EP0493638A1

EP0493638A1 - Novel composite explosives and method for making them

Info

Publication number: EP0493638A1
Application number: EP90500130A
Authority: EP
Inventors: Jose Manuel Rego Lopez; Jose Antonio Renedo Arenas
Original assignee: Union Espanola de Explosivos SA
Current assignee: Union Espanola de Explosivos SA
Priority date: 1990-12-31
Filing date: 1990-12-31
Publication date: 1992-07-08

Abstract

Novel composite explosives which comprise a molecular explosive and oxidizing salt combinations in intimate contact are described in this invention. The high degree of intimacy between the molecular explosive and the oxidizing salts has been attained by means of the melt-in-fuel emulsion technology. Accordingly, highly dense compounds which have a dispersed phase showing very small mean particle size are obtained. Emulsification between both phases takes place within seconds and therefore the composite explosive can be prepared by simply agitating vigorously or by injecting both molten phases through a static mixer. The method described allows one the use of a wide variety of different oxidizing salts and different molecular explosives. The final products obtained show good rheological properties and consequently admixing of additives is possible. The compounds of this invention can substitute the current army melt cast explosives and can also be applicable as boosters for industrial use.

Description

Field of the Invention

The present invention relates to improved explosive composites comprised of oxidizing salts in intimate contact with molecular explosives. This intimate contact has been achieved by using the melt-in-fuel technology, the molecular explosive being part of the fuel phase. The explosive matters obtained by these means show very high densities and improved explosive features with respect to the molecular explosives considered.

Field of Application

The explosive matters described in this invention can - substitute the current army melt cast ammunition like - composition B. They can also be used as boosters for - - industrial applications.

Background of the Invention

The term amatols denotes a type of pourable explosive compounds comprised of ammohium nitrate (AN) and trinitrotoluene (TNT) of varying compositions. These composite explosives are prepared by dispersing AN in molten TNT with gentle agitation. The final product is castable at processing temperatures although presents a tendency for segregation of components (typical in TNT based multi-component melt-pour explosives). Different percentages of AN produce explosive composites of differentiated physical and explosive properties. Thus, increasing AN within the final product yields: (i) increasingly less negative oxygen balance; (ii) higher gas volume evolved; (iii) higher detonation pressures; (iv) higher Gurney velocities; (v) lower detonation temperatures and (vi) lower explosion heat. Furthermore, higher detonation rates should also be related to higher AN concentration. However, this is not the case (see AMCP 706-177) since experimental densities are lower for amatols than for TNT as a consequence of AN particle size and porosity and of the presence of air bubbles dissolved during the homogenization process of the dispersion. Thus, velocities of detonation (VOD) in the range 4500 (80/20 (AN/TNT)-6430 m.s⁻¹ (50/50 (AN/TNT) are obtained which are below the values attained for TNT (6900 m.s⁻¹). These differences between theoretical predictions and real values must also be attributed to the low intimacy level between the components of the composite explosive achieved by simply mixing molten TNT and the oxidizing salt which presumably presents a high value of its mean particle size as well as a broad particle size distribution.
An intimate contact between both components of the mixture requires small particle size. There exist two different means to obtain very small particle sizes: (i) intensive milling of the salt and (ii) emulsion formation from both components which is feasible since both exhibit very different surface tensions. Milling of the oxidizing salt to very fine particles (10 µm or less) makes dearer the final product. Furthermore, a very small particle size do not ensure the intimate mixture required. On the contrary, the colloidal stabilization of very fine particles of TNT (oil in water (O/W) emulsion) or AN (water in oil (W/O) emulsion) can produce a final product in which not only intimacy is obtained but segregation and subsequent unstabilization of the mixture can also be prevented.
The U.S. Patent 4,545,829 describes methods for the preparation of W/O and O/W emulsions from TNT and AN and from TNT and ammonium perchlorate (AP). Two methods are shown in this patent. The first one requires heating of TNT to a temperature of 443 K. With regard to the second one, water is heated to 363 K and saturated with one of the salts mentioned above at this temperature. If O/W emulsions are formed, the solvent is evaporated off after emulsification has taken place. Although this preparation of amatols is undoubtedly novel, some processing and operational problems are apparent: (i) the impact sensitivity of TNT increases substantially with increasing temperature (see Picattini Arsenal). Consequently, the higher the processing temperature, the more hazardous the operation becomes. Furthermore, very high processing temperatures are associated with high electricity costs and consequently with a dearer final product; (ii) the evaporation of the solvent in the second method does not allow one direct casting of the composite explosive, but the product must be remelt after the drying stage.
Lower processing temperatures can be obtained by using water as a constituent of the oxidizing phase. In this connection, the U.S. Patent 4,310,304 describes explosive formulations sensitive to the detonator prepared from an oxidizing phase comprised of inorganic salts and water and an organic phase comprised of mixtures of molecular explosives such as TNT, dinitrotoluene and dinitroxylene. These two phases were stabilized by using an appropriate emulsifier. Typical emulsification times of 5 minutes were required to achieve emulsification. Prior to the emulsion formation, microspheres were added to the water phase as a sensitizing agent. Densities in the range 1100-1150 kg.m⁻³ were obtained.
In the present invention, lower processing temperatures have been achieved by using eutectic oxidizing mixture which show a single melting temperature well below the melting - point of the constituent individual salts and very high densities. In this way, melting temperatures ranging from 313 K to 473 K can be obtained, although working temperatures are preferably within the range 333 K to 453 K and more preferably 333 K to 413 K. Furthermore, the use of eutectics widens up the range of physical and explosive properties of the final material and allows one tailoring of the desired compound. Finally, the lower processing temperatures associated with these salt combinations and the very small mean particle sizes that can be achieved by emulsifying eutectic phase and molecular explosive yields the following benefits: (i) lower production costs; (ii) safer working conditions and (iii) improved overall performance of the explosive.

Detailed Description of the Invention

It is a first objective of the present invention to prepare high density composite explosives which show a high degree of intimacy between the salt or mixtures of salts and the molecular explosive. This high degree of intimacy can be obtained by using melt-in-fuel emulsion technology. Accordingly, the inorganic phase (eutectic mixture) would be the molten phase and the fuel phase would be comprised of molecular explosives.
Inorganic oxidizing salts which are of utility in the present invention include AN, potassium nitrate (KN), sodium nitrate (SN), nitrates of alkaline earth elements, ammonium perchlorate (AP), perchlorates of alkaline and alkaline earth elements, organic nitrates such as hydrazine nitrate (HN), ethylenediamine dinitrate (EDDN), guanidine nitrate (GN), monoethanolamine nitrate (MEAN) and urea nitrate (UN). Eutectic mixtures of inorganic oxidizers showing melting temperatures ranging from 333 to 413 K will be preferred in order to ensure a safe handling of the raw materials during the emulsification process. Among the possible eutectic candidates, those showing high densities and/or good explosive features will be preferred. Consequently, a final product having a very high density can be obtained, this property being usually related to high VOD. The stability of the melt-in-fuel emulsion obtained in the present invention is associated primarily with the crystallization kinetics of the oxidizing phase. Crystallization of this melt phase strongly depends upon droplet size, impurities of the components (heterogeneous nucleation), type of surfactant, presence or not of crystal modifiers and undercooling. With regard to droplet size, this emulsion property is related to homogeneous nucleation (the lower the particle size, the slower the homogeneous nucleation) and is influenced by: (i) interfacial tension between both phases; (ii) overall viscosity (which is related to the shearing forces which break up the droplets during the emulsification process) and (iii) type of surfactant. Regarding the other variables, undercooling appears to be of outmost importance. Thus, the higher the melting point the greater the undercooling (it should be recalled that the system is cooled to ambient temperature) and, consequently, the bigger the crystallization driving force.
Molecular explosives which can be used as the fuel phase include TNT, trinitrochlorobenzene, 2,3-dinitroxylene, 2,5-dinitroxylene, 2,6-dinitroxylene, trinitroxylene, dinitrotoluenes and mixtures of them. These explosive fuel phases are used in the molten state. Other explosive fuels which must be used in solution include: hexogen and octogen in cyclopentanone solution. These two compounds are also slightly soluble in molten TNT. Other candidates to be explosive fuel phases comprise charge-transfer complexes (or π complexes) of TNT with aromatic nitro compounds such as 1,3,5-trinitrobenzene, 1-nitronaphtalene, 2-iodo-3-nitrotoluene, 2,4-dinitroanisole, 1,3-dinitrobenzene, tetryl and hexanitrostilbene. The fuel phase must also include aromatic and aliphatic hydrocarbons which reduce the surface tension of the fuel phase. Adequate hydrocarbons are: mineral oil, parafinic and microcrystalline waxes, petroleum distillates, benzene, toluene, xylene, tetrahydronaphtalene, decahydronaphtalene, epoxy soya oil and mixtures thereof.
The more adequate emulsifying system of the present invention shows a HLB (hydrophilic Lipophilic Balance) within the range 8-12. Appropriate candidates include: isopropylamine docecylbenzene sulphonate, polyoxyethylene coconut amine, polyoxyethylene distearate, polyoxyethylene glycerol monostearate, polyoxyethylene monolaurate, sorbitan monoisostearate, sorbitan sesquioleate, tallow amine acetate, etoxylated tallow amine, ethyleneglycol oleate, glycerine monooleate, sorbitan monooleate, sorbitan monostesrate, sorbitan trioleate, polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate.
It is a second objective of the present invention to obtain explosive formulations, comprised of the constituents described above, which undergo emulsification within time intervals ranging from 2 to 5 seconds. Accordingly, this composite explosive could be prepared by two means: (i) homogenizing with a mixer at high - - revolutions ( 10000 r.p.m.) and (ii) injecting the fuel and oxidizing phases through a static mixer into which emulsification and subsequent droplet break up, as a consequence of shear forces, take place. With regard to this second mean, the processing system used here comprises: 1. Feedstock units for the oxidizing combination phase and the fuel phase wherein melting of the components is carried out; 2. A degassing system; 3. A vacuum unit; 4. A hydraulic unit for each phase; 5. A static mixer. Emulsification of the composite explosives by means of this method requires the following steps: (i) melting of the oxidizing combination and the fuel phase at adequate temperatures in their corresponding feedstocks; (ii) introduction of both phases within degassing chambers where degassification is accomplished by means of a vacuum line; (iii) metering of the appropriate volumes of both phases and subsequent injection of them by means of a hydraulic system. The injection rate depends on the volumes which must be processed in order to ensure a homogeneous mixture - - between both phases. Mixing of these phases takes place in a static mixture as well as refinement of the emulsion thus formed. The pipes through which the molten phases circulate are kept at a prestablished temperature to avoid undesirable solidifications of any of both phases within the processor which could collapse the pipes and cause damage to the hydraulic system.
It is notewhorty that the injection piston has been designed in order to prevent metal-metal frictions which could give rise to sparks and a possible subsequent detonation of the explosive compounds (due to adiabatic fracture of the explosives crystals) which are being processed. Accordingly, isolation of both phases from the pumping system has been achieved here by using a polytetrafluoroethylene (PTFE) joint Forseal-Foa which incorporates a stainless steel tension spring. Isolation is accomplished by lineal contact between the two edges of the joint, the spring being the static pressure element. The joint allows processing temperatures within the range 123 K to 493 K and shows good chemical resistance and no stick-slipping.
The uniaxial hydraulic piston of the processor of this invention is driven along the correct path by means of a glass fibre reinforced PTFE joint. Furthermore, this joint is characterized by high charge capacity, high abrasion resistance, optimum slipping qualities and absence of stick-slipping.
It is a third objective of this invention to obtain explosive formulations, comprised of the constituents described above, which are castable and allow subsequent admixing of additives in order to improve the explosive features of the final product. Suitable additives include RDX, HMX, PETN, TATB, ONTA,...
Table I includes explosive properties of composite explosive formulations which composition is disclosed in detail in the examples 1 to 6 described below. These properties have been calculated theoretically on the basis of the Chapman-Jouguet (C-J) detonation state. The Gurney velocities as well as the theoretical densities and oxygen balances are also included. The explosive properties of TNT alone have also been included for comparison. It should be noted that two have been the eutectics used for the preparation of these composite explosives: (i) a very high density one comprised of AN, KN and SN and (ii) a highly energetic one comprised of AN, KN and the explosive oxidizing salt EDDN. The properties evaluated in this way depend on the type of eutectic. Thus, formulations 1,2 and 3 show very high theoretical densities which yield very big values of VOD whereas the detonation temperature are much lower than the one calculated for TNT. Higher detonation pressures are also obtained for these formulations than for TNT alone. The Gurney velocity is also higher for these formulations than for TNT. With regard to the second eutectic, it yields composite explosives which have lower density than TNT. Despite this fact, VOD bigger than those found for TNT are obtained. The detonation temperature for these composite explosives prepared from the second - - eutectic is higher than the detonation temperature found for the formulations prepared from the first one due to the explosive character of the oxidizing salt EDDN. However, the highest detonation temperatures are obtained for TNT alone. The detonation pressures calculated for formulations 4, 5 and 6 are similar to those evaluated for TNT. The Gurney velocities exhibited by formulations 4 and 5 are also higher than those produced by TNT. Finally, these explosive matters show a less negative oxygen balance than TNT.
In the following paragraphs, examples of explosive formulations are given in conjunction with some properties of the final product in order to illustrate feasible novel-composite explosives as designed in this invention. It should be noted that these examples are not restrictive and many other formulations are also feasible. Table II summarizes briefly suitable compositions and important properties.

EXAMPLE 1

An eutectic mixture of AN (55.1 parts), KN (9.3 parts) and SN (15.6 parts) were heated above the melting point of the eutectic (403 K). The fuel phase comprised of TNT (8.04 parts), mineral oil (3.34 parts), tetrahydronaphtalene (5.3 parts) and the emulsifying system (3.3 parts) was prepared in a separate vessel at 363 K and subsequently added onto the molten eutectic mixture. The system was then agitated vigorously (10000 r.p.m.) during one minute. Emulsification of the ingredients took place almost instantly which was apparent from the high increase in the viscosity of the system observed. The composite material thus prepared was castable at 353 K. Solidification of the system proceeded fairly quickly when cooled to ambient temperature. With regard to the stability of the emulsion, it was found that crystallization of the oxidizing salts and subsequent disrupture of the droplets took place after only one week from the preparation of the system.

EXAMPLE 2

An eutectic mixture of AN (48.23 parts), KN (8.12 parts) and SN (13.65 parts) were heated above the melting point of the eutectic (403 K). The fuel phase comprised of TNT (16.2 parts), mineral oil (5.01 parts), tetrahydronaphtalene (5.8 parts) and the emulsifying system (3.3 parts) was prepared in a separate vessel at 363 K and subsequently added onto the molten eutectic mixture. As in example 1, the system was then agitated vigorously (10000 r.p.m.) during one minute. Emulsification of the ingredients took also place almost instantly. The compesite material thus prepared was also castable at 353 K. As in example 1, crystallization of the oxidizing salts and subsequent disrupture of the droplets took place after only one week from the preparation of the system.

EXAMPLE 3

An eutectic mixture of AN (41.34 parts), KN (6.96 parts) and SN (11.7 parts) were heated above the melting point of the eutectic (403 K). The fuel phase comprised of TNT (26.0 parts), microcrystalline was (6.67 parts), tetrahydronaphtalene (5.33 parts) and the emulsifying system (2.0 parts) was prepared in a separate vessel at 363 K and subsequently added onto the molten eutectic mixture. As in example 1 and 2, the system was then agitated vigorously (10000 r.p.m.) during one minute. Emulsification of the ingredients took also place almost instantly. The composite material thus prepared was also castable at 353 K. As in examples 1 and 2, crystallization of the oxidizing salts and subsequent disrupture of the droplets took place after only one week from the preparation of the system.

EXAMPLE 4

An eutectic mixture of AN (40.0 parts), KN (6.0 parts) and EDDN (34.0 parts) were heated above the melting point of the eutectic (376 K). The fuel phase comprised of TNT (8.04 parts), mineral oil (3.34 parts), tetrahydronaphtalene (5.3 parts) and the emulsifying system (3.3 parts) was prepared in a separate vessel at 363 K and subsequently added onto the molten eutectic mixture. The system was then agitated vigorously (10000 r.p.m.) during one minute. Emulsification of the ingredients took place almost instantly. The - viscosity of this system at 353 K was lower than the viscosity observed for examples 1, 2 and 3 at the same temperature. The composite material thus prepared was castable at 353 K. Solidification of the system when cooled to ambient temperature proceeded at a slower rate than for system 1, 2 and 3. The system showed a mean particle size of 1,9 µm. With regard to the stability of the emulsion, it was found that crystallization of the oxidizing salts and subsequent disrupture of the droplets was only apparent after two weeks from the preparation of the system. After four weeks, the crystallization was heavy and no droplets could be detected.

EXAMPLE 5

An eutectic mixture of AN (35.0 parts), KN (5.25 parts) and EDDN (29.75 parts) were heated above the melting point of the eutectic (376 K). The fuel phase comprised of TNT (16.2 parts), mineral oil (5.01 parts), tetrahydronaphtalene (5.8 parts) and the emulsifying system (3.0 parts) was prepared in a separate vessel at 363 K and subsequently added onto the molten eutectic mixture. The system was than agitated vigorously (10000 r.p.m.) during one minute. Emulsification of the ingredients took place almost instantly. As for example 4, the viscosity of this system at 353 K was lower than the viscosity observed for examples 1,2 and 3 at the same temperature. The composite material thus prepared was castable at 353 K. Solidification of the system when cooled to ambient temperature proceeded at a slower rate than for system 1, 2 and 3. The system showed a mean particle size of 2.1 µm. With regard to the stability of the emulsion, as for example 4, it was found that crystallization of the oxidizing salts and subsequent disrupture of the droplets was only apparent after two weeks from the preparation of the system. After four weeks, the crystallization was heavy and no droplets could be detected.

EXAMPLE 6

An eutectic mixture of AN (30.0 parts), KN (4.5 parts) and EDDN (25.5 parts) were heated above the melting point of the eutectic (376 K). The fuel phase comprised of TNT (26.0 parts), microcrystalline was (6.67 parts), tetrahydronaphtalene (5.33 parts) and the emulsifying system (2.0 parts) was prepared in a separate vessel at 363 K and subsequently added onto the molten eutectic mixture. The system was then agitated vigorously (10000 r.p.m.) during one minute. Emulsification of the ingredients took place almost instantly. As for examples 4 and 5, the viscosity of this system at 353 K was lower than the viscosity observed for examples 1, 2 and 3 at the same temperature. The composite material thus prepared was castable at 353 K. Solidification of the system when cooled to ambient temperature proceeded at a slower rate than for system 1, 2 and 3. The system showed a mean particle size of 2.5 µm. With regard to the stability of the emulsion, as for examples 4 and 5, it was found that crystallization of the oxidizing salts and subsequent disrupture of the droplets was only apparent after two weeks from the preparation of the system. After four weeks, the crystallization was heavy.

A common feature to these formulations all is their very low sensitivity. Thus, with regard to their impact sensitivity, they all show no reaction at 36 kp pistil load. The impact sensitivity is bigger than 51 Joules for them all. Accordingly, these composite materials are good candidates as very insensitive high explosives. These formulations are also insensitive to the detonator and fail with a 200 g PETN booster. Accordingly, higher sensitivity must be accomplished by admixing explosive sensitizers such as RDX, HMX, PETN, TATB, ONTA,... Table III include data relative to the experimental explosive characteristics of some of the composite materials of the present invention sensitized with various sensitizers and different sensitizer concentrations. The sensitizer particles are suspended in the composite material by slow agitation under vacuum (vacuum mixing). By this mean, higher experimental densities can be attained. The high viscosity exhibited by these materials prevented segregation of the sensitizers and homogeneous mixtures were obtained. The minimum booster required to obtain detonation is also provided.

Table II

Compositions of the six possible formulations described in the text.
	1	2	3	4	5	6
Eutectic combination	80	70	60	80	70	60
Emulsifier	3.3	3	2	3.3	3	2
Mineral oil	3.34	5.01	--	3.34	5.01	--
Microcrystalline wax	--	--	6.67	--	--	6.67
Tetrahydronaphtalene	5.3	5.8	5.33	5.3	5.8	5.33
Trinitrotoluene	8.04	16.2	26.0	8.04	16.2	26.0
Emulsification time (s)	2	2	3	4	5	5
Solidification time (min)	15	15	15	120	120	120
Mean droplet size (µm)	--	--	--	1.9	2.1	2.5
Viscosity (p) at 353 K	3950	3105	2510	2700	2310	1900
Castable (Y/N)	Y	Y	Y	Y	Y	Y

Table III

Experimental VOD (m.s⁻¹) corresponding to formulations 1, 4 and 5 sensitized with various sensitizers and sensitizer concentrations. The material densities (kg.m⁻³) are given in brackets. The minimum booster required for the material not to fail is also provided.
SENSITIZER	Formulation 1	Formulation 4	Formulation 5
15 % RDX	---	5500 (1500)	---
Minimum Booster (g)	---	100	---
20% RDX	5400 (1600)	---	---
Minimum Booster (g)	50	---	---
30 % RDX	6700 (1610)	7000 (1620)	---
Minimum Booster (g)	25	100	---
40 % RDX	7500 (1660)	7400 (1610)	7300 (1577)
Minimum Booster (g)	25	50	50
40 % PETN	---	---	7100 (1578)
Minimum Booster (g)	---	---	30

Claims

Novel composite explosives which contain oxidizing salts in intimate contact with a molecular explosive, primarily TNT, dinitrotoluenes, dinitroxylenes and mixtures thereof. The explosive compunds of the present invention can substitute the current army melt cast ammunition and can also find application as boosters for industrial use; furthermore, these explosive compounds are highly insensitive and can be categorized as insensitive high explosives.
Composite explosives according to claim 1 characterized by being formed from oxidizing salt combinations which show a single melting peak. Inorganic oxidizing salts which are of utility in the present invention as constituents of the oxidizing combinations include - - ammonium nitrate, potassium nitrate, sodium nitrate, nitrates of alkaline earth elements, ammonium perchlorate, perchlorates of alkaline and alkaline earth elements, organic nitrates such as hydrazine nitrate, ethylenediamine dinitrate, guanidine nitrate, monoethanolamine nitrate and urea nitrate; eutectic mixtures of inorganic oxidizers showing melting temperatures ranging from 333 to 413 K will be preferred in order to ensure a safe handling of the raw materials during the emulsification process. Among the possible eutectic candidates, those showing high densities and/or good explosive features will be preferred.
Composite explosives according to claims 1 and 2, characterized by being formed from a wide variety of oxidizing salt combinations having melting temperatures within the range 313 K to 473 K.
Composite explosives according to claims 1 to 3, characterized by having explosive oxidizing salts as part of the eutectic combinations.
Composite explosives according to claims 1 to 4, characterized by being prepared from a wide variety of molecular explosives, primarily TNT, trinitrochlorobenzene, 2,3-dinitroxylene, 2,5-dinitroxylene, 2,6-dinitroxylene, trinitroxylene, dinitrotoluenes and mixtures of them. These explosive fuel phases are used in the molten state. Other explosive fuels which must be used in solution include: hexogen and octogen in cyclopentanone solution. This two compounds are also slightly soluble in molten TNT. Other candidates to be explosive fuel phase comprise charge-transfer complexes (or π complexes) of TNT with aromatic nitro compounds such as 1,3,5-trinitrobenzene, 1-nitronaphtalene, 2-iodo-3-nitrotoluene, 2,4-dinitroanisole, 1,3-dinitrobenzene, tetryl and hexanitrostilbene.
Composite explosives according to claims 1 to 5 which encompasses a wide range of oxidizing phase to explosive fuel phase proportions that can be prepared; appropriate concentrations of molecular explosive range from 5 to 40% by weight of the total mass of the formulation.
Composite explosives according to claims 1 to 6, characterized by having surface tension reducers which not only decrease the surface tension of the molecular explosive but allow rapid emulsification between both phases as well; these surface tension reducers include: aromatic and aliphatic hydrocarbons and primarily mineral oil, paraffin waxes, microcrystalline waxes, tetrahydronaphtalene and decahydronaphtalene.
Composite explosives according to claims 1 to 7, characterized by being emulsified from an emulsifying system which comprises surfactants from the following group: polyxyethylene coconut amine, polyoxyethylene distearate, polyoxyethylene glycerol monostearate, polyoxyethylene monolaurate, sorbitan monoisostearate, sorbitan sesquioleate, tallow amine acetate, etoxylated tallow amine, ethyleneglycol oleate, glycerine monooleate, sorbitan monooleate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate.
Composite explosives according to claims 1 to 8, characterized by the dispersed phase presents a very small particle size (between 0.5 and 5 µm) and, consequently, a high degree of intimacy between both phases.
Composite explosives according to claims 1 to 9, characterized by good rheological properties (apparent viscosities ranging from 1000 to 5000 poises at 353 K) which enable admixing of additives, e.g. sensitizers.
Composite explosives according to claims 1 to 10, characterized by exhibiting very high densities ranging from 1400 to 1770 kg.m⁻³.
Composite explosives according to claims 1 to 11, characterized by showing improved explosive properties, viz. higher Gurney velocities, with regard to the molecular explosive present in the fuel phase.
Composite explosives according to claims 1 to 12, characterized by exhibiting high VOD (between 6000 and 8000 m.s⁻¹) once sensitized.
Composite explosives according to claims 1 to 13, characterized by the possibility of obtaining a wide range of products showing different explosive properties by simply changing of the sensitizer (RDX, HMX, PETN) and sensitizer concentration (from 0 to 40% by weight).
A method, according to claims 1 to 14, for preparing novel composite explosives by using the melt-in-fuel emulsion technology; emulsification between both phases is produced within second; the following steps are followed in order to obtain the said explosive matters: (i) melting of the oxidizing combination and the fuel phase (molecular explosive + surface tension reducers + emulsifying system) at adequate temperatures in their corresponding feedstocks; (ii) introduction of both phases within degassing chambers where degassification is accomplished by means of a vacuum line; (iii) metering of the appropriate volumes of both phases and subsequent injection of them by means of a hydraulic system; the injection rate depends on the volumes which must be processed in order to ensure a homogeneous mixture between both phases; mixing of these phases takes place in a static mixture as well as refinement of the emulsion thus formed; the pipes through which the molten phases circulate are kept at a prestablished temperature to avoid undesirable solidifications of any of both - - phases within the processor which could collapse the pipes and cause damages to the hydraulic system; the injection pistons have been designed in order to prevent metal-metal frictions which could give rise to sparks and a possible subsequent detonation of the explosive compounds which are being processed; accordingly, isolation of both phases from the pumping system has been achieved here by using a polytetrafluoroethylene (PTFE) joint Forseal-Foa which incorporates a stainless steel tension spring. Isolation is accomplished by lineal contact between the two edges of the joint, the spring being the static pressure element. The joint allows processing temperatures within the range 123 K to 493 K and shows good chemical resistance and no stick-slipping. The uniaxial hydraulic piston of the processor of this invention is driven along the correct path by means of a glass fibre reinforced PTFE joint. Furthermore, this joint is characterized by high charge capacity, high abrasion resistance, optimum slipping qualities and absence of stick-slipping.