A new pyrotechnic composition containing  Mg/KNO3/phenolic resin has been formulated and studied in detail for its  sensitivity, mechanical and thermal properties, moisture and  environmental effects and performance in a closed vessel. The data  generated reveal that this composition shows superior performance,  better mechanical properties and less susceptibility to moisture as  compared to gunpowder. In addition, performance of the composition under  extreme hot (45 degree centigrade) and cold (-26 degree centigrade)  environmental conditions is not affected at all. Differential thermal  analyser results indicate that phenolic resin plays a vital role in  reducing the ignition temperature of Mg/KNO/sub 3/ system

Mujumdar, V. A.

Redkar, A. S.

Singh, S. N.

English

Defence Science Journal

Defence Science Journal, Vol 46: No 1, January 1~96, pp 41-47@ 1996, DESIDOC IStudy on Magnesiultl-based Pyrotech,nic C~mpositionas a Priming ChargeA.S. Redkar, V.A. Mujumdar and SoN. SinghHigh Energy Materials Research Labora~~ry, Pune-411 021ABSTRACTI IA qew pyrotechnic coin position containing Mg/KNO3/phenolic resin has been formulated andstudied in detail for its senSitivity, mechanical and thermal properties, moisture and environmentaleffects and performance in la closed vessel. The data generated reveal that 1his composition shows, superior performance, better mechanical prop('.rties and I~ss susceptibility tp moisture as comp'aredI to gunpowder. In ad<!ition, performance of the composition under extreme hot (45 °C) and 'coldI (-26 °C) environmental conditions is not affected at all. Diffcrential thermal analyser results indicatet that phenolic resin pl"ys a vital role in reducing the ignition temperature of Mg/l.'NO3 system.I II. INTRODUCTION \ and improved mechanical and th~rmal properties.G d .I I d ..Further, most of the igniter compositibns based on thisunpor.v er tS common y use as a prtmlng ..J ...t . d .. t . ote h . cs a d do ble base system are nearer to the stOtChlometrlc ratio. KeepIngcomposl Ion Ian Ignl er In pyr c nI n uII t t . I H t . k these facts in view, it was considered of immense interestprope an s, respec Ive y. owever, ex enslve wor .... d t b I .I t . t d .. 1 to formulate a new pyrotechnIc composition based oncame ou y severa sci~n IS s on gunpow er pnmarl y ..., .,.. KNO h j I d I h . d . t th t Mg/KNO 3 system with phenolic resIn havIng IngredientcontaInIng, c arcoa an su p ur In IC~ es a, ...h b ' 3h ' tl j . fl d b percentage of 38/51/11, which IS a stolchlometncallyt e com ustlon p enomenoI IS grea y In uence y .., , ..h d .. f h I th t . I . th balanced compositiOn, and evaluate In detail ItSt e type an ongln o c ar Op , e par IC e size, e.tt I t d th t t 1-3 B ' d I physicochemical properties in addition to performance,mols ure con e'n an e empera urF ' esl es,I h l . th d I t I th This paper reports the results of various experimentssu p ur present In e gunpow er acce era es e. f M d . t I b d t h .1 conducted on this composition. Further, an attempt hascorrosion o 9 ppw er In me a -ase pyro ec nlC .compositions. As a result, the composi~ion reliability4 also baen made to u~derstand the role of phenolic resin. d I ff t d I . f th .!I b k d binder in combustion phenomenon by means ofIS a verse y a ec e , n view O ese ~raw ac s an. .I th ' f I. t .J., t of th g powder differential thermal analyser (DT A ) ,a so e In enlor .energy ou pu e un , I Imetal-based pyrotechnic compositions generally., ., I. 2. EXPERIMENTAL METHODScontaInIng Mg/K~O3 and bln,der system, have beenreportedly used as priming anti igniter compositions5. The composition Mg/KNO3/phenolic resinThese. compositions. show ~etter performance as (38/51/11) was prel'ared'by taking Mg p,owder of highcompared to gunpowder due to. high exotherm'ic purity (> 98 per cent) and particle size + 63 Jim/reaction. Literature survey on metal-based priming add -150 Jim and dried KNC>3' particle size -125 Jim, Theigniter compositio~s has :revealed that 'a few binders phenolic resin having softening point 68 -74 °C wassuch as plasticised ethyl Icellulose6 (PEC), faminac1, procured from the trade, Magnesium powder (38 g) waspolyvinyl alcohol and polyvinyl acetateS, etc, of varying first coated with resin lacquer which was obtained bypercentage (1-10 per cent), have been incorporated in dissolving the phenolic resin powder (11 g) in methylMg, B/KNO3 system~ to achieve better homogeneity ethyl ketone (20 ml). Subsequently, the coated MgI--Received 13 June 1994, {ev\sed 09 February 199541DEF SCI J, VOL 46,-NO 1, JANUARY 1996powder after removal of solvent vJas mixed with driedKNO3 (51 g) and then sieved through 600 Jim sieve toget a homogeneous mixture. The composition wassubjected to the evaluation tests.3.2 Thermal Characteristics3.2.1 Dejlagration TemperatureDeflagration temperature wak obtain~d on 5 !llgsample by gradually raising the temperature at the rate,of '5 °~/min. The temperature at which the sampleignited was recorded (Table,2).3.2.2 Ignition Temperature 'I \Ignition temperat~re was recorded by using DT A<laboratory made) .DT A curves were recorfed in thepresence of static~ air with 5 mg sample in aluminacrucibles at heating rate of 10 °C/min <:rable 2).3. EVALUATION I3.1 Measurement of Sensitivity.3.1.11mpact SensitivityImpact sensitivity of the composition was measuredby fall hammer method using 2 kg drop weight and20 mg of sample. The 'height given in Table 1 refers to50 per cent probability of explosion of the composition\;.3;1.2 Friction SensitivityFriction sensitivity of the composition was measuredby Julius Peter apparatus using 10 mg of the sample.The values given in Table 1 refer to the minimum weightunder which three samples did not ignite..I3.2.3 CaAorimetric Value Mea5'urementICalorimetric value ofj the comp~ition wasdetermined by Parr Bomb cal~rimeter of 3do cc volumeat 1 atm pr~ssure. ~ quantity of 1 9 of the sample wasignited and total heat output was I measured (Table 2).I,Table I. Data on sensitivity of Mg-based composition and GP-4036. 3.5.97.5I,54.0 36. 3.5.MglKNOjphenolicresinGunpowder(KNOJ/OS)~--.Tested up to the maximum limit of the apparatus.3.3 P-D18X ~e8SUreD1ent IPressure-time output of Mg-based composition aswell as gunpowder (GP-40) was tletermined in a closedvessel of 100 cc volu.me at loadibg depsities 0.02, 0.04,0.06,0.08 and 0.10 g/cc. Comp~sitions were p\aced ina cloth bag and ignited with ail electric squib. Tht resultsof P-max at ambient temperature ar~ shown i" Fig. 1.3.4 Crushing strenglh1Crushing strengt~ of the composition was measuredby Instro~ machine bsing pressed pel.lets of dimension20 mm x 20 mm. 1ihe values' report~d in Table 3 areI .the average of five pellets. ,3.1.3 Spark SensitivitySensitivity to spark was measured9 by taking ~O mgof sample between two electrodes placed at a dist~nceof 2 -2.5 mm. The energy of spark was varied from15 mJ to 5 J. The values given in Table 1 refer to theoptimum energy at which two samples di~ not ignite.3.5 Moisture Absorption I,Moisture absorption was determined by exposingthe composition (2 9 each) at ~4, 75, 84 and 96 per centITable 2. Data on thermill characteristics or Mg-based composition and GP-40>360 1784 138 452MgI KNOJ/phenolicresinGunpowder(KNOJ/OS)>360 889 252 42442IREDK\R, et al: Mg-BASED PYRQTECHNIC COMPOSITION AS PRIMING CHARGEFigure I. CV firing at different loading densities.jTte 3. Data on crushing strength after exposure to different relative humiditiesComposition Time' Crushing strength (kg/cm1 .~ ~ -(hr) Relative humidity (% )52 64 75 84 96IMgIKNO3/Phenolic {esin O244872965645525605505404724551441379401377369367387386376370361350325320IIGun powder (KNO3/0S) O2448.72965325205255255153643563453403483373023()()284215112552291681364543~eEF'SCI J, VOL 46, NO 1, JANUARY 19%relative humidity, for a period of 24, 48, 72 and 96 hr ,respective.ly. The increase in weight due to moistureabsorption was recorded (Fig. 2).4. RESULTS AND DIscuSSIONResults of sensiti~ty to impact, friction and sparkare. given in Table 1. It is seen that MglKNO3/phenolicresin-based composition is less sensitive to impact thangunpowder but values for friction and spark sensitivitiesare comparable. This may be attributed to having moreor less similar order of oxygen balance as obta~ned ~gunpowder and also the elastic nature of the phenolicresin.3.6 Environmental TestsISAT(B) tests for the composition were conductedfor 4, 13, 36 and 52 weeks as per standard procedureloto assess the functioning as well as shelf-life. The loosecomposition (1 g) placed in monotubular propellant(3.5 g) and properly sealed was taken for conductingthe tests. The P-max was recorded by cy firing aftercompleting the test in a stipulated period.3.7 IgnitabilityPyrotechnic compositions were first pressed in steeltubes having 30 mm length and 20 mm diameter in twoincrements. Magnesium-based composition as a priminghaving quantities 0.3 9 and 0.5 g, respectively werepressed on top of the main composition under 7 tondead load. The ignitability was tested with an electricsquib.Data on thermal characteristics (Table 2) indicatethat MgIKN°3/phenolic resin-based compositionpossesses twice cal-val but less gas volume as comparedto gunpowder; the composition is !elatively moreenergetic due to high exothermic reaction between Mgand oxidiser. Further, it is also seen that the ignitiontemperature of the composition is slightly higher thanthat of gunpowder .Data on closed vessel at ambient temperatureas shown in Fig. 1 indicate that P-max increases inMg-based composition as well as gunpowder withso1.0-~-zot~0[/)~<~~-0~30201024 U 72 96TIME (hr).,Figure 2. Moisture absorption by Mg-based composition and gunpowder at different relative humidities.44REpKAR, et aJ: Mg-BASED PYROTECHNIC COMPOSITION' AS PRIMING CHARGEincrease in loading ddnsity. Increase in P-max in thecomposition is 20-2S; per cent more than in gunpowderbecause of high heat' evolution in the chemical reactionof the composition. It is also s,een th~t although thereis no change in (-max (time tq altain P-max) appreciablywith increased loading density for both compositions,t-max for Mg-based composition Is 5-6 times more thanthat for gunpowder because of delay in ignit.ion of thecomposition. Secondly, the \"esults of J hot and coldtemperature conditioning tTable 4) show that (-max isleast affected under diff.erent !emperature conditions.for gunpowder, while in case of Mg-based compositionthe crushing strength decreases marginally. In addition.,the results of the composition exposed to 96 per centRH as shown in Table 5 indicate that cal-val reducesdrastically whereas ignition temperature increasesappreciably due to ingress of moisture. This means thatthe reactivity of the composition is extensively affectedby moisture. This has been further supported by cyfiring results, which reveal that pressure outputdecreases as compared to P-max at ambienttemperature. The data on ISA T(B) test (Table 6) revealTable 4. Data on cy firings for Mg-based co",position and GP-40Data 011 moisture absorption (Fig. 2) indicale thatthe composition as well as gunpowder (~P-40) are notmuch affecteq by moisture up to 75 per cent RH, butabove 80 per ,cent RH ~here is a significant moistureabsorption i~ both compositions. Secondly, thecomposition is less susc~ptible to mbisture as comparedto gunpowder. Further, it is rllso seen from Table 3 thatthe crushing I strength of Mg-based composition iscomparable with that of gunpowder up to 75 per centRH but it gets sbverely redu:ced beyond 84 per cent RHTable 5. I)ala f.n cal-vlil and cv firings after exposure to 96% RH"Compositiontl.80476 1309 126.00Mg!KNO]/phenolicresinGunpowder(KNO]ioS)12114690 6.44Table 6. Dat~ on CV firing of Mg-based composition after ISAT(B) test with double base propellantperiod ofexposure<"'Fek)Hot. Cold.P-max t-max(MPa) (ms), AmbientP-max I t-max .P-max t-max(MPa) (ms) I (MPa) (ms)..I0 12.30 225.50 13.40 218.00 12.90I4 12.00 \ 230.00 12.55 219.10 11.30~}3 I 12.25 222.10 12.40 220.00 11.3026 12.00 22R.05 12.7R 2P.()()() 12.45:11) \ 12.~() 2~.I.(NI 12..1/1 .'2.I(HJ I~HII52 I 12.25 220.(K) 12.50 2]2.()() 12.(K).C:lrlrillgl:~ wcrc C()hdili1)ncd I() +45 0(' "rnl .26 0{' "flcr c(lmrll:220.0244.8240.0247.n2..2.(1243.045DEF SCI J, VO"L 46, NO I, JANUARY 1996,phenolic resin are shown in Fig. 4. Frbm Fig. 4, it isevident that the ignition lof MglKNO3 ta~es place at495 °C whereas t~e ignition of MglKNO;/pgenolic resincompositions occurs at 452 °C. This may be attributedIto the exothermic reaction between bipder and oxidiserbetbre ~g-oxidiser reaction, thereby cau~ ing reductionin ignition temperature. This mechani m is further,supported'by the DTA c1!1rve of phenolic resin withoxidiser, which gives the on~et exotherm temperatureat 380 00, involvIng chemical reaction between freemethylene group obtained froni thermal degradationllof phenolic resin and oxidiser. :that the performanc;e of the composition is not at allaffected in different environmental conditions. ,Data on ignitabiiity of the Mg-based. compositionused as priming with pyrotechnic compositions (Table 7)Table 7. Ignition behaviour of Mg-based composition and GP-40Composition Priming:quantityMain pyrotechniccompositionMgiSr\NO3)!NaNO3/PV~1polyester(g)Results(g}0.30.50.30.515151515IgnitedIgnitedIgnitedIgnitedMg/KNO3/phenolicresinGunpowder(KNO3/OS)5. CONCLUSION tThe results obtained indicate that phenolic'resin-based compositioq is. art enJrgetic pyrotechniccomposition which can be used as a prilning forpyrotechnic compositions for better ignition teliabilityin place of gunpoider. IIIACKNOWLEDGE~ENTSThe ~uthors aie gratefull to Dr Haridwar Singh,Direc,or, High Endrgy Materials Re~e;arch L~boratory,Pune, for his valuable guidance and perpnission topublish this paper. Our sincere thanks are hlso d~e toDr J .P .Agrawal for his valuable suggestions.Iindicate that the optimum quantity fbr ignition of main\pyrotechnic composition is 0.3 g, similar to gunpowder .However, 0.2 g Mg-based composition in pressed form.is difficult to ignite with an electric squib.Mg/KNO3/phenolic resin-based composition wasfurther studied by DT A to investigate the role of binderin the combustion phenomenon. The DTA curves forphenolic resin and KNO3, are shown in Fig. 3 an~ thosefor phenolic resinlKNO3, Mg/KNO3 and Mg/KNO310~TE--<]!00z~I Figure 3. DT A curves for phenolic resin and KNOJ.46REDKAR, et aJ: Mg-BASED PYROTECHNIC COMPOSITION AS PRIMING CHARGEj .4620><~i~<3!0~~Mg/KNOJ/PHENOLICRESIN537337 452~g/KNO3495337I 442I ~~ ".:1-A- KNOJI.337 380 \ PHENoLIC.RESIN ,0 100 200 300 1.00TEMP (OC)s~o 600 700Figure 4. DT A curves for binary and ternary systems.6.7.89.REFERENdESI1. Sarse,1 R.A. Characterisation of charcoal used tomake black powder. Proceeqings of ~he 9thInternational Ryrotechnic Semihar, 1984. p. 471.2. Wood, D.J. Characterisation Jf g~npowders byclosed vessel firings. Proceed~ngs of the lOthIintertIational Pyrotechnic Seminar, 1985.pp. ~1-1-12.4 I3. Blackwood, J.D. &( Bowden, F.P. The initiation,burning and t~ermal decomposition ofgunnowder. Proc. koy. Soc., 1952, 213A, 285.4. CackJtt, J .C. Monograph of pyrotechnics. RoyalArmament Reseatch & Development Estt, UK,1965. p. 10. I10.Shidlovskiy, A.A. Principles of pyrotechnics.National Tech. Info. Service, USA, 1964, p. 475.Paul, B. Studies on properties and application ofBIKNO3. 3rd International Pyrotechnic Seminar ,1972, p. 253.Fraas, R. & Taylor, P. Combustion propagationratio of vital fuel/oxidant/bil1der system atsimulated high altitude. Proceedings of the 9thInternational Pyrotechnic Seminar, 1983. p. 151.IHaws, L.D.; Amico, R.C.D. .& Gibson, A.Design, development and applic~tion of a versatileelectrostatic sensitivity tester. ~inutes of the 17thExplosives Safety Seminar, 1976, 2, 1423.IIntensified Standard Alternating Trials (B), JointServices Guide 0102, (revised version) ~evisionNo.1 of Joint Services Document 1000, May 1984.Bikales, N.M. Plastics, resins, rubbers, fibers.Encyclopedia of Polymer Science andTechnology, John Wiley & Sons, New. York,USA, 1969, 10, p. 46.5. Singh, Harihar; SomAyajullu, ~.I. & Rao, B.R.Selectiori of an igniter ~ystem for Mg-based solidfuel-rich\propellant, Prop., Explos., Pyrblech.,1988,13,52154. I11~.17

Study on Magnesium based Pyrotechnic Composition as a Priming Charge

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Study on Magnesium based Pyrotechnic Composition as a Priming Charge

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