Review Article Cure Kinetics of Epoxy Nanocomposites ...downloads.hindawi.com/journals/tswj/2013/703708.pdfCure Kinetics of Epoxy Nanocomposites Affected by MWCNTs Functionalization:

Hindawi Publishing CorporationThe Scientific World JournalVolume 2013 Article ID 703708 14 pageshttpdxdoiorg1011552013703708

Review ArticleCure Kinetics of Epoxy Nanocomposites Affected byMWCNTs Functionalization A Review

Mohammad Reza Saeb1 Ehsan Bakhshandeh1 Hossein Ali Khonakdar23 Edith Maumlder3

Christina Scheffler3 and Gert Heinrich34

1 Department of Resin and Additives Institute for Color Science and Technology PO Box 16765-654 Tehran Iran2Department of Polymer Processing Iran Polymer and Petrochemical Institute Tehran 14965-115 Iran3 Leibniz-Institute of Polymer Research Dresden 01069 Dresden Germany4Technische Universitat Dresden Institut fur Werkstoffwissenschaft 01062 Dresden Germany

Correspondence should be addressed to Mohammad Reza Saeb saeb-mricrcacir and Edith Mader emaederipfddde

Received 21 August 2013 Accepted 24 September 2013

Academic Editors W Ding and Y Tian

Copyright copy 2013 Mohammad Reza Saeb et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The current paper provides an overview to emphasize the role of functionalization of multiwalled carbon nanotubes (MWCNTs)in manipulating cure kinetics of epoxy nanocomposites which itself determines ultimate properties of the resulting compound Inthis regard the most commonly used functionalization schemes that is carboxylation and amidation are thoroughly surveyed tohighlight the role of functionalized nanotubes in controlling the rate of autocatalytic and vitrification kineticsThe current literatureelucidates that the mechanism of curing in epoxyMWCNTs nanocomposites remains almost unaffected by the functionalizationof carbon nanotubes On the other hand early stage facilitation of autocatalytic reactions in the presence of MWCNTs bearingamine groups has been addressed by several researchers When carboxylated nanotubes were used to modify MWCNTs the rateof such reactions diminished as a consequence of heterogeneous dispersion within the epoxy matrix At later stages of curinghowever the prolonged vitrification was seen to be dominantThus the type of functional groups covalently located on the surfaceof MWCNTs directly affects the degree of polymer-nanotube interaction followed by enhancement of curing reaction Our surveydemonstrated that most widespread efforts ever made to represent multifarious surface-treated MWCNTs have not been directedtowards preparation of epoxy nanocomposites but they could result in property synergism

1 Introduction

Since discovery and bulk synthesis of the new type ofmolecular carbon structures consisting of needle-like tubesin 1991 many research efforts have been devoted to explorethe influence of incorporation of carbon nanotubes (CNTs)into different matrices [1] The unique structure of CNTitself provides a rather wide range of extraordinary char-acteristics for example excellent electrical and thermalconductivities low density high aspect ratio high surfacearea and superior mechanical properties The first paper ondealing with preparation of CNTpolymer nanocompositesin 1994 has encouraged many researchers to develop a newclass of reinforced materials with synergistic properties viaincorporation of CNTs in a variety of polymers [2] Until now

both types of CNTs that is single-walled CNTs (SWCNTs)and multi-walled CNTs (MWCNTs) have been occasionallyincorporated into different thermoplastics elastomers andthermoset polymers

Studies have revealed that the rheological characteristicsof thermoplastic nanocomposites for example PPMWCNT[3] poly(methyl methacrylate) (PMMA)SWCNT[4] high density polyethylene (HDPE)MWCNT [5]polystyreneMWCNT [6] and polycarbonateMWCNT[7] are affected by the presence of carbon nanotube aswell as increasing its content The improvement of themechanical thermal and optical properties has also beenaddressed in the literature At low frequencies the complexviscosity of thermoplastic matrices significantly increaseswith the addition of CNTs whereas the loss modulus

2 The Scientific World Journal

of nanocomposites undergoes a plateau indicating theformation of percolated CNT networks that respondelastically over long time scales The rheological percolationthreshold of CNTpolymer nanocomposites obviouslydepends on temperature On the other hand the electricalconductivity in these systems is strongly governed by thestate of dispersion that is nanotube-nanotube distance andalignment of CNTs in the matrix [3ndash6]

So many research efforts have also been dedicated toproduce various thermoset composites containing CNTsEpoxy resins have attracted much attention among ther-moset family of materials owing to their excellent prop-erties for example high modulus low shrinkage in cureand good chemical and corrosion resistance as well asacceptable adhesion characteristics Besides epoxies can becured using a various ranges of chemicals with differenttypes of curing conditions [8] Some authors have addressedthe cure behavior of epoxide thermoset composites filledwith different types of nanosized fillers Thermal studies oncure phenomenon of thermoset composites can be classifiedinto two general categories isothermal and nonisothermalkinetics Domınquez et al used different amounts of an acidcatalyst based on p-toluenesulfonic acid dissolved in water(45 aqueous solution) to study the nonisothermal curingkinetics of polyfurfuryl alcohol bioresin [9] Employingdifferent isoconversional (nonisothermal) methods that isKissinger-Akahira-Sunone (KAS) Flynn-Wall-Ozawa (FWO)and Vyazovkin (VA) they elucidated that the initial and finalstage of curing respectively possesses an acceleration anddeceleration period depending on the content of catalystused The limited movement of polymer chains andoraccumulation of reaction ingredients were the main reasonsfor the alteration of the cure mechanism Several epoxidecomposites filled with CNTs have already been studied bydifferent authors bisphenol-A glycidol ether epoxy2-ethyl-4-methylimidazole (DGEBAEMI-24) system containingpristine and amine functionalized MWCNTs by Yang et al[10 11] liquid-crystalline epoxy system of 441015840-dihydroxy-a-methyl-stilbenesulfanilamide containing carbon nanotubesand carbon black conventional filler by Bae et al [12]DGEBAEMI-24 system containing purified MWCNTs byZhou et al [13] DGEBA441015840-ethylenedianiline (DDM)epoxide systems containing amine functionalized MWCNTsby Prolongo et al [14] DGEBAdiethyltoluenediamine sys-tems with carboxyl and fluorine modified MWCNTs byAbdalla et al [15] DGEBADDM composites comprisingamine functionalized MWCNTs by Choi et al [16] DGEBA13-phenylenediamine epoxy-amine CNT-free system bySbirrazzuoli et al [17] DGEBAdiethylenetriamine (DETA)containing pristine SWCNTs by Puglia et al [18] tetra-glycidyl-441015840-diaminodiphenylmethane (TGDDM)441015840-di-aminodiphenylsulfone (DDS) system comprising MWCNTsby Xie et al [19] DGEBANovolac as an epoxyphenolicsystem containing phenol anchored multi-walled carbonnanotube by Choi et al [20] and MWCNTsDGEBAEMI-24 nanocomposites containing carboxylic functionalizedMWCNTs by Zhou et al [21]

Similar to the case of thermoplastic compositesCNTepoxy thermoset systems have been the subject of

several studies to investigate characteristics other thancuring for example the rheological and mechanical prop-erties For many different reasons which will be discussedin the next sections surface treatment or functionalizationof CNTs greatly enhances the performance of preparednanocomposites Hadjiev et al used Raman spectroscopyto measure the magnitude of residual stresses in diglycidylether of bisphenol-F (DGEBF) epoxide systems curedwith diethyltoluenediamine (DETDA) [22] They prepareddifferent types of CNTepoxy composite samples employingpristine and functionalized Kaffashi et al discussed theextent of improvement in rheological characteristicsin DGEBAmetaphenylene diamine (M-PDM) systemscontaining covalently modified and remodified MWCNTs[23] Primarily the MWCNTs were surface modified witha mixture of sulfonic and nitric concentrated acids andthen diluted with distilled water To produce remodifiedMWCNTS in-situ esterification of carboxylated MWCNTswas performed There were significant shifts in loss andstorage modulus in specimens prepared by modified andremodifiedMWCNTs Depending on the conducted strategyvarious features have been considered while performing aspecified test on the samples as the work done by Pugliaet al [24] Differently from the way used by Hadjiev et alPuglia and coworkers discussed the impact of SWNTs onthe cure reaction of DGEBADETA composites by means ofthermal analysis and Raman spectroscopyThey revealed thatSWNTs act as a strong catalyst and reduce the temperatureassigned for the exothermic reaction peak Carboxylatedand fluorinated nanotubes were used by Abdalla et al tosynthesize nanocomposites by dispersing them separately inDGEBAdiethyltoluenediamine (DETDA) thermoset system[25] Attention has been made by the authors to investigatethe role of interfacial chemistry in molecular mobilityand morphology of produced nanocomposites Kim et alreported the mechanical and rheological properties ofdiglycidyl ether of bisphenol-A epoxide systems (YD 128)cured by a modified aromatic amine hardener (TH 432)[26] Based on amine treatment and plasma oxidationthey attempted to improve the interfacial adhesion aswell as the performance of dispersion of multi-wallednanotubes in the epoxy matrix The degree of performanceof CNTepoxy systems greatly depends upon the state ofdispersion of nanotubes in the epoxy matrix Song and Youndemonstrated that the rheologicalmechanical electrical andthermal properties of YD 128TH 432 epoxy are governed bythe state of dispersion ofMWCNTs whether a solvent is usedor not [27] In epoxy-based systems andor their reinforcedcomposites Doan et al have made a lot of efforts to interpretthe alteration of some vital properties mostly adhesionand mechanical characteristics on account of interphasesituation From a practical point of view the following canbe considered as the most important works performed bycollaboration or under supervision of Mader incorporationof MWCNT and glass fiber into a DGEBA-based epoxyresin to the formation of semiconductive MWCNT-glassfibers and in turn multifunctional fiberpolymer interphases[28] evaluation of healing efficiency and tensile strength ofglass fibers with MWCNTDGEBAm-phenylenediamine

The Scientific World Journal 3

(m-PDA) nanocomposite coating affected by the typeand content of carbon nanotubes used which converselyinfluenced the dispersion state [29] evaluation of theadhesion and interlaminar shear strengths [30 31] andsurface roughness in different epoxy composites containingpoly(p-phenylene-26-benzobisoxazole) (PBO) fibers viasurface modification of PBO [32] measuring the static(constrained molecular mobility of polymer chains) anddynamic (interfacial adhesion and the tendency of fatigueresistance) properties of single andmultifiberDGEBA-basedepoxy composites modified by sizing [33] modification ofepoxy-based composites by polysulfone to improve theinterfacial and mechanical properties in its glass fibercomposites [34] tracking the topography fractography andinterphases in carbon fiberepoxy composites [35] and bondstrength measurement between glass fibers and epoxy resinat elevated temperatures using the pull-out and push-outtechniques [36 37]

Despite the fact that using CNTs may itself affect theelectrical mechanical or rheological properties it has beenproved that themain drawback of incorporation of CNTs intothe polymers is the formation of bundles or entanglementsconsisting of hundreds of individual particles by van derWaals force as a consequence of heterogeneous distributionwithin the host material In another words CNTs are verypotent to form entangled structures because of small diam-eter in nanometer scale and high aspect ratio (normally gt1000) For epoxide nanocomposites the reagglomeration ofCNTs after curing reaction has also been reported Thusultimate performance of epoxy andor other thermoset resinscontaining nontreated CNTs intensely depends upon thestate of dispersion Several techniques have been proposedby the researchers for overcoming this problem Hilding etal indicated that during grinding of MWCNTs much ofthe mechanical energy goes into complete breakup of tubesand new defects will be continuously generated on the tubesurface [38] They comprehensively gathered the availabledata to give emphasize to the effects of milling ultra sonica-tion high shear flow elongational flow functionalization andsurfactant and dispersant systems on morphology of carbonnanotubes and their interactions in the fluid phase As amodel system MWCNTs have been considered for experi-mental work owing to their accessibility in engineering-scalequantities and dispersed reproducibly in a variety of solventsand polymers To deepen the understanding of effectivedispersion Ma et al reviewed the state of dispersion of CNTsthroughout the different polymers [39] They compared thetotal surface area of well-known conventional micro- andnanoscale fillers and served a 3D illustration to visualizethe nature of dispersion problem for CNTs Accordinglydispersion of CNTs in organic solvents accompanied bysonication results in individually dispersed nanotubes inepoxide systems It was also concluded that the time ofsonication as well as the solubility parameter of the solventgreatly affects the dispersiondebundling process of untreatedCNTs Matarredona et al employed an anionic surfactantnamely sodium dodecylbenzenesulfonate (NaDDBS) toimprove the suspendability of SWCNTs in aqueous solutions[40] The degree of interaction between nanotubes and the

used surfactant was examined by varying the pretreatmentmethod that is acidic or basic purification After chemicalfunctionalization of nanotubes however it was found thatthe structure of surfactant-stabilized SWCNTs was governedby the hydrophobic forces between the surfactant tail andthe nanotube In fact each nanotube was seemingly coveredby a monolayer of surfactant molecules in which the headsformed a compact outer surface while the tails remained incontact with the nanotube walls The effects of sonicationtime and concentration of NaDDBS on suspendability ofSWNTs have also been reported Pizzuttoa et al examinedseveral parameters for example CNT content sonicationtime sonication power the use of solvent the amountof surfactant and the influence of degassing on the stateof dispersion in SWCNT-appended DGEBA-based systems[41] Among two types of SWCNTs used that is the pristineand carboxylated SWCNTs the latter resulted in lower timeand amplitude of sonication leading to higher mechanicalproperties namely Youngrsquos modulus tensile strength andbreaking elongation Likewise Gkikas et al considered dis-persion state of MWCNTepoxy nanocomposites by takingthe CNT content the sonication time and the total sonicationenergy as the inputs [42] They found that the sonicationenergy as the most influential parameter determines thetoughness properties Besides the best condition leading toaugmentation of glass-rubber transition temperature (119879

119892)

and storage modulus was achieved after 2 h of sonication and50 sonication amplitude Chapartegui et al speculated thatthe shear thinning behavior observed in their amine curedMWCNTGGEBA system is expectable as a result of relativelylow molecular weight of the epoxy used (700 gmol corre-sponding to a single repeating unit) [43] When choosingsuch a system a physical network comes into being in whichthe carbon nanotubes are able to get in touch with each otherrather than combined CNTpolymer network interactionsThe shear-induced rheological test might have destructiveeffect on the network nevertheless the rapid recovery of theMWCNT network in the prepolymer matrix was responsiblefor the lower electrical threshold than that of rheological one

Another scheme to resolve poor dispersion of CNTs inepoxy is chemical functionalization of CNTs Until nowa variety of strategies have been developed for function-alization of CNTs [44] Moreover the effect of treatednanotubes on the state of dispersion as well as ultimateproperties of CNTpolymer nanocomposites has deeply beenconcerned [39] A detailed literature survey towards theeffect of surface modification on dispersion state of carbonnanotubes in solvents and polymers have been summarizedby Kim et al [45] To properly determine the relationshipbetween surface characteristics and dispersibility of CNTssome terminologies has been employed for example thedegree of surface modification degree of substitution anddegree of dispersion The comparative approach used by theauthors on gathered information from the literature that istabulated data and illustrative perspectives fulfills a needfor functionalization to achieve appropriate dispersion ofCNTs in aqueous solutions In general both covalent andnoncovalent surface modifications have been examined Todraw a convincing conclusion on quantitative studies the


Flory-Huggins interaction parameter was considered as ameasure of solubility parameter for CNTs correspondingto dispersibility in the surrounding media Park et al com-pared the thermal conductivity of GDEBA-based compositescontaining short and long MWCNTs [46] Employing thelong-MWCNTs resulted in higher electrical and thermalconductivities especially when the degree of alignment wasincreased by mechanical stretching Albeit the epoxidationof CNT improved the mechanical properties of specimensCNT walls were damaged by peroxide acid treatment anddecreased the electrical conductivity Apparently the SWC-NTs functionalized with epoxide grafting dissolve in organicsolvents for example dimethyl formamide chloroform andmethylene chloride with relative ease [47] Other paperson the effect of CNT functionalization are also accessiblein the literature the improvement of the dispersion stateand thermomechanical properties of DGEBA systems usingcovalently and noncovalently functionalized MWCNTs byDamian et al [48] elaborating on the use of chemicallyfunctionalizedMWCNTswith aromatic amines to investigatethe cure behavior mechanical properties thermal stabilityand fracture morphology of DGEBA-based composites byGhorabi et al [49] improving the mechanical properties ofepoxy composites using MWCNTs functionalized by a novelplasma treatment by Chen et al [50] investigation of theeffects of various types of functionalizedMWCNTs (carboxy-lated (MWCNT-COOH) and directly fluorinated (MWCNT-F)) on thermomechanical and morphological properties ofepoxy based nanocomposite systems byTheodore et al [51]

Although a large number of publications have beendevoted to functionalization of carbon nanotubes there haveonly been a few papers on dealing with cure kinetics ofepoxy-based systems influenced by the functionalization ofCNTs Also certain discrepancies in the kinetic data mightsometimes happen owing to various reasons for exampleinappropriate dispersion of nanotubes functionality of theused epoxy the type of curing agent cure condition andthe type of CNT which makes the interpretation of curemechanism in epoxy nanocomposites quite difficult

Allaoui and El Bounia reviewed and analyzed the effectof untreated SWCNTs and MWCNTs on the cure behaviorof epoxy resins with emphasis on alteration of 119879

119892[52]

They compared the difference between119879119892of nanocomposites

and that of the neat resin and made sufficient effort tofind a trend through the data reported in the literatureTheir interpretations based upon the CNT type (SWCNT orMWCNT) dispersion method (grinding dissolution usingsurfactants sonication or combinatorial methods) percentby weight of CNT and the aspect ratio of the used nanotubeindicate that incorporation of SWCNTs in epoxy decreasesthe 119879119892due to rather high bundling tendency while the use of

MWCNTs often suggests an increased or unchanged 119879119892 The

acceleration effect of both types of CNTs in the early stage ofcuring of epoxide system was also reported The influence ofunmodified nanotubes on cure kinetics will be reviewed inthe next sections Irrespective of the type of curing agent andthermal history it was generally agreed that the cure reactionin epoxyCNTnanocomposites is very sensitive to the surfacetreatment

R R

R

R

R

R

R

O

O

O

C

C

C C C

C C

CC

CH

H

H

H

N

CH2

CH2

CH2lowastR

lowastR

lowastR

lowastR

XH

OH+

+

+

H

H

HOH

OH

OH

OH

NH2

H2

H2

H2

Epoxy

Epoxy Amine

Alcohol

CH2XRlowast

ORlowast

∙∙

Scheme 1 Oxirane ring opening via the nucleophilic additionreaction in an epoxide system

This paper attempts to highlight the influence of func-tionalization of MWCNTs on the cure behavior of epoxycomposites The autocatalytic noncatalytic and vitrificationmechanisms have also been considered through a literaturereview on isothermal and nonisothermal curing schemes bycalorimetry

2 The Chemistry of Curing inEpoxy Composites

Epoxy resins belong to a class of thermosetting materialscontaining two ormore oxirane rings or epoxy groups in theirmolecular structure The performance of an epoxy-basedcomposite significantly depends on its curing circumstance[54 55] Studies on curing behavior of such systems demon-strated that the epoxide molecules contributed to the curingreaction and react with themselves to form a crosslinkednetwork andor with other reactive molecules whether or nota catalyst is used [39] Depending on the type of curing agentfor example amines thiols alcohols and anhydrides as wellas curing condition that is isothermal and nonisothermalit is often possible to predict the final application of thecured resin As seen in Scheme 1 the curing reaction takesplace with oxirane ring opening via the nucleophilic additionreaction

Curing of epoxide groups with amine hardeners revealedthat the primary amine hydrogen reacts with the epoxy resinand subsequently the secondary amine hydrogen comes intoexist which can react with the other epoxy ring Scheme 2illustrates the mechanism of curing of epoxy resins withamine hardeners [56]

At the same time the hydroxyl groups generated by thereaction between the secondary amine hydrogen and epoxyresult in formation of ether links This reaction namely


R R

RR

O

O

CH

CH

OH OH

OH

H2C

H2CRlowastndashNHndashCH2ndashCH

RlowastndashNHndashCH2ndashCH

Rlowast(ndashNHndashCH2ndashCHmdashR)2

+

+

RlowastndashNH2

Scheme 2 Mechanism of curing epoxy resins with amine hardeners

RR

O

CH

RCH

OH

OH

O

H2C

H2C

RlowastndashNHndashCH2ndashCH RRlowastndashNHndashCH2ndashCH+

Scheme 3 Illustrating the mechanism of etherification reaction

etherification competes with the amine-epoxy cure reactionas shown in Scheme 3 [8 56]

In case of low reactivity of the amine group or when thereis an excess epoxy ring in the backbone this competitioncauses a fluctuation in the cuing rate and therefore makesthe interpretation of cure mechanism quite difficult

It has been generally agreed that the extent of ether-ification significantly depends on cure temperature andepoxyamine system for example the stoichiometric ratioof resin to hardener in the mixture and the functionalityof epoxy resin Also the secondary alcohols continuouslyformed during cure reactionmay accelerate the amine-epoxyreactionsThus two mechanisms compete against each otherfor curing in the system The first one is an autocatalyticreaction which occurs because of hydroxyl groups initiallyexisted in the epoxy prepolymer or those formed duringthe reaction The autocatalytic mechanism involves a ternarytransition complex (Scheme 4)

At elevated temperatures the catalyticmechanism almostvanishes due to the difficulty of forming such a ternary com-plexThe secondmechanismproposed for the cure of epoxidesystems which is a second-order noncatalytic reaction innature takes place over the entire range of temperature [8]As the fractional extent of conversion increases the 119879

119892of

the network goes higher and becomes identical to the curetemperature This transition state is called vitrification anddepends upon cure temperature and reaction kinetics In thissituation the occurrence of etherification reaction is highlyprobable [8 19 56] Acid anhydrides have extensively beenemployed as the second commonly used candidates afteramine hardeners for the curing of epoxy monomers [57]The cured epoxies by use of anhydride agents are suitablefor especial applications for example coatings and electronicdevices The main difference between the amine-epoxy andthe anhydride-epoxy reactions is that the latter undergoes achain-wise polymerization on the contrary with the former

which passes through a stepwise mechanism Therefore theanhydride-epoxy reactions involve an initiation by Lewisbases as well as propagation and termination or chaintransfer steps [57] Some of the postulated reactions areshown in Scheme 5

As in Scheme 5 the initiation step proceeds with ringopening of an epoxy monomer by aim of a tertiary amine Inthe next step the active anion reacts with an anhydride groupvery quickly to form a carboxylate anion as the active siteThis esterified constituent contributes to the cure reaction asan initiator of the chain-wise polymerization The numberof active sites affects the content of Lewis base initiator andsubsequently makes this constituent potent to react with theother epoxy group which again attacks the cyclic anhydrideAs all the mentioned mechanisms are temperature depen-dent differential scanning calorimetry (DSC) leads to con-vincing conclusions on the cure kinetics of epoxy compositesThe model-fitting and model-free kinetic approaches haveoccasionally been employed by researchers to assess the curekinetics of epoxy nanocompositesThemodel-fittingmethodoften leads to some inaccuracies or kinetic compensationeffect whereas the model-free or isoconversional method isnot sensitive to cure kinetic [9 17 58ndash64]

3 Cure Kinetics of EpoxyMWCNTsNanocomposites

Zhou et al demonstrated that the use of MWCNTs facilitatescrosslinking at the initial curing stage of bisphenol-A glycidolether epoxy2-ethyl-4-methylimidazole (DGEBAEMI-24)system by lowering the peak temperature and the heat ofreaction in turn prevents the occurrence of vitrificationby lowering the 119879

119892compared to neat epoxy resin [13] At

higher contents of MWCNTs however the overall degree ofcure declines due to the reduction of epoxy concentrationand probable agglomeration Dynamic DSC determination


R

O O

C CCH2 CH2+HH

CH

RROH

OH

BF3

BF3

BF3

∙∙

lowastRCH2ORlowast

Scheme 4 Mechanism of Lewis acid-catalyzed curing of epoxy by alcohol

R

R

R R

R

RC

C

C

C

C

C

C

CC

C C

C

C C

CH

H

H

H

CH

O

O

O

O

O

+

+

+

+

O O

OOO

OO

O

OO

O

O

OO

O

O

O O

O

A

A

A

A

A

A

A

CH2

CH2

CH2

NR3

NR3

CHlowastR

lowastR

lowastR

H2C

H2C

CH2NR3

Scheme 5 Mechanism of curing epoxy resins with anhydridehardeners

often leads to sigmoidal form of conversion-temperaturecurves being observed indicating an autocatalytic kinetic inalmost all studied systems As illustrated in Figure 1 theaddition of MWCNTs does not change the autocatalyticcure reaction mechanism of DGEBAEMI-24 system Alsoa small variation in the amplitude of heat of cure implies thatthe etherification reaction is dominant in the cure process

In case of isothermal curing of epoxide systems severalauthors employedKamal equation to investigate the extent ofautocatalytic reaction [10 12 14ndash19 24] as follows

119889120572

119889119905

= (1198961+ 1198962120572119898) (1 minus 120572)

119899 (1)

where 1198961and 119896

2are the autocatalytic and noncatalytic rate

constants 119898 and 119899 are kinetic exponents and 120572 is thefractional conversion of cure reaction respectively

Xie et al studied the cure kinetics of tetraglycidyl-4-41015840-diaminodiphenylmethane441015840-diaminodiphenylsulfone(TGDDMDDS) systems containing MWCNTs throughisothermal calorimetry [19]

The reduction of the time to the maximum rate withincreasingMWCNTs concentration typically proved the earlystage autocatalytic reaction In addition the experimentalresults agreed with kinetic model of Kamal They plotted the

10

08

06

04

02

0040 60 80 100 120 140 160 180 200 220 240

Temperature (∘C)

Frac

tiona

l ext

ent o

f con

vers

ion

Neat epoxy system1 wt MWCNTepoxy system3 wt MWCNTepoxy system5 wt MWCNTepoxy system

Figure 1 Conversion as a function of temperature at heating rateof 20∘Cmin for the neat epoxy andMWCNTs-filled epoxy systemsAfter [13]

reaction rate and the extent of reaction of TGDDMDDSand its nanocomposites as a function of time at differenttemperaturesThe one displayed at 180∘C is given in Figure 2for instance

The authors modified Kamal equation multiplying theright side of (1) by a diffusion control function to express thecontribution of diffusion to cure reaction Figure 3 illustratesthe effect of curing temperature on diffusion control functionnamely 119891

119889(120572)

If the reaction is chemically controlled 119891119889(120572) is unity

whereas in the case of full diffusion control the reaction ispractically interrupted and the diffusion control is zero Asseen in this figure at curing temperatures beyond 200∘Cwhen 120572 is greater than 07 the reaction rate significantlyincreases up to the value predicted by Kamal Model untildrop-off due to diffusion This deviation in 119891

119889(120572) demon-

strates that curing is diffusion controlled because of vitrifi-cation

It was also mentioned that this unexpected increasein the value of 119891

119889(120572) which is observed in case of neat

epoxy and 1 wt of MWCNTsepoxy systems stems mainly


005

004

003

002

001

0000 20 40 60 80 100 120

10

08

06

04

02

00

Time (min)

d120572dt

(minminus1)

120572

0 wt1 wt

5 wt

Figure 2The reaction rate and extent of reaction of TGDDMDDSepoxy and its nanocomposites as a function of time at 180∘C After[19]

14

12

10

08

06

04

02

00100806040200

Fit result using (5)

180∘C190∘C200∘C

210∘C220∘C

fd(120572)

Figure 3 Curve of diffusion control function 119891119889(120572) against extent

of reaction for 1 wtMWCNTsepoxy nanocomposites the effect ofcuring temperature After [19]

from the etherification Thus it can be concluded that thesaturation of catalyzing action is often probable in highlyfilled epoxy nanocomposites with unmodified MWCNTsSimilar trend was observed in DGEBAdiethylenetriamine(DETA) nanocomposites containing SWCNTs [18 25]

4 The Influence of Functionalization ofMWCNTs on Cure Kinetics

The CNTs bearing active groups can significantly change thesurface characteristics of these constituentsThese functionalnanotubes can react with different materials such as resins

or act as a catalyst thus enhancing the interfacial bondbetween the matrix and the CNTs dictates the applica-tion of prepared polymer nanocomposites [39 44] Curekinetics of an epoxide system is highly dependent on thenanocomposite constituents In general the reactivity ofamine hardeners increases with their nucleophilic naturetherefore employing an appropriate catalyst as well as aproper curing temperature leads to highly crosslinked net-works [8] On the other hand the functionalization of CNTsincreases their surface roughness Such a modification canbe performed physically or chemically One of the majordrawbacks of physical treatment is the lack of appropriateinterfacial adhesion as a consequence of weakness of thevan der Waals forces In case of chemical modificationhowever the interaction between nanotubes and the matrixis responsible for the strong adhesion due to formation ofcovalent bonds at the interface A variety of techniques andalso functional groups have been employed to give access tofunctionalization of CNTs [38ndash44] Among different tech-niques the carboxylation halogenation and amidation arethe most commonly used methods for enhancing structuralproperties of CNTepoxide composites In general afterfunctionalization of nanotubes the polar groups located onthe surface of filler act as curing agents and accelerate thecure reaction of epoxy To our knowledge functionalizedMWCTNs bearing reactive groups for example ndashCOOHand ndashNH

2 have been considered to evaluate cure criterion

The presence of carboxylic and other oxygen-bearing groupsat the surface of nanotubes and at defect sites promotesnanofiller reactivity However mainly due to the large aspectratio of CNTs the occurrence of sidewall functionalizationis also probable [44] Bae et al modified two kinds of CNTswith carboxylic monomers towards liquid-crystalline epoxyand stated that the increase of heat of cure and decrease ofactivation energy justifies higher nucleophilicity after surfacetreatment [12] In other words polar interaction betweencarboxylic groups and epoxide facilitates the breakage ofepoxide rings and promotes the homogeneous distributionof nanofillers The effect of polar-polar interactions on theactivation energy in such systems is more salient comparedto steric hindrance Furthermore the isothermal kineticparameters evaluated from Kamal equation provide supportfor the remarkable effect of oxidation in the early stage ofcure reaction Zhou et al indicated that ndashCOOH function-alization of MWCNTs does not change the autocatalytic curemechanism of DGEBAEMI-24MWCNTs nanocomposites[13 21] At the early stages of curing both types ofMWCNTsthat is the pristine and COOH-functionalized representcatalytic effect on the curing reaction This influence is morepronounced in case of modified filler because the ndashCOOHgroups can react with epoxide hydroxyl group to form CndashOndashC ether bonds At the later stages however the unmod-ified MWCNTs delay vitrification more than carboxylatedfillers The authors reasoned that ndashCOOH groups improvethe compatibility between the MWCNTs and epoxy matrixleading to lesser free volume and hindrance effect on vitri-fication phenomenon Figure 4 demonstrates that inflexionof activation energy curves at fractional conversions greaterthan 07 increases less with increasing COOH-MWCNTs


60

50

40

30

20

0 20 40 60 80 100120572 ()

Neat epoxy systemN1 systemN3 systemN5 system

C1 systemC3 systemC5 system

E120572

(kJm

ol)

Figure 4 Plots of activation energy against 120572 of neat epoxyuntreated systems containing 1 3 and 5wt of MWCNTs (N1N3 N5) and functionalized systems containing 1 3 and 5wt ofCOOH-MWCNTs (C1 C3 C5) Dotted lines are given for showingthe tendency After [21]

content compared to nontreated nanotube as a consequenceof constrained segmental motion in this situation [21]

Abdalla et al investigated the rheological and curecharacteristics of DGEBAEPIKURE systems comprisingcarboxylated and fluorinated MWCNTs [15 25] As seenin Scheme 6 the cure mechanism of the neat epoxy andfluorinated system is very similar wherein the heat of curesis measured to be 475 and 477 kJmol respectively

Contrarily the higher heat of reaction in case of carboxy-lated nanotubes (617 kJmol) is indicative of a completelydifferent cure mechanism Nanotubes bearing carboxylicgroups ease the ring opening and substantially generate anester bond and an alcohol group whereas the fluorinatedCNTs essentially act as an amine curing agent The rateconstants determined by Kamal model revealed that inthe fluorinated system CNTs are dispersed appropriatelydemonstrating quite a high surface area in turn the presenceof aggregates in the carboxylated system causes insufficientcatalytic effect (Figure 5)

At higher curing temperatures for example 140∘C reac-tion rates are almost independent of the surface modifica-tion Also samples containing fluorinated MWCNTs exhibitthe highest 119879

119892among all nanocomposites corroborating

existence of uniformly dispersed nanotubes The value ofcrosslink density calculated using the plateau modulus arealmost the same except for 1 wt samples where thefluorinated samples exhibit higher values Significant heatcapacity at higher temperatures in case of carboxylatednanocomposites is another evidence for constrainedmobilityof reacting species due to inhomogeneous dispersion Theauthors speculated that the density of functional groups on

008

006

004

002

000

minus002

minus0040 50 100 150 200 250

Time (min)

Hea

t flow

(Wg

)

Neat epoxy1 F-MWCNT EPON 8281 COOH-MWCNT EPON 828

Figure 5 Isothermal DSC thermograms of neat EPON828 1 wtF-MWCNTsepoxy and COOH-MWCNTepoxy nanocompositesat 120∘C After [15]

the surface of CNTs alters by the type of modifier whichis responsible for this observation The results providedsupport for the fact that further treatments on carboxylatedMWCNTs for example in situ esterification with oligomericunsaturated hydroxyl-terminated polyesters intensely affectthe rheological and fracture properties [23 66]

The effect of amine functionalization on MWCNTs hasalso been studied by researchers Shen et al used the proce-dure illustrated in Scheme 7 to prepare modified MWCNTswith amide groups from carboxylated nanotubes [53 65]

They found that the initial decomposition temperature ofnanocomposites increases about 30∘Cby addition of 025wtamino-functionalized MWCNTs corroborating strong inter-phase between epoxy and modified nanotubes When theamount of nanotubes exceeds 1 wt the decomposition tem-perature slightly decreases According to Figure 6 depressionof the 119879

119892of about 20∘C observed when 1wt of amino-

functionalized MWCNTs incorporated into compositeThis can be attributed to enhanced interfacial adhesion

with epoxy This research group also discussed for reinforce-ment mechanism of different amino-functionalized MWC-NTs in epoxy resinThey found that the119879

119892of nanocomposites

is obviously governed by the amidation because the amidegroups participate in curing reaction as a hardener Yang andcollaborators compared cure behavior of EPON828EMI-24 composites with those filled with pristine and amine-modifiedMWCNTs [9 10] For all prepared samples only onepeak appeared throughout DSC thermograms irrespectiveof the heating rate Thus etherification reaction dominantlyoccurred As in Figure 7 addition of untreated or func-tionalized MWCNTs does not change the autocatalytic curekinetics of epoxy


F+

+

H2NR

R

NH2

NHNH 2

OC

C

HCH2

NH N

CH

OH

H2

RlowastR

lowastR

Epoxy resins

+O

O

O O O

O

C

C C

C CC

HCH2

CH

CH

OH

OH

H2

H2

H2H2

Rlowast

lowastR

Epoxy resins

COOH

H3CCH3

CH3

CH3

CH3R = Rlowast =

(a)

(b)

Scheme 6 Schematic representation of the reaction between functionalized MWCNTs with DGEBA resin (a) fluorinated CNT (b)carboxylated CNT

As-received nanotubes (C1) show retarding effect on the

cure reaction of epoxy resin (C0) due to their hindrance

whereas the amino-functionalized MWCNTs (C2) acceler-

ate the curing reaction as a secondary curing agent andfacilitate the primary amine-epoxide reaction (Scheme 1)Furthermore the alteration of activation energy as a functionof extent of reaction demonstrates the accelerating effectof amine functionalized nanotubes on cure reaction inparticular at later stages of curing (Figure 8)

The autocatalytic mechanism of curing is also examinedby phenomenological model of Kamal and showed goodagreement The authors also reported that increasing theconcentration of amino nanotubes up to 3wt results inan increase in the degree of vitrification In this situation

reaction is likely to be diffusion controlled at lower heatingrates and larger conversions because of significant steric hin-drance It means that accumulation of amine groups on thesurface of MWCNTs intensifies the catalyzing effect duringthe epoxy cure reaction Employing isothermal and non-isothermal calorimetric studies a similar trend is observed inDGEBADDMcomposites containing 3 parts byweight of as-received and amine-treated MWCNTs based on 100 parts byweight of epoxy resin [16] It can be concluded that the criticalconcentration in the functionalized epoxy nanocompositesseems to be around 1wt as that of untreatedepoxy systemsProlongo et al prepared various DGEBADDM mixturescontaining different amine functionalized MWCNTs (0 01025 wt) and changed the ratio of amine to epoxy namely 119903


DSC

(mV

)

00010025

010251

45 50 55 60 65 70Temperature (∘C)

(a)D

SC (m

V)

00010025

010251

4540 50 55 60 65 70Temperature (∘C)

(b)

Figure 6 Dynamic DSC thermograms of neat epoxy and its raw MWCNTs nanocomposites (a) neat epoxy and its amino-functionalizedMWCNTs nanocomposites (b) After [53]

H2SO4

HNO3

O

O

CC

CC

C

C

OHOH

OHOH

OH

OH

SOCl2

Cl

Cl

H2NRlowastNH2

H2NlowastRHN

H2NlowastRHN

Scheme 7 The procedures used for functionalization of MWCNTsby Shen et al

as a measure of the amine hydrogen equivalents per oxiranerings [14] Irrespective of the stoichiometry only one exother-mic peak appeared throughout dynamic DSC thermogramscorresponding to amineepoxy curing reaction Figure 9 dis-plays dynamic DCS thermograms of stoichiometric mixtures(119903 = 1) with different amino-functionalized CNT contents

In case of stoichiometric mixtures (119903 = 1) the heat ofcure is lower than that of theoretical value for epoxyaminereaction enthalpy (close to 95ndash100 kJee) which suggeststhat the epoxy network is not completely crosslinked Thisunexpected deviation is more pronounced for the mixturereinforced with 01 wt nanotube As the cure reactionpromoted via step polymerization the retardation effectcould not be associated with diffusion controlled mechanismbut with adsorption of monomers into the nanotubes whichdisrupts the reaction stoichiometry When the concentration

The f

ract

iona

l ext

ent o

f con

vers

ion

(120572)

Temperature (K)

10

08

06

04

02

00360 380 400 420 440 460 480 500

C0C1

C2

Figure 7 DSC thermograms at 20∘Cmin of neat epoxy (1198620)

05 wt as-received MWCNTsepoxy nanocomposites (1198621) and

05 wt amine-modified MWCNTsepoxy nanocomposites (1198622)

Dotted lines are given for showing the tendency After [10]

of amino nanotube increased the imbalance in stoichiometryis supposed to be compensated however formation of aggre-gates facilitated the monomer adsorption effect To infer thisphenomenon the authors used an excess amount of hardener(119903 = 12) and determined the reaction enthalpy by dynamicDSC and obtained higher values (1090 983 and 1052resp for mixtures containing 0 01 and 025wt of CNTs)compared to systems with stoichiometric ratio (923 808


Table 1 The effect of functionalization of MWCNTs on cure kinetics of epoxy systems

CNT type Modificationmethod Surface modifier Epoxy type Curing condition Reference

MWCTNs Carboxylation ndashCOOH

Liquid-crystalline epoxy(440-dihydroxy-and-methyl-stilbenesulfanilamide)

Isothermal Bae et al [12]

MWCNTs Carboxylation COOHndash DGEBA EMI-24 Nonisothermal Zhou et al [21]

MWCNTs Carboxylation andfluorination ndashCOOH and ndashF DGEBA EPIKURE Isothermal Abdalla et al [15]

Kim et al [26]

MWCNTs Amino-functionalization ndashNH Epoxy resin E51 aromatic

curing agent (JX-011) Nonisothermal Shen et al [53 65]

MWCNTs Amino-functionalization ndashNH EPON828 EMI-24 Nonisothermal

Domınguez et al[9]

Yang et al [10]

MWNTs Amino-functionalization ndashNH DGEBA 441015840-methylene

dianilineIsothermal andnonisothermal Choi et al [16]

MWCNTs Amino-functionalization ndashNH DGEBA DDM Nonisothermal Prolongo et al [14]

120572

100806040200

80

70

60

50

40

30

E120572

(kJm

ol)

C0C1C2

Polynomial fit of C0Polynomial fit of C1Polynomial fit of C2

Figure 8 Plots of activation energy of neat epoxy (1198620) 05 wt

as-received MWCNTsepoxy nanocomposites (1198621) and 05 wt

amine-modified MWCNTsepoxy nanocomposites (1198622) against

degree of cure obtained by isoconversional kinetic model After [10]

and 888 resp for mixtures containing 0 01 and 025wtof CNTs) which implies different reactivity of the primaryand secondary amines Molecular simulation confirmed theconsequence ofDDMadsorption intoCNTs and reasoned thelower values of cure enthalpy after amine functionalizationThe shift of peak temperature only observed for systemsfilled with 01 wt which can be attributed to the constrainedmobility of epoxy chains as a consequence of anchored aminegroups on the surface of CNTs Applying Kamal equation ondata obtained by isothermal calorimetry demonstrated that

10

8

6

4

2

050 100 150 200 250

001

025

Exo

Temperature (∘C)

Figure 9 Dynamic DCS thermograms of stoichiometric mixtures(119903 = 1) with different amino-functionalized CNT contents After[14]

the noncatalytic constant in this kinetic model does not varyneither with CNTs addition nor stoichiometry ratio On theother hand the autocatalytic constant significantly decreasesfor epoxy nanocomposites The retardation effect of carbonnanotubes was markedly lower when the content of CNTwas 01 wt due to depression in the extent of autocatalyticmechanism Besides the 119879

119892of the epoxy matrix increased

by introducing CNTs because of constrained mobility Thishindrance was more pronounced when an excess amine wasused (119903 = 12) It is to be noted that the cure behavior of epoxycomposites containing functionalized CNTs is challengeabledue to variety andor complexity of reaction kinetics which


can be influenced by several dependent variables Table 1represents the above-mentioned works on dealing with curekinetics of functionalizedMWCNTsepoxy nanocomposites

5 Conclusion

The effect of functionalization of multi-walled carbon nan-otubes (MWCNTs) on cure kinetics of epoxy composites iscomprehensively discussed based on the available literatureAmong various types of surface treatments the carboxylationand amidation methods were particularly surveyed becauseof their importance as well as well-documented data Theextent of retardation andor acceleration in curing whenutilizing untreated and functionalized MWCNTs was alsoconsidered in regard to isothermal or nonisothermal differ-ential scanning calorimetry (DSC) On the basis of dynamicDSC thermograms it can be realized that the functionaliza-tion of MWCNTs significantly facilitates the early stage ofcuring even though the cure mechanism remains almostunaffected by the surface modification of the nanotubes Ina different way the isothermal DSC measurement impliesthat the incorporation of functionalizedMWCNTs hasminoreffect on vitrification compared with untreated nanotubesas a consequence of constrained mobility of polymer chainswhich arisesmainly from intensified interactions between thehost polymer and nanotubes In other words the state of dis-persion is greatly sensitive to either the presence or the typeof functional groups used Employing the phenomenologicalmodel proposed by Kamal it can be realized that functional-ization ofMWCNTs slightly improves the rate of autocatalyticreaction By contrast the extent of autocatalytic reaction isgreatly governed by several interactive factors for examplecuring temperature stoichiometric ratio of amineepoxideand the amount ofmodifiedMWCNTs regardless of the kindof ligands on the surface of CNTs

References

[1] S Iijima ldquoHelicalmicrotubules of graphitic carbonrdquoNature vol354 no 6348 pp 56ndash58 1991

[2] P M Ajayan O Stephan C Colliex and D Trauth ldquoAlignedcarbon nanotube arrays formed by cutting a polymer resin-nanotube compositerdquo Science vol 265 no 5176 pp 1212ndash12141994

[3] S H Lee E Cho S H Jeon and J R Youn ldquoRheological andelectrical properties of polypropylene composites containingfunctionalized multi-walled carbon nanotubes and compatibi-lizersrdquo Carbon vol 45 no 14 pp 2810ndash2822 2007

[4] F Du R C Scogna W Zhou S Brand J E Fischer andK I Winey ldquoNanotube networks in polymer nanocompositesrheology and electrical conductivityrdquo Macromolecules vol 37no 24 pp 9048ndash9055 2004

[5] J F Vega J Martınez-Salazar M Trujillo et al ldquoRheologyprocessing tensile properties and crystallization of polyethy-lenecarbon nanotube nanocompositesrdquo Macromolecules vol42 no 13 pp 4719ndash4727 2009

[6] A K Kota B H Cipriano M K Duesterberg et al ldquoElec-trical and rheological percolation in polystyreneMWCNTnanocompositesrdquo Macromolecules vol 40 no 20 pp 7400ndash7406 2007

[7] P Potschke T D Fornes and D R Paul ldquoRheological behaviorof multiwalled carbon nanotubepolycarbonate compositesrdquoPolymer vol 43 no 11 pp 3247ndash3255 2002

[8] D Ratna Handbook of Thermoset Resins Smithers RapraShawbury UK 2009

[9] J CDomınguez J C Grivel andBMadsen ldquoStudy on the non-isothermal curing kinetics of a polyfurfuryl alcohol bioresin byDSC using different amounts of catalystrdquoThermochimica Actavol 529 pp 29ndash35 2012

[10] K Yang M Gu and Y Jin ldquoCure behavior and thermalstability analysis of multiwalled carbon nanotubeepoxy resinnanocompositesrdquo Journal of Applied Polymer Science vol 110no 5 pp 2980ndash2988 2008

[11] K Yang M Gu Y Jin G Mu and X Pan ldquoInfluence of surfacetreated multi-walled carbon nanotubes on cure behavior ofepoxy nanocompositesrdquo Composites A vol 39 no 10 pp 1670ndash1678 2008

[12] J Bae J Jang and S H Yoon ldquoCure behavior of the liquid-crystalline epoxycarbon nanotube system and the effect ofsurface treatment of carbon fillers on cure reactionrdquo Macro-molecular Chemistry and Physics vol 203 pp 2196ndash2204 2002

[13] T Zhou X Wang X Liu and D Xiong ldquoInfluence of multi-walled carbon nanotubes on the cure behavior of epoxy-imidazole systemrdquo Carbon vol 47 no 4 pp 1112ndash1118 2009

[14] S G Prolongo M R Gude and A Urena ldquoThe curingprocess of epoxyamino-functionalizedMWCNTs calorimetrymolecular modelling and electron microscopyrdquo Journal ofNanotechnology vol 2010 Article ID 420432 11 pages 2010

[15] M Abdalla D Dean P Robinson and E Nyairo ldquoCure behav-ior of epoxyMWCNT nanocomposites the effect of nanotubesurface modificationrdquo Polymer vol 49 no 15 pp 3310ndash33172008

[16] W J Choi R L Powell and D S Kim ldquoCuring behavior andproperties of epoxy nanocomposites with amine functionalizedmultiwall carbon nanotubesrdquo Polymer Composites vol 30 no4 pp 415ndash421 2009

[17] N Sbirrazzuoli S Vyazovkin A Mititelu C Sladic and LVincent ldquoA study of epoxy-amine cure kinetics by combiningisoconversional analysis with temperature modulated DSC anddynamic rheometryrdquo Macromolecular Chemistry and Physicsvol 204 no 15 pp 1815ndash1821 2003

[18] D Puglia L Valentini and J M Kenny ldquoAnalysis of the curereaction of carbon nanotubesepoxy resin composites throughthermal analysis and Raman spectroscopyrdquo Journal of AppliedPolymer Science vol 88 no 2 pp 452ndash458 2003

[19] H Xie B Liu Z Yuan J Shen and R Cheng ldquoCure kineticsof carbon nanotubetetrafunctional epoxy nanocomposites byisothermal differential scanning calorimetryrdquo Journal of Poly-mer Science B vol 42 no 20 pp 3701ndash3712 2004

[20] W S Choi A M Shanmugharaj and S H Ryu ldquoStudy on theeffect of phenol anchored multiwall carbon nanotube on thecuring kinetics of epoxyNovolac resinsrdquo Thermochimica Actavol 506 no 1-2 pp 77ndash81 2010

[21] T ZhouXWangH Zhu andTWang ldquoInfluence of carboxylicfunctionalization of MWCNTs on the thermal properties ofMWCNTsDGEBAEMI-24 nanocompositesrdquo Composites Avol 40 no 11 pp 1792ndash1797 2009

[22] V G Hadjiev G LWarren L Sun D C Davis D C Lagoudasand H-J Sue ldquoRaman microscopy of residual strains in carbonnanotubeepoxy compositesrdquo Carbon vol 48 no 6 pp 1750ndash1756 2010


[23] B Kaffashi A Kaveh OMoini Jazani andM R Saeb ldquoImprov-ing rheological properties of covalently MWCNTepoxy nano-composites via surface re-modificationrdquo Polymer Bulletin vol68 no 8 pp 2187ndash2197 2012

[24] D Puglia L Valentini I Armentano and J M Kenny ldquoEffectsof single-walled carbon nanotube incorporation on the curereaction of epoxy resin and its detection by Raman spec-troscopyrdquo Diamond and Related Materials vol 12 no 3-7 pp827ndash832 2003

[25] M Abdalla D Dean D Adibempe E Nyairo P Robinson andGThompson ldquoThe effect of interfacial chemistry on molecularmobility and morphology of multiwalled carbon nanotubesepoxy nanocompositerdquo Polymer vol 48 no 19 pp 5662ndash56702007

[26] J A Kim D G Seong T J Kang and J R Youn ldquoEffects ofsurface modification on rheological and mechanical propertiesof CNTepoxy compositesrdquo Carbon vol 44 no 10 pp 1898ndash1905 2006

[27] Y S Song and J R Youn ldquoInfluence of dispersion states ofcarbon nanotubes on physical properties of epoxy nanocom-positesrdquo Carbon vol 43 no 7 pp 1378ndash1385 2005

[28] T T L Doan H Brodowsky and E Mader ldquoJute fibreepoxycomposites surface properties and interfacial adhesionrdquo Com-posites Science and Technology vol 72 pp 1160ndash1166 2012

[29] J Zhang R Zhuang J Liu E Mader G Heinrich and S GaoldquoFunctional interphases withmulti-walled carbon nanotubes inglass fibreepoxy compositesrdquo Carbon vol 48 no 8 pp 2273ndash2281 2010

[30] N A Siddiqui E L Li M-L Sham et al ldquoTensile strengthof glass fibres with carbon nanotube-epoxy nanocompositecoating effects of CNT morphology and dispersion staterdquoComposites A vol 41 no 4 pp 539ndash548 2010

[31] E Mader S Melcher J-W Liu et al ldquoAdhesion of PBO fiberin epoxy compositesrdquo Journal of Donghua University (EnglishEdition) vol 24 no 2 pp 173ndash177 2007

[32] E Mader S Melcher J W Liu et al ldquoAdhesion of PBO fiber inepoxy compositesrdquo Journal of Materials Science vol 42 no 19pp 8047ndash8052 2007

[33] J Liu S L Gao E Mader et al ldquoAdhesion issues in PBOepoxycompositesrdquo Key Engineering Materials vol 334-335 pp 233ndash236 2007

[34] E Mader S-L Gao and R Plonka ldquoStatic and dynamicproperties of single andmulti-fiberepoxy composites modifiedby sizingsrdquoComposites Science and Technology vol 67 no 6 pp1105ndash1115 2007

[35] T V Brantseva Y A Gorbatkina E Mader V Dutschk andM L Kerber ldquoModification of epoxy resin by polysulfone toimprove the interfacial and mechanical properties in glass fibrecomposites II Adhesion of the epoxy-polysulfone matrices toglass fibresrdquo Journal of Adhesion Science and Technology vol 18no 11 pp 1293ndash1308 2004

[36] S-L Gao E Mader and S F Zhandarov ldquoCarbon fibers andcomposites with epoxy resins topography fractography andinterphasesrdquo Carbon vol 42 no 3 pp 515ndash529 2004

[37] E Mader X-F Zhou S Zhandarov S R Nutt S L Gao and SZhandarov ldquoBond strength measurement between glass fibresand epoxy resin at elevated temperatures using the pull-out andpush-out techniquesrdquo Journal of Adhesion vol 78 no 7 pp 547ndash569 2002

[38] J Hilding E A Grulke Z G Zhang and F Lockwood ldquoDis-persion of carbon nanotubes in liquidsrdquo Journal of DispersionScience and Technology vol 24 no 1 pp 1ndash41 2003

[39] P-C Ma N A Siddiqui G Marom and J-K Kim ldquoDispersionand functionalization of carbon nanotubes for polymer-basednanocomposites a reviewrdquo Composites A vol 41 no 10 pp1345ndash1367 2010

[40] OMatarredona H Rhoads Z Li J H Harwell L Balzano andD E Resasco ldquoDispersion of single-walled carbon nanotubes inaqueous solutions of the anionic surfactant NaDDBSrdquo Journalof Physical Chemistry B vol 107 no 48 pp 13357ndash13367 2003

[41] C E Pizzuttoa J Suavea J Bertholdia H S Pezzina L A FCoelhoa and S C Amicob ldquoStudy of epoxyCNT nanocom-posites prepared via dispersion in the hardenerrdquo MaterialsResearch vol 14 pp 256ndash263 2011

[42] G Gkikas N-M Barkoula and A S Paipetis ldquoEffect of dis-persion conditions on the thermo-mechanical and toughnessproperties of multi walled carbon nanotubes-reinforced epoxyrdquoComposites B vol 43 pp 2697ndash2705 2012

[43] M Chapartegui N Markaide S Florez C Elizetxea M Fer-nandez and A Santamarıa ldquoSpecific rheological and electricalfeatures of carbon nanotube dispersions in an epoxy matrixrdquoComposites Science and Technology vol 70 no 5 pp 879ndash8842010

[44] A Hirsch and O Vostrowsky ldquoFunctionalization of carbonnanotubesrdquo Topics in Current Chemistry vol 245 pp 193ndash2372005

[45] S W Kim T Kim Y S Kim et al ldquoSurface modifications forthe effective dispersion of carbon nanotubes in solvents andpolymersrdquo Carbon vol 50 no 1 pp 3ndash33 2012

[46] J G Park Q Cheng J Lu et al ldquoThermal conductivity ofMWCNTepoxy composites the effects of length alignmentand functionalizationrdquo Carbon vol 50 no 6 pp 2083ndash20902012

[47] S Wang R Liang B Wang and C Zhang ldquoEpoxide-terminated carbon nanotubesrdquoCarbon vol 45 no 15 pp 3047ndash3049 2007

[48] CMDamian S A Garea E Vasile andH Iovu ldquoCovalent andnon-covalent functionalized MWCNTs for improved thermo-mechanical properties of epoxy compositesrdquo Composites B vol43 pp 3507ndash3515 2012

[49] S Ghorabi L Rajabi and A Derakhshan ldquoEpoxyfunctional-ized MWCNT nanocomposites cure behavior thermal stabil-ity mechanical properties and fracture morphologyrdquo Journal ofNanoengineering and Nanomanufacturing vol 2 pp 291ndash3032012

[50] Z Chen X J Dai KMagniez et al ldquoImproving themechanicalproperties of epoxy using multi-walled carbon nanotubes func-tionalized by a novel plasma treatmentrdquo Composites A vol 45pp 145ndash152 2013

[51] MTheodore M Hosur J Thomas and S Jeelani ldquoInfluence offunctionalization on properties of MWCNT-epoxy nanocom-positesrdquoMaterials Science and Engineering A vol 528 no 3 pp1192ndash1200 2011

[52] A Allaoui and N El Bounia ldquoHow carbon nanotubes affect thecure kinetics and glass transition temperature of their epoxycompositesmdashA reviewrdquo Express Polymer Letters vol 3 no 9pp 588ndash594 2009

[53] J Shen W Huang L Wu Y Hu and M Ye ldquoThermo-physicalproperties of epoxy nanocomposites reinforced with amino-functionalized multi-walled carbon nanotubesrdquo Composites Avol 38 no 5 pp 1331ndash1336 2007

[54] R J Day P A Lovell and A A Wazzan ldquoToughened car-bonepoxy composites made by using coreshell particlesrdquoComposites Science andTechnology vol 61 no 1 pp 41ndash56 2001


[55] J Zhang Y C Xu and P Huang ldquoEffect of cure cycle on curingprocess and hardness for epoxy resinrdquo Express Polymer Lettersvol 3 no 9 pp 534ndash541 2009

[56] L Xu and J R Schlup ldquoEtherification versus amine additionduring epoxy resinamine cure an in situ study using near-infrared spectroscopyrdquo Journal of Applied Polymer Science vol67 no 5 pp 895ndash901 1998

[57] V Trappe W Burchard and B Steinmann ldquoAnhydride curingof epoxy resins via chain reactionrdquo Makromolekulare ChemieMacromolecular Symposia vol 45 pp 63ndash74 1991

[58] G Rivero V Pettarin A Vazquez and L B Manfredi ldquoCuringkinetics of a furan resin and its nanocompositesrdquoThermochim-ica Acta vol 516 no 1-2 pp 79ndash87 2011

[59] G Gyulai and E J Greenhow ldquoA new integral method for thekinetic analysis of thermogravimetric datardquo Journal of ThermalAnalysis vol 6 no 3 pp 279ndash291 1974

[60] N Sbirrazzuoli ldquoIs the Friedman method applicable to trans-formations with temperature dependent reaction heatrdquoMacro-molecular Chemistry and Physics vol 208 no 14 pp 1592ndash15972007

[61] S Vyazovkin and C A Wight ldquoModel-free and model-fittingapproaches to kinetic analysis of isothermal and nonisothermaldatardquoThermochimica Acta vol 340-341 pp 53ndash68 1999

[62] S Vyazovkin ldquoModification of the integral iso-conversionalmethod to account for variation in the activation energyrdquoJournal of Computational Chemistry vol 22 pp 178ndash183 2001

[63] S Vyazovkin ldquoA unified approach to kinetic processing ofnonisothermal datardquo International Journal of Chemical Kineticsvol 28 no 2 pp 95ndash101 1996

[64] A Ortega ldquoA simple and precise linear integral method forisoconversional datardquoThermochimica Acta vol 474 no 1-2 pp81ndash86 2008

[65] J ShenW Huang LWu Y Hu andM Ye ldquoThe reinforcementrole of different amino-functionalized multi-walled carbonnanotubes in epoxy nanocompositesrdquo Composites Science andTechnology vol 67 no 15-16 pp 3041ndash3050 2007

[66] M Holzinger J Abraham P Whelan et al ldquoFunctionaliza-tion of single-walled carbon nanotubes with (R-)oxycarbonylnitrenesrdquo Journal of the American Chemical Society vol 125 no28 pp 8566ndash8580 2003

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


of nanocomposites undergoes a plateau indicating theformation of percolated CNT networks that respondelastically over long time scales The rheological percolationthreshold of CNTpolymer nanocomposites obviouslydepends on temperature On the other hand the electricalconductivity in these systems is strongly governed by thestate of dispersion that is nanotube-nanotube distance andalignment of CNTs in the matrix [3ndash6]

So many research efforts have also been dedicated toproduce various thermoset composites containing CNTsEpoxy resins have attracted much attention among ther-moset family of materials owing to their excellent prop-erties for example high modulus low shrinkage in cureand good chemical and corrosion resistance as well asacceptable adhesion characteristics Besides epoxies can becured using a various ranges of chemicals with differenttypes of curing conditions [8] Some authors have addressedthe cure behavior of epoxide thermoset composites filledwith different types of nanosized fillers Thermal studies oncure phenomenon of thermoset composites can be classifiedinto two general categories isothermal and nonisothermalkinetics Domınquez et al used different amounts of an acidcatalyst based on p-toluenesulfonic acid dissolved in water(45 aqueous solution) to study the nonisothermal curingkinetics of polyfurfuryl alcohol bioresin [9] Employingdifferent isoconversional (nonisothermal) methods that isKissinger-Akahira-Sunone (KAS) Flynn-Wall-Ozawa (FWO)and Vyazovkin (VA) they elucidated that the initial and finalstage of curing respectively possesses an acceleration anddeceleration period depending on the content of catalystused The limited movement of polymer chains andoraccumulation of reaction ingredients were the main reasonsfor the alteration of the cure mechanism Several epoxidecomposites filled with CNTs have already been studied bydifferent authors bisphenol-A glycidol ether epoxy2-ethyl-4-methylimidazole (DGEBAEMI-24) system containingpristine and amine functionalized MWCNTs by Yang et al[10 11] liquid-crystalline epoxy system of 441015840-dihydroxy-a-methyl-stilbenesulfanilamide containing carbon nanotubesand carbon black conventional filler by Bae et al [12]DGEBAEMI-24 system containing purified MWCNTs byZhou et al [13] DGEBA441015840-ethylenedianiline (DDM)epoxide systems containing amine functionalized MWCNTsby Prolongo et al [14] DGEBAdiethyltoluenediamine sys-tems with carboxyl and fluorine modified MWCNTs byAbdalla et al [15] DGEBADDM composites comprisingamine functionalized MWCNTs by Choi et al [16] DGEBA13-phenylenediamine epoxy-amine CNT-free system bySbirrazzuoli et al [17] DGEBAdiethylenetriamine (DETA)containing pristine SWCNTs by Puglia et al [18] tetra-glycidyl-441015840-diaminodiphenylmethane (TGDDM)441015840-di-aminodiphenylsulfone (DDS) system comprising MWCNTsby Xie et al [19] DGEBANovolac as an epoxyphenolicsystem containing phenol anchored multi-walled carbonnanotube by Choi et al [20] and MWCNTsDGEBAEMI-24 nanocomposites containing carboxylic functionalizedMWCNTs by Zhou et al [21]

Similar to the case of thermoplastic compositesCNTepoxy thermoset systems have been the subject of

several studies to investigate characteristics other thancuring for example the rheological and mechanical prop-erties For many different reasons which will be discussedin the next sections surface treatment or functionalizationof CNTs greatly enhances the performance of preparednanocomposites Hadjiev et al used Raman spectroscopyto measure the magnitude of residual stresses in diglycidylether of bisphenol-F (DGEBF) epoxide systems curedwith diethyltoluenediamine (DETDA) [22] They prepareddifferent types of CNTepoxy composite samples employingpristine and functionalized Kaffashi et al discussed theextent of improvement in rheological characteristicsin DGEBAmetaphenylene diamine (M-PDM) systemscontaining covalently modified and remodified MWCNTs[23] Primarily the MWCNTs were surface modified witha mixture of sulfonic and nitric concentrated acids andthen diluted with distilled water To produce remodifiedMWCNTS in-situ esterification of carboxylated MWCNTswas performed There were significant shifts in loss andstorage modulus in specimens prepared by modified andremodifiedMWCNTs Depending on the conducted strategyvarious features have been considered while performing aspecified test on the samples as the work done by Pugliaet al [24] Differently from the way used by Hadjiev et alPuglia and coworkers discussed the impact of SWNTs onthe cure reaction of DGEBADETA composites by means ofthermal analysis and Raman spectroscopyThey revealed thatSWNTs act as a strong catalyst and reduce the temperatureassigned for the exothermic reaction peak Carboxylatedand fluorinated nanotubes were used by Abdalla et al tosynthesize nanocomposites by dispersing them separately inDGEBAdiethyltoluenediamine (DETDA) thermoset system[25] Attention has been made by the authors to investigatethe role of interfacial chemistry in molecular mobilityand morphology of produced nanocomposites Kim et alreported the mechanical and rheological properties ofdiglycidyl ether of bisphenol-A epoxide systems (YD 128)cured by a modified aromatic amine hardener (TH 432)[26] Based on amine treatment and plasma oxidationthey attempted to improve the interfacial adhesion aswell as the performance of dispersion of multi-wallednanotubes in the epoxy matrix The degree of performanceof CNTepoxy systems greatly depends upon the state ofdispersion of nanotubes in the epoxy matrix Song and Youndemonstrated that the rheologicalmechanical electrical andthermal properties of YD 128TH 432 epoxy are governed bythe state of dispersion ofMWCNTs whether a solvent is usedor not [27] In epoxy-based systems andor their reinforcedcomposites Doan et al have made a lot of efforts to interpretthe alteration of some vital properties mostly adhesionand mechanical characteristics on account of interphasesituation From a practical point of view the following canbe considered as the most important works performed bycollaboration or under supervision of Mader incorporationof MWCNT and glass fiber into a DGEBA-based epoxyresin to the formation of semiconductive MWCNT-glassfibers and in turn multifunctional fiberpolymer interphases[28] evaluation of healing efficiency and tensile strength ofglass fibers with MWCNTDGEBAm-phenylenediamine





119892)







119892[52]





R R

R

R

R

R

R

O

O

O

C

C

C C C

C C

CC

CH

H

H

H

N

CH2

CH2

CH2lowastR

lowastR

lowastR

lowastR

XH

OH+

+

+

H

H

HOH

OH

OH

OH

NH2

H2

H2

H2

Epoxy

Epoxy Amine

Alcohol

CH2XRlowast

ORlowast

∙∙








R R

RR

O

O

CH

CH

OH OH

OH

H2C




+

+

RlowastndashNH2


RR

O

CH

RCH

OH

OH

O

H2C

H2C







119892of









R

O O

C CCH2 CH2+HH

CH

RROH

OH

BF3

BF3

BF3

∙∙

lowastRCH2ORlowast


R

R

R R

R

RC

C

C

C

C

C

C

CC

C C

C

C C

CH

H

H

H

CH

O

O

O

O

O

+

+

+

+

O O

OOO

OO

O

OO

O

O

OO

O

O

O O

O

A

A

A

A

A

A

A

CH2

CH2

CH2

NR3

NR3

CHlowastR

lowastR

lowastR

H2C

H2C

CH2NR3




119889120572

119889119905

= (1198961+ 1198962120572119898) (1 minus 120572)

119899 (1)

where 1198961and 119896





10

08

06

04

02

0040 60 80 100 120 140 160 180 200 220 240

Temperature (∘C)

Frac

tiona

l ext

ent o

f con

vers

ion





119889(120572)



119889(120572) demon-






005

004

003

002

001

0000 20 40 60 80 100 120

10

08

06

04

02

00

Time (min)

d120572dt

(minminus1)

120572

0 wt1 wt

5 wt


14

12

10

08

06

04

02

00100806040200


180∘C190∘C200∘C

210∘C220∘C

fd(120572)










60

50

40

30

20

0 20 40 60 80 100120572 ()



E120572

(kJm

ol)








008

006

004

002

000

minus002

minus0040 50 100 150 200 250

Time (min)

Hea

t flow

(Wg

)












F+

+

H2NR

R

NH2

NHNH 2

OC

C

HCH2

NH N

CH

OH

H2

RlowastR

lowastR

Epoxy resins

+O

O

O O O

O

C

C C

C CC

HCH2

CH

CH

OH

OH

H2

H2

H2H2

Rlowast

lowastR

Epoxy resins

COOH

H3CCH3

CH3

CH3

CH3R = Rlowast =

(a)

(b)









DSC

(mV

)

00010025

010251

45 50 55 60 65 70Temperature (∘C)

(a)D

SC (m

V)

00010025

010251

4540 50 55 60 65 70Temperature (∘C)

(b)


H2SO4

HNO3

O

O

CC

CC

C

C

OHOH

OHOH

OH

OH

SOCl2

Cl

Cl

H2NRlowastNH2

H2NlowastRHN

H2NlowastRHN




The f

ract

iona

l ext

ent o

f con

vers

ion

(120572)

Temperature (K)

10

08

06

04

02

00360 380 400 420 440 460 480 500

C0C1

C2














Kim et al [26]




Domınguez et al[9]

Yang et al [10]




120572

100806040200

80

70

60

50

40

30

E120572

(kJm

ol)

C0C1C2







10

8

6

4

2

050 100 150 200 250

001

025

Exo

Temperature (∘C)







5 Conclusion


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







119892)







119892[52]





R R

R

R

R

R

R

O

O

O

C

C

C C C

C C

CC

CH

H

H

H

N

CH2

CH2

CH2lowastR

lowastR

lowastR

lowastR

XH

OH+

+

+

H

H

HOH

OH

OH

OH

NH2

H2

H2

H2

Epoxy

Epoxy Amine

Alcohol

CH2XRlowast

ORlowast

∙∙








R R

RR

O

O

CH

CH

OH OH

OH

H2C




+

+

RlowastndashNH2


RR

O

CH

RCH

OH

OH

O

H2C

H2C







119892of









R

O O

C CCH2 CH2+HH

CH

RROH

OH

BF3

BF3

BF3

∙∙

lowastRCH2ORlowast


R

R

R R

R

RC

C

C

C

C

C

C

CC

C C

C

C C

CH

H

H

H

CH

O

O

O

O

O

+

+

+

+

O O

OOO

OO

O

OO

O

O

OO

O

O

O O

O

A

A

A

A

A

A

A

CH2

CH2

CH2

NR3

NR3

CHlowastR

lowastR

lowastR

H2C

H2C

CH2NR3




119889120572

119889119905

= (1198961+ 1198962120572119898) (1 minus 120572)

119899 (1)

where 1198961and 119896





10

08

06

04

02

0040 60 80 100 120 140 160 180 200 220 240

Temperature (∘C)

Frac

tiona

l ext

ent o

f con

vers

ion





119889(120572)



119889(120572) demon-






005

004

003

002

001

0000 20 40 60 80 100 120

10

08

06

04

02

00

Time (min)

d120572dt

(minminus1)

120572

0 wt1 wt

5 wt


14

12

10

08

06

04

02

00100806040200


180∘C190∘C200∘C

210∘C220∘C

fd(120572)










60

50

40

30

20

0 20 40 60 80 100120572 ()



E120572

(kJm

ol)








008

006

004

002

000

minus002

minus0040 50 100 150 200 250

Time (min)

Hea

t flow

(Wg

)












F+

+

H2NR

R

NH2

NHNH 2

OC

C

HCH2

NH N

CH

OH

H2

RlowastR

lowastR

Epoxy resins

+O

O

O O O

O

C

C C

C CC

HCH2

CH

CH

OH

OH

H2

H2

H2H2

Rlowast

lowastR

Epoxy resins

COOH

H3CCH3

CH3

CH3

CH3R = Rlowast =

(a)

(b)









DSC

(mV

)

00010025

010251

45 50 55 60 65 70Temperature (∘C)

(a)D

SC (m

V)

00010025

010251

4540 50 55 60 65 70Temperature (∘C)

(b)


H2SO4

HNO3

O

O

CC

CC

C

C

OHOH

OHOH

OH

OH

SOCl2

Cl

Cl

H2NRlowastNH2

H2NlowastRHN

H2NlowastRHN




The f

ract

iona

l ext

ent o

f con

vers

ion

(120572)

Temperature (K)

10

08

06

04

02

00360 380 400 420 440 460 480 500

C0C1

C2














Kim et al [26]




Domınguez et al[9]

Yang et al [10]




120572

100806040200

80

70

60

50

40

30

E120572

(kJm

ol)

C0C1C2







10

8

6

4

2

050 100 150 200 250

001

025

Exo

Temperature (∘C)







5 Conclusion


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







119892[52]





R R

R

R

R

R

R

O

O

O

C

C

C C C

C C

CC

CH

H

H

H

N

CH2

CH2

CH2lowastR

lowastR

lowastR

lowastR

XH

OH+

+

+

H

H

HOH

OH

OH

OH

NH2

H2

H2

H2

Epoxy

Epoxy Amine

Alcohol

CH2XRlowast

ORlowast

∙∙








R R

RR

O

O

CH

CH

OH OH

OH

H2C




+

+

RlowastndashNH2


RR

O

CH

RCH

OH

OH

O

H2C

H2C







119892of









R

O O

C CCH2 CH2+HH

CH

RROH

OH

BF3

BF3

BF3

∙∙

lowastRCH2ORlowast


R

R

R R

R

RC

C

C

C

C

C

C

CC

C C

C

C C

CH

H

H

H

CH

O

O

O

O

O

+

+

+

+

O O

OOO

OO

O

OO

O

O

OO

O

O

O O

O

A

A

A

A

A

A

A

CH2

CH2

CH2

NR3

NR3

CHlowastR

lowastR

lowastR

H2C

H2C

CH2NR3




119889120572

119889119905

= (1198961+ 1198962120572119898) (1 minus 120572)

119899 (1)

where 1198961and 119896





10

08

06

04

02

0040 60 80 100 120 140 160 180 200 220 240

Temperature (∘C)

Frac

tiona

l ext

ent o

f con

vers

ion





119889(120572)



119889(120572) demon-






005

004

003

002

001

0000 20 40 60 80 100 120

10

08

06

04

02

00

Time (min)

d120572dt

(minminus1)

120572

0 wt1 wt

5 wt


14

12

10

08

06

04

02

00100806040200


180∘C190∘C200∘C

210∘C220∘C

fd(120572)










60

50

40

30

20

0 20 40 60 80 100120572 ()



E120572

(kJm

ol)








008

006

004

002

000

minus002

minus0040 50 100 150 200 250

Time (min)

Hea

t flow

(Wg

)












F+

+

H2NR

R

NH2

NHNH 2

OC

C

HCH2

NH N

CH

OH

H2

RlowastR

lowastR

Epoxy resins

+O

O

O O O

O

C

C C

C CC

HCH2

CH

CH

OH

OH

H2

H2

H2H2

Rlowast

lowastR

Epoxy resins

COOH

H3CCH3

CH3

CH3

CH3R = Rlowast =

(a)

(b)









DSC

(mV

)

00010025

010251

45 50 55 60 65 70Temperature (∘C)

(a)D

SC (m

V)

00010025

010251

4540 50 55 60 65 70Temperature (∘C)

(b)


H2SO4

HNO3

O

O

CC

CC

C

C

OHOH

OHOH

OH

OH

SOCl2

Cl

Cl

H2NRlowastNH2

H2NlowastRHN

H2NlowastRHN




The f

ract

iona

l ext

ent o

f con

vers

ion

(120572)

Temperature (K)

10

08

06

04

02

00360 380 400 420 440 460 480 500

C0C1

C2














Kim et al [26]




Domınguez et al[9]

Yang et al [10]




120572

100806040200

80

70

60

50

40

30

E120572

(kJm

ol)

C0C1C2







10

8

6

4

2

050 100 150 200 250

001

025

Exo

Temperature (∘C)







5 Conclusion


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




R R

RR

O

O

CH

CH

OH OH

OH

H2C




+

+

RlowastndashNH2


RR

O

CH

RCH

OH

OH

O

H2C

H2C







119892of









R

O O

C CCH2 CH2+HH

CH

RROH

OH

BF3

BF3

BF3

∙∙

lowastRCH2ORlowast


R

R

R R

R

RC

C

C

C

C

C

C

CC

C C

C

C C

CH

H

H

H

CH

O

O

O

O

O

+

+

+

+

O O

OOO

OO

O

OO

O

O

OO

O

O

O O

O

A

A

A

A

A

A

A

CH2

CH2

CH2

NR3

NR3

CHlowastR

lowastR

lowastR

H2C

H2C

CH2NR3




119889120572

119889119905

= (1198961+ 1198962120572119898) (1 minus 120572)

119899 (1)

where 1198961and 119896





10

08

06

04

02

0040 60 80 100 120 140 160 180 200 220 240

Temperature (∘C)

Frac

tiona

l ext

ent o

f con

vers

ion





119889(120572)



119889(120572) demon-






005

004

003

002

001

0000 20 40 60 80 100 120

10

08

06

04

02

00

Time (min)

d120572dt

(minminus1)

120572

0 wt1 wt

5 wt


14

12

10

08

06

04

02

00100806040200


180∘C190∘C200∘C

210∘C220∘C

fd(120572)










60

50

40

30

20

0 20 40 60 80 100120572 ()



E120572

(kJm

ol)








008

006

004

002

000

minus002

minus0040 50 100 150 200 250

Time (min)

Hea

t flow

(Wg

)












F+

+

H2NR

R

NH2

NHNH 2

OC

C

HCH2

NH N

CH

OH

H2

RlowastR

lowastR

Epoxy resins

+O

O

O O O

O

C

C C

C CC

HCH2

CH

CH

OH

OH

H2

H2

H2H2

Rlowast

lowastR

Epoxy resins

COOH

H3CCH3

CH3

CH3

CH3R = Rlowast =

(a)

(b)









DSC

(mV

)

00010025

010251

45 50 55 60 65 70Temperature (∘C)

(a)D

SC (m

V)

00010025

010251

4540 50 55 60 65 70Temperature (∘C)

(b)


H2SO4

HNO3

O

O

CC

CC

C

C

OHOH

OHOH

OH

OH

SOCl2

Cl

Cl

H2NRlowastNH2

H2NlowastRHN

H2NlowastRHN




The f

ract

iona

l ext

ent o

f con

vers

ion

(120572)

Temperature (K)

10

08

06

04

02

00360 380 400 420 440 460 480 500

C0C1

C2














Kim et al [26]




Domınguez et al[9]

Yang et al [10]




120572

100806040200

80

70

60

50

40

30

E120572

(kJm

ol)

C0C1C2







10

8

6

4

2

050 100 150 200 250

001

025

Exo

Temperature (∘C)







5 Conclusion


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




R

O O

C CCH2 CH2+HH

CH

RROH

OH

BF3

BF3

BF3

∙∙

lowastRCH2ORlowast


R

R

R R

R

RC

C

C

C

C

C

C

CC

C C

C

C C

CH

H

H

H

CH

O

O

O

O

O

+

+

+

+

O O

OOO

OO

O

OO

O

O

OO

O

O

O O

O

A

A

A

A

A

A

A

CH2

CH2

CH2

NR3

NR3

CHlowastR

lowastR

lowastR

H2C

H2C

CH2NR3




119889120572

119889119905

= (1198961+ 1198962120572119898) (1 minus 120572)

119899 (1)

where 1198961and 119896





10

08

06

04

02

0040 60 80 100 120 140 160 180 200 220 240

Temperature (∘C)

Frac

tiona

l ext

ent o

f con

vers

ion





119889(120572)



119889(120572) demon-






005

004

003

002

001

0000 20 40 60 80 100 120

10

08

06

04

02

00

Time (min)

d120572dt

(minminus1)

120572

0 wt1 wt

5 wt


14

12

10

08

06

04

02

00100806040200


180∘C190∘C200∘C

210∘C220∘C

fd(120572)










60

50

40

30

20

0 20 40 60 80 100120572 ()



E120572

(kJm

ol)








008

006

004

002

000

minus002

minus0040 50 100 150 200 250

Time (min)

Hea

t flow

(Wg

)












F+

+

H2NR

R

NH2

NHNH 2

OC

C

HCH2

NH N

CH

OH

H2

RlowastR

lowastR

Epoxy resins

+O

O

O O O

O

C

C C

C CC

HCH2

CH

CH

OH

OH

H2

H2

H2H2

Rlowast

lowastR

Epoxy resins

COOH

H3CCH3

CH3

CH3

CH3R = Rlowast =

(a)

(b)









DSC

(mV

)

00010025

010251

45 50 55 60 65 70Temperature (∘C)

(a)D

SC (m

V)

00010025

010251

4540 50 55 60 65 70Temperature (∘C)

(b)


H2SO4

HNO3

O

O

CC

CC

C

C

OHOH

OHOH

OH

OH

SOCl2

Cl

Cl

H2NRlowastNH2

H2NlowastRHN

H2NlowastRHN




The f

ract

iona

l ext

ent o

f con

vers

ion

(120572)

Temperature (K)

10

08

06

04

02

00360 380 400 420 440 460 480 500

C0C1

C2














Kim et al [26]




Domınguez et al[9]

Yang et al [10]




120572

100806040200

80

70

60

50

40

30

E120572

(kJm

ol)

C0C1C2







10

8

6

4

2

050 100 150 200 250

001

025

Exo

Temperature (∘C)







5 Conclusion


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




005

004

003

002

001

0000 20 40 60 80 100 120

10

08

06

04

02

00

Time (min)

d120572dt

(minminus1)

120572

0 wt1 wt

5 wt


14

12

10

08

06

04

02

00100806040200


180∘C190∘C200∘C

210∘C220∘C

fd(120572)










60

50

40

30

20

0 20 40 60 80 100120572 ()



E120572

(kJm

ol)








008

006

004

002

000

minus002

minus0040 50 100 150 200 250

Time (min)

Hea

t flow

(Wg

)












F+

+

H2NR

R

NH2

NHNH 2

OC

C

HCH2

NH N

CH

OH

H2

RlowastR

lowastR

Epoxy resins

+O

O

O O O

O

C

C C

C CC

HCH2

CH

CH

OH

OH

H2

H2

H2H2

Rlowast

lowastR

Epoxy resins

COOH

H3CCH3

CH3

CH3

CH3R = Rlowast =

(a)

(b)









DSC

(mV

)

00010025

010251

45 50 55 60 65 70Temperature (∘C)

(a)D

SC (m

V)

00010025

010251

4540 50 55 60 65 70Temperature (∘C)

(b)


H2SO4

HNO3

O

O

CC

CC

C

C

OHOH

OHOH

OH

OH

SOCl2

Cl

Cl

H2NRlowastNH2

H2NlowastRHN

H2NlowastRHN




The f

ract

iona

l ext

ent o

f con

vers

ion

(120572)

Temperature (K)

10

08

06

04

02

00360 380 400 420 440 460 480 500

C0C1

C2














Kim et al [26]




Domınguez et al[9]

Yang et al [10]




120572

100806040200

80

70

60

50

40

30

E120572

(kJm

ol)

C0C1C2







10

8

6

4

2

050 100 150 200 250

001

025

Exo

Temperature (∘C)







5 Conclusion


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




60

50

40

30

20

0 20 40 60 80 100120572 ()



E120572

(kJm

ol)








008

006

004

002

000

minus002

minus0040 50 100 150 200 250

Time (min)

Hea

t flow

(Wg

)












F+

+

H2NR

R

NH2

NHNH 2

OC

C

HCH2

NH N

CH

OH

H2

RlowastR

lowastR

Epoxy resins

+O

O

O O O

O

C

C C

C CC

HCH2

CH

CH

OH

OH

H2

H2

H2H2

Rlowast

lowastR

Epoxy resins

COOH

H3CCH3

CH3

CH3

CH3R = Rlowast =

(a)

(b)









DSC

(mV

)

00010025

010251

45 50 55 60 65 70Temperature (∘C)

(a)D

SC (m

V)

00010025

010251

4540 50 55 60 65 70Temperature (∘C)

(b)


H2SO4

HNO3

O

O

CC

CC

C

C

OHOH

OHOH

OH

OH

SOCl2

Cl

Cl

H2NRlowastNH2

H2NlowastRHN

H2NlowastRHN




The f

ract

iona

l ext

ent o

f con

vers

ion

(120572)

Temperature (K)

10

08

06

04

02

00360 380 400 420 440 460 480 500

C0C1

C2














Kim et al [26]




Domınguez et al[9]

Yang et al [10]




120572

100806040200

80

70

60

50

40

30

E120572

(kJm

ol)

C0C1C2







10

8

6

4

2

050 100 150 200 250

001

025

Exo

Temperature (∘C)







5 Conclusion


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




F+

+

H2NR

R

NH2

NHNH 2

OC

C

HCH2

NH N

CH

OH

H2

RlowastR

lowastR

Epoxy resins

+O

O

O O O

O

C

C C

C CC

HCH2

CH

CH

OH

OH

H2

H2

H2H2

Rlowast

lowastR

Epoxy resins

COOH

H3CCH3

CH3

CH3

CH3R = Rlowast =

(a)

(b)









DSC

(mV

)

00010025

010251

45 50 55 60 65 70Temperature (∘C)

(a)D

SC (m

V)

00010025

010251

4540 50 55 60 65 70Temperature (∘C)

(b)


H2SO4

HNO3

O

O

CC

CC

C

C

OHOH

OHOH

OH

OH

SOCl2

Cl

Cl

H2NRlowastNH2

H2NlowastRHN

H2NlowastRHN




The f

ract

iona

l ext

ent o

f con

vers

ion

(120572)

Temperature (K)

10

08

06

04

02

00360 380 400 420 440 460 480 500

C0C1

C2














Kim et al [26]




Domınguez et al[9]

Yang et al [10]




120572

100806040200

80

70

60

50

40

30

E120572

(kJm

ol)

C0C1C2







10

8

6

4

2

050 100 150 200 250

001

025

Exo

Temperature (∘C)







5 Conclusion


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




DSC

(mV

)

00010025

010251

45 50 55 60 65 70Temperature (∘C)

(a)D

SC (m

V)

00010025

010251

4540 50 55 60 65 70Temperature (∘C)

(b)


H2SO4

HNO3

O

O

CC

CC

C

C

OHOH

OHOH

OH

OH

SOCl2

Cl

Cl

H2NRlowastNH2

H2NlowastRHN

H2NlowastRHN




The f

ract

iona

l ext

ent o

f con

vers

ion

(120572)

Temperature (K)

10

08

06

04

02

00360 380 400 420 440 460 480 500

C0C1

C2














Kim et al [26]




Domınguez et al[9]

Yang et al [10]




120572

100806040200

80

70

60

50

40

30

E120572

(kJm

ol)

C0C1C2







10

8

6

4

2

050 100 150 200 250

001

025

Exo

Temperature (∘C)







5 Conclusion


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials











Kim et al [26]




Domınguez et al[9]

Yang et al [10]




120572

100806040200

80

70

60

50

40

30

E120572

(kJm

ol)

C0C1C2







10

8

6

4

2

050 100 150 200 250

001

025

Exo

Temperature (∘C)







5 Conclusion


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





5 Conclusion


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials
























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Review Article Cure Kinetics of Epoxy Nanocomposites ...downloads.hindawi.com/journals/tswj/2013/703708.pdfCure Kinetics of Epoxy Nanocomposites Affected by MWCNTs Functionalization: