Intrinsically flame retardant epoxy resin Fire performance and background Part I


Toldy, A.; Anna,P.; Csontos, I.; Szabó, A.; Marosi, G.Y.

Polymer Degradation and Stability 92(12): 2223-2230

2007


The flame retardant effect of newly synthesized phosphorus-containing reactive amine, which can be used both as crosslinking agent in epoxy resins and as a flame retardant, was investigated. The effect of montmorillonite and sepiolite additives on the fire induced degradation was compared to pristine epoxy resin. The effect of combining the organophosphorous amine with clay minerals was also studied. It could be concluded that the synthesized phosphorus-containing amine, TEDAP can substitute the traditional epoxy resin curing agents providing additionally excellent flame retardancy: the epoxy resins flame retarded this way reach 960 C GWFI value, 33 LOI value and V-0 UL-94 rating e compared to the 550 C GWFI value, 21 LOI value and "no rate" UL-94 classification of the reference epoxy resin. The peak of heat release was reduced to 1/10 compared to non-flame retarded resin, furthermore a shift in time was observed, which increases the time to escape in case of fire. The flame retardant performance can be further improved by incorporating clay additives: the LOI and the HRR results showed that the optimum of flame retardant effect of clay additives is around 1 mass% filler level in AH-16eTEDAP system. Applying a complex method for mechanical and structural characterization of the intumescent char it was determined that the flame retarded system forms significantly more and stronger char of better uniformity with smaller average bubble size. Incorporation of clay additives (owing to their bubble nucleating activity) results in further decrease in average bubble diameter.

Available
online
at
www.sciencedirect.com
.'
ScienceDirect
Polymer
Degradation
and
Stability
ELSEVIER
Polymer
Degradation
and
Stability
92
(2007)
2223-2230
www.elsevier.com/locate/polydegstab
Intrinsically
flame
retardant
epoxy
resin
Fire
performance
and
background
Part
I
A.
Toldy*,
P.
Anna,
I.
Csontos,
A.
Szabo,
Gy.
Marosi
Department
of
Organic
Chemical
Technology,
Budapest
University
of
Technology
and
Economics,
PO
Box
91,
1521
Budapest,
Hungary
Received
15
January
2007;
received
in
revised
form
2
April
2007;
accepted
5
April
2007
Available
online
15
August
2007
Abstract
The
flame
retardant
effect
of
newly
synthesized
phosphorus-containing
reactive
amine,
which
can
be
used
both
as
crosslinking
agent
in
epoxy
resins
and
as
a
flame
retardant,
was
investigated.
The
effect
of
montmorillonite
and
sepiolite
additives
on
the
fire
induced
degradation
was
com-
pared
to
pristine
epoxy
resin.
The
effect
of
combining
the
organophosphorous
amine
with
clay
minerals
was
also
studied.
It
could
be
concluded
that
the
synthesized
phosphorus-containing
amine,
TEDAP
can
substitute
the
traditional
epoxy
resin
curing
agents providing
additionally
ex-
cellent
flame
retardancy:
the
epoxy
resins
flame
retarded
this
way
reach
960
°C
GWFI
value,
33
LOI
value
and
V-0
UL-94
rating
compared
to
the
550
°C
GWFI
value,
21
LOI
value
and
"no
rate"
UL-94
classification
of
the
reference
epoxy
resin.
The
peak
of
heat
release
was
reduced
to
1/10
compared
to
non-flame
retarded
resin,
furthermore
a
shift
in
time
was
observed,
which
increases
the
time
to
escape
in
case
of
fire.
The
flame
retardant
performance
can
be
further
improved
by
incorporating
clay
additives:
the
LOI
and
the
HRR
results
showed
that
the
optimum
of
flame
retardant
effect
of
clay
additives
is
around
1
mass%
filler
level
in
AH-16—TEDAP
system.
Applying
a
complex
method
for
mechanical
and
structural
characterization
of
the
intumescent
char
it
was
determined
that
the
flame
retarded
system
forms
significantly
more
and
stronger
char
of
better
uniformity
with
smaller
average
bubble
size.
Incorporation
of
clay
additives
(owing
to
their
bubble
nucleating
activity)
results
in
further
decrease
in
average
bubble
diameter.
©
2007
Published
by
Elsevier
Ltd.
Keywords:
Epoxy
resin;
Clay;
Organophosphorous
reactive
amine
flame
retardant;
Flame
retardance;
Degradation
mechanism
1.
Introduction
Epoxy
resins
are
extensively
used
as
adhesives,
surface
coat-
ings,
laminates
and
matrix
materials
in
electronic,
transport
and
aerospace
industries
due
to
their
exceptional
characteristics
like
good
adhesion
to
many
substrates;
moisture,
solvent
and
chem-
ical
resistance;
low
shrinkage
on
cure;
outstanding
mechanical
and
electronic
resistant
properties.
However,
having
an
organic
matrix,
their
thermal
and
fire
resistance
needs
to
be
enhanced
in
many
application
areas.
Fire
retardancy,
as
an
outstanding
ele-
ment
of
safety,
is
one
of
the
key
challenges.
There
are
two
main
approaches
to
achieve
flame
retardancy:
the
additive
and
the
reactive
approaches.
*
Corresponding
author.
Tel.:
+36
1
463
1348;
fax:
+36
1
463
1150.
E-mail
address:
(A.
Toldy).
0141-3910/$
-
see
front
matter
©
2007
Published
by
Elsevier
Ltd.
doi:10.1016/j.polymdegradstab.2007.04.017
Although
the
additive
way
provides
a
simple
and
cost-effective
solution,
it
has
some
drawbacks
as
well:
in
most
cases
to
achieve
adequate
effect
high
percentage
of
the
additive
is
needed,
which
significantly
influences
the
properties
of
the
polymer
matrix.
Furthermore
as
the
additive
is
not
chemically
incorporated
into
the
polymer
structure,
it
can
lead
to
the
possibility
of
loss
from
the
polymer
during
either
high
temperature
processing
by
migra-
tion
to
the
surface
or
in
the
early
stages
of
combustion.
Addition-
ally,
the
transition
of
additives
to
the
gaseous
phase
can
cause
the
smoke
from
the
burning
material
to
become
loaded
with
toxic
compounds.
The
above
mentioned
disadvantages
of
this
approach
may
be
eliminated
with
nano-level
dispersion
of
the
additive:
due
to
high
specific
surface
of
the
additive
and
nano-scale
interactions
with
the
polymer
matrix,
even
at
very
low
filler
concentration
nano-
composites
often
reveal
remarkable
improvement
of
mechanical
properties,
thermal
properties
and
flame
retardancy
compared
to
2224
A.
Toldy
et
al.
I
Polymer
Degradation
and
Stability
92
(2007)
2223-2230
virgin
polymer
and
conventional
microcomposites
[1-3].
Espe-
cially
great
attention
has
been
paid
to
clay
nanoadditives
due
to
their
low
cost
and
large
quantity.
Furthermore,
the
migration
to
the
polymer
surface,
mentioned
as
one
of
the
disadvantages
of
additive
flame
retardants,
can
become
an
advantage
in
this
case,
as
clay
nanoparticles
migrating
to
the
surface
of
the
poly-
mer
matrix
form
an
excellent
mass
and
heat
barrier
improving
flame
retardant
properties.
Nevertheless,
clay
nanoparticles
alone
do
not
provide
sufficient
fire
retardant
effect,
and
it
is
nec-
essary
to
combine
them
with
other,
approved
flame
retardants.
Lately
the
reactive
type
of
flame
retardancy
was
given
much
attendance
because
of
the
disadvantages
of
additive
flame
retar-
dants
described
above.
In
addition,
the
increasing
focus
on
the
health
and
environmental
compatibility
of
flame
retardants
has
drawn
attention
to
the
organophosphorous
reactive
flame
retar-
dants
[4-6].
The
new
European
Directive
2002/95/EC
[7],
requiring
the
substitution
of
some
widely
used
brominated
flame
retardants
(polybrominated
biphenyls
(PBB)
and
poly-
brominated
diphenyl
ethers
(PBDE))
in
new
electrical
and
elec-
tronic
equipment
put
on
the
market
from
1
July
2006,
also
facilitates
the
growth
of
phosphorous
flame
retardants.
Understanding
the
concept
of
the
reactive
flame
retardancy
serves
as
a
model
for
planning
the
flame
retardancy
of
other
polymers.
In
case
of
epoxy
resins
the
phosphorus-containing
chemical
unit,
providing
the
flame
retardant
effect,
can
be
in-
corporated
into
the
epoxy
component,
the
crosslinking
agent
or
into
both.
From
the
many
possible
alternatives
the
combina-
tion
of
an
aliphatic
epoxy
component
more
difficult
to
flame
retard
than
the
aromatic
ones
and
a
simple
phosphorus-
containing
crosslinking
agent
was
chosen.
In
this
work
the
effect
of
montmorillonite
and
sepiolite
ad-
ditives
on
the
fire
induced
degradation
was
compared
to
pris-
tine
epoxy
resin
matrix.
The
flame
retardant
effect
of
newly
synthesized
phosphorus-containing
reactive
amine,
which
can
be
used
both
as
crosslinking
agent
in
epoxy
resins
and
as
flame
retardant,
was
investigated.
The
effect
of
combining
the
organ-
ophosphorous
amine
with
clay
minerals
was
also
studied.
2.
Experimental
2.1.
Materials
The
polymer
matrix
was
ER
type
Eporezit
AH-16
(non-
modified,
resin
like
reactive
dilutant,
epoxy
equivalent:
160-
175;
viscosity
at
25
°C:
800-1800
mPa
s;
density
at
25
°C:
1.24
g/cm
3
)
applied
with
Eporezit
T-58
curing
agent
(amine
number:
460-480
mg
KOH/g;
viscosity
at
20
°C:
100-
200 mPa
s;
density
at
20
°C:
0.944
g/cm
3
;
curing
time:
2
days
at
25
°C)
supplied
by
P
+
M
Polimer
Kemia
Kft.,
Hungary.
Schemes
1
and
2
show
the
main
components
of
Eporezit
AH-
16
and
Eporezit
T-58.
A
newly
synthesized
phosphorus-containing
reactive
amine,
TEDAP
(amine
number:
510-530
mg
KOH/g;
viscosity
at
20
°C:
400
mPa
s;
curing
time:
7
days
at
25
°C,
4
hr
at
80
°C)
was
used
as
flame
retardant.
Unmodified
Na
montmorillonite
(MMT)
(product
of
Microtec,
Eurotrade)
and
Bentone
SD-1
(bentonite
based
CH
2
-CH
-CH
2
-0-CH
2
CH
2
-
O-CH
2
-CH
-CH
2
\
o
/ \
o
/
/
C
/ \
CH
2
-CH
-CH
2
-0-
CH
2
CH
2
-
O-CH
2
-CH
-CH
2
\
o
/ \
o
/
Scheme
1.
Main
component
of
Eporezit
AH-16.
organoclay
product
of
Rheox
Inc.)
type
montmorillonite
(MMT);
Pangel
S9
(untreated)
and
Pangel
B40
(organomodi-
fied)
sepiolites
(SEP)
(products
of
Tolsa
Ltd)
were applied
as
clay
additives.
This
way
ER
samples,
respectively,
containing
1,
2
and
5%
MMT
and
SEP
were
prepared.
2.2.
Methods
The
epoxy
and
amine
components
were
mixed
at
room
tem-
perature
or
in
case
of
TEDAP
at
its
melting
point,
by
hand
in
a
glass
beaker
in
order
to
obtain
a
homogenous
mixture.
The
clay
particles
were
added
to
the
epoxy
component
and
stirred
for
1
h
with
a
magnetic
stirrer
at
80
°C
in
order
to
obtain
a
good
dispersion.
A
silicone
mould
120
mm
long,
15
mm
wide
and
3
mm
thick
was
used
for
preparing
the
cured
samples.
Amine
number
of
the
curing
agents
was
determined
by
titration
according
to
ASTM
D2074-92(1998).
The
fire
resistance
was
characterized
by
Mass
Loss
Calo-
rimeter
(according
to
ISO
13927,
Fire
Testing
Technology,
heat
flux
of
50
kW/m
2
),
glow
wire
flammability
index
test
(GWFI,
according
to
IEC
60695-2-12),
UL-94
test
(according
to
ASTM
1356-90
and
ANSIJ/ASTM
D-635/77,
respectively)
and
limiting
oxygen
index
measurement
(LOI,
according
to
ASTMD
2863).
A
theological
method
for
char
characterization
elaborated
by
Duquesne
et
al.
[8]
was
developed
further
for
more
detailed
mechanical
and
structural
characterization
of
the
char.
Mea-
surements
were
carried
out
in
a
TA
Instruments
AR2000
type
rheometer,
at
room
temperature,
applying
1
Hz
frequency
and
0.1%
relative
elongation
and
1000
µm
gap.
One
gram
of
the
epoxy
resin
samples
was
cured
in
the
lower
plate
of
the
rheometer
at
room
temperature.
The
plates
of
the
rheometer
were
opened
to
the
maximum
distance,
then
the
sample
of
given
amount
in
the
lower
plate
was
heated
up
to
450
°C.
Due
to
the
heat
effect
char
formation
occurred.
Then
the
upper
plate
was
moved
to
the
lower
with
constant
speed
(30
µm/s)
and
the
normal
force
transduced
by
the
charred
layer
was
con-
stantly
detected
and
registered.
The
lower
and
upper
plates
had
the
same
diameter,
in
order
to
obtain
an
average
result
charac-
terizing
the
whole
sample
surface.
Scanning
electron
microscopy
(SEM)
images
were
taken
with
JEOL
5500
LV
instrument.
CH3
CH
2
NH
2
Scheme
2.
Main
component
of
Eporezit
T-58.
H
3
C
N
2
H
-(
A.
Toldy
et
al.
I
Polymer
Degradation
and
Stability
92
(2007)
2223-2230
2225
/
CI
0 =
P
+3
HO—CH
2
CH
2
NH
2
CI
/ 0
CH
2
CH
2
NH
2
.HCI
0 =
P-0
CH
2
CH
2
NH
2
.HCI
0
CH
2
CH
2
NH
2
.HCI
2h
a
<90°C
0—
CH
2
CH
2
NH
2
.HCI
0 =
P-0—CH
2
CH
2
NH
2
.HCI
0
CH2CH2
NH
2
.HCI
3
Na0Et
0
CH2CH2
NH2
Et0H
0 =
P—
0
CH2CH2
NH2
+
3
NaCI
+
3
Et
0
H
\
0
CH
2
CH
2
NH
2
Scheme
3.
Synthesis
of
TEAR
The
MS
FAB
measurements
were
performed
on
ZAB-2SEQ
spectrometer.
The
MALDI-TOF
measurements
were
taken
on
Bruker
BiFlex
111
MALDI-TOF
apparatus
and
evaluated
with
XMASS
5.0
software.
The
31
P
NMR
spectra
were
taken
on
a
Bruker
DRX-500
spectrometer
operating
at
202.4
MHz.
Chemical
shifts
are
downfield
relative
to
85%
H
3
PO
4
.
The
infra-
red
spectroscopic
measurements
were
made
on
Bruker
Tensor
37
type
FTIR
apparatus,
using
NaCl-window,
resolution:
4
cm
-1
,
detector:
DTGS.
3.
Results
and
discussion
3.1.
Synthesis
of
the
organophosphorous
compounds
3.1.1.
Synthesis
of
P(0)(OCH
2
CH
2
NH
2
)
3
(TEAP)
from
POCl
3
The
synthesis
of
P(0)(OCH
2
CH
2
NH
2
)
3
from
starting
mate-
rial
POC1
3
was
carried
out
according
to
the
literature
[9]
(Scheme
3).
To
6.03
ml
(0.1
mol)
of
H
2
NCH
2
CH
2
OH
3.11
ml
(0.033
mol)
of
POC1
3
was
added
dropwise
with
continuous
stirring
in
2
h
at
a
rate
that
the
temperature
of
the
reaction
mixture
does
not
exceed
90
°C.
After
2
h
20
ml
of
toluene
was
added
and
the
mixture
was
stirred
for
1
h.
Toluene
was
removed
by
de-
cantation and
a
solution
of
6.8
g
(0.1
mol)
NaOEt
and
40
ml
of
96%
EtOH
was
added
and
the
mixture
was
stirred
for
3
h
at
60
°C.
The
formed
NaCl
was
filtrated
to
give
the
product
in
90%
yield.
The
product
was
characterized
by
31
P
NMR
chem-
ical
shifts
and
mass
spectroscopical
data
obtained
from
MS
FAB.
31
P
NMR
(CDC1
3
)
6
2.79;
MS,
m/z
(rel.
int.)
228
(M
t
,
7).
3.1.2.
Synthesis
of
P(0)(NHCH
2
CH
2
NH
2
)
3
(TEDAP)
from
POCl
3
The
synthesis
of
P(0)(NHCH
2
CH
2
NH
2
)
3
from
starting
ma-
terial
POC1
3
was
carried
out
analogously
to
the
reaction
described
above
(Scheme
4).
/
CI
2h
0
P—
CI
+
3
H
2
N
CH
2
CH
2
NH
2
60°C
CI
To
the
solution
of
10
ml toluene
and
2.67
ml
(0.03
mol
+
0.01
mol
access)
of
H
2
NCH
2
CH
2
NH
2
solution
of
20
ml
toluene
and
0.93
ml
(0.01
mol)
of
POC1
3
was
added
dropwise
with
con-
tinuous
stirring
in
30
min
at
a
rate
that
the
temperature
of
the
reaction
mixture
cooled
to
0
°C
does
not
exceed
5
°C.
After
stir-
ring
for
2
h
at
60
°C
the
toluene
was
removed
by
decantation
and
a
solution
of
2.04
g
(0.03
mol)
NaOEt
and
60
ml
of
96%
EtOH
was
added
and
the
mixture
was
stirred
for
3
h
at
60
°C.
The
formed
NaCl
was
filtered
to
give
the
product
in
80%
yield.
The
product
was
characterized
by
31
P
NMR
chemical
shifts,
mass
spectroscopical
data
obtained
from
MS
MALDI-TOF
and
FTIR
spectra.
31
P
NMR
(DMSO)
6
6.64;
MS,
m/z
(rel.
int.)
225
(M
t
,
64);
1-1'1R
(cm
-1
)
740
(P—N—C),
950
(P—N—C),
1216
(P
=
0),
3354
(N—H).
3.2.
Application
of
clay
additives
and
organophosphorous
compounds
in
epoxy
resin
matrix
3.2.1.
Incorporation
of
montmorillonite
and
sepiolite
additives
into
epoxy
resin
matrix
The
effect
of
clay
additives
on
flame
retardancy
was
inves-
tigated
by
LOI,
UL-94,
HRR
and
mass
loss
measurements.
According
to
the
LOI
results
(Table
1)
it
can
be
concluded
that
the
clay
additives
improved
the
LOI
of
the
reference
AH-
16—T-58
epoxy
resin
and
by
increasing
their
quantity
the
LOI
slightly
increased.
Both
in
case
of
MMT
and
SEP
the
untreated
clays
had
more
significant
effect
on
the
flame
retardancy.
The
best
result
was
achieved
using
5%
untreated
SEP.
The
effect
of
clay
additives
was
also
investigated
by
HRR
and
mass
loss
measurements.
The
HRR
of
AH-16—T-58
matrix
containing
1,
2
and
5%
of
untreated
MMT
and
SEP,
respec-
tively,
can
be
seen
in
Figs.
1
and
2.
The
clay
additives
reduced
the
peak
of
HRR
and
in
case
of
1%
additive
a
shift
in
time
to
ignition
was
observed,
especially
in
case
of
untreated
MMT
additive.
It
is
also
an
interesting
notifi-
cation
that
by
increasing
the
amount
of
clay
additives
the
form
/
NH
CH
2
CH
2
NH
2
.HCI
0=
P—
NH
CH
2
CH
2
NH
2
.HCI
NH
CH
2
CH
2
NH
2
.HCI
/
NH
—CH
2
CH
2
NH
2
.HCI
0
P—
NH
—CH
2
CH
2
NH
2
.HCI
NH
—CH
2
CH
2
NH
2
.HCI
NH—
CH
2
CH
2
—N
H
2
3
Na0Et
0
P
NH
CH
2
CH
2
—NH
2
+
3
NaCI+
3
Et0H
Et0H
NH—
CH
2
CH
2
—N
H
2
Scheme
4.
Synthesis
of
TEDAP.
AH-16
T-58
1%
untreated
MMT
AH-16
T-58
2%
untreated
MMT
AH-16
T-58
5%
untreated
MMT
AH-16
T-58
50
100
150
200
250
Time
(s)
300
350
400
2226
A.
Toldy
et
al.
I
Polymer
Degradation
and
Stability
92
(2007)
2223-2230
Table
1
LOI
and
UL-94 results
of
AH-16—T-58
samples
containing
clay
additives
Clay
mineral
additive
AH-16—T-58
matrix
LOI%
UL-94
21
1%
Untreated
MMT
24
HB
2%
Untreated
MMT
24
HB
5%
Untreated
MMT
25
HB
1%
Organophillized
MMT
21
HB
2%
Organophillized
MMT
22
HB
5%
Organophillized
MMT
22
HB
1%
Untreated
SEP
25
HB
2%
Untreated
SEP
26
HB
5%
Untreated
SEP
27
HB
1%
Organophillized
SEP
24
HB
2%
Organophillized
SEP
24
HB
5%
Organophillized
SEP
25
HB
of
the
HRR
curve
changes:
the
second
peak
of
HRR
is
gradually
diminishing.
This
phenomenon
may
be
explained
by
consider-
ing
the
following
processes
during
burning:
The
main
heat
re-
lease
peak
caused
by
the
burning
of
the
evolved
gas
phase
degradation
products
is
followed
by
a
plateau
on
the
HRR
curve
due
to
the
protective
layer
formed
from
solid
decomposition
products.
When
the
pressure
of
the
evolved
gases
becomes
higher
than
the
value
that
the
barrier
layer
can
bear,
the
combus-
tible
gases
burst
out
and
the
whole
process
starts
again.
The
gradually
diminishing
second
peak
of
HRR
is
suggesting
a
rein-
forcing
effect
of
clay
on
the
char
that
maintains
this
way
its
bar-
rier
effect
and
thus
avoids
the
reactivation
of
the
heat
releasing
process.
Thus
it
was
essential
to
find
a
method
for
complex
char-
acterization
of
the
char
developed
during
the
burning
process
and
to
estimate
the
effect
of
clay
additives
and
flame
retardants
on
the
mechanical
and
structural
characteristics
of
the
char.
3.2.2.
Incorporation
of
organophosphorous
crosslinking
agent
into
epoxy
resin
matrix
According
to
preliminary
LOI
and
UL-94
measurements,
from
the
two
synthesized
organophosphorous
compounds
TE-
DAP
seemed
to
be
more
suitable
as
flame
retardant:
it
increased
the
LOI
of
the
AH-16—T-58
epoxy
resin
from
21
to
33,
and
the
UL-94
value
from
no
rate
to
V-0,
while
TEAP
increased
the
LOI
only
to
28
and
resulted
in
HB
UL-94
classification.
Fur-
thermore
the
synthesis
of
TEDAP
was
more
convenient
than
the
synthesis
of
TEAP.
1000
E
900
800
AC
700
m
600
500
cn
as
400
TD
300
200
100
0
Fig.
1.
Effect
of
untreated
MMT
on
HRR
in
AH-16—T-58
epoxy
resin
matrix.
50
100
150
200
250
300
350
400
Time
(s)
Fig.
2.
Effect
of
untreated
SEP
on
HRR
in
AH-16—T-58
epoxy
resin
matrix.
In
order
to
investigate
the
flame
retardant
effect
of
TEDAP,
T-58
curing
agent
was
replaced
by
TEDAP
in
20,
40,
60,
80
and
finally
in
100
mass%.
The
appropriate
amount
of
TEDAP
to
replace
T-58
was
calculated according
to
its
amine
number
in
order
to
reach
the
same
level
of
curing.
The
fire
retardancy
of
these
samples
was
evaluated
by
LOI,
UL-94,
HRR
and
mass
loss
measurements.
The
LOI
and
UL-94
results
are
given
in
Table
2.
Increasing
the
proportion
of
TEDAP
and
so
the
P
concentra-
tion
in
the
system,
a
clear
increase
of
the
flame
retardancy
can
be
seen.
To
achieve
the
V-0
UL-94
classification
60
mass%
of
the
original
crosslinking
agent
T-58
was
replaced
by
TEDAP.
Best
results
LOI
of
33
and
V-0
UL-94
classification
were
reached
when
the
original
amine
was
completely
replaced
by
TEDAP,
which
provides
3.5
mass%
of
P
in
the
epoxy
resin.
The
flame
retardancy
was
also
investigated
by
mass
loss
and
HRR
measurements.
The
heat
release
rate
(HRR)
of
AH-16—T-58—TEDAP
series
in
the
function
of
TEDAP
pro-
portion
can
be
seen
in
Fig.
3.
According
to
the
HRR
results
it
can
be
determined
that
by
in-
creasing
the
proportion
of
TEDAP
and
so
the
phosphorus con-
tent,
the
peak
value
of
HRR
is
decreased
which
shows
a
good
correlation
with
LOI
and
UL-94I
results.
The
biggest
decrease
in
peak
HRR
was
observed
when
the
original
amine
was
com-
pletely
replaced
by
TEDAP:
the
peak
HRR
was
reduced
to
ap-
proximately
its
tenth
value.
Also
a
significant
shift
in
time
was
observed,
which
increases
the
time
to
escape
in
case
of
fire.
3.23.
Combination
of
montmorillonite
and
sepiolite
additives
with
reactive
amine
flame
retardant
The
fire
retardancy
of
these
samples
was
evaluated
by
LOI
and
mass
loss
and
HRR
measurements.
The
LOI
and
UL-94
results
are
given
in
Table
3.
Table
2
LOI
and
UL-94
values
in
the
function
of
TEDAP
proportion
in
case
of
AH-
16—T-58
samples
Sample
P-content
(mass%)
LOI
(%)
UL-94
AH-16—T-58
reference
21
No
rate
AH-16—T-58-20%
TEDAP
0.7
26
HB
AH-16—T-58-40%
TEDAP
1.4
29
HB
AH-16—T-58-60%
TEDAP
2.1
29
V-0
AH-16—T-58-80%
TEDAP
2.8
29
V-0
AH-16-100%
TEDAP
3.5
33
V-0
6;
1000
E
900
AL
800
700
t
o
.
600
500
cn
400
co
300
TD
200
To'
100
=
0
0
AH-16
T-58
5%
untreated
SEP
AH-16
T-58
2%
untreated
SEP
AH-16
T-58
1%
untreated
SEP
AH-16
T-58
A.
Toldy
et
al.
I
Polymer
Degradation
and
Stability
92
(2007)
2223-2230
2227
N
1000
E
900
AH
16
T-58
AH-16
TEDAP
AH-16
TEDAP
1%
untreated
MMT
AH
16
TEDAP
2%
untreated
MMT
AH-16
TEDAP
5%
untreated
MMT
50
100 150
200 250
300
350
400
Time
(s)
50
100 150
200 250
300 350
400
Time
(s)
1000
900
800
AC
700
Id
600
500
(
8
400
300
200
as
X
w
100
0
AH
16
T-58
AH-16
T-58
20%
TEDAP
AH-16
T-58
40%
TEDAP
AH-16
T-58
60%
TEDAP
AH-16
T-58
80%
TEDAP
AH-16
TEDAP
_Ne
w
ea
co
800
700
600
500
400
300
200
100
-
0-
0
Fig.
3.
Heat
release
rate
in
the
function
of
TEDAP
proportion
in
case
of
AH-
16—T-58
samples.
According
to
these
results
it
can
be
concluded
that
in
addi-
tion
to
the
effect
of
TEDAP
there
was
a
further
increase
in
LOI
applying
1%
clay
additive.
However,
incorporating
more
addi-
tive
did
not
improve
the
LOI
results,
moreover,
in
case
of
SEP
it
deteriorated
the
LOI
values.
The
effect
of
clay
additives
was
also
investigated
by
HRR
and
mass
loss
measurements.
The
HRR
of
AH-16—T-58
reference
and
AH-16—TEDAP
matrix
containing
1,
2
and
5%
of
untreated
MMT
and
SEP,
respectively,
can
be
seen
in
Figs.
4
and
5.
By
replacing
the
T-58
with
the
phosphorus-containing
TE-
DAP
the
peak
HRR
value
decreased
approximately
to
its
1/10
value,
furthermore,
a
shift
in
time
to
ignition
of
about
50
s
was
observed.
By
adding
clay
additives
to
the
AH-16—TEDAP
matrix
better
results
were
obtained
only
in
case
of
applying
1%
additive:
the
value
of
peak
HRR
decreased
or
stayed
at
same
level
and
a
further
significant
shift
in
time
to
ignition
was
detected.
If
2
or
5%
clay
was
added
the
peak
of
HRR
in-
creased
compared
to
the
AH-16
TEDAP
matrix,
although
the
above
mentioned
shift
in
ignition
time
was
observed
as
well.
Both
the
LOI
and
the
HRR
results
showed
that
the
optimum
of
flame
retardant
effect
of
clay
additives
is
around
1
mass%
filler
level.
In
order
to
investigate
this
behaviour
the
Table
3
LOI
and
UL-94
results
of
AH-16—TEDAP
samples
containing
clay
additives
Fig.
4.
Effect
of
untreated
MMT
on
HRR
in
AH-16—TEDAP
epoxy
resin
matrix.
mechanical
and
structural
characterization
of
the
char
was
done
by
a
method
described
above
(Fig.
6).
Fig.
7
shows
the
normal
force
transduced
by
the
char
as
a
function
of
the
distance
between
the
plates
of
the
rheometer.
Moving
the
upper
plate
downward
the
normal
force
takes
up
a
nearly
constant
value,
which
can
be
considered
proportional
to
the
strength
of
the
individual
bubbles.
After
breaking
the
charred
structure
the
normal
force
increases
significantly
be-
cause
of
the
compression
of
the
charred
layer.
As
the
mass
of
the
samples
was
the
same,
the
first
point
of
the
measurement
characterizes
the
char
volume,
while
the
gap,
before
sudden
in-
crease
of
the
normal
force,
is
proportional
to
the
remained
mass
of
the
sample.
In
contrast
to
the
previously
reported
method
[10],
where
the
decreasing
gap
was
expressed
in
percentages
taking
into
account
the
initial
height
of
the
char,
in
this
case
the
value
of
the
gap
was
displayed
as
an
absolute
value
in
order
to
be
able
to
compare
the
real
char
volumes.
The
average
normal
force
before
sudden
increase
of
the
normal
force
can
be
consid-
ered
as
a
characteristic
parameter
of
the
char
strength,
while
the
scattering
of
the
normal
force
correlates
with
the
diameter
of
the
formed
bubbles
in
the
char:
small,
uniform
fluctuation
refers
to
small
bubble
diameter
and
uniform,
flexible
char;
while
sudden
decrease
in
normal
force
proves
the
presence
of
bubbles
with
big
diameter,
which
causes
the
char
to
have
an
uneven,
rigid
structure.
Comparing
the
AH-16
T-58
reference
and
AH-16—TEDAP
flame
retarded
systems
(Table
4),
it
can
be
determined
that
the
Clay
mineral
additive
AH-16—TEDAP
matrix
LOI%
UL-94
1000
E
900
AH
16
T-58
33
V-0
800
AH-16
TEDAP
AH-16
TEDAP
1%
untreated
SEP
AH
16
TEDAP
2%
untreated
SEP
700
1%
Untreated
MMT
35
V-0
w
600
AH-16
TEDAP
5%
untreated
SEP
2%
Untreated
MMT
33
V-0
5%
Untreated
MMT
33
V-0
0
500
400
1%
Organophillized
MMT
36
V-0
I
2%
Organophillized
MMT
35
V-0
300
5%
Organophillized
MMT
35
V-0
"
200
1%
Untreated
SEP
34
V-0
100
=
2%
Untreated
SEP
30
V-0
0
5%
Untreated
SEP
30
V-0
0
50
100 150
200
250
300 350
400
1%
Organophillized
SEP
34
V-0
Time
(s)
2%
Organophillized
SEP
31
V-0
Fig.
5.
Effect
of
untreated
SEP
on
HRR
in
AH-16—TEDAP
epoxy
resin
5%
Organophillized
SEP
32
V-0
matrix.
2228
A.
Toldy
et
al.
I
Polymer
Degradation
and
Stability
92
(2007)
2223-2230
.`,
4
"
.
••
‘"•'
..
sik
rot
t,
/
411
6
/
1
.11h.
Fig.
6.
Mechanical
destruction
of
the
intumescent
char
of
AH-16—TEDAP
system.
flame
retarded
system
forms
significantly
more
char
than
the
reference.
Furthermore,
the
char
of
the
reference
sample
is
a
more
rigid
char,
with
bigger
average
bubble
diameter,
while
the
flame
retarded
system
provides
a
stronger,
more
uniform
char
with
smaller
average
bubble
size.
Including
untreated
SEP
in
the
reference
system
the
average
bubble
diameter
de-
creases
resulting
in
a
more
uniform
char.
In
case
of
the
flame
retarded
systems
the
incorporation
of
the
untreated
SEP
de-
creases
the
average
bubble
size,
but
this
is
a
relatively
smaller
effect
compared
to
the
already
significant
effect
of
intumescent
flame
retardant.
No
significant
difference
was
observed
in
the
function
of
clay
amount,
so
further
investigation
is
needed
to
in-
terpret
the
different
effect
of
the
increasing
amount
of
clay
on
the
LOI
and
HRR
results
in
the
reference
and
the
flame
retarded
systems.
Most
probably
the
bubble
nucleating
effect
of
the
clay
additive
is
dominant,
which
requires
only
a
small
filler
content
to
reach
the
appropriate
effect.
Furthermore,
as
TEDAP
is
more
polar
than
the
original
T-58
hardener,
it
can
be
assumed
that
by
increasing
the
additive
amount
the
decrease
in
cros
slinking
en-
thalphy
(due
to
adsorption
of
the
crosslinking
agent)
becomes
more
significant
than
in
case
of
T-58
(reported
elsewhere
AH-16
T-58
reference
AH-16
T-58
2%
untreated
SEP
AH-16
TEDAP
AH-16
TEDAP
2%
untreated
SEP
_„s,„,4,/‘
25000 20000
15000
10000
5000
0
Gap
(gm)
Fig.
7.
Effect
of
untreated
SEP
on
the
char
characteristics.
[11]),
which
leads
to
lower
crosslinking
density
and
deteriorat-
ing
flame
retardancy.
In
order
to
make
the
bubble
size
reducing
effect
of
clay
ad-
ditives
even
more
clear
several
SEM
images
were
taken
(Figs.
8
and
9)
and
analysed
by
Olympus
DPSoft
imaging
software.
The
estimated
average
bubble
size
was
410
±
30
gm,
while
the
incorporated
1%
untreated
MMT
reduced
it
to
255
±
30
gm.
GWFT
measurements
were
done
in
order
to
estimate
the
in-
dustrial
applicability
of
this
new
flame
retarded
epoxy
resin
system
in
electrical
and
electronic
equipments.
By
increasing
the
amount
of
TEDAP
and
so
the
proportion
of
phosphorus
a
linear
increase
in
GWFI
can
be
seen
(Table
5).
Applying
100%
TEDAP
the
best
GWFI
value
according
to
the
standard
can
be
achieved:
The
GWFI
value
of
960
°C
means
that
the
epoxy
resin
cured
with
TEDAP
can
be
used
in
electrical
and
electronic
equipments
for
unattended
use
continuously
loaded,
or
equipment
to
be
used
near
the
central
supply
point
of
a
building;
both
in
parts
in
contact
with,
or
retaining
in
posi-
tion
current-carrying
parts
and
in
enclosures
and
covers
not
retaining
current-carrying
parts
in
position.
4.
Conclusions
The
synthesized
phosphorus-containing
amine,
TEDAP
can
substitute
the
traditional
epoxy
resin
curing
agents,
addition-
ally
providing
excellent
flame
retardancy:
the
epoxy
resins
flame
retarded
this
way
reach
960
°C
GWFI
value,
33
LOI
value
and
V-0
UL-94
rating
compared
to
the
550
°C
GWFI
value,
21
LOI
value
and
"no
rate"
UL-94
classification
of
the
reference
epoxy
resin.
The
peak
of
heat
release
was
re-
duced
to
its
1/10
compared
to
non-flame
retarded
epoxy
resin,
furthermore
a
shift
in
time
was
observed,
which
increases
the
time
to
escape
in
case
of
fire
event.
The
flame
retardant
perfor-
mance
can
be
further
improved
by
incorporating
clay
addi-
tives:
the
LOI
and
the
HRR
results
showed
that
the
optimum
5
4
z
3
71
2
0
J
A.
Toldy
et
al.
I
Polymer
Degradation
and
Stability
92
(2007)
2223-2230
2229
Table
4
Effect
of
untreated
SEP
on
the
char
characteristics
Maximum
gap
(.tm)
Gap
before
total
Average
normal
Maximum
normal
Maximum
compression'
(.tm)
force
before
total
force
before
total
deviation
(N)
compression'
(N)
compression'
(N)
AH-16—T-58
reference
8021
1632
0.427
2.09
9.08
AH-16—T-58-2%
Pangel
S9
12
820
1121
0.172
0.85
0.78
AH-16—TEDAP
24
075
2119
1.71
2.48
1.52
AH-16—TEDAP-2%
Pangel
S9
24
075
3295
2.31
3.11
0.2
a
Point
in
the
normal
force
vs
gap
diagram
where
the
normal
force
suddenly
begins
to
increase
due
to
total
compression
of
char.
r
4
-
.
0
^Ns.
Fig.
8.
SEM
image
of
AH-16—TEDAP
char.
„.,7
-;
YF
,v•
15.kL,1
X30
0
0
.urn
Fig.
9.
SEM
image
of
AH-16—TEDAP
1%
untreated
MMT
char.
Table
5
GWFI
values
in
the
function
of
TEDAP
proportion
in
case
of
AH-16—T-58
samples
P-content
(mass%)
0.7
1.4
2.1
2.8
3.5
of
flame
retardant
effect
of
clay
additives
is
around
1
mass%
filler
level
in
AH-16—TEDAP
system.
A
new
method
was
elaborated
for
mechanical
and
structural
characterization
of
the
char:
it
can
be
determined
that
the
flame
retarded
system
forms
significantly
more
and
stronger
char
of
better
uniformity
with
smaller
average
bubble
size.
Incorpora-
tion
of
clay
additives
(owing
to
their
bubble
nucleating
activity)
results
in
further
decrease
in
average
bubble
diameter.
According
to
these
results
the
epoxy
resin
flame
retarded
by
this
phosphorus-containing
amine
is
appropriate
for
all
elec-
tronic
appliances,
the
achieved
GWFI
value
(960
°C)
means
that
it
can
be
used
in
equipment
for
unattended
use
continuously
loaded
under
stringent
conditions.
Varying
the
ratio
of
the
non-
phosphorous
curing
agent
and
the
phosphorus-containing
one
the
widest
range
of
demand
for
various
level
of
flame
retardancy
can
be
fulfilled.
Acknowledgements
The
authors
acknowledge
the
financial
support
received
through
the
EU-6
Framework
Program
(NMP3-CT-2004-
505637
and
1P-026685-2)
and
Hungarian
Research
Foundation
OTKAT049121,
Foundation
of
European
Union
and
Hungarian
State
GVOP/3.1.1.-2004-0531/3.0,
Public
Benefit
Association
of
Sciences
and
Sport
of
the
Budapest
University
of
Technology
and
Economics.
References
[1]
Alexandre
M,
Dubois
P.
Polymer-layered
silicate
nanocomposites:
prep-
aration,
properties
and
uses
of
a
new
class
of
materials.
Mat
Sci
Eng
R
Reports
2000;28(1):1-63.
[2]
Pandey
Jitendra
K,
Reddy
K
Raghunatha,
Kumar
A
Pratheep,
Singh
RR
An
overview
on
the
degradability
of
polymer
nanocomposites.
Polym
Degrad
Stab
2005;88:234-50.
[3]
Camino
G,
Tartaglione
G,
Frache
A,
Manferti
C,
Costa
G.
Thermal
and
combustion
behaviour
of
layered
silicate—epoxy
nanocomposites.
Polym
Degrad
Stab
2005;90(2):354-62.
[4]
Lu
SY,
Hamerton
I.
Recent
developments
in
the
chemistry
of
halogen-
free
flame
retardant
polymers.
Prog
Polym
Sci
2002;27:1661-712.
[5]
Price
D,
Bullett
KJ,
Cunliffe
LK,
Hull
TR,
Milnes
GJ,
Ebdon
JR,
et
al.
Cone
calorimetry
studies
of
polymer
systems
flame
retarded
by
chemi-
cally
bonded
phosphorus.
Polym
Degrad
Stab
2005;88(1):74-9.
[6]
Braun
U,
Balabanovich
A,
Schartel
B,
Knoll
U,
Artner
7,
Ciesielski
M,
et
al.
Influence
of
the
oxidation
state
of
phosphorus
on
the
decomposition
and
fire
behaviour
of
flame-retarded
epoxy
resin
composites.
Polymer
2006;47(26):8495-508.
Sample
AH-16—T-58
reference
AH-16—T-58-20%
TEDAP
AH-16—T-58
—40
%
TEDAP
AH-16—T-58
—60
%
TEDAP
AH-16—T-58-80%
TEDAP
AH-16-100%
TEDAP
GWFI
value
(°C)
550
550
650
750
850
960
2230
A.
Toldy
et
al.
I
Polymer
Degradation
and
Stability
92
(2007)
2223-2230
[7]
http
:
lleur-lex
europ
a
.
eu/LexUriServ/LexUriServ.do
?uri-
=CELEX:
32002L
0095
:
EN:
HTML
.
[8]
Duquesne
S,
Delobel
R,
Le
Bras
M,
Camino
G.
A
comparative
study
of
the
mechanism
of
action
of
ammonium
polyphosphate
and
expandable
graphite
in
polyurethane.
Polym
Degrad
Stab
2002;77(2):333-44.
[9]
Sokolovskii
MA,
Zavlin
PM.
Zh
Obshch
IChim
1960;30:3562-5.
[10]
Jimenez
M,
Duquesne
S,
Bourbigot
S.
Multiscale
experimental
approach
for
developing
high-performance
intumescent
coatings.
Ind
Eng
Chem
Res
2006;45:4500-8.
[11]
Toldy
A,
Toth
N,
Anna
P,
Keglevich
Gy,
Kiss
K,
Marosi
Gy.
Flame
retardancy
of
epoxy
resin
with
phosphorus-containing
reactive
amine
and
clay
minerals.
Polym
Adv
Technol
2006;17(9-10):778-81.