Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF MANUFACTURING AN EXPLOSIVE COMPOSITION
The present invention relates to a non-detonable fluid composition and to a
method of
manufacturing said composition. The invention further relates to an explosives
composition based on the non-detonable fluid composition and to a method of
manufacturing such an explosives composition. The invention relates yet
further to a
method of loading a blasthole and to a method of blasting.
Explosives compositions, such as emulsion explosives compositions, are
typically formed
by sensitising otherwise non-detonable fluid compositions comprising fluid
energetic
materials. However, the transportation of sensitised explosives is subject to
considerable
regulatory restriction and cost and the provision of a non-detonable fluid
composition
requiring little explosive sensitisation at the mining site would therefore be
desirable. It
would be of particular advantage to provide a non-detonable composition which
requires
the minimum amount of processing at the blast site in order to sensitise it.
In one aspect,
the present invention seeks to provide such a non-detonable fluid composition.
When a mass of earthen material is blasted, all the external dynamic loads are
supplied by
pressurised gas which is produced in the blastholes by the detonation of
explosive charges.
Lateral gas pressure, acting progressively on fresh parts of a blasthole wall,
creates waves
which propagate away from the blasthole and reflect from nearby free faces.
The complex
wave fields damage, fracture and fragment the earthen material. Eventually the
gas vents
from the blasthole, increasing the fracturing and fragmentation, and heaving
fragments
through the air. The explosive must release enough energy to carry out these
tasks
satisfactorily. Modern blast practice demands explosives with high energy
density as one
means of expanding blasthole patterns for greater efficiency. High-energy
density
explosives are potentially cheaper than the alternative of drilling blastholes
with bigger
diameters or drilling a large number of more closely spaced blastholes.
In soft media such as overburden or coal, efficient blasting also requires
that the energy
should be released relatively slowly, implying low velocities of detonation.
If the
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detonation proceeds too fast, energy will be wasted in creating excessive
fines close to the
blasthole. The desired explosive for blasting soft media therefore combines
high energy
density with a low velocity of detonation.
Conventional explosives compositions tend to exhibit moderate energy density,
relatively
low density and high velocities of detonation. The present invention seeks to
provide
explosives compositions which exhibit high energy density, relatively high
density and low
velocity of detonation. Further, the invention provides explosives
compositions in which
the velocity of detonation may be controlled with negligible or minimal
influence on
energy density.
Accordingly, the present invention provides a fluid composition which
comprises a fluid
energetic material and a multiplicity of cavities dispersed therein, wherein
the cavities have
an average particle size of at least 3.Smm and wherein the total volume
occupied by the
cavities is such that the fluid composition is non-detonable.
As used herein, the term "non-detonable" means that the fluid composition of
the present
invention gives a negative result in the Koenen test, the Time/Pressure test
and the UN
Gap test for solids and liquids. These tests are well-known in the art and
are, for instance,
described in United Nations, 1995, Recommendations on the Transport of
Dangerous
Goods - Manual of Tests and Criteria, second revised edition, United Nations
Publication,
New York. The Koenen test is intended to determine the sensitivity of solid
and liquid
substances to the effect of intense heat under high confinement. The
Time/Pressure test is
used to determine the effects of igniting a substance under confinement in
order to
determine if ignition leads to a deflagration with explosive violence at
pressures which can
be attained with substances in normal commercial packages. The UN Gap test is
intended
to measure the ability of a substance, under confinement in a steel tube, to
detonate by
subjecting it to detonation from a booster charge.
In these tests a negative (or fail) result, where the substance under test
fails to respond to
application of the prescribed stimuli is indicative that the substance is non-
detonable. The
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tests are recognised internationally as the standard tests for classification
of explosive
materials by all national competent authorities.
The cavities present in the non-detonable fluid composition of the present
invention have
an average particle size of at least 3.5 mm. Mixtures of cavities having
different sizes may
be used provided the average particle size satisfies this requirement. The
cavities usually
have an average particle size in the range of from 3.5 to l2mm, more
preferably 4 to 8 mm.
In practice of the invention cavities having an average particle size of 4, 6
or 8 mm are
conveniently used.
The shape of the cavities is not critical, although essentially spherical
cavities are
convenient. The definition of the particle size of irregularly shaped cavities
is difficult.
However, a cavity may be considered to have an effective size for compression
by
considering various elements of the cavity. The cavity will be understood to
have a
particle size of at least 3.Smm where at least a part of the cavity has a
minimum dimension
in every direction of at least 3.5 mm. It is preferred that the at least part
of the cavity has a
minimum dimension in every direction in the range of from 3.5 mm to 12 mm,
more
preferably from 4 to 8 mm.
The multiplicity of cavities having a dimension of at least 3.5 mm are
provided by
multivoid particles. Multivoid particles may comprise cellular voids within
plastic,
carbonaceous, cellulosic or mineral materials. The cavity provided by the
multivoid
particles shall be considered to be the volume from which the fluid
composition is
excluded
It is preferred that the multivoid particles comprise a fuel as the materials
of construction
thereof. Such multivoid particles which comprise a fuel include material such
as cork,
balsa wood, coke or the like. It is particularly preferred that the multivoid
particles
comprise expanded polymeric foams, such as polystyrene, polyurethane,
polyethylene,
polypropylene, polyvinylchloride, polybutadiene rubber, or copolymers of these
materials.
Most preferably the multivoid particles are expanded polystyrene or
polyurethane foam.
AMENDED SHEET
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Other multivoid particles which comprise a fuel include carbohydrate expanded
organic
fuels such as popcorn, puffed rice and puffed wheat.
Multivoid materials which employ non-fuel materials may also be used in the
present
S invention and include expanded porous rock or other expanded salicaceous
materials.
Such materials include pearlite, vermiculite and fly ash.
The cellular structure of the multivoid materials is preferably such that the
multivoid
material has a high proportion of closed cells. The thickness of the walls of
the cellular
structure is preferably sufficient to prevent the collapse of the cellular
structure prior to and
during the incorporation of the multivoid materials into the fluid
composition. However,
the walls should be sufficiently thin to so as to enable the cells to be
ruptured during the
detonation of the fluid blasting agent.
The cavities typically have a density of 0.3 g/cc or less, for instance, 0.1
g/cc or less. In an
embodiment of the invention, the density of the cavity is 0.02 g/cc or less,
for instance
about 0.009 g/cc. Foamed materials such as polystyrene typically have
densities as low as
this. The density of such materials will in part depend upon the extent to
which the
foamed material is expanded.
As noted above, the total volume (voidage) occupied by the cavities, based on
the total
volume of the fluid composition, is such that the material is non-detonable.
Amongst
others things this critical volume will depend upon the average particle size
and the density
of the individual cavities. The critical volume for a given type or types of
cavity may be
determined by reference to the tests mentioned above.
The total volume occupied by the cavities is less than about 10% by volume
based on the
volume of the fluid composition. Thus, the fluid composition of the invention
usually
includes a small volume of relatively large sized cavities. For instance, the
voidage may
be from 3 to 8% by volume.
AMENDED SHEE-a
~/AU
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The % voidage provided by the cavities may be calculated using the following
equation:
V = d' d Z x 100
d,
where V is the voidage of the cavities based on the total volume of the
composition, d~ is
the density of the fluid composition prior to addition of the cavities and d2
is the density of
the fluid composition when the cavities are present. In other words, the
voidage is
calculated based on the theoretical maximum density of the fluid composition.
Although linked to cavity density and the volume occupied by the cavities, the
cavities
usually make up less than 0.15% w/w of the non-detonable fluid composition,
for instance,
the amount may be less than 0.1 % w/w, preferably from 0.05 to 0.1 % w/w of
t_h_P non-
detonable fluid composition. With low density cavities (density of about 0.009
g/cc or
less) the amount of cavities is usually about 0.075% w/w.
The most commonly used cavities are expanded (foamed) polystyrene particles
having an
average particle size of from 4 to 8 mm and a particle density of less than
about 0.009 g/cc.
It is then typical that the quantity of such multivoid particles present in
the composition is
about 0.075% w/w based on the total weight thereof.
The fluid energetic material used in the present invention is itself non-
detonable and may
be any material which when appropriately sensitised may be detonated thereby
causing an
explosive blast. The fluid energetic material may be a liquid energetic
material comprising
oxidiser and fuel molecules homogeneously mixed, forming a non-detonable
matrix. For
instance, it may be a liquid material produced by molecular scale mixing of
known oxygen
releasing agents with organic fuel materials in a common aqueous/non-aqueous
solvent.
This means it may be a concentrated aqueous or non-aqueous liquid. It may be a
solvent-
diluted explosive material forming a non-detonable energetic liquid.
Furthermore, it may
be an eutectic material of oxidisers with fuels or their melts. It may also be
an emulsion
matrix comprising discontinuous an oxygen releasing salt component dispersed
in an
organic medium forming a continuous phase, or vice versa, stabilised by
emulsifier. This
may embrace compositions of water-in-oil or oil-in-water emulsions.
Preferably, the fluid
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energetic material is in the form of a water-in-oil emulsion, melt-in-oil
emulsion or melt-
in-fuel emulsion. For the sake of convenience the invention will now be
described with
reference to water-in-oil type emulsions although it will be apparent that the
advantages
described will be applicable to the other fluid energetic materials.
Suitable oxygen releasing salts for use in the aqueous phase of the emulsion
include the
alkali and alkaline earth metal nitrates, chlorates and perchlorates, ammonium
nitrate,
ammonium chlorate, ammonium perchlorate and mixtures thereof. The preferred
oxygen
releasing salts include ammonium nitrate, sodium nitrate and calcium nitrate.
More
preferably the oxygen releasing salt comprises ammonium nitrate or a mixture
of
ammonium nitrate and sodium or calcium nitrates.
Typically the oxygen releasing salt component of the emulsion comprises from
45 to 95
w/w, and preferably from 60 to 90 % w/w, of the total emulsion composition. In
compositions in which the oxygen releasing salt comprises a mixture of
ammonium nitrate
and sodium nitrate the preferred composition is from 5 to 80 parts of sodium
nitrate for
every 100 parts of ammonium nitrate. Therefore, in the preferred composition
the oxygen
releasing salt component comprises from 45 to 90 % w/w (of the total emulsion
composition) ammonium nitrate or mixtures of from 0 to 40 % w/w, sodium or
calcium
nitrates and from 50 to 90 % w/w ammonium nitrate.
Typically the amount of water employed in the emulsion is in the range of from
0 to 30
w/w of the total emulsion composition. Preferably the amount employed is from
4 to 25
w/w and more preferably from 6 to 20 % w/w.
The water immiscible organic phase of the emulsion comprises the continuous
"oil" phase
of the emulsion composition and is the fuel. Suitable organic fuels include
aliphatic,
alicyclic and aromatic compounds and mixtures thereof which are in the liquid
state at the
formulation temperature. Suitable organic fuels may be chosen from fuel oil,
diesel oil,
distillate, furnace oil, kerosene, naphtha, waxes such as microcrystalline
wax, paraffin wax
and slack wax, paraffin oils, benzene, toluene, xylenes, asphaltic materials,
polymeric oils
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such as the low molecular weight polymers of olefines, animal oils, vegetable
oils, fish oils
and other mineral, hydrocarbon or fatty oils and mixtures thereof. Preferred
organic fuels
are liquid hydrocarbons generally referred to as petroleum distillates such as
gasoline,
kerosene, fuel oils and paraffin oils.
Typically, the emulsifier of the emulsion comprises up to 5 % w/w of the
emulsion. Higher
proportions of the emulsifying agent may be used and may seine as supplemental
fuel for
the composition but in general it is not necessary to add more than 5 % w/w of
emulsifying
agent to achieve the desired effect. Stable emulsions can be formed using
relatively low
levels of emulsifier and for reasons of economy it is preferable to keep the
amount of
emulsifying agent used to the minimum required to form the emulsion. The
preferred level
of emulsifying agent used is in the range of from 0.1 to 3.0 % w/w of the
water-in-oil
emulsion.
In accordance with the present invention, the non-detonable fluid composition
may be
sensitised to form a detonable explosives composition. This is achieved by
inclusion of a
sensitising agent. It is believed that the sensitising reactions depend on the
number of
relatively small size hotspots. Adiabatic compression of the hotspots by
shockwaves
causes sensitising reactions to occur. The interactions between numerous
thermal
explosions enable the propagation of the detonation wave by supplying the
necessary
chemical energy to the shock wave.
In accordance with the present invention it is desirable that the non-
detonable fluid
composition is sensitised by the addition of the minimum amount of sensitising
agent. The
minimum amount of sensitising agent which is used is that which has the effect
of just
sensitising the fluid composition. In other words, the volume of cavities
present in the
composition is advantageously very close to the critical volume at which the
cavities
would themselves sensitise the non-detonable composition. The use of small
amounts of
sensitising agent is beneficial in terms of cost and ease of preparation of
the explosives
compositions and has implications in terms of achieving a low velocity of
detonation. As a
general rule, the inclusion of higher volumes of sensitising agent will
increase the observed
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velocity of detonation. By varying the relative proportion of cavities and
sensitising agent,
the velocity of detonation may be controlled and tailored. Usually, the volume
ratio of
cavities to sensitising agent is about 70:30 to 55:45, more typically about
65:35.
In the sensitised explosives compositions, the total voidage, i.e. the voidage
provided by
the relatively large cavities and the voidage provided by the sensitising
agent usually does
not exceed about 15% by volume. Typically, the total voidage will be from 7 to
12% by
volume. In practice, the total voidage provided by the sensitising agent is
usually less than
about 5% by volume, for instance less than 3% by volume. It is preferable to
sensitise the
non-detonable fluid composition to form an explosive composition with (void)
agents
having a size of 30 to 300 microns, preferably 100 to 200 microns, more
preferably 150 to
200 microns.
Suitable sensitising agents include self explosives but preferably include a
discontinuous
phase of small void agents. Suitable small void agents include glass or
plastic
microballoons, expanded polymeric (e.g. polystyrene) beads and gas bubbles,
including
bubbles of nitrogen generated in situ by chemical gassing agents and entrained
air.
Mixtures of these agents may be used. Chemical gassing is the most preferred
means of
sensitizing the non-detonable fluid energetic material.
The resultant sensitised explosives compositions in accordance with the
present invention
may have high energy densities but relatively low velocity of detonation. The
velocity of
detonation of the compositions is usually in the range 40 to 70%, for instance
50 to 60%,
of the ideal (theoretically calculated) velocity for a given explosives
composition. It is
believed that the voidage and nature of the voidage in the explosives
compositions of the
present invention is influential on the velocity of detonation observed. The
volume
strength of the explosives composition is usually greater than that of
straight ANFO.
A further interesting aspect of the compositions of the invention is that
relatively low
velocities of detonation may be observed even when the compositions are
detonated under
strong confinement. Usually with emulsion explosives there is a relationship
between
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charge diameter and velocity of detonation. Smaller charge diameters tend to
provide
lower velocities of detonation. As charge diameter increases, so does the
velocity of
detonation. At infinite charge diameter, the maximum velocity of detonation
would be
observed. Explosives which have a velocity of detonation that varies with
confinement are
said to exhibit non-ideal detonation behaviour.
Steel pipe of 60-70 mm diameter and Smm thick is considered to be strong
confinement
and detonation velocities obtained under such confinement conditions may be
taken as
representative of ideal, maximum values. It has been found that explosives
compositions
in accordance with the present invention exhibit surprisingly low velocity of
detonation
under such strong confinement. Furthermore, it has been found that the
velocity of
detonation observed may be independent of charge confinement.
The non-detonable fluid composition of the present invention may be formed
conveniently
at a central manufacturing facility and, in the case of ammonium nitrate based
materials, at
or adjacent to an ammonium nitrate plant. Other facilities, such as mobile
manufacturing
units may also be employed with advantage to form the fluid energetic
material. In general
terms the composition is formed by dispersing the cavities in a fluid
energetic material
until a suitable voidage is achieved. The non-detonable fluid composition is
usually
prepared in advance and then transported to on-site where it is sensitised
before blast-hole
loading takes place.
The multiplicity of cavities may be dispersed in the fluid energetic material
at the site at
which the fluid energetic material is formed and then, as the resulting
composition is non-
detonable, be transported to the blast sites. The fluid composition may
transported by any
convenient and permissible means. Suitable means for transport include
standard tankers
for the transport of fluids, rubber bladders and the like. Preferably the
transport includes a
suitable pump for the transfer of the non-detonable fluid composition. The
fluid energetic
material used in the composition may be manufactured by any convenient means,
either
before or during the dispersing of the multiplicity of cavities therein.
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For mixing light, porous cavities in a relatively high viscosity fluid, the
equipment which
may be used includes:
1. High Speed Pin Blenders or Mills
2. Single or Duplex Paddle Blenders
3. Various Ribbon Blenders
4. Stirring Pots
5. Stationary Mixing Devices
The feeding of the light, porous cavities into mixing equipment may be
achieved by augers
or other volumetric feeders. In many instances it is advantageous to utilise
the weighing
belts mass feeding. Pneumatic air conveying methods are also possible.
The explosives compositions of the present invention may be formed by a
dispersal of
sensitising agent in the non-detonable fluids composition. This may be
achieved by any of
the conventional means.
In a particularly preferred embodiment, the fluid energetic material, fluid
composition or
subsequently sensitised explosives composition may have incorporated therein
additional
energetic materials to control the energy output of the ultimate explosive
composition. It is
preferred that the incorporation of additional energetic materials be at the
blast site, at or
about the time at which the non-detonable fluid composition is sensitised. The
energetic
material may have an impact on the energy density of the explosives
composition and on
the velocity of detonation observed. The energy density will typically
increase and the
velocity of detonation typically decrease. This should be taken into account
when an
additional energetic material is included.
It is preferred that the fluid energetic material or fluid composition and, in
particular,
water-in-oil emulsions are mixed with substances which are oxygen releasing
salts or
which are themselves suitable as explosive materials. For example, a water-in-
oil emulsion
may be mixed with prilled or particulate ammonium nitrate and/or ammonium
nitrate/fuel
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oil mixtures and/or finely divided aluminium. It is preferred that prilled
ammonium nitrate
having a particle size in the range of from 2 to 12 mm, preferably 2 to 5 mm
in diameter be
used. When ammonium nitrate is used the amount present is usually less than
40% by
weight, for instance, from 10 to 30% by weight, based on the total weight of
the
formulated explosives composition.
In another aspect the present invention provides a method of loading a
blasthole
comprising the steps of:
a) sensitising a non-detonable fluid composition, as described herein, to form
an explosives
composition; and
b) loading the explosives composition into the blasthole.
The method of loading a blasthole in accordance with the present invention
permits the
mixing and delivery of the blasting agent by providing rapid and efficient
mixing of the
sensitising agent (e.g. gassing solution) and, when required, energising
materials into the
non-detonable fluid composition. Sensitisation, when by in situ generation of
gas, may be
completed after the product is loaded into the blasthole.
The sensitised explosives composition may be loaded into the blasthole by any
convenient
means. Sufficiently fluid blends may be pumped by pumps such as progressive
cavity
pumps, rotary lobe pumps (rubber rotor) through plastic or rubber hoses of
various
diameter/length depending on type of boreholes or applications. The thicker
and drier
blends may be augured into the boreholes. It may also be possible to load by
gravity
utilising the concrete mixer type trucks.
The present invention provides an explosives composition whereby the rate of
energy
release may be controlled by the incorporation of the multiplicity of cavities
and voids as
described above. It is particularly advantageous that the rate of energy
release be
controlled so that the explosives composition may be tailored to suit the
particular
geological environment in which the blast is to occur. This enables the
explosives
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composition to be manufactured to more particularly meet the geological blast
pattern
design and customer requirements. Advantageously, the non-detonable fluid
composition
of the present invention has a predisposition to detonate at very low
velocities of
detonation. This may be achieved by inclusion of a small voidage of relatively
large
volume cavities and subsequent sensitisation with a small voidage of
relatively small
sensitising agent.
Additionally, it is possible to vary the total energy output of the explosives
composition of
the present invention whilst maintaining a low velocity of detonation. This
may be
achieved by varying the propoution of energising solids which are incorporated
prior to
sensitisation. The solid energising materials such as ammonium nitrate and/or
ANFO
and/or aluminium as described above may be employed to increase the total
energy. It has
been found that the use of larger, porous particles of ammonium nitrate may
obtain further
reductions in velocity of detonation.
The present invention further provides a method of blasting which comprises
detonating an
explosives composition described herein. The composition may be detonated by
conventional means.
The present invention will now be described with reference to the following
non-limiting
examples.
Examples 1 and 2
A water-in-oil emulsion was prepared by blending components in the weight
percentages
shown below.
Oxidiser Solution:
Ammonium nitrate 74.82
Water 18.80
Acetic acid 0.28
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Thiourea 0.05
Soda ash 0.05
Fuel Blend:
Emulsifier 1.46
Paraffin oil 4.54
The emulsion formed had a density of 1.35 g/cc.
Non-detonable fluid compositions in accordance with the present invention were
then
prepared by dispersing cavities in the emulsion. In Example 1 the cavities
were expanded
polystyrene particles having an average particle size of 7 mm. The density of
the resulting
composition was 1.28 g/cc which corresponds to a voidage of 5.19%. In Example
2 the
expanded polystyrene particles had an average particle size of 4 mm. The
density of the
resulting composition was 1.26 g/cc corresponding to a voidage of 6.67%.
The fluid compositions were then subjected to the Koenen, Time/Pressure and
LJN Gap
tests. The results are given below.
Example 1 Example 2
Koenen Test Negative. Negative.
No reaction. (Series 2) No reaction (Series 1 )
Time/Pressure Negative. Negative.
Test No bursting of disc. No disc bursting
UN Gap Test Negative. Negative.
260 mm pipe unfragmented. 290 mm pipe unfragmented.
Witness plate domed. (Series 1) Witness plate domed. (Series 1)
[The Series l and 2 tests include minor variations in test apparatus. These
variations are
documented] .
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These results show that the fluid compositions in accordance with the present
invention are
non-detonable. They may therefore be categorised as "not UN Dangerous Goods
Class 1"
Example 3
Compositions in accordance with the following table were prepared. The
composition of
sample no. 1 was a water-in-oil emulsion having the composition shown above.
To this
formulation was blended cavities of expanded polystyrene having an average
particle size
of 4 mm and/or sensitising agent in the form of glass microspheres or gas
bubbles of 0.03 -
0.20 mm diameter. Detonation of each composition was attempted by use of a
commercial
primer (400g Anzomex) and the velocity of detonation (VOD) recorded where
detonation
was observed.
The velocity of detonation of the compositions was measured utilising an
optical fibre
method. In this method two lengths of optical fibre with clean cut ends were
inserted a
known distance apart (typically 100mm) into the explosive under test in a
steel pipe. The
other ends of the optical fibres were connected to the terminals of an
electric timer which
is capable of timing light pulses which are generated at the detonation front
of the tested
explosive, from a start and stop signal. The optical fibre located in the
explosive charge
closest to the detonator provides the start signal for the timer. The second
optical fibre at a
known distance (100mm) stops the timer. The timer times the light pulse from
the
detonation front as it passes the start and stop optical fibres and displays
the time in
milliseconds. The velocity of detonation is calculated form the time taken for
the
detonation front to pass from the first to the second fibre.
The density of the formulations, voidage, confinement conditions and
detonation results
are shown in the following table.
Sample Density Voidage Charge diameter VOD
No. (%vol)
(g/cc) 4m 0.03 - 0.20 steel confinement(km/s)
mm (mm)
1 1.35 - - 60 fail
2 1.28 - 5.2 60 6.00
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3 1.30 3.7 - 70 fail
4 1.29 4.4 - 70 fail
1.27 5.9 - 70 fail
6 1.25 7.4 - 70 fail
7 1.26 3.7 3.0 70 3.33
8 1.25 4.4 2.3 70 4.08
9 1.24 5.9 3.0 70 4.35
1.21 7.4 3.0 70 4.20
The same experiments were repeated using expanded polystyrene particles having
an
average particle size of 7 mm. The results are shown in the following table.
Sample Density Voidage Charge diameter VOD
No. (%vol)
(g/cc) 7mm 0.03 - 0.20 steel confinement(km/s)
mm (mm)
11 1.28 - 5.2 60 6.00
12 1.32 2.2 - 60 fail
13 1.31 3.0 - 60 fail
14 1.29 4.4 - 60 fail
1.26 6.7 - 60 fail
16 1.28 2.2 3.0 60 3.03
17 1.25 3.0 4.4 60 3.77
18 1.26 4.4 2.3 60 3.60
19 1.22 6.7 2.9 60 4.60
5
The unadditised (voidless) material fails to detonate even when initiated by
strong primer
(Sample no. 1).
10 Fluid energetic materials which include a relatively low voidage of small
voids (0.03 -
0.20 mm), but which do not include any expanded polystyrene particles,
detonate at
relatively high velocity of detonation (Sample nos. 2 and 11 ).
CA 02375217 2001-12-17
WO 00/78695 PCT/AU00/00681
-16-
Fluid energetic materials with a relatively low voidage of large multivoid
polystyrene
particles failed to detonate when initiated by strong primer (Sample nos. 3-6
and 12-I5).
Fluid energetic materials with a low voidage of large multivoid polystyrene
particles which
previously failed to detonate become detonable when a low voidage of small
(0.03 - 0.20
mm) voids are added. The velocity of detonation then observed was relatively
low
(Sample nos. 7-10 and 16-19).
This experimental work utilised charges in 60-70 mm diameter, 5 mm thick steel
pipes. It
is generally accepted that such pipes are classified as ideal confinement,
which affords the
theoretical maximum velocity of detonation.
Those skilled in the art will appreciate that the invention described herein
is susceptible to
variations and modifications other than those specifically described. It is to
be understood
that the invention includes all such variations and modifications which fall
within its spirit
and scope. The invention also includes all of the steps; features,
compositions and
compounds referred to or indicated in this specification, individually or
collectively, and
any and all combinations of any two or more of said steps or features.
Throughout this specification and the claims which follow, unless the context
requires
otherwise, the word "comprise", and variations such as "comprises" and
"comprising", will
be understood to imply the inclusion of a stated integer or step or group of
integers or steps
but not the exclusion of any other integer or step or group of integers or
steps.
