THERMAL SPARK CONDUCTOR TUBE USING NANOMETRIC PARTICLES

Abstract

THERMAL SPARK CONDUCTOR TUBE USING NANOMETRIC PARTICLES, refers to the Invention Patent for a thermal spark conductor tube, applied as a signal transmitter for connection and initiation of explosive columns, which employs a low toxicity nanometric pyrotechnic mixture, with superior thermal performance of the spark which maintains the advantages of the current pyrotechnic shock tube and has additional advantages of reducing or even eliminating the use of contaminants from underground water, presenting a lower risk of conducting an electrostatic discharge of the human body to its end, and to use pyrotechnic mixture production process quite simple and with less risk of accidents due to friction and mechanical shocks.

Claims

1. A thermal spark conductor tube using nanometric particles, in the form of a flexible plastic tube, with internal diameter between 1.0 and 1.5 mm, and outer diameter between 2.8 and 3.4 mm, substantially hollow, containing a thin powder pyrotechnic mixture deposited on its inner wall, characterized in that the pyrotechnic mixture has the following formulation at weight percentage: Aluminum powder with flake type morphology, minimum purity 99.5%, covered and stabilized by silica or other electrically insulating material, with a mean particle diameter between 5 and 18 m: 35% to 62%; Nanometric iron oxide with faceted almost spherical morphology, average particle diameter between 10 and 100 nm: 32% to 60%; Potassium Perchlorate ranging from 0% to 25%; and Talc: Ranging from 0.8 to 1.5%.

2. The thermal spark conductor tube using nanometric particles, for common applications where the passage through kinks and knots is not important, in the shape of a flexible plastic tube, with internal diameter between 1.0 and 1.5 mm, and outer diameter between 2.8 to 3.4 mm, substantially hollow, containing a fine powder pyrotechnic mixture deposited on its inner wall, according to claim 1, characterized in that the pyrotechnic mixture has the following preferential formulation at weight percentage: Aluminum powder with flake type morphology, minimum purity 99.5%, covered and stabilized by silica or other electrically insulating material, with a mean particle diameter of 11 m: 45%; Nanometric iron oxide with faceted almost spherical morphology, with a particle diameter of 30 nm: 54%; and Talc: 1%.

3. The thermal spark conductor tube using nanometric particles, for applications where the passage through folds and knots is important, in the shape of a flexible plastic tube, with internal diameter between 1.0 and 1.5 mm, and outer diameter between 2.8 and 3.4 mm, substantially hollow, containing deposited on its inner wall a fine powder pyrotechnic mixture according to claim 1, characterized in that the pyrotechnic mixture has the following preferential formulation at weight percentage: Aluminum powder with flake type morphology, minimum purity 99.5%, covered and stabilized by silica or other electrically insulating material, with a mean particle diameter of 11 m: 45%; Nanometric iron oxide with faceted almost spherical morphology with a particle diameter of 30 nm: 44% Potassium Perchlorate: 10%; and Talc: 1%.

4. A thermal spark conductor tube using nanometric particles, in the shape of a flexible plastic tube, having an internal diameter between 1.0 and 1.5 mm, and an outer diameter between 2.8 and 3.4 mm, substantially hollow, containing a thin powder pyrotechnic mixture deposited on its inner wall, characterized in that alternatively the pyrotechnic mixture has the following formulation at weight percentage: Nanometric aluminum powder with a flake type morphology, minimum purity 99.5%, covered and stabilized by silica or other electrically insulating material, with a mean particle diameter of 20 to 100 nm: 35% to 62%; Nanometric iron oxide with faceted almost spherical morphology, mean particle diameter between 10 and 100 nm: 32% to 60%; Potassium Perchlorate ranging from 0% to 25%; and Talc: Ranging from 0.8 to 1.5%.

Description

[0039] The present invention solved the following problems that the solutions of the technical state-of-art did not solve:

[0040] 1. The low temperature substances of Tammann which actually functioned commercially for the product of the prior invention were inorganic perchlorates, notably potassium perchlorate, which has been the subject of regulatory bans in a number of countries, such as the USA and European Union, because perchlorates contaminate water sources, which can cause methemoglobinemy and hyperthyroidism by eliminating iodine. The main target has been explosives based on inorganic perchlorates, especially explosive emulsions for use in underground mines, which have sodium, ammonium or potassium perchlorate in their formulations;

[0041] 2. The very characteristic of low activation energy of low temperature compounds provides a higher sensitivity to the friction and shock in pyrotechnic mixtures containing such substances, increasing the risk of accidents;

[0042] 3. Sodium and potassium perchlorates are also in the form of crystalline salts of very large particle mean diameter for direct application to the spark-generating mixtures of the prior invention (mean diameter greater than 40 m), so that a prior micronization (particle size reduction) operation is required in micronizers by mechanical shock of compressed air jets, in multiple costly steps in both price and power consumption, until a mean particle diameter of 1.5 m or less is obtained; and

[0043] 4. The negative (inadequate) result in the flash-over test, ie the specific test of the European Union which requires that the pyrotechnic mixture when disposed in final form inside the tube does not increase the breaking distance of the dielectric resistance of the atmospheric air of this same interior. Such a requirement is due to the risk that an electrostatic discharge of the level of energy normally accumulated in the human body occurs at the opposite end of a tube which has come into contact with an electrostatically charged individual, which may initiate a fuze connected to this tube. In other words, the pyrotechnic mixture must have a low electrical conductivity. However, both aluminum and ionic potassium perchlorate are good conductors of electricity.

[0044] In the present invention, these problems have been solved by using only two non-forbidden components (aluminum and iron oxide or copper oxide in particle diameters of the order of nanometers), and which, due to Tammann temperatures higher than perchlorate, present higher activation energy and make their pyrotechnic mixtures less sensitive to friction and mechanical shocks.

[0045] The aluminum of the present invention is in the electrically insulating form because its particles are coated by a hard layer (mechanically resistant) of silica (silicon oxide) or electrically insulating aluminum oxide. Potassium perchlorate has been eliminated or substantially reduced in the present invention because even low moisture of the air is sufficient to make pyrotechnic mixtures containing readily electrically conductive ionizable salts to the extent of being disapproved in the flash-over test. The use of the minimum amounts of perchlorate applies mainly in some applications where passage through folds or knots may occur.

[0046] The object of the present patent has the advantages of dispensing with the use of low temperature substance of Tammann, therefore the pyrotechnic mixture inside it, is less sensitive to friction and shock, dispenses the use or allows substantial reduction of perchlorate contaminants from underground water, it is approved for the flash-over test, ie it has a lower risk of conducting an electrostatic discharge from the human body to its end, and the production process of the pyrotechnic mixture is quite simple by simply mixing the components in an elastic polymer ball mill.

[0047] Several tests were carried out to determine the percentage ranges of the components, following the name and detailed description of each of them:

[0048] 1)Flash-Over Test

[0049] This test is performed on flash-over equipment according to European Standard EN 13763-24: Explosives for Civil UseDetonators and TransmittersPart 24: Determination of the electrical non-conductivity of the shock tube. The test is briefly described below:

[0050] Thirty samples of spark conductor tube of 100 mm length are used in the test, which consists of traversing two thin rod-shaped electrodes, one at each end of the sample, perfectly aligned with the center of the tube, applying a voltage of 10 kV in direct current between the electrodes, and approach its tips slowly until the passage of a spark between them occurs. The distance in millimeters in which 5) the greater the more electrically conductive the tube inner medium, the greater the risk of conducting an electrostatic discharge from the human body into the tube inner. The specification limit of the European Standard is a maximum of 20 mm.

[0051] 2) Propagation Speed Test

[0052] A length of tube measuring 5 m in length is placed between two optical sensors connected to a precision timer. When the tube is started, the light of the spark, when passing the first sensor, starts counting time, and, when it passes the second sensor, stops this count. The propagation speed is obtained by dividing 5 by the time obtained in seconds.

[0053] 3) Test of Minimum Space of Propagation Between Folds

[0054] In 10 samples, the spark of the tube must pass through 10 folds of 180 carried out in the same, at a certain distance between them. The shortest distance between the following: 1 in, 50 cm, 30 cm, 20 cm and 10 cm in which all samples propagate to the tip is recorded as minimum distance between folds.

[0055] 4) Test of Maximum Traction Effort by Knots

[0056] The 80 cm length tube sample with a single knot in half its length, made without tightening, attached at its ends is attached to a traction device with a load cell capable of measuring the tensile stress with accuracy of 100 gf and a digital display of the load cell traction effort. The tube is manually drawn through a lever, and when the desired traction effort is reached, the tube is started at one of its ends by a hand-operated actuator with ear fuze. The passage of the spark by the knot or failure of the spark continuity by the knot is observed by the relative darkening of the tube in the burned session. If the tube fails, a less effort traction will be attempted with a new sample. If the spark passes through the knot, greater effort traction will be attempted on a new sample. The test result will be the highest traction in which 5 successive samples work without fail

[0057] 5) Initiation Test by Low Core Load Detonating Cord (% of Failures)

[0058] 100 samples of 1 m of tube are placed on the ignition with detonating cord with load of 2 g PETN/m linear, known in the industry as NP-02, attached to the cord through a J-type connector. The number of failed parts is noted as percentage of cord initiation failures.

[0059] 6) Impact Sensitivity Test

[0060] The test is performed on BAM Fall Hammer equipment originally developed by the BAM Federal Institute for Research and Testing of Materials from Germany in accordance with European Standard EN 13631-4: Explosives for Civil UseHigh ExplosivesPart 4: Determination of Sensitivity to Impact of Explosives. The test is briefly described below:

[0061] A sample of the powdered mixture shall be subjected to the impact of a known free falling weight from a given height.

[0062] The energy in which 5 successive samples deflagrate is calculated by the formula E=m.g.h, where m=mass of free falling weight; g=acceleration of local gravity and h=minimum height for ignition.

[0063] 7) Slow Delay Element Sensitivity Test

[0064] A delay element of 9 s delay time with a 30 mm column length containing slow delay mixture without additional initiator mixture layer is positioned at the glass PVC hose tip of 6 mm of diameter with variable length, with the end of a spark conductor tube in accordance with the formulations of the present invention, of 1 m in length aligned with the other end of the PVC hose. When the tube is started, the spark must cross the free space inside the hose and start the delay element. The longer the hose length in which the elements start a minimum of 5 successive elements, the better the thermal performance of the spark. The longer hose length at which the elements start without failure is noted as Slow Delay Element Sensitivity.

[0065] 8) Tube-to-Tube Air Gap Test

[0066] A piece of 3 in length spark conductor tube is cut transversely into two 1.5 in halves, and these halves are spaced apart with a given spacing, keeping them aligned within an aluminum guide in the shape of half-round. The largest distance in which the spark, when crossing the open air space between the tube portions, starts the second portion in 5 successive samples, is annotated as Tube-to-Tube Air Gap.

[0067] 9) Test after Exposure to Hot Explosive Emulsion

[0068] Thirty 12 in tube samples, with the ends sealed by a rubber bushing and a fuze capsule according to the industry standard, are immersed in conventional explosive emulsion with marine diesel oil, which causes greater aggressiveness to the plastic, at a temperature of 65 C. for twenty-four hours. The tubes are started and the percentage of failed parts is recorded as Failures by Exposure to Hot Explosive Emulsion.

[0069] 10) Mixture Adhesion Test to the Tube.

[0070] Ten tube samples with a length of 3 in each are weighed in a laboratory scale with an accuracy of 0.0001 g. Thereafter, the inside of the tubes is blown out of compressed air nozzle at a pressure of 0.2 kgf/cm.sup.2 gauge, and a flow rate of 0.2 Nm.sup.3/min. for 2 min, in order to remove the fraction of non-adhered powder to the inner wall of the tube. The tube is weighed again, with accuracy of 0.0001 g. Then the inside of the tubes is washed with a flow of 0.2% aqueous Sodium Hydroxide solution for dissolution of the Aluminum and of the possible Perchlorate and drag of the nanometric Iron Oxide and Talc at a flow rate of 200 ml/min., for a minimum of 3 min. The tube with all the powder removed is again flushed with Acetone at a flow rate of 200 ml/min. for 1 min, and then dried by a dry compressed air flow rate of 0.2 Nm.sup.3/min. at a pressure of 0.5 Nm.sup.3/min. for a minimum of 3 min. for drying the Acetone. The empty, dry plastic tube is weighed with an accuracy of 0.0001 g. The mass of powder initially present in the tube and the mass of the powder remaining adhered to the tube after initial withdrawal with compressed air are calculated by differences, and then the percentage by mass of loose powder in relation to the total mass of powder initially present in the tube is calculated.

[0071] Several tests were carried out to determine the percentage ranges of the components with, for example, the following test which obtained the preferred formulation of the present patent: a ball mill was mixed with polyvinyl rubber balls for 30 minutes of electrically insulating powdered Aluminum coated with Powdal 2900 type silica of Schlenk Metallpulver from Germany, ferric oxide (Fe.sub.2O.sub.3) with a mean particle diameter of 30 nm of Nanophase from England, and talc in the following proportions at weight percent: [0072] Aluminum Powdal 2900: 45%; and [0073] Iron oxide NanoArc FE-300 Nanophase 30 nm: 54%. [0074] Talc: 1%.

[0075] It was also tested the nanometric powdered aluminum with particle diameter of 20 to 100 nm electrically insulating coated with aluminum oxide along with iron oxide nanometric and compatible results were obtained.

[0076] As in the fold and knot tests the distance limits between folding for full functionality and passage of the spark by knots under tensile stress were below that expected for many practical applications, it was tested the use of formulations with small amounts of potassium perchlorate that allow to improve the limits in the test of folds and knots, obtaining the minimum value of 6% of potassium perchlorate and recommended range of 8 to 12%.

[0077] The following results were obtained as described in TABLE 1 shown at final of this report.

[0078] With the tests carried out it was concluded that the formulation of the thermal spark conductor tube of the present invention has the following formulation at weight percent: [0079] Powdered aluminum with a morphology of flake, minimum purity 99.5%, covered and stabilized by silica or other electrically insulating material, with a mean particle diameter between 5 and 18 m, as Powdal 2900 from SchlenkMetallpulver or similar: 35% to 62%; [0080] Nanometric iron oxide with faceted almost spherical morphology, mean particle diameter between 10 and 100 nm, such as NanoArc FE-300 Nanophase or similar: 32% a 60%; [0081] Potassium Perchlorate ranging from 0% to 25%. [0082] Talc: ranging from 0.8 to 1.5%

[0083] With the tests carried out it was also concluded that the preferred formulation of the thermal spark conductor tube of the present invention is as follows at weight percent: [0084] Powdered aluminum with a flake type morphology, minimum purity 99.5%, covered and stabilized by silica or other electrically insulating material, with a mean particle diameter of 11 m, such as Powdal 2900 or similar: 45%; [0085] Nanometric iron oxide with faceted almost spherical morphology, mean particle diameter of 30 nm, as NanoArc FE-300 Nanophase or similar: 54%; and [0086] Talc: 1% for common applications, where it is not important to go through folds and knots; or alternatively: [0087] Powdered aluminum with a flake type morphology, minimum purity of 99.5%, covered and stabilized by silica or other electrically insulating material with a mean particle diameter between 5 and 18 m, such as Powdal 2900 or similar: 45%; [0088] Nanometric iron oxide with faceted almost spherical morphology, mean particle diameter of 30 nm, such as NanoArc FE-300 Nanophase or similar: 44% [0089] Potassium Perchlorate: 10%; and [0090] Talc: 1% for applications where it is important to go through folds and knots;

[0091] With the tests carried out it was concluded that alternatively the formulation of the thermal spark conductor tube of the present invention may be as follows at weight percent: [0092] Nanometric powdered aluminum with a flake type morphology, minimum purity of 99.5%, covered and stabilized by silica or other electrically insulating material with a mean particle diameter of 20 to 100 nm: 35% to 62%; [0093] Nanometric iron oxide with faceted almost spherical morphology, mean particle diameter between 10 and 100 nm: 32% to 60 [0094] Potassium Perchlorate ranging from 0% to 25%; and [0095] Talc: ranging from 0.8 to 1.5%.

TABLE-US-00001 TABLE 1 Results of Practical Tests INITIATION MAXIMUM BY LOW TRACTION CORE MINIMUM EFFORT LOADING PROPAGATION OF DETONATING FLASH- SPACE PASSAGE CORD OVER PROPAGATION BETWEEN BY (% OF FORMULATION DISTANCE SPEED FOLDS KNOTS FAILURES) AI POWDAL 2900 64.5% 6 mm 964 m/s 1 m 3 f-kg 8% Fe.sub.3O.sub.4NanometricNanoArcFE300 from Nanophase 34.5%, talc 1.0% AI POWDAL 2900 45% 7 mm 1091 m/s 1 m 3 f-kg zero Fe.sub.3O.sub.4NanometricNanoArcFE300 from Nanophase 54%, talc 1.0% AI 62% 11 mm 1083 m/s 1 m 4 f-kg zero Fe.sub.3O.sub.4NanometricNanoArcFE300from Nanophase 32% KClO.sub.4 5%, talc 1.0% AI 45% 15 mm 1142 m/s 40 cm 9 f-kg zero Fe.sub.3O.sub.4NanometricNanoArcFE300from Nanophase 44%, KClO.sub.4 10%, talc 1.0% AI 35% 22 mm 1260 m/s 30 cm 2 f-kg zero Fe.sub.3O.sub.4NanometricNanoArcFE300from Nanophase 39%, KClO.sub.4 25%, talc 1.0% Standard HMX/Al mixture of 6 mm 2000 m/s 1 m 2 f-kg zero conventional shock tube with single layer of plastic Standard HMX/Al mixture of 6 mm 2000 m/s 50 cm 8 f-kg zero conventional shock tube with double layer of plastic FAILURES TUBE AFTER SLOW TO EXPOSURE MIXTURE SENSITIVITY DELAY TUBE TO HOT ADHERENCE TO ELEMENT AIR EXPLOSIVE TO FORMULATION IMPACT SENSITIVITY GAP EMULSION TUBE AI POWDAL 2900 64.5% 9.2 N 6 cm 30 nm 25% 5% Fe.sub.3O.sub.4NanometricNanoArcFE300 from Nanophase 34.5%, talc 1.0% AI POWDAL 2900 45% 9.2 N 7 cm 30 nm zero 5% Fe.sub.3O.sub.4NanometricNanoArcFE300 from Nanophase 54%, talc 1.0% AI 62% 9.2 N 6 cm 80 nm zero 3.8% Fe.sub.3O.sub.4NanometricNanoArcFE300from Nanophase 32% KClO.sub.4 5%, talc 1.0% AI 45% 9.2 N 12 cm 100 nm zero 6% Fe.sub.3O.sub.4NanometricNanoArcFE300from Nanophase 44%, KClO.sub.4 10%, talc 1.0% AI 35% 9.2 N 5 cm 15 nm 15% 3.2% Fe.sub.3O.sub.4NanometricNanoArcFE300from Nanophase 39%, KClO.sub.4 25%, talc 1.0% Standard HMX/Al mixture of 3.8 N Fails to 10 mm not performed Not conventional shock tube with single ignite, even performed layer of plastic at zero distance Standard HMX/Al mixture of 3.8 N Fails to 10 mm not performed Not conventional shock tube with double ignite, even performed layer of plastic at zero distance