Polymerization and Thermal Characteristics of Acrylonitrile/Dicyclohexylammonium 2-Cyanoacrylate Copolymers for Carbon Fiber Precursors

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1 Cron Letters Vol. 12, No. 1 Mrch 2011 pp Polymeriztion nd Therml Chrcteristics of Acrylonitrile/Dicyclohexylmmonium 2-Cynocrylte Copolymers for Cron Fier Precursors Ki-Young Kim 1, Woo-Lee Prk 1, Yong-Sik Chung 2, Dong Geun Shin 3 nd Jin Wook Hn 3, 1 Convergent Textile Technology Group, Kore Institute of Industril Technology, Ansn , Kore 2 Deprtment of Textile Engineering, Chonuk Ntionl University, Jeonju , Kore 3 Deprtment of Chemistry, College of Nturl Science, Hnyng University, Seoul , Kore e-mil: jwhn@hnyng.c.kr (Received Jnury 16, 2011; Accepted Ferury 24, 2011) Astrct This study experimentlly investigted dicyclohexylmmonium 2-cynocrylte (CA) s potentil comonomer for polycrylonitrile (PAN) sed cron fier precursors. The P(AN-CA) copolymers with different CA contents ( mol% in the feed) were polymerized using solution polymeriztion with 2,2-zois(isoutyronitrile) s n inititor. The chemicl structure nd composition of P(AN-CA) copolymers were determined y proton nucler mgnetic resonnce nd elementl nlysis, nd the copolymer composition ws similr to the feeding rtio of the monomers. The effects of CA comonomer on the therml properties of its copolymers were chrcterized differentil scnning clorimetry (DSC) in nitrogen nd ir tmospheres. The DSC curves of P(AN-CA) under nitrogen tmosphere indicted tht the initition temperture for cycliztion of nitrile groups ws reduced to round 235 o C. The het relese nd the ctivtion energy for cycliztion rections were decresed in comprison with those of PAN homopolymers. On the other hnd, under ir tmosphere, the P(AN-CA) with 0.78 mol% CA content showed tht the initition temperture of cycliztion ws significntly lowered to o C. The ctivtion energy vlue showed 116 kj/mol, tht ws smller thn tht of the copolymers with 0.82 mol% of itconic cids. The therml stility of P(AN-CA), evidenced y thermogrvimetric nlyses in ir tmosphere, ws found higher thn PAN homopolymer nd similr to P(AN-IA) copolymers. Therefore, this study successfully demonstrted the gret potentil of P(AN-CA) copolymers s cron fier precursors, tking dvntges of the temperture-lowering effects of CA comonomers nd higher therml stility of the CA copolymers for the stilizing processes. Keywords : Dicyclohexylmmonium 2-cynocrylte, Polycrylonitrile copolymer, Cron fier precursor, Stiliztion ehvior 1. Introduction Cron fiers were commercilly introduced in the erly 1970s, nd they hve een one of the most importnt reinforcing mterils for dvnced composites thnks to their high strength nd stiffness [1]. The opening pplictions of cron fiers were minly driven y high performnce industries such s erospce nd defense pplictions due to high cost of cron fiers. However, in recent decdes, cron fiers hve found extensive pplictions in civilin ircrft, lnd trnsporttion, construction, sports, leisure, electrics/electronics nd industril sectors owing to the incresing wreness of potentil for high performnce nd lightweight mterils since cron fiers technologies ecme mture with cost reduction nd fier qulity improvements [2,3]. Polycrylonitrile (PAN) sed precursors hve proved to e the most populr for high strength cron fiers ecuse they re more esily converted to cron fiers, give higher cron yield, nd llow to e processed more economiclly for commercil production thn cellulosic nd pitch precursors [1]. The nitrile (CN) groups re preferly positioned in PAN polymers for cycliztion of nitrile groups to produce the ldder structures during therml stiliztion, which is the first stge to covert precursor fiers to cron fiers followed y high temperture croniztion process. However, PAN homopolymers re not suitle for use s cron fier precursors ecuse of sudden uncontrollle exothermic rection t reltively high temperture, resulting in chin scission y therml degrdtion nd poor cron fier qulity. Therefore, PAN copolymers re predominntly used s precursors y the incorportion of suitle comonomers such s itconic cid (IA), crylic cid (AA), mthcrylic cid (MAA), nd methyl crylte (MA) to ssist in the spinning nd stiliztion processes for etter precursors nd resulting cron fiers. Such comonomers hve stimulted significnt interests in the effects of comonomers on spinning nd stiliztion processes of precursor fiers, which hve een reported y numer of the previous studies [4-8].

2 32 Ki-Young Kim et l. / Cron Letters Vol. 12, No. 1 (2011) This study experimentlly investigted dicyclohexylmmonium 2-cynocrylte (CA) s potentil comonomer for PAN sed cron fier precursors. It is nticipted tht the presence of one cronyl group nd one nitrile group in CA should fcilitte stiliztion processes with esy exothermicity nd improve the productivity with high cron yield for high strength cron fiers. To the uthors knowledge, the study of P(AN-CA) copolymers hs not een reported yet with regrds to chrcteristics of cron fier precursors. This pper exmines the effect of CA on therml stiliztion ehvior of P(AN-CA) copolymers y compring with PAN homopolymers nd P(AN-IA) copolymers, prticulrly with n emphsis on the cycliztion rection of nitrile groups nd therml stility of PAN precursor polymers during het tretment. 2. Experimentl 2.1. Mterils Cynocetic cid (99%, Aldrich, USA), prformldehyde (95%, Aldrich), dicyclohexylmine (99%, Acros), triethylmine (99%, Junsei, Jpn), hexne (95%, Smchun, Kore), nd enzene (99.5%, Dejung, Kore) were used without dditionl purifiction for the synthesis of dicyclohexylmmonium 2- cynocrylte. Acrylonitrile (95%, Dejung) ws dried y moleculr sieve 4Å nd distilled t tmospheric pressure for purifiction. Dimethyl sulfoxide (DMSO, 99%, Junsei) ws distilled t 70 o C under vcuum of Torr, nd 2, 2 - zois(isoutyronitrile) (AIBN, 99%, Dejung) ws used s polymeriztion inititor fter recrystlliztion two times from methnol. IA (99%, Junsei) ws purified y recrystlliztion with distilled wter Synthesis of dicyclohexylmmonium 2-cynocrylte A mixture of cynocetic cid, prformldehyde, dicyclohexylmine, nd triethylmine in enzene ws refluxed for 20 min using Den-Strk pprtus. The solution ws filtered to remove polymerized species nd solvent ws evported y vcuum drying. The resulting solid ws suspended in hexne nd filtered, nd then purified y recrystlliztion from enzene to give CA [9] Copolymeriztion of PAN copolymers Acrylonitrile homopolymers nd copolymers with IA nd CA were prepred y solution polymeriztion technique in DMSO under nitrogen tmosphere t 60 o C, using 1000 ml rector fitted with n overhed stirrer. The molr frction of IA ws 0.82 mol%, nd the molr CA content ws vried from 0.19 to 0.78 mol% to investigte the effects of CA content on polymer properties. Polymeriztion ws initited y AIBN (0.5 wt% of monomers) nd the rection ws crried out t stirring speed of 200 rpm for 16 h. After the polymeriztion ws completed, the polymers were solidified in distilled wter nd pulverized to powder. They were wshed severl times with distilled wter to remove residul monomers, nd dried for 24 h y vcuum oven. The conversion of copolymers ws clculted using the following eqution (1): Conversion( wt %) = Weight of dried smple fter wshing( g) Weight of smple( g) Weight frction of monomer Chrcteriztion A nucler mgnetic resonnce (NMR) spectrometer (Mercury 400 MHz; Vrin, USA) ws used to investigte the chemicl structure of PAN copolymers y proton NMR ( 1 H NMR) spectr in DMSO-d 6 solutions t room temperture using the proton signls of CA monomers nd copolymers. The viscometric mesurement ws crried out in 0.5 g/dl concentrted dimethylformmide solution t 30±0.1 o C with n Uelohde viscometer. The viscosity verge moleculr weight, M v, ws clculted from the following reltionship [10]: [η] = (2) Μ v The chemicl composition of the copolymers ws determined y elementl nlysis with Thermofinnign EA1108 in stndrd conditions. Therml ehvior ws chrcterized y TA Instruments (USA) differentil scnning clorimetry (DSC) Q20 t different heting rtes of 2, 5, 10 nd 20 o C/min from room temperture to 450 o C in nitrogen nd ir environment. Thermogrvimetric nlysis ws performed to chrcterize therml stility in nitrogen nd ir tmospheres t heting rte of 10 o C/min from room temperture to 600 o C with TA Instruments TGA Q Results nd Discussion 3.1. Preprtion of PAN copolymers Poly(crylonitrile-co-dicyclohexylmmonium 2-cynocrylte), P(AN-CA) copolymers were prepred with different molr frctions of CA rnging from 0.19 to 0.78 mol%. The polymeriztion scheme is shown in Fig. 1. The polymeriztion chrcteristics re listed in Tle 1 s function of monomer feeding contents in the feed. The conversion of P(AN-CA) copolymers is similr to tht of PAN homopolymer nd P(AN-IA) copolymer, ut decreses with incresing the mount of CA comonomer. Moreover, the moleculr weight nd intrinsic viscosity of P(AN-CA) show significnt reduction in the higher CA content. This is proly due to the lower rectivity etween AN nd CA

3 Polymeriztion nd therml chrcteristics of crylonitrile/dicyclohexylmmonium 2-cynocrylte copolymers for cron fier precursors 33 Fig. 1. Polymeriztion scheme for P(AN-CA) nd P(AN-IA) copolymers. monomers y stereo hindrnce of the side chin in CA. In inry copolymeriztion, the presence of the second monomer increses the mutul termintion rections nd the cross termintion rte [11]. When CA concentrtion ws incresed, the rte of polymeriztion (R p ) nd the degree of polymeriztion (D p ) of P(AN-CA) copolymers were decresed, leding to the decrese in conversion, moleculr weight nd intrinsic viscosity. The 1 H-NMR nd elementl nlyses were performed to identify P(AN-CA) copolymers. Fig. 2 shows the 1 H-NMR spectr of AN nd CA monomers, nd P(AN-CA) nd P(AN-IA) copolymers. In the spectrum of AN monomer, methine (-CH) proton signl of AN monomer ppers etween 5.96 nd 6.03 ppm, nd two doulet signls re oserved t δ6.21 nd δ6.35 due to the methylene (-CH 2 ) protons of AN. The signls t δ6.27 nd δ6.51 in the CA spectrum re ssigned to the methylene (-CH 2 ) protons of CA monomer. The methylene (-CH 2 ) proton peks of Fig. 2. Proton nucler mgnetic resonnce spectr of monomers nd polycrylonitrile (PAN) precursors. Tle 1. Polymer Chrcteristics s Function of Monomer Content in the Feed Smple code Monomer in feed (mol%) Conversion M w PDI M v [η] c AN IA CA (wt%) ( 10 4 ) (M w /M n ) ( 10 4 ) (dl/g) PAN-homo AI AC AC AC AC AN: crylonitrile, IA: itconic cid, CA: dicyclohexylmmonium 2-cynocrylte, PDI: Polydisperse Index, PAN: polycrylonitrile. Mesured y Gel permetion chromtogrphy. Mesured y Uelohde viscometer. c [η] = Mv 0.733

4 34 Ki-Young Kim et l. / Cron Letters Vol. 12, No. 1 (2011) Tle 2. Elementl Anlysis nd Chemicl Composition of Copolymers Smple code Feed rtio Component (wt%) Copolymer composition (mol%) C H N O (mol%) PAN-homo 100: AI : :1.48 AC : :0.12 AC : :0.22 AC : :0.37 AC : :0.75 PAN: polycrylonitrile. cyclohexyl groups strongly pper etween δ1.09 nd δ1.97. In the 1 H-NMR spectrum of P(AN-CA), two rod signl peks t δ2.07 nd δ3.13 re presented due to methylene (- CH 2 ) protons in AN nd CA nd methine (-CH) protons in AN, respectively. However, the 1 H-NMR spectrum shows no chrcteristic pek of P(AN-CA) ecuse the spectrum is lmost identicl to tht of PAN homopolymer, s shown in Fig. 2. Since it is hrd to determine the chemicl composition of the copolymers y 1 H-NMR due to the overlpped signls of methylene (-CH 2 ) protons in AN nd CA, elementl nlysis ws crried out to mesure the content of cron, hydrogen, nitrogen, nd oxygen in the copolymers. The results re summrized in Tle 2, indicting tht the oxygen content in P(AN-CA) increses with incresing the feeding mol frction of CA. It is evident tht the increse in CA mol frction in the copolymers confirms the successful incorportion of CA nd copolymeriztion of P(AN-CA) copolymers Therml nd cycliztion ehvior of copolymers Differentil scnning clorimetric nlysis in nitrogen nd ir tmospheres Fig. 3 presents the DSC thermogrms of P(AN-CA) copolymers contining vrious molr mss of CA for the comprison with those of PAN homopolymers nd P(AN-IA) in nitrogen tmosphere. They ll hve only single shrp exothermic pek, which is ttriuted to cycliztion without oxidtion rection during het tretment. As the DSC chrcteristics re tulted in Tle 3, the PAN homopolymer shows the initition temperture of exothermic trnsition (T i ) t 252 o C nd finl temperture (T f ) t 296 o C with the pek temperture of 275 o C nd evolved het ( H) of J/g while P(AN-IA) hs the lower DSC chrcteristic tempertures with H of J/g. This result is not consistent with the previous report [4] tht IA comonomer plys neither evident fcilitting nor inhiiting role on cycliztion rection in nonoxidtive tmosphere, in other words, efficiency of IA in inititing nitrle group cycliztion cn e found only in the oxidtive condition during therml stiliztion of PAN. However, for P(AN-IA) nd P(AN-CA) copolymers in this study, the lower T i nd roder exotherm Fig. 3. Differentil scnning clorimetry thermogrms of polycrylonitrile (PAN) precursor in nitrogen tmosphere t heting rte of 10 o C/min. trce implies tht the incorportion of IA nd CA cn ffect the cycliztion rection temperture nd rte for stiliztion process. As shown in Tle 3, the shift of exothermic onset temperture to lower temperture during het tretment suggests tht the cycliztion should e esily initited through n ionic mechnism rther thn rdicl mechnism. For cron fier production, PAN sed precursors normlly re sujected to therml tretment, so clled stiliztion process in ir or oxygen-contining tmosphere t temperture rnge of o C for long period time. The oxidtive stiliztion produces stle ldder structure for the trnsformtion of thermoplstic polymers into stle nd infusile intermedite to sustin high temperture croniztion tretment for cron fier production [5]. The DSC thermogrms in ir tmosphere re shown in Fig. 4, indicting tht two or three mximum peks re responsile for complicted rections such s cycliztion, primry nd secondry oxidtion [6]. The DSC curve of PAN homopolymer exihiits the visile shoulder/pek/shoulder in ir t out 270 o C, 319 o C nd 390 o C, respectively, ut it hs only one shrp pek in nitrogen. The ir tmosphere

5 Polymeriztion nd therml chrcteristics of crylonitrile/dicyclohexylmmonium 2-cynocrylte copolymers for cron fier precursors 35 Tle 3. DSC Chrcteristics of PAN Precursors in Nitrogen Atmosphere t Heting Rte of 10 C/min Smple code T i ( o C) T f ( o C) T c ( o C) d T pk ( o C) H e (J/g) H/ T (J/g min) PAN-homo AI AC AC AC AC DSC: differentil scnning clorimetry, PAN: polycrylonitrile. Ti = initition temperture. Tf = finish temperture. c T = Tf T i. d Tpk = mximum pek temperture. e H = the mount of het relesed y cycliztion rection. Fig. 4. Differentil scnning clorimetry thermogrms of polycrylonitrile (PAN) precursor in ir tmosphere t heting rte of 10 o C/min. decreses the onset temperture (T i ) nd increses the finl temperture (T f ) with roder exothermic pek nd higher overll enthlpy of exothermic rection, compred with the DSC trce in nitrogen tmosphere [4]. In P(AN-IA), T i is further reduced to 181 o C ecuse the cycliztion rection cn e more esily initited in the oxidtive condition through n ionic mechnism y croxylic cid. It is well known tht IA is the most effective comonomer in the ese of oxidtion nd exothermicity, nd high cron yield [12,13]. P(AN-CA) copolymer is most effective to reduce the initition temperture, T i, mong the PAN copolymer precursors, s shown in Tle 4. T i decreses with n increse in CA content. For ll the P(AN-CA) copolymers except AC-0.19, T i is lower thn PAN homopolymer nd P(AN-IA) copolymer. Similrly to the DSC curves for P(AN-IA) in ir, the exothermic multiple peks in the form of shoulder re oserved with roder exotherms. It is generlly elieved tht the first pek t the lower temperture is ttriuted to oth cycliztion nd dehydrogention rections, nd the other pek nd shoulder t the higher temperture re due to the oxidtion rection [6]. The totl het of exothermic rection ( H) for ll the P(AN-CA) is lower thn tht of PAN homopolymers nd AC-0.78 is comprle to tht of P(AN-IA). The rte of het evolution ( H/ t) indictes het liertion per unit time. The lower Tle 4. DSC Chrcteristics of PAN Precursors in Air Atmosphere t Heting Rte of 10 o C/min Smple code T i ( o C) T f ( o C) T c ( o C) d T pk ( o C) H e (J/g) H/ T (J/g min) PAN-homo AI AC AC AC AC DSC: differentil scnning clorimetry, PAN: polycrylonitrile. Ti = initition temperture. Tf = finish temperture. c T = Tf T i. d Tpk = mximum pek temperture. e H = the mount of het relesed.

6 36 Ki-Young Kim et l. / Cron Letters Vol. 12, No. 1 (2011) het rte of P(AN-CA) is eneficil in the production of cron fiers ecuse higher rte of het evolution during thermo-oxidtive stiliztion process would led to urning out the core, resulting in poor qulity of cron fiers [7]. It is concluded tht the presence of cronyl groups nd nitrile groups in P(AN-CA) cn fcilitte the exothermic rection t lower temperture nd reduce het evolution. Since CA hs one cronyl nd one nitrile groups in its moleculr, cycliztion rections cn e initited t lower temperture y cronyl groups through n ionic mechnism. The decresed rte of exothermic rection, s evidenced from the lower H/ t nd roder exothermicity in Fig. 4, my e due to steric hindrnce or interruption in AN sequence imposed y ulky side groups in P(AN-CA), therey dversely ffecting the cycliztion process [6,8]. In ddition, the more extent of oxidtion rection implies the enhnced oxidtion rection in P(AN-CA). This is proly due to the increse of morphous region in the polymers y the incorportion of CA [6,8]. The higher morphous region due to ulkier side groups cn led to the higher diffusion rte of oxygen nd greter possiility of contct etween oxygen nd molecules. Such oxygen uptke to mke oxygen contining groups (C=O, -OH) in polymer ckones fcilitte the formtion of thermlly stle cron networks nd insures high cron yield during croniztion [4] Activtion energy for cycliztion rection The Kissinger method [14] ws used to determine the ctivtion energy (E ) of cycliztion rection using the DSC dt [5,7,15]. The generl eqution of the Kissinger method is expressed s the following eqution: where R, i nd T pk re the gs constnt, the heting rte nd the mximum pek tempertures, respectively. Fig. 5 demonstrtes the effect of the heting rte on therml ehvior of PAN polymers in nitrogen tmosphere. As the heting rte increses, the exotherms shift to higher temperture with higher intensity. The ctivtion energy cn e determined from the slope y plotting ln( i/t 2 pk ) ginst 1/T pk, s shown in Fig. 6. As mentioned erlier, PAN homopolymer nd copolymers hve only one pek in the DSC thermogrms under nitrogen tmosphere. However, the rod DSC curves re oserved with two or three mxim peks under ir tmosphere due to cycliztion, dehydrogention nd oxidtion rection during het tretment. Grms-32 softwre ws used for Gussin curve fitting of whole exotherm to resolve into three peks. The typicl revolved DSC curves re shown in Fig. 7, where the first pek temperture corresponding to cycliztion rection is used to Fig. 5. Differentil scnning clorimetry thermogrms in nitrogen tmosphere t different heting rte of 2, 5, 10, nd 20 o C/ min. Fig. 6. Plot of ln( i/t 2 pk ) ginst 1/T pk for the ctivtion energy of cycliztion. PAN: polycrylonitrile.

7 Polymeriztion nd therml chrcteristics of crylonitrile/dicyclohexylmmonium 2-cynocrylte copolymers for cron fier precursors 37 Fig. 7. Typicl resolved differentil scnning clorimetry curves of polycrylonitrile homopolymer in ir tmosphere. Tle 5. Activtion Energy for Cycliztion in Nitrogen nd Air Atmosphere Smple code Activtion energy (kj/mol) Nitrogen Air PAN-homo AI AC AC AC AC PAN: polycrylonitrile. Fig. 8. Thermogrvimetric nlysis curves of polycrylonitrile (PAN) precursors in nitrogen tmosphere t heting rte of 10 o C/min. clculte the ctivtion energy of cycliztion. The clculted ctivtion energy under nitrogen nd ir tmospheres is compiled in Tle 5. Under nitrogen tmosphere, the vlues of E for PAN homopolymer nd P(AN-IA) re out kj/mol nd kj/mol, respectively. The ctivtion energy of P(AN-CA) decreses to kj/mol with incresing the CA content to 0.78 mol%. It is reconfirmed tht the incorportion of CA in PAN copolymers is effective to fcilitte the initition of cycliztion rection due to the lower E for cycliztion rection. The ctivtion energy of ll the precursor polymers under ir is lower thn tht of nitrogen condition due to esier cycliztion under the oxidtive tmosphere. Especilly, the vlue of ctivtion energy of AC-0.78 (116.0 kj/mol) is lower thn tht of AI-0.82 (127.8 kj/mol) despite the similr content of comonomer. This indictes tht CA comonomer seems to e more effective thn IA in lowering the initition temperture of cycliztion rection Thermogrvimetric nlysis in nitrogen nd ir tmospheres Figs. 8 nd 9 show the thermogrvimetric nlysis (TGA) Fig. 9. Thermogrvimetric nlysis curves of polycrylonitrile (PAN) precursors in ir tmosphere t heting rte of 10 o C/ min. curves of AN homopolymer nd copolymers in nitrogen nd ir tmospheres, respectively. The TGA curves in nitrogen for the given polymers cn e divided into 3 steps ccording to the extent of weight loss. The curves show very smll weight loss in the first zone up to round 250 o C for PAN nd P(AN-IA). In conjunction with the mentioned-ove DSC results, only cycliztion rection tkes plce in this step ecuse nitrile cycliztion theoreticlly does not ccompny the sustntil weight loss. In the following second step, up to the pproximtely pek tempertures of the DSC curve (round 270 o C), the TGA curves indicte the rpid nd fst rections with the gretest rte in the weight loss due to dehydrogention nd moleculr frgmenttion. The lst step ove the DSC exotherms shows the stedy rte of weight loss, where polymer chin scission occurs producing voltile prticles with weight loss.

8 38 Ki-Young Kim et l. / Cron Letters Vol. 12, No. 1 (2011) The TGA curves in ir show slightly different therml ehvior from those in nitrogen. The first step shows no sustntil weight loss up to round 270 o C nd 250 o C for AN homopolymers nd copolymers, respectively. This step is ccompnied only y cycliztion rection for ll the polymers. Aove the tempertures, the second step shows the grdul weight loss with ll types of rections such s cycliztion, dehydrogention, nd chin scission. However, the totl weight loss in ir is significntly less thn tht in nitrogen due to dditionl oxidtion rections. The oxygen uptke rections undoutedly compenste for weight loss due to chin frgmenttion nd dehydrogention. The importnce of oxygen uptke into the moleculr chin ws reported y the previous reports [4,5] for the stility of the polymer chins. The higher therml stility of P(AN-CA) nd P(AN-IA) during stiliztion processes leds to the stle cron structures with high cron yield nd less dmges in cron structures, consequently providing etter precursor polymers for high performnce cron fiers. 4. Conclusions P(AN-CA) copolymers were successfully synthesized vi solution polymeriztion to develop new precursor polymers for high performnce cron fiers. Their chemicl structures nd composition were confirmed y 1 H-NMR nd elementl nlyses. Therml nlyses such s DSC nd TGA in nitrogen nd ir tmospheres were crried out to infer the stiliztion ehvior of P(AN-CA), which ws compred with PAN homopolymer nd P(AN-IA) copolymers. It is discovered tht P(AN-CA) copolymer ws most effective to reduce the initition temperture, T i, mong the PAN copolymer precursors. Their ility to llevite het relese ws comprle to tht of P(AN-IA) copolymers in ir or nitrogen. The TGA nlysis indicted the higher therml stility of P(AN-CA), which could led to high cron yield nd less dmge in cron structures. These findings in this study suggest tht the incorportion of CA should mke cler contriutions to fcilitte therml stiliztion rections y reducing onset temperture nd exothermicity, nd improving therml stility which re the indispensile processing prmeters in the mnufcture of high performnce cron fiers. Acknowledgements This reserch ws supported y grnt from the Fundmentl R&D Progrm for Core Technology of Mterils funded y the Ministry of Knowledge Economy, Repulic of Kore. References [1] Morgn P. Cron Fiers nd Their Composites, Tylor & Frncis, Boc Rton (2005). [2] Growth opportunities in the glol cron fier mrket , E-Composites Inc. (2004). [3] Chnd S. J Mter Sci, 35, 1303 (2000). [4] Yu M, Wng C, Zho Y, Zhng M, Wng W. J Appl Polym Sci, 116, 1207 (2010). [5] Fitzer E, Muller DJ. Cron, 13, 63 (1975). [6] Gupt AK, Pliwl DK, Bjj P. J Appl Polym Sci, 59, 1819 (1996). [7] Bhrmi SH, Bjj P, Sen K. J Appl Polym Sci, 88, 685 (2003). [8] Jmil SNAM, Dik R, Ahmd I. J Polym Res, 14, 379 (2007). [9] Krwczyk H. Synth Commun, 30, 657 (2000). [10] Berce M, Morriu S, Ion C, Ion S, Simionescu BC. Eur Polym J, 35, 2019 (1999). [11] Devsi R, Reghundhn Nir CP, Sivdsn P, Ninn KN. Polym Int, 54, 1110 (2005). [12] Ouyng Q, Cheng L, Wng H, Li K. Polym Degrd St, 93, 1415 (2008). [13] Devsi R, Reghundhn Nir CP, Ninn KN. Eur Polym J, 39, 537 (2003). [14] Kissinger HE. Anl Chem, 29, 1702 (1957). [15] Bjj P, Sreekumr TV, Sen K. Polymer, 42, 1707 (2001).