Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~2~
FIRE VR FLAME BARRIER l!iATERI~qL
The present invention relates to a fire or
flame barrier material and more particularly, to a
high temperature, heat barrier material having
S selective, thermoprotective properties at elevated
temperatures.
BACRGROUND O~ T~E INVEMTION
Heretofore, various materials have been
proposed as flame or fire retardants. For instance,
in the field of fire resistant cable transits, such
materials based on neoprenes, silicon foam~
inorganic molding materials and mineral wool ~ats
have been utilized. While these known materials
exhibit various useful insulation and resistance to
fire ha2zard properties, none of them, simultane
ously, exhibits ~1) good ther~al conductivity under
normal use conditions, ~2) expansion and plugging.
properties at elevated temperatures and (3~ heat
insulating and mechanical protective ~roperties at
very high temperatures, suc~ as are encountered
during a fire
The present invention, however, is directed
to a fire or flame barrier material whichr in
addition to exhibiting the above-mentioned charac-
teristics, also has, si~ultaneously, additional
operational and flame or fire resistant propertiesr
.
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and is capable of being produced using relatively
inexpensive processes and components.
: General Description of the Invention-
When exposed to fire or elevated tempera-
tures the fire or flame barrier material of thepresent invention exhibit~ two basic properties
which together provide an active heat barrier
thereby protecting objects requiring protection:
(1) ~hen heated to certain elevated
temperatures, foaming and an endothermic reaction
occur. One of the by-products of this endothermic
reaction is water which, in the course of evapo-
ratin~, delays the heat rise at the heat exposed
surface and acts as a foaming agent; and
(2) The material of the present invention,
when directly exposed to elevated temperatures is
transformed into an intumescent polymeric foam like
layer having a firm, ceramic-like structure. This
intumescent layer shields the remaining non-exposed
portion of the thermoprotective material and has
qood heat insulating properties at temperatures up
to 2300CF and higher.
The heat barrier properties of the material
of the present invention are present only at
temperatures above 200C. At temperatures above
200~C, the polymeric matrix component of the
material begins to swell and forms a porous, thermal
insulating material. Simultaneously, water vapor is
given off which delays a temperature increase and
which contributes ~o a build-up of a non-combustible
atmosphere around the material of the present
învention.
During this swelling period it has ~een
observed that the material of the present invention
swells approximately 30-40 percent on a linear basis
(e.g~ >100~ on a volume basis).
Below 200C, the material of the present
: invention is a relatively good heat conductor~,
thereby ~issipating excess heat. During heat
exposure the material softens at a temperature of
about 95C. Because its melt viscosity is so high,
non-loaded specimens maintain their shape during
heating, swelling and eventually sintering. It has
al.so been observed that the material of the present
invention does not drip during softening and burning
stages.
The fire or flame barrier material of the
present invention, broadly, is a highly filled
polymer based composite, the principal components of
which are an ethylene copolymer, aluminum hydroxide,
i.e. Al(OH)3 and calcium carbonate. This fire or
flame barrier material is, as extruded or molded, or
coated at ambient temperature a solid having well
defined physical and chemical properties. On
heating the fire or flame barrier material of the
present invention from ambient temperature to a
temperature of about 1200C, the material undergoes
a series of complex chemical and physical trans-
formations. On cooling the flame barrier materialof the present invention from an appropriately high
temperature to which it has been subjected,~the
cooled material can be characterized as a porous,
mechanically solid and mainly inorganic mass. It
has been observed that the thermal conductivity of
the material during this heating-cooling operation
is reduced to one-tenth of its thermal conductivity
in the virgin state.
It has also been observed that the heat
barrier effect of the material of the present inven-
6~
tion is hi9hly complex. The sequence of changesthat the material undergoes can best be described by
observing the process when a ~lab of the fire~or
: flame barrier material of the invention is heated on
one side thereof with a high input heat source of
about 1200C.
Under these conditions, the fire or flame
barrier material begins to soften at the surface
directly exposed or in contact with the said heat
source. As the temperature of the said surface
increases to about 200C a gradual increase in
surface softness occurs and the temperature front
moves relatively rapidly into the polymeric matrix
due to its relatively high thermal conductivity.
The ethylene copolymer does not truly melt but
rather goes from a soften state to pyrolysis.
However, at about 200C when the polymer is soft but
still chemically int~ct, the aluminum hydroxide
begins to decompose and this decomposition increases
in intensity until the temperature reaches about
300C, at which point the decomposition is complete
and the residue includes significant amounts of
A12O3 (note: 1 kg of aluminum trihydrate gives
365 9 of water. Por instance 1 kg of a preferred
composition of this invention develops 252 9 of
water.) During this transformation the rapid
evolution of water vapor produces a foaming of the
polymer matrix. The calcium and/or magnesium
carbonates togeth~r with the aluminum oxide residue
are dispersed in the resulting foamed polymer
matrix.
The fire or flame barrier material at this
point is observed to have a cellular structure
characterized by a low thermal conductivity, but it
is still a polymer matrix. On further heating the
carbonates are transformed into their oxides and the
result is an essentially inorganic clellular
structure comprising a combination of calciumi
: magnesium and aluminum oxides. A surprising ~nd
remarkabie feature of the present invention is that
this cellular structure exhibits sufficient
mechanical integrity so as to be self-supporting and
to be sufficiently resistant to moderate mechanical
attack, particularly as it is believed that the
polyme~ and even the carbon content of the barrier
material at these elevated temperatures are
pyrolyzed to, for instance CO and CO2. Thus, at the
surface of the fire or flame barrier material
exposed or in contact with the high temperatures,
such as are encountered in a fire, the decomposition
of the aluminum hydroxide produces an endothermic
effect. The endothermic heat by decomposition is
300 KJ/mol A12O3 in accordance with the following
reac:tion 2 Al(O~)3 ~ A12O3 ~ 3H2O, and thus limits
the temperature rise as long as all the aluminum
hydroxide is not decomposed.
Moreover, the vapor formation foams the
polymer matrix thereby reducing substantially its
thermal conductivity. Both effects combine to
redure the heat flow rate to the underlying
softening polymer material.
Thus, as indicated above, on heating the
fire or flame barrier material of the present
invention at an appropriate elevated temperature, an
intumescent layer is formed close to the heat source
while the portion of the material more remote from
the heat source undergoes only the aforementioned
endothermic reaction and does not advance to the
intumescent stage.
~`
The fire or flame barrier material of the
present invention, is free of halogens, sulfur,
phosphorus and ~ther components tha~ give off~acidic
products during a fire.
-Moreover, dense smoke generation from the
material of the present invention can hardly be
observed during fire exposure. Rather, a low amount
of a light gray smoke is observed during a fire.
Smoke level, measured in Arapahoe equipment (gravi-
metric method) showed less than 0.5 wt ~ smoke of
burned material, which confirms essentially a non-
dense smoke generation during a fireO
The fire or flame barrier material of the
present invention can be rigid or flexible to a
certain extent (at least 20% elongation at break).
It can also be laminated or reinforced with conven-
tional materials.
The fire or flame barrier material of the
present invention is usefully employed, for
instance, in the production of walls, floors,
ceilings, rooms and cabins where fire protection is
required or desired. It can also be employed as a
protective covering or coating for mechanical and
electrical equipment such as electrical cabinets or
housings, fittings, pipes, hoses, cables, panels,
cable transits, doors and hatches. Moreover, it is
usefully employed in the production of coverings for
tanks and pipes, housing or carrying explosive
contents and found in chemical plants, refineries,
vehicles, ships and aircraft. Moreover, the fire or
flame barrier material can be provided in granular
form oE any desired shape or dimension and can ~e
employed as an insulating material between an inner
and an outer surface o~ a storage unit, such as a
storage tank or vessel, especially those of a large
~Q~
size. Because or its granular form, the fire or
flame barrier material of the present invention ca~
easily fill the space between said surfaces, thereby
provid,ng desirable insulation means. ~uring a fire
these granules, on exposure to elevated tempera-
tures, provide a heat barrier eEfect as described
above. Because of the loose ~torage or packin~ of
the granules in the space between said surfaces, the
granules expand and fuse together so as to
ultimately form a firm, intumescent intermediate
layer without imparting undue or deleterious
pressure on said surfaces.
DETAILED D~SCRIPTION OP THE INVENTION
The fire or flame barrier material of the
lS present invention comprises 60-100 parts by weight
of an ethylene copolymer; 0-40 parts by weight of an
elasticizer such as EPDM rubber; 0-10 parts by
weight of a polymer softening agent such as poly-
isobutylene; 0-15 parts by weight of a lubricating
agent such as a paraffin wax; 0-15 parts by weight
of calcium oxide; 50-450 parts by weight of aluminum
hydroxide; 150-600 parts by weight of calcium
carbonate or calcium-magnesium carbonate and if
desired an effective amount of a coloring agent,
such as carbon black, for instance about 1 part by
weight.
The ethylene copolymer can be selected from
the group consisting of ethylene-vinylacetate;
ethylen~-acrylic acid; ethylene-methacrylic acid;
ethylene-ethyl acrylate; ethylene-vinyl acetate-
methacrylic acid; ethylene-isobutyl acrylate;
~thylene-methyl methacrylate and ethylene-vinyl
acetate-carbon monoxide. Ethylene-ethyl acrylate is
preferred.
In one embodiment of the present invention
: the fire or flame barrier material can be rigid.
The rigid version of the fire or flame barrier
material has ~uccessfully been tested and evaluated
as fire resistant seal material for cable penetra-
tions and as fire insulating material for steel
constructions. In this embodiment the material
compris~s, preferably lO0 parts by weight of
ethylene copolymer, preferably ethylene-ethyl
acrylate, 220 parts by weight of aluminum hydroxide,
220 parts by weight of a member selected from the
group consisting of calcium carbonate and calcium
lS magnesium carbonate, lO parts by weight of a
paraffin wax lubricating agent, 11 parts by weight
o~ an elasticizer such as EPDM rubber, ll parts by
weight of calcium oxide and l part by weight of
carbon black. A preferr~d form of this material is
hereinafter referred to as Product P.
In nother embodiment of the present inven-
tion, the fire or flame barrier material can be
somewhat fle~ible. In this embodiment the material
comprises 80 parts by weight of ethylene-copolymer,
preferably ethylene-ethyl acrylate, 150 parts by
weight of aluminum hydroxide, 150 parts by weight of
a member selected from the group consisting~of
calcium carbonate and calcium-magnesium carbonate,
lO parts by weight of paraffin wax as a lubricating
agent, 30 parts by weight of an elasticizer such as
EPDM rubber, ll parts by weight of calcium oxide, l
par~ by weight of a coloring agent such as carbon
black and lO parts by weight of a polymer softener
such as polyisobutylene. A preferred form of this
material is hereinafter referred to as Product C.
.~
~2~6~
When the fire or flame barrier material of
the present invention is used for the production of
fire resistant cable transits it will expand due to
the presence therein of aluminum hydroxide, under
the influence of intense heat, for example, fire or
radiated heat, such that the material blocks any
permeation of smoke, warm gases and flames along the
transits.
At temperatures above the combustion
temperature of the organic components, e.g., in a
fire situation, the fire or flame barrier material
o the present invention, as indicated previously,
forms a strong intumescent layer having good thermal
insulation properties and high thermal stability,
i.e., it will withstand heat up to temperatures of
at least 1100C. The intumescent layer contributes
to an effective thermal and mechanical insulation of
the particles or objects coated or covered with the
fire or flame barrier material of this invention.
Before burning, the fire or flame barrier
material of this invention is elastic and is very
resistant to vibrations and mechanical loads.
The fire or flame barrier material of the
present invention can also be formulated into a
composition for coating or painting the object to be
protected from fire. Thus, it can be present as a
suspension of particulate matter in an alkyd,
polyurethane, vinyl acetate or acrylate coating or
paint vehicle.
The present invention also relates to a
method for producing the fire or flame barrier
material defined above, said process comprising
mixing the components thereof, dry, at ambient
temperature, extruding the resulting admixture at a
fusion temperature of about 150-200C to form
extrudates in continuous form and subdividing said
extrudates. Conventional processing equipment, such
as extruders and molding equip~ent can be utilized
- to process the material of the present invention.
-The extrudates in continuous form, e.g.
string-like form, can be cut into smaller lengths or
cubes for temporary storage. These subdivided
extrudates can then be extruded at a temperature of
about 150C so as to produce covers for the articles
or objects to be protected from fire or they can be
employed as an insulator~
Moreover, the flame or fire barrier
material ~f the present invention can easily be
extruded to form coatings for cables which are
exposed, or more importantly, for cables hidden in
walls.
~ ests made with the flame or fire barrier
material of the present invention, used as fire stop
material in cable penetrations, show that, for a
class A fire test, the ma~erial withstood fire for
180 minutes, at which point the test was stopped.
At this fire exposure, only approximately l inch of
a 6 inch penetration or fire stop was decomposed.
By comparison, known PVC materials under essentially
the same class A fire test conditions withstood fire
for only about 60 minutes at which point the PVC
material completely decomposed and produced
dangerous chlorine gas.
The flame or fire barrier material of the
present invention can al~o be prepared ~y mixing
together the components thereof, essentially in
powder form to produce a loose admixture~ The
resulting dry mixture can then be extruded through a
double screw extruder at a temperature of approxi-
3~ mately 130~C. The resulting extrudate is partially
~Z~6(~(~
11
cooled and fed through a perforated plate to bechopped into granular form at the exit of the
plate. The granules can be stored temporarily at
: room temperature. Thereafter the granules c~n be
used as insulation m~ans or processecl into pipe or
conduit form through an extruder with gradual
heatin~ up to approximately 150C.
The extruded conduit can be provided with a
reinforcing means such as metal braicling or a
coating, and optionally an outer protective cover,
made of, for instance, a plastic material.
A conduit made of the flame or fire barrier
material reinforced i~ this manner is especially
useful as a flame-resistant shell for electric
cables.
The reinforced conduit described above,
forms, when exposed to fire conditions, a strong
intumes~ent layer having good thermal insulation
properties and high thermal stability. The
intumescent layer contributes to an effective
thermal and mechanical insulation of the cables
housPd therein. The intumescent layer is supported
by the reinforcing coating.
As an example of a flame or fire barrier
material of the present invention, produced
especially in the form of a conduit for protecting
electric cables, the following components were mixed
together at a temperature of about 30C, the
components being essentially in powder form: 80
parts by weight of ethylene-ethyl acrylate
copolymer, 30 parts by weight of a synthetic rubber
such as EPDM rubber, 10 parts by weight of polyi50-
butylene, 10 parts by weight of paraffin wax, 11
part~ ~y weiqht of calcium oxide, 1 part by w~ight
of carbon black, 150 parts by weight of aluminum
; ~ 5
~,~
6~
12
hydroxide and lS0 parts by weight calcium
carbonate. The resulting dry mixture is then fed
through a double screw extruder at a temperature of
- 130C, and the extrudate~ in partially coole~
condition, is then fed through a perforated plate
and chopped into granular form at the exit from the
plate.
The resulting granules can be stored, if
necessary, at normal room temperature for later use,
or they can be led directly to an extruder with
gradual heating to approximately 150C for extruding
into pipe or conduit form.
The extruded conduit is provided with an
outer reinforcement after which, the reinforced
conduit is covered with an outer protective coating
of, for example, polyvinylchloride, if desired.
The polymeric matrix material, i.e.
ethylene-ethyl acrylate copolymer and the synthetic
rubber form the elasticizer components of the
resulting conduit, and the relative amounts of these
two components can be balanced depending on the
degree of elasticity desired relative to the amount
of filler material which i5 to be absorbed in the
polymeric mixture. Polyisobutylene is added as an
aid in the process of mixing the filler material in
the polymeric mixture, and paraffin wax is added as
a lubricating agent to give the mixture sufficient
pliability during the manufacturing process.
Calcium oxide, which absorbs moisture in
the mixture is added in suitable quantities as a
drying agent to reduce the danger of pore effects
when the polymeric materials and the various
additives are mixed. The calcium oxide also
contributes to a more homogeneous mass.
~z~
Carbon black is employed as a coloring
agent. It also imparts to the mixture a certain
degree of protection against oxidation.
The aluminum hydroxide and calcium
carbonate, when the material of the invention is
exposed to combustion conditions, produce a porous
material which does not burn, and the mutual
relationship between the additives ~ives the correct
consistency to the foam which occurs on combustion.
This foam later is transformed to a strong
intumescent organic and inorganic layer having good
thermal insulation properties and high thermal
stability.
The pipe or conduit shaped protective
article of the present invention provides good
mechanical protection under normal conditions of use
and does not produce halogen gases or appreciable
smoke upon combustion. Apart from the or~anic
materials, the protective conduit of the present
invention does not burn easily and at high
temperatures it forms a thermally stable, ceramic-
like foam, organic and inorqanic intumescent layer
which has good thermal insulating properties, and
which is held in place with the aid of reinforcement
means such as a braiding of metal or other conven-
tional material.
Under combustion conditions the chemical
reaction produces water which as noted earlier has a
delayed heat increase or heat rise. The material of
~o the present i~vention also has a low heat of
combustion, approximately 10 MJ/kg. The protective
conduit of this invention can be made using standard
equipment, and is relatively inexpensive due to
easily available raw materials.
14
Typical of the materials of the present
invention are those having the following
characteristics:
Tensile strength, (MPa) 10.3 6.9
Elongation of break, (%~ 7 23
Censity, virgi~ material,
(kg/m ) 1840 1640
Density, charre3d material,
(kg/m ) 490 330
__ Giow loss/1000C/hr,
(wt ~) 50 56
Smoke density generation,
Arapahoe, (wt %) 0.5 0.5
Oxygen index, (% 2) 37
Combustion energy
(MJ/kg) 9 12
Energy consumption,
200-300C, (MJ/kg) ~ 0.430.38
Thermal conducCivity
virgin material - 20C (W/mK) 0.69
char material - 20C (~/mK) 0.07
char material - 20-1000 (W/mK) 0.06 D.06
Thermal resistivity
virgin sheet - 9.2 mm (2R/W) 0.0133
charred sheet - 9.2 mm (2K/W) 0.244
Volume expansion at 200-300C
(Volume %) 100 200
Rlectrical volume resistance
(ohm-cm) 2.7-l.D"2.7-10"
Halogen content (wt ~) 0 0
Water resistance ExcellentExcellent
O;l resistance Good Good
Weight content of fillers,
(wt %)
The material of the present invention has
also been subjected to fire tests. Typical of such
tests are the following.
A 6 foot long; 5 foot wide and 4 foot high
brick cabinet or furnace was constructed. Draft
slots are provided at the bottom of t:he cabinet.
~he heat source is a huge propane burner located at
the bottom and in the center of the cabinet. Also
centered within the cabinet is a steel cable mounted
horizontally.
The test samples are placed on the ladder
running through the cabinet in 6 foot lengths. The
cabinet, or furnace, is pre-heated to expel any
moisture in the bricks and cabinet itself in order
to prevent artificial cooling by the moisture.
The cabinet is then cooled for a time just
sufficient to place therein the sample cables
protected with the heat barrier material of the
present invention and to connect the 110 volt power
lines and thermocouples.
During the test, the thermocouples measure
the flame/fire temperatures at four selected loca-
tions in the fire so as to provide continuous
temperature readouts. The average temperature
within the cabinet is maintained at or about 2000F
by adjusting the amount of injected propane fuel
into the cabinet.
The temperature within the cabinet reaches
this 2000F level within about 2-4 minutes from the
time of fuel ignition and actual start of the test
timing. The test monitors temperature (with
recordin~), circuit integrity of each individual
conductor powered by ll~v, time elapsed from
ignition and fuel injection. The test terminate~
when one or more circuits short and ~he timer is
~2Z~6~
16
automatically stopped. Time elapsed with full
circuit integrity represents the critical
performance. --
- The test was carried out twice at ambient
temperature of 90F, 50-60~ relative humidity with a
variable wind velocity of less than lS mph.
The test sample cable was a 3 conductor
(0.5 cm2) 12 AWG Flex-Flame BU cable loosely
enclosed by a tubing made from the material of the
present invention.
The first test lasted 18 l/2 minutes while
the second test lasted 20 l/3 minutes. The results
were impressively consistent and passed the pre-
selected 15 minute circuit integrity time require-
ment.
Cables of large sizes, such as 3 x 16 mm2,~imilarly protected with the material of the present
invention were also tested in essentially the same
fashion. Equally favorable results were achieved as
indicated by a circuit integrity time of more than
16 minutes.
In a somewhat similar second fire test a
cabinet or furnace measuring Sm long, 4m wide and lm
high was constructed. A fuel pit was provided
underneath the cabinet as were air inlets in the
lower part of the cabinet walls.
The cable samples provided with thç protec-
tive material of the present invention were wrapped
to steel beams and laid on top of the cabinet, the
steel beams bein~ supported at the mid portion
thereof to prevent saq.
At the beginning of the test the fuel
employed was a mixture of diesel fuel and gasoline.
Thereafter only pure diesel fuel was employed. The
temperature within the cabinet rose to 1800F one
17
minute after ignition and reached a temperature of
2000F five minutes after ignition.
The cable samples tested were 2 x 2.5 mm2
BU cables protected within a tubing made of the
material of the present invention. The BU cable
consisted of tinned seven strand copper wrapped with
mica tape, insulated with EPDM and jacketed with a
halogen-free Vamac base elastomer.
The samples tested provided circuit
integrity times of 14.23, 14.41, 16.58 and 16.58
minutes which times were significantly greater than
times achieved using mineral insulated cables and
the like, which times ranged from 6-2 to 81 minutes.
The material of the present invention has
also successfully passed the IEEE 645-1978 test
~IEEE Standard Cable Penetration Fire Stop
Qualification Test). This test showed that the
material of the present invention swelled, sintered
and formed complete fire and smoke tight penetration
and which functioned for burn times longer than 180
minutes.
Because of convincing fire barrier
properties of the material of the present invention,
this material is usefully employed as a fire
insulating material for steel constructions.
Steel tubes were insulated with known fire
insulating materials including mineral fiber mats,
ceramic fiber mats, gypsum, magnesium-oxychloride
cement, mica-Portland cement, intumescent cladding
and intumescent paint.
Similarly steel tubes and an H-beam were
insulated with the material of the present inven-
tion.
The thus insulated steel tubes and H-beams
were exposed to ISO and hydrocarbon fire time-
,
18
temperatures ranging up to 1100C and up to 180minutes.
~ he results showed that the material of the
present invention at thickness of 2.5 and 9 mm,
formed crack-free and excellent thermal insulating
sintered char which maintained its mechanical
strength and did not degrade even after 2 hours of
testing. However, others of the materials tested
showed cracking and melting. The steel beam
insulated with the material passed the H-60 test.
As indicated above, the flame barrier
materials of the present invention, when used as
insulation materials are of great importance for the
protection of electric cable from fire.
The following study has been carried out so
as to characterize changes in the structure of flame
barrier materials of the present invention under
different conditions of temperature.
Three samples were studied: (1) Product P,
defined above; (2) Product C, also defined above;
and (3) Product A, a material in accordance with the
present invention, but based on another copolymer
within the same family. Product A, like Products P
and C, is a highly filled polymer based composite
2S whose main components are an ethylene copolymer,
calcium carbonate, CaCO3, and aluminum hydroxide,
Al(~)3~
In a first phase of this study, thermo-
gravimetric experiments, TG, and differential
thermal analysis, DTA, were carried out with a
Mettler automatic recording thermo-analyser.
For DTA measurements, A1~03 calcinated at
1300C was applied as a reference material. The
incoming gas, nitrogen or oxygen, was adiusted to a
flow rate of five litres per hour. The gas was
~2~6~
19
dried by passing through silicagel columns before
introduction into the furnace.
From a sample sheet material of 3 mm
thickness, discs of 3 mm diameter were cut out and
weighed.: Two discs weighing about 60 mg were placed
into a platinum crucible on the one side of the PtRh
10% - Pt thermocouple. The other crucible of the
thermocouple was filled with the A12O3 reference
material. The automatically controlled heating rate
was 25C per minuteO Simultaneous TG/DTA and
temperature curves werP recorded with a chart speed
of 12 inches per hour.
The gases evolved during thermal analysis
were sampled discontinuously and analyzed by mass
spectrometry. Glass sampling bul~s (250 ml) were
used and fitted with Teflon stopcocks and cylindri-
cal septa (Supelco Inc. Bellefonte, PA) for the
collection of evolved gases. These bulbs, with
opened stopcocks, were connected during the
temperature changes indicated in Table 1 below to
the gas outlet of the Mettler DTA apparatus and the
evolved gases, diluted in nitrogen or oxygen
streamed through the bulb at a flowrate of
5 l/hour. As soon as the upper temperature of the
indicated temperature range was reached, the
stopcocks were closed and the bulb was disconnected
~rom the DTA apparatus. 5.~ ml of the gas sample
were withdrawn from the bulb through the septum with
a 5 ml Precision 5ampling Syringe fitted with a
Mininert valve ~Kontron AG, Zurich) and introduced
into the pre-evacuated heated reser~oir of the mass
spectrometer. By opening a MV38 valve tA.E.I.
Scientific Ltd, Harlow, ~ssex) a continuous gas flow
was maintained from the reservoir into ~he source of
the mass spectrometer and the spectra were recorded
immediately.
A double-focusing A.E.I. MS:30 mass
- spectrometer with electron-impact ionization was
used. The source temperature was 150C. The source
pressure varied from 3.10 6 to 1.10-5 torr. The
electron energy was 70 eV and the accelerating
voltage was 4kV. The spectra were recorded on a
Bryans Southern Series 10-4306 Ultraviolet
Oscillograph, using 30 sec/decade scan speed.
From each mass spectrum, obtained with
different collector sensitivities, the corresponding
background spectrum was subtracted.
, . . .
Q~
TABLE 1
Summary of ~vol~ed Gas A~alysis By Mass Sp~ctrometry
_
~e~ed : Te~perature
Mate~ialAt~ospher~ raDge (C) ~ases f~und
_
N2 240-450 H2O
440-550 C4H8.C5Hlo
725-950 C2
Product C
2 200-400 CO, H2O
500-700 C2
725-1000 C2
N2 200-400 CH4, CO
400-600 CH4, C2H6, CO~
750-950 C0, much C02
Product P
2 200-460 H20, C0, C02, C3H8
500-700 H20, CO, C02
725-1000 H20, CO, C2
N2 240-450 C2H6
450-550 unsaturated ali~
phatic hydro-
carbons CnH2n~2*
725-950 C2
Product A _ _ _ _
as 2 240-450 H20, C02:
730-950 H20, C02
.
* during the DTA analysis waxy material condensed on the
outlet tube of the furnsceo the ~ass spectrum of this
material shGwed that it is like polyethylene.
":: white smoke appeared in the gas collection bulb~
22
Thermal stability tests of Products P, C
and A were carried ~ut using the system schematical-
ly represented in Figure 1. Each thlermal treatment
is carried out simultaneously on the three samples
(Product P, Product C and Product A) in order t~
give a better comparison.
Each sample was supported by a stainless
steel plate ~6 x Ç x 1 mm). After treatment, the
samples were cooled down to room temperature.
The thermal stability tests were carried
out as follows:
(1) ~ast Heating Rate in Nitrogen - the
three samples were introduced directly in the hot
section of the furnace;
(2) Fast Heating Rate in Air - same
conditions; and
(3) Slow Heating Rate in Nitrogen - the
three samples were introduced into the central
section of the furnace at room temperature and the
heating then started.
For each test the heating rate is reported
as C/sec for the fast heating rate and as ~C/60 sec
for the slow heating rate. The increase of the
temperature was measured using a ohromel/alumel
thermocouple set below the sample support. It is
important to note that the heating is carried out
mainly by radiation. This means that the tempera-
ture of the surface of the sample can be higher than
the temperature of the sample itself. For each
sample the weight deorease was measured.
The results of the above tests are
discussed below.
The thermogra~s of samples under dynamic
nitrogen atmosphere are shown in Figure Z. A
decomposition in three steps can be observed. The
,
2~
first sta~ted at about 245C (290C for Product A)
and was accompanied by an intense endothermic
effect. This step is att~ibuted to the decomposi-
tion of Al(OH)3 and loss of water.
The sec~nd, which ~egins at 415C, is
accompanied by a small endothermic effect. This
step ended at 560C. The wei~ht loss of this is
caused by the volatilization of polyethylene. The
vapors were transported with the nitrogen flow and
condensed in the ~as outlet tubing. The condensed
material was identified by IR and mass spectrometry
as low molecular weight polyethylene.
The last step began at 730C and ended at
945-955C. It was also accompanied with an endo-
thermic effect. The weight loss of this step is
attributed to decomposition of CaCO3 with elimin~-
tion of C2
The thermograms of samples obtained under
dynamic oxygen atmosphere are shown in ~igure 3.
Under these conditions only two steps of
weight loss were observed.
The first one started at about 230C and
ended at 380C (440C for Product A). This weight
loss under oxygen atmosphere corresponds to the sum
~5 of steps 1 and 2 under nitrogen atmosphere and are
attributed to the decomposition of Al(OH33 and
burning of polyethylene, in the same time.
The second step began at 730C and was
accompanied with an endothermic effect. This is
similar to the step 3 obtained under nitrogen
atmosphere. It is caused by the decomposition of
CaC03 ~
The summary of the TG measurements are
presented in Table 2, below.
~2~6~
TABL~ 2
Chara~teri~tics of Th~rmal Degradation of Sa~pl~s
. _ .
: Tempera~ure Loss of
Product Atmosphere range (C) weight (Z)
.
N2 245-415 13.3
415-560 22.1
Product P 730-95S 15.8
2 230-380 35.9
730-995 15~8
__
N2245-415 12.7
415-560 27.2
730-945 15 3
Product C
2 230-380 39,9
730-970 15.3
~2290-415 20.6
41S-560 22.2
7 0-930 15.2
Product A
v _ _
2 230-440 41.5
730-930 15.1
The DTA thermograms obtained under dynamic
nitrogen atmosphere are given in Figure 4. .
The explanation of the most important
thermal effects are the following.
A mild endothermal effect observed at about
100C is caused probably by a second-order transi-
tion of the plastic material. This one is followed
by another more pronounced endothermal peak at
.....
~`
approximately 352C. It is attributed to decomposi-
tion of Al(OH)3 and loss of water.
At 415-455C only the Product P and C
samples gave an endothermal peak, caused probably by
a melting transition of the polyethylene.
All samples showed a little endotherm at
450-500C results from the vaporization of poly-
ethylene.
The endothermal effects between 730C-940C
are indicative of CO2 formation by the decomposition
of CaCO3.
The DTA thermograms obtained in dynamic
oxygen atmosphere (Figure 5) showed the same
profiles as in nitrogen with the exception of the
step at 250~-400C. At this temperature two
phenomena occurred simultaneously: the endothermal
dehydration of Al(OH~3 and the burning of plastic
material with a very intense exothermal effect which
perturbed the linearity of the heating.
The thermal effects developed during the
DTA is shown in Table 3, below.
~2~
26
TABLE 3
Characteristic~ of DTA of Samples
~ Tempera-
Product : At~- ture range TherEal
phere (C) Ef f er t Pheno~ena
_
~2 75-120 endo Glass transition of PE
245-415 endo Al(OH)3 decomposition
420-480 endo Polyethylene (PE)
melting
480-580 endo PE vsporization
740-940 endo CaC03 decomposi~ion
Product P _ _ _ _
2 80-130 endo Glass transition of PE
230-390 endo Al(OH)3 decomposition
330-360 exo-' PE burning
730 940 endo CaC03 decomposition
-
N2 75-120 endo Glass transition oÇ PE
245-390 endo Al(OH)3 decomposition
390-4~0 endo PE melting
440-580 endo PE vaporization
740~940 endo CaC03 decomposition
Product C
2 80-130 endo Glass transition of PE
230-320 exo PE crystallization
300-390 endo Al(OH)3 decomposition
330-370 exo~- PE burning
735-945 endo CaCO3 decomposition
N2 90-}20 endo Glass transition of PE
290-415 endo Al(OH)3 decomposition
450-550 endo PE vaporization
730-910 endo CaC03 decomposition
Product A _ _
2 90-110 endo Glass transition of PE
250-320 exo PE crystallization
280-440 endo Al(0~)3 decomposition
350-415 exo* burning
730-885 endo CaCO3 decomposition
* this exotherm effect occurred during the endotherm effect of
Al(OH)3 decomposition.
~2~
27
Table 1, abovei summarizes the results
obtained in the qualitative analysis of the evolved
~ases.
At 700DC, CaCO3 is the unique crys.alline
phase for the Product P and the main phase for the
Products C and A. Few additional difraction lines
have been observed in the Products C and A with a
very small peak intensity. These unidentified
diffraction lines were the following:
Product C 2.40 ~ 2.04 A 1.70
Product A 2.89 ~ - 2.04 ~ -
~ t this temperature the thermal decomposi-
tion of A12O3 . 3 H2O with the formation of
y-alumina (AlOOH) and A12O3 can be expected. As no
line has been observed on the diffraction diagram,
the aluminium based inorganic phases are probably
amorphous.
At 1200C with a fast heating rate in air,
the phases which are observed are the following:
20 Product P CaCO3 main phase
CaO. A123
3 CaO, A12O3
Product C CaCO3 main phase
CaO, A123
3 CaO, A12O~
Product A CaCO3 main phase
- 3 CaO, A12O3
12 CaO, 7 A12O3
This means that due to the high heating
rate ~he thermal decomposition of CaCO3 is not
9L22~
28
completed. This results from the low heat transfer
into the material.
At 1100C with a slow heating rate and 12
hours annealing the following phases have been
5 observedO
Product P 12 CaO, 7 A12O3 main phase
CaO, A12U~
Product C 1~ CaO, 7 A12O3 main phase
CaO, A12O3
10 Product A CaO, A12O3 main phase
12 CaO, 7 A12O3
AlOOH traces
CaCO3 traces
The three samples differ clearly from the
point of view of their morphology. A laminar
structure is observed for Products P and C while a
more isotropic structur is observed for Product Ao
The non-laminar structure of Product A is related to
the fact that such a product is expected to be
shaped by direct casting of a homogeneous mixture.
The laminar structure of Products P and C is such
that lateral exudation of the organic phase is
observed below 400C. Products P and C are superior
regarding intumescence.
At elevated temperature ~> 800C) the three
products differ by the nature of the mineral phase.
A12O3, resulting from the decomposition of A12O3 .
3 H~O reacts wi~h the CaO resulting from the thermal
dec~mposition of CaCO3.
The rate of mineralization (formation of
CaO-A12O3 compounds) is higher for the Products P
29
and C than for the Product A. Such differences can
result either from the characteristics of the raw
materials and more precisely from their refractor-
icity and particle size.
