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Joa o cientic & Indstial eseac

ol 6 , Novembe 2002 899-9

Solid Propellant Binders

R ai*

eament o Aeosace Engineeing, Indian Insttue o cience Bangaloe 5600

oli d oel ans ae wide y sed in mode ockets and mis sil es Alt hogh te hi stoy o soli d ockes cold be tacedto the disovey o gnowde ove a tosand yeas ago he tecnology cold be eected only by he late ha o (the 0lhcenty he aile o gnowd ocets was lagely de to te nknown consolidating techniqe o te owdecomosition he megence o lae solid oellan motos had to awai the dawn o olyme science andtecnology(&. eciic synteses o nctionaly teminaed olymes having coss-lnkin caability led to temegene o castng tecnology o solid comosite oellans his eview descibes te vaios olyme elbindsysems sd o consideed o se in solid oellants I i ncldes a bie backgond advantaes and shocomins o tevaios systems an accont o te cUently sed bindes and a citical svey o he advaned olymes envisaged o tesage cial emasis as ben laid on ecenty syntesized olymes havin N-N bonds in thei stctes and on teeasibilty of develoing smokeless oellants based on ammonim nit ate

Inoducion

emica propeas are te mai sorce o

propsio eery o ockets ad missies. eeormos amot o eery eeded to ac a spaceeice is proided by te cotoed combstio o acemica combiatio o a 'e ad a 'oidizerko as propeat A rocket e is basicay a

edci ae ic e oidized od reeasei eat eery ad aseos prodcts O te arios

e/oidizer combiatios depedi o teirpysica states soid composite prope atscomprised a poder oidzer embedded i a mati oa e are te oes sed ery idey e soidpropeat rockets are easier to ade ad i eadytose coditio a te time iiay te soidpropeats ere mea or combat rockets oy btteir simpicity ad aaiabiity i amost imitedsize ae ed em to be sed as te mai sstai er orbooster care or may types o ockets admissies e imese poress i soid ockets may

be oticed by compari te size o te soidboosters e ist booster cae deeoped orAO (etAssisted akeO) aicrat eied oy282 k ie te iat size booster sed i pacette e is a 3.7 m diam ad 3847 m o raiai 504 t o propea t.

*Proesso meits

Hisoical Backgound

Historicay te irst soid rockets erepojectie acers i ar based o poder (asoko as back poder) comprisi a mitre opotassim itate (oidizer) carcoa ad spr(e/bider). e compressed mitre cotaied i ameta tbe it a oe o oe ed ormed te crderocket ipp ta te ki o Mysoe i te ate

8 cetry sed tem prosey i is battes. ose days miitary rockets ere ot i se Erope bt ey ere i eistece i dia eyere borroed by te Bitis ater ai beetemsees eposed to rocket attack eareiapatam i 1 799 i as aaist ipp. eseee oeer crde rockets acki rae saetyad accracy ad arey eiabe

e pode sticks (rais) made simpy bycompressi te cae to a reasoaby i desityto make it iorm caot be deectree ascompressi akes te rai ecessiey britte.Britte cares deeop airi e cracks iis ibe to te

eye o temperatre cae dri sorae or ietasporti rom oe pace to aoter ecombstio o popeats ai cracks o oes iserratic ad ote rests i eposio

is ieret a o te poder rocketsoeer as ot destood ti te ate part o te1 9 cetry t is ts obios tat are size ocketais cod ot be made by te care compressioteciqe

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900 SCI ID RS VO 6 NOV MR 2002

xt mportat stp combat rockts ast troducto of smokss podr comprstrocuos NC) ad troycr NG) by A

Nob 1 890 so-cad, 'doub bas toxposv compots) or omoous propatas a pastczd mass of NC ad NG. propasurry mad by us a sovt coud b v a saptr by xtruso procss or by cast tocotars. omoous propats arsstay dfctfr ad trfor, mor raby av b xtsvy usd soud rocktsad as sustar ras for mss s. Prop at raszs vary from 60 to 200 mm outr dam ad 5 to 200 k av b dvopd fordffrt appcatos. Hovr, t s dffcut to makvry ar sz ras by t ydrauc xtruso

procss or by t cast tcqu sc tpropat mass bcoms porous drv aayt rsdua sovt

tcooy of mak ar sz rasmrd ao t t basc udrstad ofpoymr scc. socad compost sodpropats cam to xstc ary bcaus of tsfcat advacs mad dvop poymrcast tcqus soo aftr WW . t as dd acvr da of cmsts to us fuctoay trmatdorac poymrs c coud b usd bot as ry fus ad aso as bdrs to cosodat tpodr oxdzr. t as vsad tat vscous pr

poymrs coud b mxd t sod podrcomposto to form a surry tat coud b curd insitu aftr cast sut ab mouds

Energetics

por of a propat s oft xprssd trms of spcfc mpus sp) t s dfd as tmpus tust x t m) pr ut t of prop at quatos rat sp t t cmcaparamtrs ar dscrbd as foos :

sp = F x T I W; sp (H)1I2 ; sp e T l Me

r, F=

trust T=

tm, W=

t, =

at ras t of combusto) pr ut t ofpropat, Te = cambr tmpratur, ad M =avra mocuar t of combusto producs

t s obvous tat at of combusto ado mocuar t products ar t bascrqurmts for acv r sp Sc t atof combusto s dpdt upo t ats offormato of t propat costtuts fu ad

oxdzr), t s dsrab tat ty av ats offormato Fu s ad ox dzrs av postv or oatv ats of formato ar, trfor prfrrd

Sary o mocuar t product spcs p mprov t sp Hydro for tat mattr s ooy a ood fu but aso a dsrd xaust product.

Soid Oxidizes

Lk t upodr a compost propat s atroous mxtur of bascay a podrorac oxdzr ad a fu bdr Usuy amta k podr aumum ad otr rdts araddd to mprov t prformac caractrstcs.

Sc t ma crtra of a propat composto s to produc at of combusto ad omocuar t asous products, sod oxdzrs

produc compty asous products ar trforprfrrd A quck survy of t varous oracoxdzrs ctrd usuay aroud t trat adprcorat sats, rvad tat ammumprcorat NHC) ad ammoum tratNHN) coud b t rt caddats. Ukpotassum trat ad potassum prcorat usd upodr ad aspat propats, rspctvy,ts oxdzrs producd totay asous productsBsds, ammoum prcorat AP) ad vryfavourab otr proprts, k avaaboxy, dsty, oyroscopcty asystorabty, ad o sstvty. s caractrstcs

av mad AP t orkors oxdzr of sodpropats dd, t as b t moopoyoxdzr of vrtuay a t arsz sod propatrockts, ordovr for t past 50 y or so .

Ammoum trat N) aso producscompty asous products c ar smokss. t s aso raty vry cap but tsrt caractrstcs k o ry,yroscopcty a akard pas ca aroudroom tmpratur ad vry o bu ratdscussd atr) av b dtrrts to ts arsca us sod prop at composto s, so far.

Otr omtac oxdzrs av aso bxamd bu t av ot b foud su tab for us foro raso or t otr Ntroum prcoratNC ), vstatd xtsvy 1 970s, ,as a postv at of formato ad a yfaourab oxy baac but as dscardd bcausof ts stabty t prsc of mosturAmoum dtramd ADN) aso as avaab oxy ad a ratv y o atv at of

_

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t

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A: SOLD PROPLLAT BDERS 01

ormaio b is syhesis · is hazardos adcomplicaed, ad repored o be exorbialy cosly ihe US cormed repors sgges ha he

Rssias hae sed DN i cerai missiles, ad aay has bee od o syhesize his maerialcheaply Hydraziim sals lie he iroormaemoo- ad di-perchloraes, hae also bee examied,b eiher hey hae lile aailable oxyge or arehighly sesiie o explosio

Pymeri inder

er haig seleced ammi perchlorae ashe oxidizer o choice h emphasis o research asshied o eolig he righ yp o els (bidersHere agai he chemical composio o he elshold be sch ha basically i is high combsio

eergy (calormeric ale ih P ad looleclar eigh prodcs carl cosideraio ohe combsio eergies o he elemes reealed hahe oly elemes ha prodced relaiey highcombsio eergy ad also prodced gaseosprodcs are hydroge ad carbo lhogh mayligh meals lie Li Be B Mg ad l hae highercobsio eergies b hey prodce codesed(soli d as pdcs hs ol los ha he search orsolid propella els has o be ocsed primarily ocompods o hydroge ad carbo or simply saed,hydrocarbos Frher, sice hydroge has highercombsio eergy per i eigh ha carbo a

hydrocarbo i h hi g C raio is preerred processed solid propella grai ms possess

good mechaical sregh order o proide hesrcral iegriy o he poder oxidizer, i as elha he el sed shold ecessarily be a log chaimolecl hich cold orm a cross-lied marix ocrig Orgaic polymers made o log chaihydrocarbos hs became he prime coeders opropella ormlaios, as hey cold sere he dalprpose o a high-eergy el as ell as a marixorig bider

he mai idea behid he se o polymers i

propella ormlaio as o eole a casigechology o large-size, deec-ree grais s saedearler he idea as o mix he poder oxidizer ih a

iscos pre-polymer haig si able ed-grops ad acrig age, o orm a porable slrry hich coldbe cas i a coaier o a predeermied size adgeomery he crig reacio (process o crossiig) old be so chose ha he ed-grops ii h he crig age iho liberaig ay small

molecles, like H, CO, S , ec, sice heliberaio o sma moleces ad/or heir sbseqeremoal maes he grai poros ad hece is

desirable he slrry old soidiy (cre simplyo raisig he emperare or o sadig or a hilehe ix o ld he coai a o xidizer embedded ia marix o polymer (el Sc h a grai o ld be reeo oids, ad orm a moolihic srcre oldalso possess he desired mechaical sregh becaseo he crosslied polymer-marix srcre

Early Systems

he hisory o solid composie propellas coldbe raced bac o he pioeerig or o VoKarma Fra Malia, oh Parsos ad EdardForema a he Gggeheim eroaical

Laboraory Calioria sie o echology(GLCt US hile deelopig a solid elrocke or JO aircra i 193 he charge orO cosised o ammoim irae as he oxidizerih blac poder ad cosarch as he el adihibor ad gle as he combsible bider

oher ormlaio GLC 53 , as irodced i142 cosised o poassim perchlorae as heoxidizer, dispersed i meled asphal (as boh el adbider ad pored hile ho io cylidrical moldsWhe cooled do he cred" propella cylidersere isered io he roce casig h is as he rscas" solid propella ha permied he prodcio

o solid roces o ay size or shape Hoeer heaspha composies ere od o hae poor physicalproperies, sch as poor esile sregh ad cracigder ormal emperare cyclig

Based o he experiece ih he asphalcomposiios i soo became eide ha beerphysical properies cold be achieed by he se ocrossliked hermoseig polymers Polyslphiderbber as a casable elbider as adaped i 145by Barley a GLC

Propella composiios

haig po assim ad/or ammoim perchlorae erecas ih hiool LP- poyslphide liqid polymrhis became he basis or he mos mode large

scale cas solid-el roces he polymer, ehylormal polyslphide, as prepared rom dichloroehylormal ad sodim poyslphide sig a smalamo o richloropropae cross-ier May

#Te GALCT wo evetual ly l ed to t e oato o te AerojetEgeeg Cororato 1 942 ad to e eabliset o ·Calec' s Jet Proulso Laboraory 1 944.

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902 J S N RS VOL 6 1 NOVMBR 2002

ariatios i th poymr ormatio r oodsbsqty Stdis o ths matrias i prop atormatios carrid ot at PL hioko hmica

orp ad at othr propat compais t o asiiicat drstadi o th chmistry o soidpropats h prsc o hay sphr atoms ith poysphd rbbrs hor dcrass thprormac hc ths rbbrs r sbsqtyrpacd by hydrocarbo NO po ymrs

By th is priod th chmstry o soid propatsas ary drstood hmists k th bascrqirmts a poymr shod ha ordr to castarsiz hhry rais hai ood mchaicapropris Sr poymrc bdr systms rod, amos simtaosy at PL rojGra hioko ad Gra r, ad Rbbr

chmica corporatios

Unure Polyeser

O o th arst poymr systms aaiabad cosidrd or propat ormatio as thsatratd poystrs Poysr systms, i ra,ha hhr as tha th poysphids adcod b maactrd to spcic mocar ihtsad iscosity h satratd poystrs ar sayprpard by codsi a dicarboxyic acid th adihydric acoho o or both o hich cotai thoiic bods hs bods ar tiizd i crosski ia simp iy moomrs ik styr ad

thyacrya h addto o th o mocariht o idi zs th prop at mix h crossk procss cod b iitiatd by proxds adcotrod by th mbr o satrad sits i thpoystr prpoymr ddtioa pasticzrs codb sd to adjst th propat mix proprtis

Sra accptab popat ormatos rdopd partcary by th rojt compayarod 946 h rais mad ih styr/poystrshad ood ai charactristics bt had hard strctrad cod ot bod to amim or st as, thsr stab or cas bodi hy r aso

smoky ad ot hih prormi h poystrpropats ha o b rpacd by hihprormi poybtadi compositios

Pltol Propelln

h pastiso propats aso ko as Ppropats dir rom composit propats i thtchq o so diyi th mass Whi i compositpropats th soidiicato cri is accompishd

by crossiki th prpoymr si a trictioa crati or opip o iy bods ipastiso propats it is achid throh soatio

sotio o th rsi podr i a ooat iqidhch a s acts as a pastici zr or th rsi

Usay, poyy chorid P podr issd as th rsi ad a str ik diocty phthaat asa pasticzr Fiy diidd P podr is mixdith th pasiczr i amost qa amots o thrsti srry a oxidizr ik P scit tooxidiz both PV ad th pasticzr is addd aoith othr irdts sch as a mta podr adsabizrs h mix s pord ito mods ad hatdto abot 70 so that P dissos ito thpasticzr h mixtr o coo to roomtmpratr soidiis ito a homoos mass

ha ood ts strth ad smooth srac

Usd idy i sodi rockts ad tactcamssis, th P propats ar ot casbodabati th P at hih tmpratr cass it todcompos patay spitti \ Modicatios icompositio ad procssi procdr o PVpropats ha b rcty rportd or thpas so procss is si tab or maki ar rais

Polyurehne

bidr systm capab o may aatsrsts rom th ractio o dictoa acohos

dios ith diisocyats to orm poyrthas hotorthy atr o this ractio is that o smamocs ar spit ot h th to moitis arjod tothr k th codsatio racto hhydroxy trmiatd prpoymr backbo may barid; t cod b a poystr poythr orpoybtadi Usay to diisocyaat is sdas chai xtdr or poyrtha ormatio h poymr has diisocyaat drops hichcod b sbsqty crosskd si a trio ikycro O th thr typs o prpoymrs thpoystrs optyycoazat ar otdsrab bcas o thir ratiy hh viscostyad o spciic imps sp th P oxidizr hhydroxy trmatd poythrs k poyoxyppropyyco ar asiy aaiab, ha oiscosity ad adqat rat o cr ad ood aicharactristics bt i or prormac

Hyroxl Termne Polybuene HTPB

h PB poyrtha bdr systm is thhihst spcic imps ith P oxidizr

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JA: SLID PRPELLANT BNDERS 903

relatively late coer, HTPB is te only prepolyerwic was specificay syntesized for its use as apropellan binder. It s usuay produced by te freeradical solut on poyerization of 1 ,3butadieneusing ydrogen peroide initiator Te prepolyeras olecular weigt in te range, 2500 to 2800;average functionality, 22 to 2. and viscosity, 65 Pat 30°C Orginally arketed by Atlantic RicfiedCopany, UA, under te trade nae ARCO R-5,in India it was synteszed and developed at VC(RO, Trivandru and te process know-owtransferred to Ms NOCIL, India, for producton

Besides HTPB te IRO as aso developed twoore ydroy terinated binders, naely te IROPolyol nd a yroyl ternated natural rubber,(HTNR. Te IRO Polyo, based on castor oil is a

saturated ester wt low olecular weigt (2000,neary bi-functional aving a viscosity of about 20 Pa roo teperature Te eyl pendant groupsipart good low teperature properties in additon toaking it a self-plasticized syste It is cured witisocyanates and triydroy copounds siiar toHTPB Copolyuretanes of HTPB and IRO Polyoade wit diisocyanates of touene andeaetylene ave aso been studed 7. Te IROPoyol propellants ave been used in soundingrockets

Many favourable properties of te poyuretanesyste like ig densty, rapid burning rate, ig

tensie strengt, ecelent fuel vaue, etc, akes it abnder of-coice As a atter of fact te ost widelyused binder syste used currenty is based on HTPBpolyuretane

Polyuretane binders for solid propelants wereindependently developed by ceists at Aerojet in198, and at JPL in 1953 (ref8. Te first successfuuse of te propellant based on poyuretane wit APas oidizer was ade by Aerojet for te Hawksurfaceto-ar issile syste in 195 It was a iglysuccessful propellant; te Aerojet supplied over0000 Hawk otors to te U Ary fro 1 95 to

990 (ref Minutean was Aericas first allsolid-fue ICBM wose developent started in 1 958 .Te propellant used in its second stage waspolyuretane AP/alui nu powder Te HTPBpolyuretane is e ost suitable and widely usedbinder syste for large solid boosters For eaplete giant Deta and Titan IV rockets, te Arian strapon boosters and te apanese H-II, al use HTPBbased propellants. In India te solid boosters of te

satellite l aunc ve icles, AL V, PLV and GV arebased on HTPB propellants Te ain first stage ofte PL V cons ists of a 2 8 d ia core oor aving10 t of HTPB/AP/A propell ant providing over 500 tof trust In addition, e Roini series of soundingrockets ranging fro RH75 to 560- dia otorsaso contain HTPB propellan ts.

Crboxyl Terined Polybudenes

Carboyl groups condense easil y w t epoidesand aziridines witout l iberating any sall oleculesTis reaction as been te basis of evolving prepolyers based on carboyl terinated polybutadiene(CTPB. Liquid polybutadiene pre-polyers and itscopolyers wit acrylic acid and acrylonitrile avingcarboyl groups ave been syntesized and usedetensively in producng very large size propellantgrains Bei ng coposed of alost a pure ydrocarboncain, polybutadienes ave ig calorietric values,and are preferred fuels As binders ey provide igsolid loadings and satisfactory ecanical propertiesto te grain over a wide range of teperatures.

Polybutadiene-acrylic acid (P BAA wa s te firstbutadiene copoyer to be used in a rocket otorappication Owing to te etod of preparation teliquid polyer s a ture of nonfunctional, ono,di- and polyfunctional segents As a result teepoide-cured syses sow poor reproducibility ofecanica properties and terefore, PBAA IS noore used as a binder

Te terpolyer polybutadiene-acrylic acidacrylonitrile (PBAN provides uc better storageand ecanical caracteristics to te propellant grainTe introduction o f acrylonitrile oiety iproves tespacing between te carboyl species and providesbetter control of curing process ince its introductionin 1957, ore solid rockets were produced wtPBAN tan any oter polyer till 1975 ince tenPBAN as been largely replaced by ore energeticpolyers CTPB, and HTPB Te pace uttleboosters are based on PBAN propellants Te firstIndian atelli te aunc Ve icle (LV 3 , launcedsuccessfully in 1980, also used te PBAN/APpropellants.

Bot, n P BAA and PBAN e carboyl groupsappear as pendent groups Te rando locaion of tecarboyl groups was leading to open cain ends atwer not effective in providing good pysicalproperties Ultiately, polybutadienes weredeveloped wit carboyl groups in te terinationposition to take full advantage of te entire lengt of

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90 SC ES VO 6 NOVMBR 2002

te polymer cn Tese prepolymers mrkeed sTokol HC3 nd Butre CTL were syntesedby free rdcl or ltum ntted tecnue to n

verge moeculr weg of 3500-5000 nd dnely b-functonl strucure e. one crboylgroup t ec end of e poymer cn. Te cung(crosslnkng of CTPB s ceved by rectng wrfunctonl epodes (eg Epon X-0 l or rdneseg. MAPO Tese trbutes of CTPB elped ncevng subsntlly mproved mecnclbevor of gy loded sold propellntspculrly low emperures. Te CTPB bsedpropents povde very g specfc mpulseust bou I s less n te TPB/polyuenesysem.

A pe-poymer kn o CTPB clled EF 20

s been deveoped by RO I s lconetermned polybutdene vng molecur wegtof bou 3000 nd vscosty n te nge 200300 PI gves supeor mecncl popertes s compredo CTPB e sme sold lodng. I ws usedn te uppe stges of LV3 nd ALV rockesnd s pogee kck motor o put e Apple selleno orb

Epoxy Resin

Resns vng epoy end-groups ve been useds propeln bnders s tey ebt good

processbly low cost ecellen cse-bondngnure nd good mecncl propees. Frly gIsp could be ceved wt epoy bndes. roustypes of epoy resns re vl ble commerc lly emost common beng te one bsed on bspenolATe epodes cn be esly convered otermosettng poymers by recng w curnggents lke prmry or secondry mnes nddcrboylc cds One of te mportnt dvntgesof te epoy resns s ere s vrtully no cngen volume (srnkge fte crng. Ltelydglycdylmne epoy resns bsed on bsydrones vng bonds n te bckbone

(dscussed lter ve been prepred specfclly forer use n sold propell nts

E B· d1 0 · 3

nrgtlc r .

Of te mny ssues reltng to e rockeperformnce mmng te specfc mpulse (spas remned te mjor creron so fr Mos studesve been amed to ceve ger Isp by opng formore energetc oders nd fues (bnders

Approces to mprove e energetcs of e bndernvolves e nroducton of eplosopore groups l keN ON NF nd N n e polymerc cn

Tese groups contrbute o ncrese n te et offormton (mkng t more posve of te polymend ence ennce te overll e of combuson.Te densty of te polymer s so ncresed wcmens ger moun of te o der could be lodedper unt volume Te presence of n odngelements n te bnder could be dvntgeous s reduces te mount of lodng of e powdernorgnc oder (AP equred for compleecombuston eeby mkng e mng of engredents esy Ts s ndeed benefcl from bote pocess ng nd peformnce spect s. For AP/�propellnts e stocometrc (oder/fuel ro

beng 905/9.5 t s not possbe n prctce toprocess grns vng suc g oder lodngwt deue mecnc sengt Te upper lm oflodng beng bou per cent most AP-bsedpropellnts re fuelrc nd ence gve ess n eepected teoretcl specfc mpuse.

Anote pproc s to ntroduce mel eementsno te polyme bckbone. nce lgt metls veger ets of combuson ter nroducon n tepolymer tself nsted of ddng s powder ( melpowde s usuly dded to e propen m oncrese te Isp would resul n ennced energy

W ts vew severl polymers contnng AMg nd Boron n e bckbone were synesed nte 190s.

Wle mny of tese optons ook ttrcvetere re severl ssoced nerent problems. Fornstnce te use of energetc bnders often cusesstbly nd compblty poblems Te energetcmerl contnng oygen nd fluorne groupswc re ntroduced te epense of ydrogenlower te Isp o some eten Te eologclproperes re so dversely ffeced n most csesMoreover te ntroducton of bot te oder nd

fuel groups n te sme molecule mkes t overlysenstve nd rdous to ndle peclprecutons ve to be tken prtculrly nsyntesng suc mterls Besde tere re mnyoer consdertons tt ve ssumed gretersgnfcnce n recen yers Tese re cos sfetyrelblty envronmentl mpc trnsportton longselflfe etc. Any new b nder produced must prove tobe beer performer wt respect o ese spects oo

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A SLD PPELLA BDES 905

Azi Polmrs

Te ot proinent aong te energeticpolyer are te one containing te azido group

Te ydroxyl terinated polyer of azidoetyloxirane (epoxi de) and oxetane ave been prepared forteir ue a binder Of tee te ot widely tudiedi te glycidyl azide polyr (GAP) of te oxiranefaily It i a un-crolined polyol and i a vicouliquid at oo tepeature. It a an averagefunctionality of 27 ydroxyl group, and olecularweigt, 700 Ti polyer a been pepared atvariou propellant reeac laboratorie by reactingpolyepicloroydrin wit odiu azide varying infunctionality a wel a oecular weigt GAP inow coercia y available, areted by te pecialCeical Divi ion of 3M company. GAP cured wit

a diiocyanate by itelf utain cobution andence a been exained a a fuel for integrated rarocet.

Wen ued a a platicizer, it i found to

enance te buin g rate of AP/epoxide propellant ISAP/GAP propellant ave poor ecanicalpropertie, epecially te elongation at lowteperature

Oter proiing azide polyer are te poly(biazidoetyl)oxetane (BAMO) and poly(azidoetyletyl)oxetane (AMMO) Poly BAMOi a tiff olid, wile poly AMMO i a oft elaticpolyer Copolyer of BAMO and AMMO, ave

been uccefully ynteized at Tiool, wic areteroplatic in nature

Te teroplatic

elatoer (TE) aving ard and 'oft egentare uefu ince teir cocrytallization itelf forte neceary treedienional networ of interlined oft unyetrical polyer boc No croliner are ued in te olidification proce

Te concept of uin g te TE, av ing ard andoft egent a binder i relatively new teentially evolved becaue of te iene difcultyfaced in dipoing te olid propellant grain wicare actually teroetting type crolined

copoite. Te only way to detroy uc a a(after it ueful ife) i by buing, wic cauepollution if carried out in open atopereDegrading te grain ceically and dipoing in acloed cyce reactor i very expeni ve and not an eayta In fact, ore effort are being ade in findingefficient way to dipoing a olid propellant graintan o produce a new one! Te TPE binder yteare preeed ecaue tey can avoid ti detruction

proce Te pyical crolin fored on cocrytal l ization between te ard and oft egent arereverible and diappear above te elting point of

te crytalline ard bloc Te propellant ingredientcould tu be reclaied by iply elting tepropellant grain and ubecting te to recoveryprocee t i a wonderfu concept if it worOxetane teroplatic elatoer ave te potentialto play a major role in te next generaton ofpopellant, exploive, and pyrotecnic yteaccording to Mil ler

Mix Polmr Norks

Altoug te HTPBpolyuretane yteprovide te iget pecific ipule for A-baedpropellant in certain ituation adjutent of te

cobution and ecanic al caracteritic are neededdepending upon te iion requireent Mixedbinder networ yte, copoed of two copolyer, or interpenetrating polyeric cain avebeen propoed to iprove tee propertie tudie onAP propellant wit intepenetrating polyer cainof HTPB and polytyrene or poyetyletacrylatea binder, ave proven te uefune of ticoncept. 6 t elp in fne tuning te propellantcaracteritic iiarly te copoyuretane adeof HTPB and RO Polyol ave been exaned indetail . I t i noticed tat by vaying te ratio of te twoydroxyl prepolyer, cain extender, and cro

liner, copolyuretane aving a wide range oftenile trengt and elongation could b obtainedWen tee copoyuretane are ued a a binder,tey are own to alter te buing rate andecanical propertie of AP propellant A detailedtudy pertaining to caracterization and odeling ofnetwor paraeter of copolyuretane a beencarried out 8 .

N-Bon Polmrs927

Polyer aving nitrogennitrogen (NN) bondin teir tructure are relatively new coer Te elfigniting (ypergolic) nature of NN onded

copound, ie te ydrazine and even olidydrazone on cong into contact wit liquidoxidizer lie nitric acid and nitrogen tetroxide, iwell nown t wa conidered wortwile toynteize polyer aving N-N bond, initially afuel for ypergolic ybrid rocet For te frt tie,epoxy terinated ydrazone rein were prepared inte autor laboratory at te ndian ntitute ofcience Tee polyer are low olecular

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906 J C D RE O 6 OR 2002

wegt vcou ren of carbono or tocarbonoydrazone avng dglycdyane epoy endgroup Te ynte of tee ren ple non

aardou and ceap Te overall attracvecaractertc of ee polyer led to eanatonof ter role a bnder for old copotepropellant. everal new dgycdylane epoyternated dcarboyl b(ydrazone) wereprepared ubequently and a detaled udyfolowed t nteretng to note tat a varety ofren coud be yntezed py by cangngbackbone and alo te ubttuen group but ungte ae procedure. Te uc dered aleraton nter properte to ut pecfc propellantcaractertc could tu be ade by plycoong te ot utable polyer. Of late te

ydroyl ternated NNbonded ren ave alobeen yntezed.

aracterzaton data of oe of teeren lted n Table 1 reveal tat tey aveadequate vcoty for g old loadng andrelavely g deny. A ger denty of teeren ean tat te denty pecc pule (Ipd)of propelant could be u ger tan toe baedon polybutadene bnder

Te an role of a bnder to provde adequaeructural ntegrty to te propellant gran Tepolybutadene bnder are uc preferred becaue of

ter rubbery nature In general e propeant granproceed wt carbono or ocarbonoydrazonebaed ren ave ard tructure. owever typcalcopreon trengt data of e AP baedpropellant own n Table 2 ndcae tat t couldbe vared conderably Apparently te ecancaltrengt of e dcarboyl ydrazone ren baedyte depend upon te nuber of te pacer (Cgroup n te parent olecule Propelant proceedwt te ren avng egt pacer group (eg.DEBu) ave ecancal properte qute cloe totoe baed on TPB

A general weakne of any propelant yteconcern t burnng rate Te control of BR anportant apect of old propellant forulatonPropellant avng dfferent BR are neededdependng on te on requreent nce te BReentally depend o n te cecal copoton e odzer, fuel and ter rato (at a partcularpreure t fed once te copoton decdedTe varaton requred uually eected by ungcatalyt altoug tey are leat dered a teyadverely add to te dead wegt and alo affect te

abl I - opeies of some -bonded esins and C

Resin

Diepoxide o bsuualdehydeabonohydaone (DEFCH

Diepoxid o f bis fuualdhydehioabonohydazone DECH)

Diepoxide o seaoyl b sufualdehydehydazone DEFH)

Dpoxde o adpoyl bisbuanonehydazone (DEAuH)

Diepoxide of sebaoyl bisbuanonehydaone (DuH)

Caboxyl emnaed oybuadiene (C)

i sosiy a 3 °C(poise)

4047

4674

00

7

75 

0

Hea o ombusion(al/

74

600

64

664

7 3

70

able 2 Compession senh daa of A popelan s based on - bonded esins and C

nde Umae ompession e en ompession odulus

(20 pe en) enh (k/m) (k/m)

DEFH 400 7 20

DEAu 20 4 00

DEu 20 0 400

C 300

Densy/

3 7

1 37

22

1 .

02

�

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A: SOLD POPLAN BDS 907

gng crrc. T BR o AP propn coudo nncd o om n y ung urn prc o AP. Bu mkng nd orng o urn podr dcu k. nd rng BR y cngng u (ndr gy drdpropoon ud mnor componn « 1 4pr n u mk n o dvop n ndrn gncn ncr n h BR rqurd n con nrng o no NNondd poymr hn ud ndr ncr urnng r gncny (T 3 or APpropn n mo hr-od ncr urnngr ovr h rocd oybudn (CTPBndr nocd. Th gncn ncrmno mgnud n h BR no normy poh ydrocron (CHO ndr.

prnc o N-N ond n h bndr ch ron or h gh comuon rcvy n propn ym.

Bd h nhncmn n h BR h prnco nrogn n poymr c h ocomrcO ro vourby. bcom much or cmn gr moun o h bndr coud bud o roc h propn. n or ord moun o TPB/CTPB rqurd or procngocomrcy bncd AP ron mry9.4 r cn h moun ndd or h n N-Nbondd poymr nry 14 r cn ch

abl 3 Brn ra o A PSA and AP ad proplacompoo

Proplan compoon Bu ra Pura 7 am nd

oxdrndr=8/ mm/

AN/DC 78 33

PSAN KNDCH 8 8

PSA KDCH 59 8 >8

PS A KDETCH 5.39   >8

PS AN KCrDCH 5

PSA K/CTPB 2 7 7

A/CPB 2 1 1 68

AP/DSBuH 8 63

APDSH 2 1 . 1 6

AP/CPB 8 2

ucn o c prcc pr cn od odng.T condron mk h N-Nbondd poymrvry rcv ndr or AP propn.

Dawbacs f A PITPB Ppas

A cd rr AP/HTPB n cnym ncorporng mny drb ur kgh nrgy rong bndng chrcrc yy ndng ry g urn r nd rvyo co. n mo dy ud odpropn ord ovr. Prp ony roudrck roduc o combuon cncud g k HC nd corn cumorc pouon nd mok T n cu o conc n rcn yr prcury unc c or rg moor or mp n ch

unc o c u od propnoor u 1 2.9 o HC nd 24. 1 o chornn mohr Smr h c h Arn-5 o od oor c hodng 237 oropn. ncrng conc or cn mophrn rn yr c or compng nd ordvopng co-rndy cn propn ymAr rom pouon concrn moky propn rundrd or mry ppcon. Dn mokcoud producd by AP propn coud d oy dcon o h unc . Y or rongn AP propn hr corrov uproduc (chorn nd HC nd gh m

mprr hc mk m unu ggnror ud o r nd drv g urn.

Smss AN-bas Ppas

Ammonum nr bng rcondrdrouy n od zr or od propn n rcnyr o ovrcom probm ocd h AP. vry cp mr nd vb n-pny, commony ud rzr nd n cvpov. combuon produc r oynnocuou nd mok Aough AN-bdpropn hv bn ud g gnror AN om unvourb chrcrc o u on-o

on ubu or AP ygrocopc, ndundrgo cry ph chng ccompnd by voum chng (pnon room mprur, duo hc prop n grn dvop crck durngorg Ao AN propn bu vry oy ndv o nrgc. Eor d n rcn yr omprov h chrcrc o mk ubpropn odzr hovr, hv rgy bnuccu.

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90 J SI IN D ES VO 61 NOVEMBE

T narabint tpratur pa (IV -IIItranition, g i no or a riou probl In actt cryta tranoration o AN av bn tudidby nurou invtigator uing a varity oprintal tcniqu a citd in our rcntrviw Our own obrvation av provd byonddoubt tat t awkward pa (IV III tranitio ncould b arrtd copltly by cocrytalliing ANwit an appropriat aount o a potaiu alt.

Intrtingly t propllant apl aving 0 prcnt olid oading o t pa tabiid aoniunitrat PAN uing potaiu dicroat owalot nil panion iiarly potaiudinitraid (KDN i rportd to av a draaticpatabiiing ct Morovr, AN patabilid wit KDN i bivd to giv iprovd

ballitic proranc incrad trut pr unit ti,rducd variabily and bttr prdictability copard wit AN witout KDN. Intrtingly tygrocopicity o AN i alo rducd on cocrytaliing wit K+ at.

T probl o low burning rat o ANproplant a bn tackld by dirnt approacT inc ud t u o catalyt uc a croiucopound addition o ta lik Mg, u o a atburning oidir lik AP, and u o nrgticbindr uc a aid polyr O t tapproac bad on nrgtic bindr i ot

proiing Howvr, any probl, ik poorignitability cobution intability tra tability,inadquat canical proprti, and ig rictionnitivity aociatd wit t aid polyr yt31·� b . - a to ovrco por to t u.

Intrtingy, a own in Tabl 3 t N-Nbondd rin av a igniicant nlunc on tburning rat o AN propant A ubtantialnancnt in t BR i obrvd wn PANintad o AN i ud. Burning rat clo to tAP/TPB yt coud b acivd wn AN paodiid wit potaiu uorid and an N-N

bondd bindr wr ud T rult paral toobtaind by Mnk t . on proplant bad onPAN aving t aid bindr It i igniicant to nottat t pa odiication not only prvnt tunwantd volu cang around t abinttpratur but ao lp in nancing t burningrat o AN proplant. Indd t vry igniicannancnt in t BR a pavd way or taibil ity o PAN propant n actua uag.

T at iu raining prtain to t poornrgtic o AN propllant. ingly tr i noway AN propllant nrgtic coud b ad at par

wit to bad on AP ipy bcau it a igrat o oration, dnity and oygn balanc tanAN Howvr cooing t rigt kind o bindr canak o iprovnt poibl For apl,TPB or HTPB i not a uitab bindr or ANpropllant at lat or two raon. Firt tTPB/AN propant burn vry lowy at abouton-ourt t rat o TPBAP proplant.condly, bcau o t lo w avaiab oygn in ANt aount o oidir ndd or atoiciotrically balancd copoition i 94. prcnt, wic i too ig a loading to cat in a grainap A a rul t t AN/TPB propllant grain ar

alway igly u-ric, giving uc owr tan ttortical Ip Rcnt invtigation on ANpropant cat wit NNbondd bindr rval tatnot only t buing rat i iprovd igniicantly antiond arlir, but t cat grain could b adtat av an alot oygn balancd copoitioninc a owr aount o AN (5 pr cnt i nddor coplt (toiciotric cobution.

A coparion o t tortica prorancparatr o variou propllant aving dirntoidir, i ad in Tabl 4 It i vidnt tat tIp o AN propllant procd wit NNbonddbindr i igniicanty igr. For ap at a

practical 5 pr cnt AN loading, t tortica Ipwit TPB bindr i only 05.5 it coud bnancd to by uing an N-N-bondd bindr.T cabr tpratur (c) and t cactriticvocity (C*) ar alo apprciably igr Evn atquivalnc ratio, , = 1 (toiciotric balanc tNNbondd rin giv uprior paratr tanTPB or AN yt It i tu vidnt at t Ipo t AN yt can b iprovd upon by uingappropriat bindr To u up, t rult claryow tat AN coud b ad to work by uingappropriat bindr and pa odiir a apotntial oidir or o id proplant.

Prop ant copoition bad on AP and ADNalo giv uprior proranc paratr wit N-Nbondd bindr at 5 pr cnt oli d loading A ltougbttr proranc could b acivd wit tpolybutadin bindr at toiciotric loading it inot poib to aciv in practic witout dvryacting t canical proprti. At practical olidoading t N-Nbondd rin giv igr Ip tan

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,

JAN: OLD POPELLANT NDE 909

Tbl 4 Prform prmrs o propls 85 pr soh omr sol loi

Oxzrr (pr ) <

DEFCH AN ( 85) 1 \ 0

DEFTCH AN (85) 1 0

CT AN (85) 60

DEFTCH AN (898) 0

DEFH AN (91 0) 1 0

CTP AN (942) 1 0

DEFTCH AP (85) 0.9

DEFH AP (85) 03

DEBuH AP (85) 1

CTP AP (85) 3

DEFTCH AP (837) 1 0

DEFH AP (856) 0

DEBH A P ( 8 7 ) 1 0

CTP AP (900) 1 0

DEFTCH ADN (85) 1

CTPB ADN (85) 1 6

DEFTCH ADN (872) 1 0

CTP ADN (927) 0

that cold be obtaned wth CTPB rrespectve o theodzer (AN AP or ADN se d. Th s ephaszes theoverall scoe and selness o the N-Nbondedpoyerc bnders n sold propellants

Oh Coidaio

ging

Agng s one o the pre areas o concern. Asold propelant partclary a cobat rocket granhas to be stoed or several years beore an event

occrs when t has to be red Ye t st be kept nreadness all the te retanng ts pre-deternedcharacterstcs lke the brnng rate and pressrende echancal propertes and strctral ntegrty,naltered Ths s partclarly dclt becase theodzer and the el are n physcal contact al thet e and there s every l kel hood they wold ndergoslow reacton between theselves, whch cold berther catayzed by the addtves lke the BR

[sp (s) T K C* m/s)

2 19 2 2156 2291 1358

2220 2197 230 3 7 1

2055 622 1945 266

2283 2370 2393 407

2256 2296 2359 1393

2236 2249 2326 1384

244 1 2992 282 1475

2452 2952 2746 484

2 4 1 2868 2636 482

2426 2770 2 4 2 1 504

2474 3027 2806 488

245 2941 2759 1479

2447 2990 2909 1 4 8 1

2530 3046 2678 1528

2594 3079 250 585

2486 2625 21 26 1 549

2606 3058 2527 574

265 3061 2442 1 602

oders, drng storage The gran cold becoeporos acted pon by ostre or t cod evenchange ts characterstcs by oozng ot soe o thelastczer, sed Ths there are any actors thatcontrbte to agng. Bt the irst and oreost s thatthe proposed new bnder st be least reactve wththe odzer n the sol d state

There s no satsactory ethod to evalate apror the sae le o a sold ropelant granAccelerated agng studes are carred ot byontorng BR or echancal propertes perodcally

at elevated teperatres, bt they hardy correlatewth the roo teperatre agng data The onlyrelable way s to condct a coprehensve stdynder storage condtons over a nbe o years andevalate the sae le bt t s te consng and soconvenently orgotten. As a conseqence therelablty o the syste becoes qestonable Veryoten, a new or oded propellant syste perorsas per the speccatons n the ntal testng stage bt

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90 SC D ES VO 6 NOVEMBE 22

i ts urning rate e.g. is changed drsticay just i n afew monhs storing ti me In other words prope an

mean to e good for 5 y my fai after sy 5mons ony For his reason athough sever newenergeic poymers hve een evoved hey have

hardy een used in pracice Engineers pu muchfith in proven sstem ik the AP/AHPB or

CTP in view of the uncertain ging chrcteristicsof the new system. Aso from he manufacurers'point of view it is not eneficia to invest in new

system un ess it is v asty superior zardfre and the same time coseffecive .

P Li

For casing rg solid oosers he propean

ingrediens mixing (s lurr ming) is crrid out inarge atches using one or wo ton mixrs It is

imperative that he sury after adding the curtivesdoes no strt setting in he mixer itsef, ut do soony fter casting into e mouds. he ime tken togel in g (po ife) should e ong nough to permi he

opertions of proper mixin g deaerating nd vcuumcsting Methods vai ae to enghen te po

ife incude choosing proper curatives andor

chain xenders inder/curive rio mixingemperture ec.

Sid Ladng

Oxidizers ike AP have just enough aviaeoxygen to Yidize completey out 0 per cent of ahydrocaron (CH2) poymer uel) . With so l it leamount of the inder i i s very difficut even o mke

a uniform mix wit nearly 90 per cen soids, eaveaside fowae s urry requi red to cast the prope antmix in norma circumstnces his seemingyimpossil task s made feasile o some exent y

using imoda or even rimoda partice s ize mi x Thesieved powder hving fine and course pricesmixed n a fixed rtio is added o the mixer inatches o achieve the maximum oading o chieve

mximum Isp however it is desirae hat either theinder cbone shoud hve reactive incomustion mode) inages ie N-N onds orgroups th do not need extr oxygen for comusionor the oxidizer must ave higer viae oxygen.Oxidiers ie n tronium perchorte nd hydrzin iumdi perch orte av ing muc h eter oxygen anc e arehig hy su ied ut they hve the ir own drwcs

Colusios

he emergence of specificy snthesized

poymers hs payed ey roe in csing lrge size

soid propelant motors Grins having desredstructura strength and combustion characterisics

coud e successfuy cas using functionalyterminaed viscous polymers. Efforts o develop

propel n composit ions giving high speci fic impuseuti mey ed o he synthes is of ydroxy terminted

poyudiene a inder used currently wodover in

csting very argesi soid oosters. Continuedserch for inders suie for specific purposes has

resuted in several ineresing systems. Of ths ehermoplastc estomers seem to e pomising s

hse could aso help in esy dispos of the aged

propellns The newly deveopd Nonded

pomers ppear to ppopriatey suite orenhancing the performnce parmetres nd theuing rtes of oth ammonium perchore nd

ammonium nire ased propents. These indersseem to have prtiulry hg poeni fordveoping smoeess propelants sed on phse

sai i zd mmonium nirate

Akwledgeets

The uthor is greful o the Universiy Gransommission New Dehi for wrding an meriusFe owshi p during t course of his researc.

RefeesMazng G Y. Compaav aalys o eopm n ave an eav mo o projon n to ket ad atrOa y D Co an A MSpnr. AAS oy Sr, Vol.4 AmanAonaa Soy San Do 3 4

2 Oommn C & an S . Ammonm na: A pomnrok opl an oer. J 1aard Matr A67 ( 25-2 8

3 Ma na rs ATOs Ammonm nae. ornara pow an Jt Pr J / Nocet . 26 56) 5

Wnr & am G S. h o 5 yea o Aeoj.a ponrn Aman ok Company nto of rokt an d atrona t y P n AAS

sory Sr oI22 Amran Aronaal Soey. SanDo 8 pp 53

5 Bo V S & Baojv D Dj Moe polyvyl hloreas ropan es ol n Popllan expoves.rok an gs, Pro Seond t Ee Mate O &Eht II Mad y S Knan an S K AanA Plrs Cnna Dmr 8. pp 5-

6 Sn g nry marals resar an vopmen nna J op Po 1 5 88855

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'-

JAN SOLD POELAN BDES 9 1 1

7 n S Skkr V & Knmy VN Mnl ndwlln proprte o PBbd opolyrtnntwork J App PoYl S. 48 ( 9 93 - 3

8 Kl K T propeln m t ontr ton to modn

okt lt memoir n ory o oketry ndtont AAS itory Sr VoS eded y L Corntt ( Amin Aontl Soty Sn Deo993pp 009

9 Jn S Rr on new enert bnder o ol dpropln. Plnry Ppe P id l i Il MaOl ald ibi iuvalaapm ( EnyMtrl Soy o Ind Deember 2000 pp 5

0 Boto J Reen dvne n expov nd ol dpropln Ild. 996. 925

I Bomn S Adned enret mterl or m try ndpe ppton l lg Nws ( 9 9 8 - 1

Bol . Overvew on nret polymer. nDompoon omon nd dtonton emtry oent ml edted y B Br T P Rel W C

o nd R C Wde MRS SY Po Boon Vol 48 .(Mterl Reer Soy Ptr) 996. pp 9 I 0

3 Mll R S r on nw neret mrl nDeompoton. omton nd dtonton emty ofenret mtel edd by T B Brll P ell. W o nd R C Wrde MRS S Pro Boon Vol. 48M el Ree Soty. Pttr 996 pp 3

S S K. Cvn M Y kr J V Kk S G & PdS P Peomne evton o lydy zd polymer ntertd m roke popellnt n ropln expovokt nd n. Po Sond l Hig El Ma ibi Mada edted y S Krnn nd S K Atn(Al d plir Ltd Cnn 998 pp 6 30

Nre A N. An S N & Sn Bevo ommon prot wit lydyl d polymer n

Propellnt. xpove okt nd n P Sold lHig l Mar o! ibi Mada dted y SKrnn nd S K Atin (Aled Pr Ltd Cnn)9 9 8 p p 6 6 6

Pn S Rnndn B N & n S . nerpnetrtnpolyme nework ndr or od proplnt D Si .I42 9 9 7 6

7 Skkr V m o M Krnmrty V N & Jn S Et o bndr ompoon on t popere o ompotold poplnt. n Proplnt xpov roket ndn P Sold l Hig Elr Mae on ald Exibi Mads dtd by S Knn nd S K Attn (AledPl d Cenn) 998 pp 3 539

8 Skk V Rm Ro M Kr nmty V N & Jn S Modln o polyrtne ntwork bed on PB nd

poly(l ydroxy tr d -o-) tr polyo

orreltion o ntwok prmtr wt menlpropete. J App Po Si 2 9 9 6 3 737

9 Tmtevrn P M & Jn S Synte ndreron o tioroydrzon bd poxy rn JPo S Pa A Pom m 9 99 6 6 7

0 n S R bib je bild o bid ssl. FnReport SO- S Spe Tenooy Cell ( ndn ntto Sene Bnlo J y 99

Tnmvrn P M & in S . New Nbonddpoxde ndr or ypro l rn J Aros SoIldia, 4S 9 93 9 0

Oommen C & n S R Petld mmonim ntrted propellnt n bndr wt N bond J PpPow. 16 000 33 8

3 Jn S & Amnl S ew ene poxy ndr. nDeompoton. omton nd dtonon emtry oeneret mr. dd y B Brl P l. W Co nd R C Wrdl MRS Smp P. Boton Vo 48M er Reer Soty Ptr 996 pp 39

Anll S & Jn S Synt nd rtrtion oNN- pt droxy bydrzone. J Pom Si Pa: Pl Gl 3S ( 997 83528

5 Sidr K & n S . Synt nd rtton onovel ydroxy trmnted -Nondd rn J App PoSi. 8 ( 00 33

6 Amnl S SVlsis ald aarizaiol 'o N-N-bolddpoxy il as bil dr o oid prop/al s. P D Indn I nttte o Sene Bnlor 1997

7 7 Oommn C Pa odaion and ombliol sudieOl ammonim ni and propal cmposiion P D ndn Intt o Sin Bnlore 997

8 8 n S Oommn C & Amnll S. Brn rt ndpromn tde on old propln vn nrtbnd n Proplnt explov rokt nd n PSond In Hig Er Mar (ol Eibi liT MadasEdtd by S Kinn nd S K Atn (Alld PblerCenn 998 pp 59

9 9 Jn S veopll oa buil soid popalsFn Report SOS Sp enoloy Cll ndnnttte o Sn Bnlor Jly 997

30 30 Oommn C & Jn S P modton ommonim ntrt by pom lt J Trm AlayiCaoil SS 9 99 ) 939 8

3 Mnke K BoinMb J & Sbert Crtertproprt o A/GAP propllnt Pop/ ExpoPyoln. 2 9 9 6 3 9 - 5

Frnl M B. Grnt & Fnn J toldvelopmnt o lydyl d polym J Propu Por 8

99) 3663