Note: Descriptions are shown in the official language in which they were submitted.
67~7
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THIS INVENTION relates to an incendiary composition.
In particular the invention relates to an incendiary
composition; a method of making the composition; to
products including the composition such as igniter
cord, an igniter cord connector and an electric
fuse head.
According to the invention an incendiary composition
comprises
an oxidizing agent,
a reducing agent, and
a water miscible binder,
the binder forming the continuous phase of the composition
in which the oxidizing agent and reducing agent are
dispersed.
`' '
Naturally, if desired, the composition according
to the invention can include more than one oxidizing
agent, more than one reducing agent and the water
miscible binder may also comprise a mixture of materials.
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~4G757
The composition may be malleable, so that products
made therefrom such as igniter cord can be flexible,
i.e. capable of belng bent or shaped without cracking
or breaking.
The composition may be waterproof, in that it is
capable of burning af-ter having been wet, for example
by being sprayed with water or immersed in water.
Preferably, the composition is capable of burning
under water.
The composition may be one in which, after dispersion
of the oxidizing agent and reducing agent in the
binder, the binder has been cross-linked. This cross-
linking may be achieved by any suitable method, such
as the use of a suitable catalyst or a two component
system, or by subjecting the composition to suitable
irradiation, but cross-linking by heat is preferred~
''
The binder may be selected from the group
consisting in acrylics, latices, and polyvinyl
acetates. The applicant also believes that there may be
~` starches plasticized with polyols, or polybutadienes which
can act as suitable blnders ac~ording to the invention.
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f~",L~ 757
The oxidizing agent may be selected from the group
consisting in potassium perchlorate, lead
dioxide, red lead, potassium nitrate, ammonium
perehlorate, sodium perchlorate, potassium permanganate
and sodium dichroma-te. The oxidizing agent may be
` sparingly soluble in water, such as potassium
perchlorate or substantially insoluble in water,
such as red lead, and is preferably, say, no more
than twice as soluble as potassium perchlorate at
ambient temperatures.
The reducing agen-t may be selected from the
group consisting in carbon, silicon, ferrosilicon,
aluminium, copper, zinc and tungsten, and is
preferably no more than sparingly soluble in water
at ambient temperatures.
.
Further according to the invention a method of
making the composition described above comprises mixing
: the components together in the presence of water
. followed by drying of the composition.
:,
The method may include modifying the viscosity of the
mixture by mixing the components together with a
viscosity modifier, such as a thickener or an
agent which reduces the viscosity of the mixture,
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57
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depending on what is convenient for the process of
manufacture, and on the proportions of the various
components, including water, in the mixture.
Mixing may be by means of a mechanical mixer. As
the presence of water renders the composition safe, the
mixing can be performed by almost any type of mixer,
such as edge-runner, concrete, planetary and ribbon
~ mixers, and the mixing can be effected for long periods
; of time. secause of this safety, the method may
include pumping the mixture, for example via a 15 mm
ring main and a Mono pump, from the location where it
is mixed to another location prior to drying. In this
way the paste or slurry produced can be distributed
after mixing to application points by a mechanical
distribution system rather than by a manual distribution
system.
As the composition is water based, it does not
require heating to render it fluid for mixing or handling.
The method may thus involve maintaining the components
at ambient temperature prior to drying.
; After the mixing, the binder may be cross-linked.
; As mentioned above, the cross-linking may be effected
by the use of a catalyst or a two component system, or
the composition may be subjected to suitable irradiation
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or the cross-linking may be affected by heating. This
cross-linking acts to enhance the waterproof qualities
of the composition, as the contlnuous phase constituted
by the cross-linked binder at least partially encap-
sulates or encloses the particles of reducing agent and
oxidizing agent dispersed in the binder.
The drying is thus conveniently effected by heating,
so that the heating of the drying acts also to cross-
link the binder. In ordex to speed up the drying
and/or reduce the temperature of the drying, the composition
may be subjected to a vacuum during the- drying.
The method may include mixing the components
together with a surfactant, such as a wetting agent, to
enhance the wettin~ of insoluble components in the
mixture, to facilitate preparation of the mixture.
The composition of the invention can be put to a
number of uses, such as the manufacture of igniter
cord, igniter cord connectors, delay elements, flares,
fuse heads, or the like.
The invention thus provides an igniter cord which
cornprises a core having a composition according to the
invention as described above, applied thereto.
757
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The core may be a metal wire, or the core may be
made up of a plurality of yarns or strands, such as
textile yarns and/or metal strands.
The core may be enclosed by a flexible extruded
incendiary sleeve. The incendiary sleeve may be of a
flexible incendiary composition as described above. At
least part of the core, under the sleeve may be treated
with an incendiary material, and the incendiary material
may be an incendiary composition, preferably flexible,
as described above. Thus a composition according to
the invention as described above may be used for the
sleeve and/or for treating the core under the sleeve,
the treating of the core with the composition under the
sleeve being of particular application when the core is
made up of a plurality of yarns or strands.
The igniter cord may have an extruded plastics
outer coating, in which case the cross-sectional
profile of the cord may be of angular outline. Having
the cross-sectional profile of the cord of angular
outline, such as square outline, is believed to enhance
the formation of air spaces between the coa~ing and the
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~675~7
cord, thereby permitting forward venting of hot gases
during burning and thus increasing the burning speed
of the igni-ter cord.
It will be appreciated that an important aspect of
the process of making -the incendiary composition according
to the invention is that the mixing can take place in
the presence of water. The drying of the composition
can be natural in -that the composition is merely left
until it dries by itself, or it can be forced in that
it is subjected to heating and/or a vacuum, etc, to
cause rapid drying. Thus the mixture, prior to drying,
is incapable of being ignited with a match, but will be
capable of such ignition after drying. The choice of
suitable components and the proportions used in the
mixture enable a slurry or paste to be formed which can
be pumped, or formed into any suitable shape rior to
drying, and can provide an incendiary composition which
after drying can be flexible and can be capable of
burning under water. Provided sufficient water is
always present at the stage when the oxidizing agents
are brought together with the reducing agents or fuels,
for example by always adding water to the mixer first,
the order of addition of the components during mixing
canno-t affect the non-incendivity of the paste. Furthermore,
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mixing times and rates of mixing or rates of addition
can be adjusted to any desired value in order to optimize
production rates.
In the making of igniter cords, any suitable
means can be used to apply the paste or slurry at the
application point to the metal wire or the yarns or
strands which make up the core of the igniter cord.
Suitable means of application can be, for example,
kettle application, extrusion by conventional worm
extruders, Mono pump feeding or auger feeding, the
iqniter cord which results preferably being flexible
and waterproof r and being capable o burning under
water as described above.
Although simple extrusion of the composition
according to the invention onto cores made of metallic
wire such as a single copper wire, or onto composite
cores made up of yarn threads or metallic strands, may
be suitable to provide igniter cord o~ relatively slow
burning rates such as about 30 - 45 seconds a metre,
such extrusion can be unsuitable for providing igniter
cords having a burning rate faster than about 16
seconds a metre. The reason for this i~s that the burning
rate is increased by reducing the quantity~of water
miscible binder present in the composition, and the
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10- -
excessive reduction of this binder can lead to an
unacceptable loss of flexibility in the igniter cord
product.
To make a fast burning igniter cord, typically
having a burning rate of 8 - 16 seconds a metre or as
fast as one second a me-tre, a composite core made up of
spun yarn or threads of metallic and/or non-metallic
nature can be used. This core is first drawn through a
kettle or bath containing a slurry-like incendiary
composition to form what is called a semi-cord. This
semi-cord is then coated by means oE extrusion with a
plastic incendiary sleeve. This process has the advantage
that longitudinally extending air spaces created
between the semi-cord and its extruded flexible incendiary
sleeve permit forward venting of hot gases produced
during combustion which increases the burning rate of
the cord over that of cords which do not have the air
spaces and which rely on simple forward heat conduction
to determine the burning rate. The slurry-like incendiary
composition in the kettle or bath and the incendiary
sleeve are preferably both of compositions including a
water miscible binder according to the invention as
described above. However, as mentione'd above either
the slurry-like incendiary composition or the incendiary
sleeve may be of conventional incendiary compositions which
do not include a water miscible binder.
,7
The invention also provides an igniter cord connector
comprising a metal tube having a plug of an incendiary
composition according to the invention as described
above, the plug being recessed from an open end of the
tube.
Both ends of the tube may be open, the plu~ extending
to the end of the tube opposite the end from which it
is recessed. Instead, the connector may be of a
construction in which the end of the tube opposite the
open end is closed, the side of the tube at the closed
end having a transverse slot therein for receiving an
igniter cord, the slot extending through the plug. In
each case the open end of the tube from which the plug
is recessed is intended for crimping or other suitable
connection to a safety fuse, and the ign1ter cord can
thus be provided with such safety fuse inserted into
and connected to the end of the tube from which the
plug is recessed, and "open end of the tube" is to be
construed accordingly as covering the situation where
it is in fact closed , bu-t closed with a safety fuse
inserted into it.
The exposed part of the plug remo~te fro~ the
recessed end ie the opposite end of the tube when both
ends of the tube are open or the part of the plug
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- 12 -
exposed by the slot when -the tube has a slot, is intended for
being initiated by an igniter cord, and this exposed part may
be sealed against water penetration, conveniently by a suitable
sealant, and depending on the nature of the water miscible binder
used for the incendiary composition according to the invention,
this binder may be suitable for use as the sealant.
The invention also provides an electric fuse head
comprising a fuse head skeleton enclosed by a composition
according to Claim 1.
In the drawings;
Figure 1 shows in graphical form the variation of burning
speed in proportion to the level of binder in cords;
Figure 2 shows a connector composition being placed into
a mould;
Figure 3 shows a connector and ignitercord combination;
and
Figure 4 shows mould filling with a syringe injector
system.
The invention will now be described with reference to
the following illustrative and non-limiting Examples.
EXAMPLE 1
A paste composition in accordance with the invention
was made by thoroughly mixing together, on a weight basis, 14.5%
water, 8.6% of a water miscible acrylic binder available as A272
from Revertex S.A. (Proprietary) Limited, Durban, 16.1% potassium
perchlorate, 38.7% red lead, 21.9% ferrosilicon and 0.2% of a
10% weight a~ueous carboxymethyl cellulose solution. The potassium
perchlorate and red lead were the oxidizing agents -
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757
while the ferrosilicon and carboxymethyl cellulose
respectively formed the reducing agent and a thickener.
This composition beEore drying was Eound to be incapable
of ignition with a match, and it was arranged in the
mixing that the oxidizing and reducing agents were
brought into contact in the presence of the water, so
that no stage was an incendiary material produced prior
to drying.
EXAMPLE 2
The composition according to Example 1, prior to
drying, was extruded as a water-based paste onto a
copper wire using an auger feeder, to provide an incendiary
sleeve around the copper wire, and the paste was dried
at a sufficient temperature to cause cross-linking of
the acrylic binder. The product was then finished by
extruding a plastics (polyethylene) outer coating around
the sleeve to provide a flexible incendiary igniter
cord capable of burning under water which burnt at a
rate of 24,5 seconds a metre in air. The use of a
water-based paste permitted thorough mixing leading to
enhanced reproducibility of the igniter cord burning
speed. Ten one metre lengths of the igniter cord burnt
at an average value of 24,5 seconds a me-tre with a
7S7
standard deviation of 0,97 seconds a metre, whereas
igniter cord of comparable speed made by conventional
methods burnt at 23,9 seconds a metre with a standard
deviation of 1,99 seconds a metre.
It was found that the burning speed of the igniter
cord produced according to Examples 1 and 2 can be
altered easily by a number of methods, for example by
changing the proportion of binder in the composition
produced according to Example 1, or by changing the
shape of the extrusion die. When the incendiary sleeve
was extruded with a square die, the cord was found to
burn more quickly than with a round die, and without
being bound by theory it is believed by the applicant
that the use of a square die having an angular cross-
sectional profile leads to the formation of air spaces
between the ethylene outer coat and the sleeve, leading
to forward venting of hot gases during burning and
enhance the speed.
The process of Example 1 was repeated with variations
in the proportion of binder, and varia~ion of burning
speed in air with variation in the proportion of binder
for round cords is shown in Figure 1.
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757
-15-
It was found -that paste rheology could be altered
to suite the method oE applica-tion. For example, a
runny paste of approximate viscosity of 1000 poise
suitable ~or kettle application could be produced,
whereas a thick paste having a viscosity of about 5000
poise could be produced for auger feeding. The viscosity
was altered by changing the amount of water in the
composition and/or by the incorporation of suitable
viscosity modifiers. Thus in Example 1 14j5% water was
employed to ensure non-incendivity of the wet paste,
but as a thick paste was required for auger feeding
0,2% of the 10% carboxymethyl cellulose solution was
added as a thickener.
EXAMPLE 3
An incendiary composition in the form of a runny
paste in accordance with the invention was made having
a composition of 150 parts by weight of water, 40 parts
by weight of a polyvinyl acetate water miscible binder
available as MOWILITH*DC from Hoechst South Africa
(Proprietary) Limited, Industria, 75 parts by weight of
potassium perchlorate, 175 parts by weight of red lead
and 100 parts by weight ferrosilicon. This incendiary
paste was runny and was suitable for coating a core
comprising cotton cord, by drawing the core through an
application kettle.
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The proportion of water was then reduced to 70
parts by weight (the proportions of the other components
being unaltered) and 2 parts by weight of a viscosity
modifier (reducer) comprising ammonium polybutylacrylate
available as POLYSALZ*S from BASF South Africa (Proprietary)
Limited, Johannesburg, was incorporated, to obtain a
runny paste of substantially the same viscosity capable
of application to a cotton cord by drawing through an
application kettle in the same fashion.
In each case a round igniter cord was produced,
which was not provided with an extruded sleeve and was
not coated with a plastics coating, and which was found
to burn at a speed of 37 seconds a metre.
EXAMPLE 4
Alternative formulations to the composition of
Example 1 were made and tested, in which the potassium
perchlorate and particularly the red lead were replaced
with other oxidizing agents such as lead dioxide,
-~ potassium nitrate, ammonium perchlorate, sodium perchlorate,
potassium permanganate and sodium dichromate. These
formulations were all found to provide suitable general
purpose incendiary compositions with the advantage
that, before drying, the enhanced safety provided by
the invention was present. However, as the oxidizing
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" 1~4~57
agents tested were all more soluble in water than red
lead, in the production of igniter cord they tended to
crystallize at the surface of the cord during drying,
having been brought to the surface by the evaporating
water. They thus suffered loss of flexibility and
waterprooEness, and were found to be somewhat inhomoge-
neous, although burning rates were unaffected. Red lead
on the other hand, is virtually insoluble in water, and
potassium perchlorate is only sparingly soluble in
water.
In these tests a surfactant was used as a wetting
agent, to facilitate the paste preparation, and to
enhance the wetting of the insoluble components of the
paste. In particular, the surfactant available as
TAMOL NNO from BASF South Africa (Proprietary) Limited,
~ohannesburg, compr~sing the sodium salts of the
condensation product of naphthalene sulfonic acid with
formaldehyde, was used. The TAMOL was used in a 1%
aqueous solution.
:
EXAMPLE 5
- An incendiary composition in the form of a slurry
in accordance with the invention was made up from 1340
parts by weight of a 1% by weight TAMOL solution, 150
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~6757
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parts by weight of A272 acrylic binder, 250 parts by
weight potassium perchlorate, 600 parts by weight red
lead and 340 parts by weight ferrosilicon together with
3,25 parts by weight of a 10% by weight carboxymethyl
cellulose solution. This slurry was applied by drawing
two parallel paper yarns -through a kettle containing
the slurry, followed by drying, followed by countering
(spinning) with one jute yarn and three rayon yarns, to
produce a semi-cord.
This semi-cord was then coated by means of extrusion
with a conventional plastic incendiary composition (not
according to the invention) comprising suitable proportions
of red lead and potassium perchlorate as oxidizing
agents, a suitable proportion of ferrosilicon as reducing
agent, and a suitable proportion of plasticized nitrocellulose
as a binder, followed by a polyethylene outer coating
or sheath. Burning of twenty five one metre lengths
produced a mean burning rate of 7,7 seconds a metre
with a standard deviation of 0,56 seconds a metre.
Use of the same slurry, but with three parallel
paper yarns having the slurry applied thereto and
countered (spun) with three rayon ya~ns followed by
coating with the nitrocellulose-containing plastic
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incendiary composition and the polythene sheath, yielded
an igniter cord which burnt at a rate of 2,3 seconds a
metre with a standard deviation of 0,~3 seconds a
metre.
The cords produced above and haying an extruded
sleeve of the nitrocellulose-containing plastic incendiary
composition did not burn under water. However, when
the extruded sleeve was replaced by a sleeve according
to the formulation of Example 1, an igniter cord was
obtained capable of burning under water. Likewise,
when the slurry applied in the kettle to the parallel
paper yarns was replaced by a conventional slurry-like
incendiary composition com~rising one or more suitable
oxidizing agents, one or more suitable reducing agents
and nitrocellulose dissolved or suspended in acetone
or a similar volatile solvent to form the semi-cord,
followed by extrusion of a sleeve of a composition
according to the invention of the formulation of
Example 1, and a polythene sheath, a flexible igniter
cord was obtained, which was once again waterproof, and
capable of burning at 6 seconds a metre in air, and 30
seconds a metre under water.
fast burning flexible igniter cord could thus be
obtained by extruding a sleeve of flexible incendiary
material according to the invention on semi-cord, the
i75~7
-20-
semi-cord being produced either from a sluxry in accordance
with the invention or a conventional slurry. A conventional
plastic incendiary composition sleeve can also be
extruded over a semi-cord made with slurry in accordance
with the invention, although this does not have the
advantage oE waterproofness. In each case, without
being bound by theory, the applicant believes that air
spaces, permitting forward venting of hot gases during
burning, are created between the semi-cord and the
sleeve. The igniter cords were of round cross-sectional
profile.
EXAMPLE 6
A paste formulation incendiary composition according
to the invention was made. 25,0% by weight MOWILITH DM772
water miscible binder (a copolymer dispersion of
acr~lic acid esters available from Hoechst South Africa
(Proprietary) Limited) was mixed together with 0,625%
by weight POI.YSALZ S, 15,625% potassium perchlorate,
37,5% red lead and 21,25% ferrosilicon. This paste was
spread with a blade across a board containing conventional
aluminium igniter cord connector tubes inserted in
holes therein, and e~tending downwardly'therefrom.
These tubes were filled to the required depth with plugs
of the composition.
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A diagrammatic drawing is shown in Figure 2,
generally designated 10. The board is designated 12,
the blade being shown by reference numeral 14 as part
of a knife 16. The blade ls shown being drawn in the
direction of arrow 18, to spread a mass 20 of the paste
on the upper surface 22 of the board into the tubes 24
in the openings in the board. The depth to which the
paste enters the tubes is determined by pedestals 26 and
the paste forms plugs 28 in the tubes. The upper
surfaces of the pedestals can be covered with a suitable
tape, such as polytetrafluoroethylene tape, to prevent
adhesion of the paste to the pedestals.
The tubes, as shown, were open at both ends, and
after withdrawing the tubes from the board the plugs
were dried and cross~linked by heating and the ends of
the tubes from which the plugs were recessed, were
crimped onto lengths of safety fuse by conventional
means. Twenty five connector capped fuses made in this
way were inserted into conventional plastic adaptors
used for such open ended igniter cord connectors, and
attached to a length of igniter cord. They all fired.
; Figure 3 shows a diagrammatic representation of
the connectors in use, the same reference numerals
being used unless otherwise specified. Reference numeral
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57
-22-
30 generally shows the arrangement, with the adaptor being
shown by reference numeral 32, the igniter cord
belng shown by reference numeral 3~, and the safety
~use shown by reEerence numeral 36 crimped as at 38
into the tube, the exposed end 28.1 of the plug in use
touching the igniter cord.
In an alternative possible construction the tubes
24 can have the end where the plug is located closed,
and a transverse slot through the side wall of the tube
and the plug at the closed end for receiving the
igniter cord. The closed end is shown at 24.1 and the
slot at 24.2 in Figure 3. With this construction the
adaptor 32 is not used and the igniter cord is merely
pressed into the slot into contact with the plug.
.
EXAMPLE 7
A composition according to the invention similar to
the paste of Example 6 was made Erom 25,0% by weight A272
acrylic binder, 0,625% POLYSALZ S, 15,625% potassium
perchlorate, 37,5% red lead and 21,25% ferrosilicon.
This paste was dosed into connector tubes raised on
pedestals covered with polytetrafluoroethylene tape.
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This arrangement is shown in Figure 4, by
reference numeral 40, and unless otherwise specified,
` like reference numerals refer to like parts. The
dosing can be effected by any convenient means, and
in practice a hypodermic syringe 42 was used.
; 1500 connectors made in this fashion showed no
failures in dry burning tests of the type described
in Example 6. Also 50 assemblies tested under water
and 50 tested under water spray all burnt. When more
severe tests were carried out in the assemblies, such
as burning after immersion in a water pot pressurised
to 30 psi for 10 minutes, it was found to be
necessary to seal the open end of the tube opposite
the crimped recessed end, by covering the plug with
a layer of the acrylic binder used in the incendiary
composition for 100% firing.
.~ .
Both in Example 6 and in the present Example
water was not added to the formulations, because the
acrylic binders used in each case contained about 15%
by weight wa-ter which amount was sufficient to render
the paste insensitive to match ignition, the other
components being added to the binders, and the
POLYSALZ S being used to control viscosity. With
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757
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these compositions a possiblity exists tha-t connectors
: could be produced merely by dipping the ends of the
safety fuses into the compositions, followed by
drying, i.e. omitti.ng the aluminium tubes. This
connec-tor would however have the disadvantages of ~ow
: mechanical strength and possible water pick-up by the
black powder core of the safety fuse..
EXAMPLE 8
A number of electric fuse heads were made by
dipping fuse head skeletons into the composition of
. Example 7. After drying, fuse heads with an acceptable
appearance were obtained, which were crimped into
detonator tubes. In use, all the fuse heads which
ignited initiated the detonators, but it was found
that a relatively high current (temperature) was
required for ignition, and at conventional current
strengths the tubes did not all ignite.
A futher paste in accordance with the invention
was thus formulated, comprising 24,4% by weight A272,
15,2% potassium perchlorate, 0,6% POLYSALZ S, 36,6%
red lead, 20,7% ferrosilicon and 2,5% pyropowder (comprising
89% by weight nitrocellulose, 7% dinitrotol~ene, and
4% dibutylphalate). In this case, fuse heads were
obtained which gave a 100% success rate at the
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~25-
lower conventional ignition -temperature. It was
found that incorporation of the pyropowder lowered
the ignition tempera-ture when measured on a
differential scanning calorimeter from 431C to
247C, when compared wi-th the formulation of Example
7, without making the water based pas-te sensitive to
ini-tiation with a match flame. When the pyropowder was
used, 100% success rate was obtained at the lower
ignition temperature which is conventionally used for
electric fuse heads wherein the incendiary compostions
are -typically lead mononitroresorcinate/ potassium
chlorate, charcoal/potassium chlorate, nitrocellulose/
diethyl ether, etc. On the other hand, when the pyropowder
was omitted, and the formulation according to Example
7 was used, there was in fact a 66% ignition, using
the same current strengths as are used for said
conventional formulations.
A principal advantage of the invention, when
compared with known flexible incendiary compositions
capable of burning under water, is that the fire
hazard is reduced. Such other flexible incendiary
compositions lcnown to the applicant use materials
such as nitrocellulose and plasticized organic
materials such as nitroglycerin or dibutylphthalate, as
their continuous flexible phase. Plas-ticized
57
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nitrocellulose is extremely hazardous to process, and
the equipment used for the manufacture of the incendiary
composition has either to be extremely well protected
against accidental ignition or well dispersed so that
-the effects of ignition are minimized. Also, because
plasticized nitrocellulose does not flow readily at
ambient temperatures, it often has to be heated in
order to be cast in the required shape. The hazardous
nature of the materials determines that mixing times
are kept to a minimum, resulting in large variations in
the burning speed of the incendiary composition arising
from ina~equate mixing in the manufacture. The present
invention on the other hand, as it is water based and
non-incendive, is inherently less hazardous, does not
require to be heated in order to be cast in the required
shape, and any desired mixing time can be employed to
reduce variations in burning speed.
These advantages are particularly useful, in
making waterproof igniter cord which is fast burning in
air, and which can burn under water if necessary. In
this case, previous semi~cords known to the applicant
were made from a slurry incendiary composition typically
~ comprising a mixture of one or more oxidizing agents,
one or more.reducing agents, and nitrocellulose dissolved ~.
or suspended in acetone or a similar volatile solvent.
~fl~;'7~7
-27-
t This incendiary slurry used in the kettle or bath is
~ extremely sensitive to impact and friction, and after
.
coating the semi-cord, it must be heated to dry off the
solvent. ~-t this stage the previous processes are
particularly dangerous. Use of the slurry composition
in accordance with the present invention avoids or at
least substantially reduces these dangers. The components
of the compositions according to the present invention
can now be mixed together in great safety, provided
that water is always present and at no time un-til the
final drying and processing of the product is a potentially
dangerous product present. This enables the process to
be carried out in a much simpler and more compact
fashion, and permits large batches to be mixed for an
extensive period, thereby reducing batch to batch
variation and variations in burning speed in a single
batch.
~ lso when applied to igniter cord connectors, the
applicant is aware that previously the connectors were
made of aluminium tubes which were open at both ends or
closed at one end and having a slot as described above,
and that prior art incendiary products were pressed
into these tubes under pressure. When a tube closed at
one end was used, the slot was cut to provide a contact
area on the incendiary plug for initiation by an igniter
-
.
-28-
cord. Typically, 100 mg of an incendiary connector base
composition was gravity fed into an open ended aluminium
tub`e and pressed at about 1200 lb. force, followed by
80 mg of black powder pressed in as a pill at the same
pressure. The connector base composition was a
homogeneous mixture of pyro powder, lead peroxide,
antimony sulphide and silicon powder. These connectors
were crimped, as described above, onto lengths of
safety fuse, for transferring the flame from igniter
cord to black powder cored safety fuses. Despite the
high pressure used during filling, water was still
found to penetrate the previous connectors and to
cause the black powder pill to fail. The connectors
according to the present inventi.on, on the other
hand, are relatively waterproof, and relatively safe
to prepare and handle, and whereas -the previous
connectors had a failure rate at the 0,1~ level, the
failure rate of connectors according to the present
invention is comparitively negligible.
