tributive
pattern
have
not
been
well
addressed
for
China
fir
wood
(Cunninghamia
lanceolata).
Therefore,
the
absorption
of
FR
treated
specimens
was
controlled
at
constant
value
for
various
concentrations
of
solution
by
vacuum
or
full-cell
process,
and
treated
for
varying
lengths
of
time.
The
specimens
were
tested
in
ac-
cordance
with
the
third
grade
surface
FR
performance
as
Holzforschung
/
Vol.
56
/
2002
/
No.
2
©
Copyright
2002
Walter
de
Gruyter
Berlin
New
York
specified
by
CNS
6532
standard
(1993).
This
study
discusses
the
effects
of
retention
and
distribution
of
FR
chemical
on
surface
FR
performance
of
FR
treated
China
fir
wood.
Materials
and
Methods
Specimens
Plantation
trees
of
China
fir
(_Cunninghamia
lanceolata)
were
used
in
this
study.
The
average
air-dried
specific
gravity
and
moisture
content
of
all
samples
were,
respectively,
0.36-0.41
and
12-14
%.
Specimens
21
cm
x
21
cm
x
1
cm
of
non-FR
treated
(controls)
and
FR
treated
wood
were
cut
in
accordance
with
the
CNS
6532
standard
(1993).
Fire-retardant
chemicals
The
FR
chemical
was
a
mixture
of
ammonium
phosphate,
dia-
mmonium
phosphate,
aimnonium
sulfate,
aimnonium
bromide,
boric
acid
and
borax.
A
FR
chemical
solution
with
concentration
of
4
%
to
30
%
solid
weight
was
used.
Treatment
with
fire-retardant
chemical
In
this
study,
the
void
volume
of
wood
full
of
FR
chemical
solution
was
considered
to
have
a
distributive
percentage
of
100
%.
The
void
volume
(C)
of
oven-dried
specimens
of
China
fir
with
spe-
cific
gravity
of
0.35
(as
compared
to
air-dried
specimens
with
specific
gravity
of
0.37)
was
calculated
as
followed:
C
=
1.0067
x
0.35
x
100
%
=
76.7
%.
Therefore,
the
theoretically
saturated
absorption
of
wood
with
a
distributive
percentage
(DP)
of
100
%
was
805
kg/m
3
(76.7
%
x
1050
kg/m
3
).
The
actual
maximum
absorption
content
was
797
kg/m
3
when
China
fir
was
treated
with
a
FR
chemical
solution
with
a
concentration
of
10
%
using
a
full-cell
process
(the
chemical
solution
contained
safranin
0
of
210
H.-B.
Chuang
and
S.
Y.
Wang:
Fire-Retardant
Reated
China
Fir
Wood
1
%).
This
experimental
value
was
only
about
1
%
lower
than
that
of
the
theoretical
value.
Furthermore,
the
specimens
had
been
completely
stained
by
safranin
0
recognizable
by
photomicro-
graph,
and
the
crystals
of
the
FR
were
visible
in
the
region
stained
with
safranin
0
under
scanning
electron
microscopy.
Thus
it
was
reasonable
to
consider
the
saturated
absorption
content
of
797
kg/m
3
of
FR
chemical
solution
to
have
a
DP
of
100
%.
In
this
study,
the
absorption
content
of
FR
chemical
solution
(AB)
for
FR-treated
specimens
was
controlled
at
272
kg/m
3
,
385
kg/m
3
,
494
kg/m
3
,
606
kg/m
3
,
717
kg/m
3
and
797
kg/m
3
,
re-
spectively.
Samples
were
impregnated
with
varying
concentra-
tions
of
FR
chemical
solution
(4
%-30
%)
using
vacuum
or
full-
cell
processes.
A
specimen
volume
of
0.441
x
10
-3
m
3
produced
an
actual
absorption
content
(m2)
for
each
group
of
specimens
of
120
g,
170
g,
219
g,
268
g,
318
g,
and
352
g
with
the
respective
distributive
percentage
(DP)
of
34
%,
48
%,
62
%,
76
%,
90
%
and
100
%.
The
DP
value
of
FR
treated
specimens
may
be
expressed
as:
DP
(%)
=
(AB/797)
x
100
In
this
study,
the
FR-treated
specimens
with
a
DP
of
90
%
and
100
%
were
treated
with
a
full-cell
process.
However,
the
FR
treated
specimens
with
a
DP
of
76
%,
62
%,
48
%,
and
34
%
were
treated
with
a
vacuum
process.
Before
treatment,
the
mass
of
each
specimen
was
measured
(ml),
and
after
FR
treatment
the
speci-
mens
were
dried
at
40
°C
over
48
h.
Then
FR
treated
specimens
were
conditioned
at
20
°C
and
65
%
RH
for
more
than
2
weeks.
The
FR
chemical
retention
(CR)
of
FR
treated
specimens
may
be
expressed
as:
CR
(kg/m
3
)
=
(m
2
-ml)
x
C/V,
where
C
is
the
concentration
of
FR
chemical
solution
and
V
is
the
volume
of
specimen&
The
vacuum
and
full-cell
process
were
carried
out
as
follows.
Vacuum
process:
Specimens
were
randomly
assigned
to
a
position
in
a
desiccator.
A
vacuum
of
0.0925-0.0926Mpa
was
applied
for
10
min.
After
im-
pregnation
of
FR
chemical
solution,
the
vacuum
was
released.
This
condition
was
maintained
for
2
h,
and
the
mass
of
each
specimen
was
measured
at
intervals
of
10
min.
For
lower
DP
of
FR
chemical,
lower
vacuum
values
were
used.
Full-cell
process:
Specimens
were
randomly
assigned
to
a
position
in
a
vertical
cylindrical
vessel.
A
vacuum
of
0.0946MPa
was
applied
for
10
min.
After
impregnation
with
FR
chemical
solution
the
va-
cuum
was
maintained
for
10
min.
The
pressure
was
increased
to
0.98MPa
for
2
h,
and
then
the
vacuum
was
released
to
atmo-
sphere.
Specimens
were
removed
to
determine
their
mass
and
immediately
returned
to
the
vessel
for
another
30
min
of
impre-
gation
at
atmospheric
pressure
to
allow
the
FR
chemical
to
diffuse
continuously
into
the
inside
of
the
specimen.
After
30
min,
speci-
mens
were
removed
to
determine
their
mass
again.
If
the
speci-
mens did
not
reach
90
%
or
100
%
of
DP
level,
the
pressure
process
was
repeated
as
above.
Surface
fire-retardant
performance
Before
the
surface
FR
test,
the
specimens
were
dried
at
40
±
1
°C
over
48
h,
and
then
conditioned
in
a
desiccator
containing
silica
gel
for
24
h.
AToyo
SEIKI
Model
F2-RE3
fire-retardant
tester
for
building
materials
was
used
for
the
test.
The
third
grade
of
surface
FR
performance
of
all
specimens
was
evaluated
according
to
the
rules
specified
by
CNS
6532
standard,
in
which
the
specimens
were
heated
3
min
using
sub-heat
(liquid
propane
gas)
and
heated
an
additional
3
min
by
a
main
heater
(electric
heater).
Total
heating
time
was
6
min.
According
to
the
standard
of
third
grade
surface
FR
perfor-
mance
as
specified
by
CNS
6532
(1993),
the
specimens
must
meet
the
following
specifications
after
6
min
of
heating:
(1)
tc
values
considered
to
be
the
combustibility
index
of
materials
must
be
more
than
180
seconds.
(2)
td0
values
considered
to
be
the
burning
heat
quantity
index
of
materials
must
be
less
than
350
min
°C.
(3)
CA
values
considered
to
be
the
smoking
quantity
index
of
mate-
rials
must
be
less
than
120.
(4)
tl
values
considered
to
be
the
flame
lingering
time
index
of
materials
must
be
less
than
30
second&
Results
and
Discussion
Specific
gravity
of
fire-retardant
treated
wood
The
surface
FR
performance
of
specimens
is
influenced
significantly
by
the
FR
chemical
retention
(CR).
How-
ever,
the
FR
chemical
retention
of
specimens
is
affected
by
their
specific
gravity
(SG).
Thus
in
this
study,
the
SG
of
specimens
in
an
air-dried
condition
was
controlled
in
the
range
from
0.35-0.41,
with
an
average
of
0.37.
When
im-
pregnated
with
the
FR
chemical
solution,
the
SG
of
FR
treated
specimens
increased
with
the
increase
in
CR
as
shown
in
Figure
1.
Its
relation
may
be
represented
by
a
positive
linear
regression
formula
as
follows:
S.
G.
=
0.001CR
+
0.362.
R
2
=
0.973.
F
=
834**,
where
**
represents
significance
t
=
.01
confidence
level
by
F
value
test.
Relation
between
distributive
percentage
level
and
concentration
of
fire-retardant
solution
Specimens
were
treated
with
FR
chemicals
ranging
in
concentration
from
10
%-20
%.
A
significant
correlation
was
found
between
the
DP
level
and
CR
values
of
speci-
mens
as
shown
in
Figure
2.
Their
relationship
can
be
represented
by
a
positive
linear
regression
formula
as
follows:
Concentration
of
10
%:
CR
=
0.74DP+3.03.
R
2
=
0.995.
F
=
721**
15
%:
CR
=
1.16DP+2.36.
R
2
=
0.994.
F
=
635**
20
%:
CR
=
1.59DP+1.25.
R
2
=
1.
F
=
19546**
Figure
2
also
demonstrates
that
the
higher
concentra-
tion
of
FR
chemical
solution
produced
higher
CR
values
under
the
same
DP
level.
In
other
words,
the
lower
con-
centration
of
FR
chemical
solution
had
higher
DP
level
under
the
same
CR
values.
0.55
0.5
0.4
0.35
0
50
100
150
200
chemical
retention
(kg/m
3
)
Fig.
1.
Relationship
between
specific
gravity
of
FR
treated
wood
and
FR
chemical
retention.
Holzforschung
/
Vol.
56
/
2002
/
No.
2
400
300
200
0
100
0
0
50
100
150
200
Chemical
retention
(kg/m
3
)
500
.
E
400
s.)
300
200
100
0
0
50
100
150
200
Chemical
retention
(kg/m
3
)
H.-B.
Chuang
and
S.
Y.
Wang:
Fire-Retardant
'Heated
China
Fir
Wood
211
-
200
150
100
50
0
20
34
48.
62
76
90
Distributive
percentage
(%)
Fig.
2.
Relationship
between
FR
chemical
retention
and
distri-
butive
percentage
of
FR
chemical.
(Concentration:
=
20
%,
A
=
15
%,
=
10
%)
Fig.
3.
The
distribution
pattern
of
various
DP
level
for
China
fir.
Legend:
A
=
34
%
of
DP
level;
B
=
48
%
of
DP
level;
C
=
62
%
of
DP
level.
D
=
76
%
of
DP
level;
E
=
90
%
of
DP
level;
F
=
99
%
of
DP
level.
The
distribution
patterns
of
FR
chemicals
in
specimens
The
actual
distribution
patterns
of
FR
chemical
for
six
different
DP
levels
of
FR
treated
specimens
are
shown
in
Figure
3.
It
was
found
that
in
the
case
of
a
DP
level
of
34
%,
most
FR
chemicals
were
localized
in
the
region
of
early-
wood
around
5
cm
from
the
end
section
of
specimens.
Whereas
some
latewood
for
each
growth
ring
showed
staining,
no
FR
chemicals
were
doserved
in
the
central
position
of
specimens.
The
increase
in
DP
level
produced
a
distribution
of
FR
chemicals
that
expanded
from
the
end
section
into
the
central
region
of
each
specimen.
Further-
more,
the
distribution
of
FR
chemicals
in
each
growth
ring
expanded
from
earlywood
to
latewood
regions.
When
the
DP
level
reached
90
%,
FR
chemicals
extended
fully
into
the
growth
ring
with
an
even
distribution
except
in
the
latewood
region.
The
fire-retardant
performances
of
non-fire
retardant
treated
wood
The
surface
FR
performance
of
non-FR
treated
China
fir
wood
(control
group)
after
surface
FR
performance
test
is
shown
in
Tablel.
The
tc
values
of
50
seconds
were
less
than
the
required
180
seconds,
td0
values
of
416
min•
°C
were
greater
than
the
CNS
6532
standard
of
350
min•
°C,
tl
values
of
156
seconds
were
greater
than
the
minimum
30
seconds,
the
CA
value
of
86
was
less
than
120,
and
the
crack
did
not
occur
on
the
back
side
of
specimens.
Non-FR
treated
China
fir
wood
(control
group)
cannot,
therefore,
pass
the
third
grade
standard
of
surface
FR
performance
as
specified
by
CNS
6532
(1993).
The
effect
of
FR
chemical
retention
on
fire-retardant
performances
The
surface
FR
performance
of
FR
treated
China
fir
wood
with
a
DP
level
of
100
%
is
shown
in
Figure
4.
It
was
found
that
the
tc
values
increase
with
the
increase
in
CR
values
until
they
reach
95.8
kg/m
3
,
at
which
point
tc
values
be-
come
constant.
Correspondingly,
the
values
of
td0
and
tl
decrease
with
the
increase
of
CR
values,
and
the
values
of
td0
and
tl
tend
to
0
with
CR
values
of
95.8
kg/m
3
and
75.2
kg/m
3
.
The
values
of
CA
decrease
with
the
increase
of
CR
values,
but
when
CR
values
reach
39.2
kg/m
3
,
then
CA
values
increase
with
the
increase
in
CR
values.
From
the
above-mentioned
observation,
it
was
found
that
the
increase
in
CR
values
had
a
positive
effect
on
the
factors
tc,
td0,
and
tl.
However,
when
CR
values
reached
39.2
kg/m
3
,
the
increase
in
CR
values
had
a
negative
effect
on
the
value
of
CA.
This
may
be
due
to
the
fact
that
the
better
flame
resistant
performance
of
FR
treated
wood
100
80
60
40
20
0
0
50
100 150
200
Chemical
retention
(kg/m
3
)
Fig.
4.
The
relationship
among
surface
FR
performance
indexes
and
FR
chemical
retention.
Legend:
tc
=
combustility
index
of
materials;
CA
=
smoking
quantity
index
of
materials;
tl
=
flame
lingering
time
index
of
material&
180
150
120
90
60
30
0
0
50
100
150
200
Chemical
retention
(kg/m
3
)
Holzforschung
/
Vol.
56
/
2002
/
No.
2
&
180
150
120
90
60
30
0
212
H.-B.
Chuang
and
S.
Y.
Wang:
Fire-Retardant
Reated
China
Fir
Wood
Table
1.
Effects
of
FR
chemical
retention
and
distributive
percentage
of
FR
chemicals
on
surface
FR
performance
indexes
of
wood
Concen-
Absolute
Distribu-
Specific
tration
FR
che-
five
per-
gravity
mical
so-
centage
lution
of
FR
chemical
g
FR
che-
mical
re-
tention
kg/m
3
tc
td0
CA
tl
wl
Judge-
ment
°C
min
CO
0
797
100
50
416
86
156
32.4
x
C4-100
4.0
797
100
0.39
30.1
210
127
28
67
27.3
x
C5-100
5.0
797
100
0.40
39.2
215
91
26
50
26.0
x
C6-100
6.5
797
100
0.41
49.2
227
76
27
24
23.6
0
C7-100
7.5
797
100
0.42
58.2
248
41
32
17
21.0
0
C12-100
12.0
797
100
0.46
95.8
353
1
38
0
15.3
0
C10-34
10.0
272
34
0.39
27.7
176
182
62
124
28.9
x
C10-48
10.0
385
48
0.40
37.8
198
127
59
99
23.6
x
Cl
0-62
10.0
494
62
0.40
50.6
220
87
49
59
22.9
x
C]0-76
10.0
606
76
0.41
59.1
233
53
35
33
21.8
x
Cl
0-90
10.0
717
90
0.42
71.2
265
32
33
15
19.2
0
C10-100
10.0
797
100
0.43
75.2
302
11
33
3
17.6
0
C15-34
15.0
272
34
0.40
41.2
194
126
67
125
23.4
x
C15-48
15.0
385
48
0.41
56.0
215
84
58
79
22.1
x
C15-62
15.0
494
62
0.43
77.6
239
36
48 48
18.7
x
C15-76
15.0
606
76
0.44
91.3
286
16
44
26
17.2
0
C15-90
15.0
717
90
0.45
108.9
350
1
44
1
15.6
0
C15-100
15.0
797
100
0.47
115.8
360
0
43
0
13.0
0
C20-34
20.0.
272
34
0.41
54.6
197
105
62
106
22.9
x
C20-48
20.0
385
48
0.43
78.2
231
64
65
55
19.3
x
C20-62
20.0
494
62
0.45
100.5
243
30
58
37
17.6
x
C20-76
20.0
606
76
0.47
121.8
297
13
49
23
16.0
0
C20-90
20.0
717
90
0.50
144.1
360
0
47
4
14.5
0
C20-100
20.0
797
100
0.52
160.4
360
0
48
0
12.1
0
C8-90
8.0
606
76
0.41
56.5
242
50
33
20
21.4
x
C9-76
9.0
606
76
0.41
55.2
232
62
38
40
21.8
x
Cl
1-62
11.0
494
62
0.41
54.8
225
76
46
58
22.4
x
C30-48
30.0
385
48
0.47
115.8
239
57
67
48
17.8
x
0
or
x
:
represent,
respectively,
passed
or
did
not
pass
the
third
grade
of
FR
performance
test
as
specified
by
the
CNS
6532
standard
(1993).
produced
more
smoke
(Brenden
1975;
Lei
1992;
Handa
et
al.
1979).
This
suggests
that
the
FR
treated
wood
has
an
optimal
CR
value
when
CA
begins
to
increase
with
the
increasing
CR.
To
meet
the
requirement
of
third
grade
FR
performance
as
specified
in
CNS
6532
standard
this
study
proposes
optimal
CR
values
of
49.275.2
kg/m
3
.
0
50
100
150
200
Chemical
retention
(kg/m
3
)
Fig.
5.
The
relationship
between
flame
lingering
time
index
(tl)
and
FR
chemical
retention.
It
was
found
that
the
indexes
of
tc,
tdO,
and
CA
of
FR
treated
wood
met
the
CNS
6532
standard
(Table1).
How-
ever,
index
of
tl
did
not
pass
the
standard
when
the
DP
level
of
the
specimens
had
not
reached
specific
values
(76
%).
Thus
the
flame
lingering
time
index
of
material
(tl
index)
should
be
considered
as
the
control
indicator
for
passing
the
third
grade
standard
of
surface
FR
performance.
The
relation
between
CR
values
and
the
tl
index
is
presented
in
Figure
5.
It
was
found
that
the
tl
index
de-
creases
with
the
increase
in
CR
values.
Figure
5
also
shows
that
some
FR
treated
wood
could
pass
the
third
grade
standard
with
CR
values
lower
than
49.2
kg/m
3
.
On
the
other
hand,
some
FR
treated
wood
did
not
meet
the
third
grade
standard
under
higher
CR
values
of
115
kg/m
3
,
sug-
gesting
that
the
surface
FR
performance
will
be
affected
by
both
CR
values
and
DP
level
of
FR
treated
wood.
Effect
of
distributive
percentage
of
FR
chemicals
on
fire
retardant
performance
Figure
6
demonstrates
that
the
FR
treated
wood
could
pass
the
third
grade
standard
with
a
DP
over
76
%.
Further-
more,
it
varied
with
the
change
in
concentration
of
FR
Holzforschung
/
Vol.
56
/
2002
/
No.
2
P
H.-B.
Chuang
and
S.
Y.
Wang:
Fire-Retardant
'Heated
China
Fir
Wood
213
1:10
120
90
60
30
20
34
48
62
76
90
Distributive
percentage
I(%)
Fig.
6.
The
relationship
between
flame
lingering
time
index
(t1)
and
distributive
percentage
of
FR
chemical
under
various
con-
centrations
of
FR
(Concentration:
=
20
%,
1=15
%,
0=
10
%).
1
34
W.
VD
34
4S
6.2
76
90
IA
intruslkyr
ververuoip
{N)
I-
D000
34
ag
62
76
.x.7
Lw
Nt.orpliapc
rhl
Fig.
7.
The
relationship
between
surface
FR
performance
in-
dexes
and
distributive
percentage
of
FR
chemical
under
the
same
FR
chemical
retention.
chemical
solution.
The
FR
treated
wood
must
have
a
DP
of
90
%
to
meet
the
third
grade
standard
when
treated
with
a
FR
concentration
of
10
%.
However,
the
FR
treated
wood
need
only
have
a
DP
of
76
%
to
meet
the
standard
when
impregnated
with
a
FR
chemical
solution
with
a
concen-
tration
of
15-20
%.
This
is
because
FR
treated
wood
with
the
same
DP
exhibited
higher
CR
values
after
treatment
with
higher
concentrations
of
FR
chemical
solution.
It
was
also
found
that
the
tl
indexes
decrease
with
the
increase
in
the
DP
for
FR
treated
wood
impregnated
with
three
different
concentrations
of
FR.
In
order
to
investigate
the
effects
of
various
DPs
on
the
indexes
of
surface
FR
performance
under
the
same
CR
values,
six
different
FR
treated
woods
(included
C7-100,
C8-90, C9-76,
C11-62,
C15-48
and
C20-34)
were
investi-
gated.
All
samples
exhibiting
the
same
CR
values
of
56
±
2
kg/m
3
were
selected
for
analysis
as
shown
in
Figure7.
It
was
found
that
although
these
six
different
samples
had
the
same
CR
values,
only
90
%
of
the
DP
for
C8-90
FR
treated
wood,
and
100
%
of
the
DP
for
C7-100
FR
treated
wood
met
the
requirement
of
the
third
grade
standard,
and
the
four
other
woods
could
not
pass
the
third
grade
stan-
dard
due
to
insufficient
DP
level.
From
the
above-mentioned
observation,
we
conclude
that
the
surface
FR
performance
is
influenced
significantly
by
the
DP
level.
Particularly
under
the
lower
DP
level,
the
distribution
of
FR
chemical
in
specimens
showed
uneven-
ness,
with
the
result
that
burning
may
occur
in
regions
in
which
FR
chemical
was
not
distributed,
thus
reducing
the
surface
FR
performance
of
FR
treated
woods.
Therefore
investigations
which
only
considered
the
CR
values
in
surface
FR
performance
and
neglected
the
DP
level
could
not
obtain
accurate
results.
Minimum
CR
values
needed
to
pass
the
third
grade
standard
of
FR
performance
From
the
above-mentioned
results,
it
was
found
that
the
CR
values
of
FR
treated
woods
that
met
the
third
grade
standard
differed
by
about
three
times
between
the
lowest
and
highest
levels.
This
means
that
if
FR
chemicals
are
distributed
evenly
in
the
specimens,
adequate
surface
FR
performance
will
be
exhibited,
assuming,
of
course,
that
it
reaches
the
minimum
CR
values.
Table
1
shows
that
the
minimum
CR
values
must
be
49.2
kg/m
3
,
where
the
DP
level
was
100
%.
If
the
CR
values
were
lower
than
49.2
kg/
m
3
,
for
example
39.2
kg/m
3
,
its
tl
index
could
not
be
re-
duced
to
less
than
30
seconds,
so
that
it
could
not
meet
the
third
grade
standard.
When
compared
to
the
minimum
CR
values
of
FR
treated
woods
exhibiting
DP
levels
of
100
%,
90
%
and
76
%
in
which
they
had
minimum
CR
values
of
49.2
kg/m
3
,
56.5
kg/m
3
,
and
913
kg/m
3
respectively.
The
minimum
CR
values
of
FR
treated
woods
for
90
%
and
76
%
of
DP
levels
were
respectively,
1.2
and
1.9
times
greater
than
those
100
%
DP
levels.
When
the
FR
treated
woods
were
treated
to
exhibit
62
%
34
%
DP
levels,
although
their
CR
values
were
raised
up
to
100.5
kg/m
3
115.8
kg/m
3
,
they
also
could
not
qualify
for
the
third
grade
standard
as
specified
by
CNS
6532
(1993).
These
results
were
in
agreement
with
the
effects
of
DP
level
on
surface
FR
performance
under
the
same
CR
values.
It
suggests
that
it
could
effectively
reduce
the
minimum
CR
values
for
meeting
the
requirement
of
the
third
grade
standard
by
raising
the
DP
level
of
the
FR
treated
wood.
It
was
alsofound
that
boththe
DP
level
and
CR
values
had
the
same
importance
for
the
surface
FR
performance.
How-
ever,
considering
that
we
desire
to
maintain
the
surface
FR
performance,
and
reduce
the
CR
values
to
save
the
costs
and
environmental
impact,
the
DP
level
is
of
greater
impor-
tance.
For
example,
when
the
DP
level
was
maintained
at
90
%,
CR
values
of
49.2-56.5
kg/m
3
were
adequate
for
meeting
the
requirement
of
the
third
grade
in
this
study.
Conclusion
(1)
The
specific
gravity
of
FR
treated
woods
increased
with
the
increase
of
CR
levels
and
its
relation
could
be
represented
by
a
positive
linear
regression
formula.
300
250
200
7;150
1.1}0
50
0
120
Z00
130
c
c'
46
20
0
60
50
40
30
2C/
10
4S
62
76
90
ti:ID
Pixtri6w
Iva
peroaitege
.0Q
Holzforschung
/
Vol.
56
/
2002
/
No.
2
214
H.-B.
Chuang
and
S.
Y.
Wang:
Fire-Retardant
Reated
China
Fir
Wood
(2)
The
CR
values
of
FR
treated
woods
increased
with
the
increase
of
DP
level
under
the
same
concentration
of
FR
chemical
solution
and
their
relations
could
be
represented
by
the
positive
linear
regression
formulas.
(3)
The
minimum
FR
chemical
retention
for
meeting
the
requirement
of
the
third
grade
standard
were,
respec-
tively,
48.8
kg/m
3
and
56.6
kg/m
3
for
specimens
with
a
DP
of
100
%
and
90
%.
However,
the
specimens
ex-
hibiting
62
%
-34
%
of
DP
level,
though
their
FR
chemical
retention
reached
up
to
100.5-115.8
kg/m
3
,
could
not
qualify
for
the
third
grade
standard.
(4)
The
factors
of
surface
FR
performances
were
influ-
enced
significantly
by
DP
level
of
specimens,
and
the
factor
of
tl
(flame
lingering
time
index
of
material)
of
FR
treated
woods
could
be
considered
as
a
marker
for
meeting
the
requirement
of
the
third
grade
standard
in
this
study.
Acknowledgements
This
study
was
supported
by
a
grant
(NSC-88-2313-B-002-201)
from
the
National
Science
Council
of
R.
0.
C.
Parts
of
this
paper
was
presented
at
the
International
Conference
on
Effective
Utilization
of
Plantation
Timber
held
in
Taiwan,
R.
O.
C.
on
May
21-23,1999.
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Received
September
19
th
2000
Dr.
H.-B.
Chuang
Department
of
Botany
College
of
Science
National
Taiwan
University
NO
1,
Sec.
4,
Roosevelt
Rd.
Taipei
Taiwan,
R.
0.
C.
Tel.
886-2-23630231-2773.
Fax.
886-2-23918940.
E-mail:
[email protected]&cc.ntu.edu.tw.
Prof.
Dr.
S.-Y.
Wang
1
Department
of
Forestry
College
of
Agriculture
National
Taiwan
University
NO
1,
Sec.
4,
Roosevelt
Rd.
Taipei
Taiwan,
R.
0.
C.
Tel:
886-2-23630231-2510.
Fax:
886-2-23631736
,
886-2-23654520.
E-Mail:
1)
Corresponding
author.
Holzforschung
/
Vol.
56
/
2002
/
No.
2