Title of Invention

"A PYROTECHNIC COMPOSITION FOR ENERGY RICH PROPELLANT"

Abstract This invention relates to a pyrotechnic composition for energy rich propellant, comprising of a metal fuel, an oxidizer and a binder wherein, titanium powder as metal fuel is 25 to 60% by weight, potassium nitrate as an oxidizer is 70 to 35% by weight preferably 55 to 45% by weight, binder is the solution of plasticised ethyl cellulose in toluene which is around5% by Wight.
Full Text FIELD OF INVENTION :
This invention relates to a titanium based pyrotechnic composition for energy rich composite propellants.
PRIOR ART:
Ignition system for energy rich composite propellants are required to provide rapid but smooth ignition of propellant charge under the specified temperature range of -40° C to + 60°C and under environmental conditions. An increase in temperature, pressure and oxygen concentration facilitate ignition. There is a minimum ignition pressure/heat flux per unit area of propellant below which ignition is unreliable and erratic.
Conventionally gun powder having high gas to solid ratio has been used as an efficient igniter for ignition of double based propellants at ground level.
The disadvantage of using gun powder as igniter is that it fails to ignite at high altitude.
Another disadvantage of using gun powder as igniter is that it is not a reliable igniter for composite propellants which have high auto ignition temperature and poor mechanical properties.
Yet another disadvantage of using gun powder as igniter is that its performance is highly sensitive to the amount of moisture/ volatile matter content.
Further disadvantage of using gun powder as igniter is that it is not very efficient for propellants which have low structural integrity and require low critical pressure for steady state of combustion.
A pyrotechnic composition usually contains a small percentage of binder which may be of natural origin or man made organic polymer, which holds fuel (metal) and oxidiser components in homogenous blend. Some other pyrotechnic compositions with metal powders such as Al, Mg, B as fuel and KNO3 as oxidiser, with or without binder have also been used as igniter for the propellants.
However, disadvantage of using these pyrotechnic compositions without binder is that on storage the ingredients of constituent composition are likely to segregate.
Another disadvantage of using these pyrotechnic compositions without binder is that the composition becomes sensitive to mechanical impulse.
Yet another disadvantage of using these pyrotechnic compositions without binder is that the composition is susceptible to ingress of moisture which affects the final performance.
Still another disadvantage of using these pyrotechnic compositions without binder is that the composition does not have pelleting property and thus are unsafe.
Further disadvantage of using these pyrotechnic compositions without binder is that the composition does not give reproducible and reliable results.
Still further disadvantage of using these pyrotechnic compositions without binder is that the composition do not have high compressive strength.
The conventional metal/oxidant compositions which can funtion in wide operating temperature environments are Mg/K NO3 and B/KNO3.
The disadvantage of Mg based ignition composition is that the Mg readily reacts with water and leads to deterioration of performance.
The disadvantage of Boron based ignition composition is that the boron used should of high purity and ultra fine particle size (less than 1 micron) which is very costly and its availability is limited.
Generally pyrotechnic compositions usually contain a small percentage of binder which may be of natural origin or man made organic polymer, which holds metal and oxidizer components in uniform blend. Some compositions with Titanium as metal fuel and potassium nitrate as oxidiser use natural resins like Gum Arabica/ wax as binder.
The disadvantage of such natural resins is that their chemical composition is not constant which results in inconsistency in performance.
Another disadvantage of natural resin is that they are susceptible to moisture and thus absorb moisture on storage resulting in deterioration of performance.
Yet another disadvantage of igniters using natural resins is that the natural resins have their softening point very low which makes composition to lose their structural integrity at higher storage temperatures.
Some compositions with Titanium as metal fuel and potassium nitrate as oxidiser use nitrocellulose as binder for increasing the energy content.
Disadvantage of nitrocellulose as binder is that it increases the sensitivity of the composition towards impact and friction.
Another disadvantage of nitrocellulose as binder is that it reduces the shelf life of the composition on storage.
The disadvantage of using pyrotechnic composition with organic polymer binder viz Ethyl cellulose without plasticisation, the composition is prone to oxidation in presence of light and temperature above the softening point (150°C).
Another disadvantage of using pyrotechnic composition with ethyl cellulose without plasticisation as binder is that on storage the composition deteriorates and pellet becomes brittle in nature.
OBJECTS OF THE INVENTION
The primary object of the present invention is to propose a formulation of a titanium based pyrotechnic composition for energy rich propellants.
Another object of the present invention is to propose a formulation of a titanium based pyrotechnic composition with minimum ignition delay.
Still another object of the present invention is to propose a formulation of titanium based pyrotechnic composition which has optimum burning time to reach pressure maximum i.e. optimum mass consumption rate.
Yet another object of the present invention is to propose a formulation of titanium based pyrotechnic composition which has good ageing characteristics.
Still another object of the present invention is to propose a formulation of titanium based pyrotechnic composition which has superior mechanical properties to sustain stresses during handling and transportation.
Further object of the present invention is to propose a formulation of titanium based pyrotechnic composition which is stable.
Yet further object of the present invention is to propose a formulation of titanium based pyrotechnic composition which is reasonably insensitive and easy to process.
Still further object of the present invention is to propose a formulation of titanium based pyrotechnic composition which provides efficient ignition of energy rich propellants even with low mechanical properties.
SUMMARY OF INVENTION
1. According to this invention there is provided a pyrotechnic composition for energy rich propellant, comprising of a metal fuel, an oxidizer and a binder wherein: -
a. titanium powder as metal fuel is 25 to 60% by weight
b. potassium nitrate as an oxidizer is 70 to 35% by weight
preferably 55 to 45% by weight
c. binder is the solution of plasticised ethyl cellulose in
toluene which is around5% by Wight.
This present invention proposes a process for preparation of titanium based pyrotechnic composition with plasticised ethyl cellulose as binder, potassium nitrate as an oxidizer in an igniter for energy rich propellant which require hot solid slag or incandescent particles to achieve efficient and sutained combustion. The process uses titanium powder of purity higher than 98% and of particle size 8to 12 microns. Plasticisation of ethyl cellulose is done with diethyl phthalate. Solution of dried plasticised ethyl cellulose was prepared using distilled toluene as solvent, with constant stirring. Titanium powder and potassium nitrate are separately mixed and sieved 3-4 times. To 50 % of the solution of plasticised ethyl cellulose (PEC), the homogenized mixture of titanium and potassium nitrate powder is added and the remaining 50% is poured over the mixture and thoroughly mixed to get a homogenous mix.
The composition and process of the present invention differ in use of, polymeric binder that is Ethyl Cellulose, as against use of Gum Arabic which is a natural resin. Ethyl Cellulose binder being synthetic one has fixed chemical composition as against variable chemical composition of natural resins. This binder has high resistance to moisture in contrast to high susceptibility of natural resins toward moisture. Due to above two reasons pyrotechnic compositions using ethyl cellulose as binder give consistent and rehable performances as against unreliable and inconsistent performance of pyrotechnic compositions using natural resins. These advantageous features of ethyl cellulose are further enhanced by plasticisation of ethyl cellulose with Diethyl phthalate. The novelty of formulated compositions are that they can be easily prepared, safe to handle and efficiently used in volume limited applications.
The formulations of present invention with 50% with weight of titanium are safe to manufacture, handle, transport, store and use as it is less sensitive to impact and insensitive to friction upto 30 kg of load. This composition shows smooth and reproducible pressure - time profile at hot (+50°C), ambient and cold (-20°C) temperature.
DESCRIPTION OF INVENTION
According to the present invention, there is provided a formulation of titamum based pyrotechnic composition, preparation of which comprises of the steps of:-
a) Preparation of Plasticised Ethyl Cellulose
Plasticised ethyl cellulose (PEC) is prepared by plasticisation of ethyl cellulose with diethyl phthalate taking 70 to 80 % preferably 75 to 77.5% by weight of ethyl cellulose and 30 to 20% preferably 25 to 22.5% by weight of diethyl phthalate.
The composition based on titaniun powder plastisum nitrate and a binder to not realiting only
in aggreastion of proparties, instead there is synergiest and these ingreadients are not realiting
chemically .
b) Preparation of Solution of Plasticised Ethyl Cellulose
8 to 10% solution of 5% by weight of dried plasticised ethyl celulose (PEC) is prepared by dissolving PEC in toluene in a suitable vessel with constant stirring to get uniform solution.
c) Preparation of Mixture ol Fitap and Nitric Powders,
25 to 60% preferably 40 to 50% by weight of titanium powder with purity higher than 98%, particle size preferably of 8 to 12 microns is mixed with 70 to 35% preferably 55 to 45% by weight of potassium nitrate. The mixture is sieved 3-4 times to get homogeniety.
d) Mixing of (Ti+KNCM in PEC Solution
The composition of the present invention is prepared by mixing around 5% by weight of PEC solution with 50% of the mixture of titanium powder and potassium nitrate as prepared above. The remaining 50% PEC solution is poured over mix and is throughly mixed to get homogenous mix. The mix is allowed to become semi-solid which is then granulated by passing through a sieve. These granules are dried in a water jacketed oven at 60±5°C for about 2 to 6 hours to reduce the volatile matter to around 1%.
The invention will now be illustrated with an example which is intended to illustrate the working of the invention and is not intended to be taken restrictively to imply any limitation on the scope of the present invention.
Example 1
The plasticised ethyl cellulose (PEC) was prepared by 29% plasticisation of ethyl cellulose N-200 with diethyl phthalate. A 10% solution of dried plasticised ethyl cellulose was prepared using distilled toluene as solvent in a suitable vesel wth constant stirring to get uniform solution.
Twenty five (25) percent of titanium powder with purity 98% particle size 8-12 microns and seventy (70) percent of potassium nitrate were weighed accurately and mixed on a was paper using horn spatula. This mix was then sieved 3 times throug 25 MESH sieve to get homogeneity. A 10% solution
of five percent of PEC prepared & out of which approximately 50% of this solution was taken in the mixing vessel & weighed mix of Titanium & potassium nitrate was added carefully avoiding the spillage of material. The remaining 50% of PEC solution was poured over mix and was thoroughly mixed using horn spatula to get homogeneous mix.
The mix was poured on conducting polythene sheet kept in tray and allowed to become semisolid. The semisolid'mass/dough was then granulated by passing through 25 BSS (600 microns) sieve. The sieved granules were then retained on 52 BSS (300 microns) sieve and retained material was dried in water jacketed oven at 60 + 5° C for 2 to 6 hours to reduce the volatile matter to 1.0%. The dried granules were used for characterisation. The qualified granules were used for making pellets in a pelleting machine using appropriate die & punches. The pellets are used for further tests.
Example No 2 to 8
For example No 2 to 8 the procedure for preparation of commpositions is identical to that of example No 1 except that percent of titanium was increased linearly by 5 percent, from 30 percent for example No 2 to 60 percent for example No 8, while percent of the potassium nitrate was reduced by five percent linearly from 65 percent for example 2 to 35 percent for example 8. Five (5) percent of binder (PEC) was used for all the above examples. These pyrotechnic formulations and their properties are summarised in Table 1.
The calorimetric value of each composition was determined in the 300 cc julius paters bomb Calorimeter. The Ignition temperature was determined for each composition by idigenously developed Micro DTA The sensitivity toward impact were determined by Fall Hammer /appearatusjusing 2 kg weight and friction sensitivity was determined by julius Peter Friction Sensitivity Equipment. The formulated compositions were evaluated for Pressure maximum, ignition delay etc in a closed vessel (free volume 700 cc) designed for this purpose at loading density O.Olg/cc. The results are given in Table-2.
The results in Table-I indicates that the cal values linearly increases with increase in titanium content upto 50%. However, with further increase in Ti the cal values decreases. For example No. 6 for 50% Titanium
composition the cal-val is highest 1890 cal/g. The ignition temperature of compositions goes on decreasing with increase in titanium content i.e. from 822° C for example 1 with 25% Titanium to 725° C for example 8 with 60% titanium. The oxidation of pure Titanium starts at 780° C which is responsible for high ignition temperature of Titanium based compositions as compared to Boron or magnesium based compositions. This property makes the Titanium based pyrotechnic compositions highly stable & safe at high temperature.
The sensitivity study shows that height of 50% explosion found to be 138 cm for 25 % Titanium composition & goes on reducing with increase in Titanium content and reaches minimum making composition mosty sensili\e at 40% of Titanium. This is near stoichiometric composition. With further increase in Titanium % the height of 50% explosion goes on increasing making composition safe for processing, storage and use. All the formulated compositions are insensitive to friction upto 36 kg dead load.
The above results reveal that compositions with 40, 45, & 50 % of Titanium are more energetic. However, compositions with 40 & 45% of titanium are comparatively more sensitive to impact.
The results of closed vessel studies are given in Table - 2, which show Pmax & ignition delay values for compositions with 30, 35, 40, 45, 50, 55 & 60% of Titanium compositions. However, burning time to reach Pmax (BTPm) values for 25 % & 30% Titanium compositions show that the combustion of these compositions are sluggish whereas these values for 40-60% Ti compositions are at very attractive levels.
Energy rich composite propellants were subjected to static evaluation using titanium based igniter fonnulations. The pressure - Time (p-t) profile is found to be smooth for igniter fonnulations with 45, 50 & 55% of of titanium at ambient temperaure conditions. However, composition with 50% Titanium gives smooth p-t profile for energy rich composite propellant even at +55°C & (-) 20°C making it an attractive igniter composition for ignition of energy rich but even mechnically poor composite propellants.
TABLE - 1
Heat Output and Sensitivity Data of Titanium Based Pyrotechnic
Compositions
(Table Removed)
TABLE-2 Pressure Output in 700 cc Closed Vessel (Loading Density 0.01 g/cc)
(Table Removed)
It is to be understood that the process of the present invention is susceptible to modifications, adaptations, changes by those skilled in art. Such modifications, adaptations, changes are intended to be within the scope of the present invention, which is further set forth under the following claims :-




WE CLAIM
1. A pyrotechnic composition for energy rich propellant,
comprising of a metal fuel, an oxidizer and a binder wherein: -
(a) titanium powder as metal fuel is 25 to 60% by weight
(b) potassium nitrate as an oxidizer is 70 to 35% by weight preferably 55 to 45% by weight
(c) binder is the solution of plasticised ethyl cellulose in toluene which is around5% by Wight.

2. A pyrotechnic composition as claimed in claim 1 wherein said titanium powder is present in an amount of 40 to 50% by weight.
3. A pyrotechnic composition as claimed in claim 1 wherein said potassium nitrate is present in an amount of 55 to 45% by weight.
4. A pyrotechnic composition as claimed in claim 1 wherein the composition is dried at 60+5°C for 2 to 6 hours to reduce the volatile matter to about 1%
5. A pyrotechnic composition for energy rich propellants as substantially described herein.

Documents:

991-del-1997-abstract.pdf

991-del-1997-claims.pdf

991-del-1997-complete specification (granted).pdf

991-del-1997-correspondence-others.pdf

991-del-1997-correspondence-po.pdf

991-del-1997-description (complete).pdf

991-del-1997-form-1.pdf

991-del-1997-form-19.pdf

991-del-1997-form-2.pdf

991-del-1997-form-3.pdf

991-del-1997-gpa.pdf


Patent Number 243596
Indian Patent Application Number 991/DEL/2000
PG Journal Number 44/2010
Publication Date 29-Oct-2010
Grant Date 27-Oct-2010
Date of Filing 06-Nov-2000
Name of Patentee THE ADVISER,DEFENCE RESEARCH & DEVELOPMENT ORGANISATION
Applicant Address DEFENCE RESEARCH & DEVELOPMENT ORGANISATION MINISTRY OF DEFENCE, GOVT OF INDIA, B-148, SENA BHAWAN, DHQ P.O. NEW DELHI-110011, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 NANDKUMAR TRIMBAK CHITALE HIGH ENERGY MATERIALS RESEARCH LABORATORY SUTARWADI, PUNE 411021, INDIA.
2 ANIL GANPAT DUGAM HIGH ENERGY MATERIALS RESEARCH LABORATORY SUTARWADI, PUNE 411021, INDIA.
3 HARISH JOIATAIRAM GANDHI HIGH ENERGY MATERIALS RESEARCH LABORATORY SUTARWADI, PUNE 411021, INDIA.
4 SANJAY MADHUKAR KALBHOR HIGH ENERGY MATERIALS RESEARCH LABORATORY SUTARWADI, PUNE 411021, INDIA.
5 VARSHA SANJEEV BHINGARKAR HIGH ENERGY MATERIALS RESEARCH LABORATORY SUTARWADI, PUNE 411021, INDIA.
PCT International Classification Number C06B 46/34
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA