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Copyright copy 2011 American Scientific PublishersAll rights reservedPrinted in the United States of America

Journal ofNanoscience and Nanotechnology

Vol 11 7369ndash7373 2011

Carbon Nanotube Modification Using Gum Arabic andIts Effect on the Dispersion and Tensile Properties of

Carbon NanotubesEpoxy Nanocomposites

Man Tae Kim1 Ho Seok Park2 David Hui13 and Kyong Yop Rhee1lowast1Department of Mechanical Engineering Kyung Hee University Yongin 446-701 Republic of Korea2Department of Chemical Engineering Kyung Hee University Yongin 446-701 Republic of Korea

3Department of Mechanical Engineering University of New Orieans New Orieans LA 70148 United States

In this study the effects of a MWCNT treatment on the dispersion of MWCNTs in aqueous solu-tion and the tensile properties of MWCNTepoxy nanocomposites were investigated MWCNTswere treated using acid and gum arabic and MWCNTepoxy nanocomposites were fabricated with03 wt unmodified oxidized and gum-treated MWCNTs The dispersion states of the unmodifiedoxidized and Gum-treated MWCNTs were characterized in distilled water The tensile strengths andelastic modulus of the three nanocomposites were determined and compared The results indicatedthat the gum treatment produced better dispersion of the MWCNTs in distilled water and that gum-treated MWCNTepoxy nanocomposites had a better tensile strength and elastic modulus than didthe unmodified and acid-treated MWCNTepoxy nanocomposites Scanning electron microscopeexamination of the fracture surface showed that the improved tensile properties of the gum-treatedMWCNTepoxy nanocomposites were attributed to the improved dispersion of MWCNTs in theepoxy and to interfacial bonding between nanotubes and the epoxy matrix

Keywords MWCNTs Gum Arabic Epoxy Tensile Strength Fracture Surface

1 INTRODUCTION

It is well-known that multiwall carbon nanotubes(MWCNTs) should be dispersed uniformly in the matrixto function properly as reinforcing nanomaterials Accord-ingly a number of studies have been performed to developmethods for homogeneous dispersion of MWCNTs intothe polymer matrix One method is an oxidative processutilizing strong acids in which hydroxyl and carboxylicacid moieties are created on MWCNTs The oxidizedMWCNTs show better solubility and can form electro-statically stabilized colloidal dispersions in water as wellas in alcohols1ndash3

The silanization of MWCNTs is another preferredmethod used to enhance the dispersion and interfacialadhesion between the MWCNTs and the epoxy45 How-ever the acid-treatment and silane treatment of MWCNTsare chemical functionalizations New attempts have beenmade to achieve environmentally-friendly modification ofMWCNTs using natural materials

lowastAuthor to whom correspondence should be addressed

For instance Bandyopadhyaya et al reported theformation of homogeneous dispersions of individualMWCNTs in gum arabic (GA) solution and demonstratedthat adsorption of GA led to disruption of the inter-tube interactions in the crystalline ropes6 At presentvery few studies have been performed on the effect ofGA modification of MWCNTs on the tensile behavior ofMWCNTpolymer nanocompositesFor the present study we investigated the effect of

MWCNT treatment with GA on the tensile properties ofMWCNTepoxy nanocomposites Tensile tests were per-formed on the untreated acid-treated and GA-treatedMWCNTepoxy nanocomposites SEM examinations ofthe fracture surfaces were performed to investigate theeffect of GA treatment on dispersion in the epoxy matrix

2 EXPERIMENTAL DETAILS

The carbon nanotubes used in this study were MWCNTssynthesized via catalytic chemical vapor deposition (CM-95 Iljin Nanotech Korea) The following reagents wereused without further purification nitric acid (60ndash62

J Nanosci Nanotechnol 2011 Vol 11 No 8 1533-48802011117369005 doi101166jnn20114791 7369

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CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites Kim et al

Junsei Japan) sulfuric acid (95 Junsei Japan) ethanol(99 Aldrich USA) and distilled water Gum arabic(Junsei Japan) was used as a surface active agent theepoxy used was 1182 geq of diglycidyl ether of bisphe-nol A (Kukdo Chemical Korea) and the hardner was60 geq of polyamidoamine (Kukdo Chemical Korea) Theoxidized treatment of MWCNTs (O-MWCNTs) was per-formed as follows Three grams of untreated MWCNTs(U-MWCNTs) were dispersed in 300 ml of concentratedH2SO4HNO3 (32 vv) solution at 50 C and stirred for20 h The solution was filtered with distilled water until aneutral pH was obtained to eliminate mixing an acid solu-tion The resulting oxidized MWCNTs were then driedunder vacuum at 80 C for 12 h The Gum Arabic mod-ification of MWCNTs (G-MWCNTs) was performed asfollows Ten grams of Gum Arabic (GA) was dissolvedin 200 ml of distilled water and stirred for 30 min Thentwo grams of untreated CNTs was dispersed in the GAsolution and stirred for 1 h The Gum treated MWCNTs(G-MWCNTs) were separated by filtration using ethanoland dried under vacuum at 80 C for 12 h

MWCNTepoxy nanocomposites were fabricated as fol-lows U-MWCNTs O-MWCNTs and G-MWCNTs weredispersed in the ethanol solution and ultrasonication was

(a)

(b)

Fig 1 Sedimentation of dispersed MWCNTs (A unmodified MWC-NTs B oxidized MWCNTs C Gum treated MWCNTs) in distilledwater (a) 10 min after ultrasonication (b) 240 h after ultrasonication

performed for 5 min After sonication 03 wt each ofU-MWCNTs O-MWCNTs and G-MWCNTs were mixedwith the epoxy resin and then stirred for approximately2 h at 80 C to completely evaporate the ethanol Afterremoving the ethanol a hardener was added (epoxy andhardener at a 21 ratio) and the mixture poured into ateflon mold The mixture was de-gassed in a vacuumoven at 760 mm Hg for 30 min and hardened in anoven at 120 C for 4 h The fabricated nanocompositeplates were machined as tensile specimens and the dimen-sions of the gauge section were 5 mm thicktimes 80 mm

(a)

(b)

(c)

Fig 2 TEM images of dispersion states (a) unmodified MWCNTs(b) oxidized MWCNTs (c) Gum treated MWCNTs

7370 J Nanosci Nanotechnol 11 7369ndash7373 2011

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Kim et al CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites

longtimes15 mm wide Tensile tests were performed in a uni-versal test machine according to the ASTM D 6387 Atleast three tensile tests were performed for the three typesof nanocomposites

3 RESULTS AND DISCUSSION

Unmodified Acid-treated and Gum-treated MWCNTs(U-MWCNTs O-MWCNTs and G- MWCNTs) were dis-persed in distilled water via ultrasonication to determinethe effect of Gum treatment on dispersion in the aque-ous solution Figure 1 shows the dispersion states of theU-MWCNTs O-MWCNTs and G-MWCNTs observed attimes of 10 min and 240 h As shown in Figure 1(a)U-MWCNTs O-MWCNTs and G-MWCNTs showedgood dispersion in distilled water after 10 min of ultrasoni-cation However the U-MWCNTs gradually settled due totheir agglomeration and hydrophobic nature whereas theO-MWCNTs and G-MWCNTs exhibited good suspensionstability even after 240 h of sonicationThis agrees well with the results in the Ref [8] Accord-

ing to Bagheri et al Gum Arabic adsorbs to the aggre-gated MWCNTs and works as a repulsive force Thus theoverall potential of the intertubes becomes repulsive andthe dispersion of the MWCNTS becomes thermodynami-cally stableThe microscopic structures of MWCNTs with dif-

ferent surface modifications were investigated usingTEM Figure 2 presents TEM images of U-MWCNTsO-MWCNTs and G-MWCNTs As shown in Figure 2(a)the U-MWCNTs were severely agglomerated and their endtips were closed which are the features of unmodifiedMWCNTsFor O-MWCNTs as shown in Figure 2(b) the agglom-

eration of the carbon nanotubes was reduced and the endtips of many carbon nanotubes were open which enablesthe generation of functional groups at the open endsSimilar dispersion results were obtained for Gum-treatedMWCNTS As shown in Figure 2(c) the dispersion of thenanotubes was significantly improved compared to that ofthe U-MWCNTs Figure 2 also shows that the MWCNTsretained their external average diameter of 10ndash15 nm afteroxidation and Gum treatment which is in good agree-ment with the suspension stabilities described in Figure 1Figure 3 shows the comparison of the tensile strengths ofuntreated acid-treated and Gum-treated MWCNTepoxynanocomposites The tensile strength was on the orderof the G-MWCNT O-MWCNT and U-MWCNTepoxynanocomposites Specifically the tensile strength of theG-MWCNTepoxy nanocomposites was 22 higher andthat of the O-MWCNTepoxy nanocomposites was 15higher than that of the U-MWCNTepoxy nanocompos-ites Figure 4 shows the comparison of the three nanocom-posites Similar to the tensile strength results the elasticmodulus was improved by the Gum treatment with the

Fig 3 Comparison of tensile strength of unmodified oxidized andGum treated MWCNTepoxy nanocomposites

elastic modulus of the G-MWCNTepoxy nanocompositesbeing higher than that of the O-MWCNTepoxy nanocom-posites The elastic modulus of the G-MWCNTepoxynanocomposites was 29 higher and that of theO-MWCNTepoxy nanocomposites was 13 higher thanthat of the U-MWCNTepoxy nanocomposites Thefracture surfaces of the U-MWCNT O-MWCNT andG-MWCNTepoxy nanocomposites were examined bySEM Figure 5 shows the comparison of the fracturesurfaces of the MWCNTepoxy nanocomposites In theU-MWCNTepoxy nanocomposites (Fig 5(a)) the car-bon nanotubes curled entangled and pulled out fromthe epoxy matrix which indicates poor dispersibility andweak interfacial bonding between the U-MWCNTs andthe epoxy matrix However as can be observed fromFigures 5(b) and (c) the oxidation and Gum treatment ofthe MWCNTs increased the dispersibility In both casesthe MWCNTs were tightly held to the epoxy matrix and

Fig 4 Comparison of elastic modulus of unmodified oxidized andGum treated MWCNTepoxy nanocomposites

J Nanosci Nanotechnol 11 7369ndash7373 2011 7371

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CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites Kim et al

Fig 5 SEM photographs of fracture surfaces of (a) unmodified (c) oxidized and (e) Gum treated MWCNTepoxy nanocomposites (b) (d) (f) aremagnified images of boxed region in (a) (c) (e) respectively

many surface cleavages were observed which indicates animprovement in the interfacial bonding between function-alized MWCNTs and the epoxy matrix However it canbe observed in the O-MWCNTepoxy nanocomposites thatsome nanotubes were pulled out from the matrix whichshows that the stress transfer from the matrix to theO-MWCNTs was lower than to the G-MWCNTs The uni-form dispersion of nanotubes restricted the mobility ofpolymer chains under loading and improved the modulusand strength of the MWCNTepoxy nanocomposites

4 CONCLUSION

It was found that Gum-treated MWCNTs showed gooddispersion stability even after 240 h of ultrasonica-tion but exhibited little difference in dispersion fromthe acid-treated MWCNTs The improved dispersionstability of Gum-treated MWCNTs was due to theirenhanced negative ion abilities due to the functional-ization effect on their surfaces TEM analysis showedthat little damage occurred on Gum-treated MWCNTscompared to acid-treated MWCNTs The tensile strength

7372 J Nanosci Nanotechnol 11 7369ndash7373 2011

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Kim et al CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites

and modulus of G-MWCNTepoxy nanocomposites wereimproved by 22 and 29 respectively comparedto the U-MWCNTepoxy nanocomposites whereas theimprovements were 15 and 13 respectively overO-MWCNTepoxy nanocomposites This enhancement isattributed to the good dispersibility and strong interfacialbonding energy between the functionalized MWCNTs andthe epoxy matrix

Acknowledgment This research was supported by theCenter for Science amp Technology Research (CSTR) grant(CSTR-002-100701-03) and Basic Science Research Pro-gram through the National Research Foundation of Korea(NRF) funded by the Ministry of Education Science andTechnology (2010-0023106)

References and Notes

1 M S P Shaffer X Fan and A H Windle Carbon 36 1603(1998)

2 J Sandler M S P Shaffer T Prasse W Bauhofer K Schulte andA H Windle Polymer 40 5967 (1999)

3 F H Gojny J Nastalczyk Z Roslaniec and K Schulte Chem PhysLetters 370 820 (2003)

4 P C Ma J K Kim and B Z Tang Compos Sci Technol 67 2965(2007)

5 J Kathi K Y Rhee and J H Lee Composites Part A 40 800(2009)

6 R Bandyopadhyaya E Nativ-Roth O Regev and R Yerushlmi-Rozen Nano Lett 2 25 (2002)

7 ASTM D 638 Standard test method of tensile properties of plasticsASTM International USA (2003)

8 B Bagheri M Abdouss and A M Shoushtari Mat Wiss U Werk-stofftech 41 234 (2010)

Received 20 November 2010 Accepted 28 February 2011

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CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites Kim et al

Junsei Japan) sulfuric acid (95 Junsei Japan) ethanol(99 Aldrich USA) and distilled water Gum arabic(Junsei Japan) was used as a surface active agent theepoxy used was 1182 geq of diglycidyl ether of bisphe-nol A (Kukdo Chemical Korea) and the hardner was60 geq of polyamidoamine (Kukdo Chemical Korea) Theoxidized treatment of MWCNTs (O-MWCNTs) was per-formed as follows Three grams of untreated MWCNTs(U-MWCNTs) were dispersed in 300 ml of concentratedH2SO4HNO3 (32 vv) solution at 50 C and stirred for20 h The solution was filtered with distilled water until aneutral pH was obtained to eliminate mixing an acid solu-tion The resulting oxidized MWCNTs were then driedunder vacuum at 80 C for 12 h The Gum Arabic mod-ification of MWCNTs (G-MWCNTs) was performed asfollows Ten grams of Gum Arabic (GA) was dissolvedin 200 ml of distilled water and stirred for 30 min Thentwo grams of untreated CNTs was dispersed in the GAsolution and stirred for 1 h The Gum treated MWCNTs(G-MWCNTs) were separated by filtration using ethanoland dried under vacuum at 80 C for 12 h

MWCNTepoxy nanocomposites were fabricated as fol-lows U-MWCNTs O-MWCNTs and G-MWCNTs weredispersed in the ethanol solution and ultrasonication was

(a)

(b)

Fig 1 Sedimentation of dispersed MWCNTs (A unmodified MWC-NTs B oxidized MWCNTs C Gum treated MWCNTs) in distilledwater (a) 10 min after ultrasonication (b) 240 h after ultrasonication

performed for 5 min After sonication 03 wt each ofU-MWCNTs O-MWCNTs and G-MWCNTs were mixedwith the epoxy resin and then stirred for approximately2 h at 80 C to completely evaporate the ethanol Afterremoving the ethanol a hardener was added (epoxy andhardener at a 21 ratio) and the mixture poured into ateflon mold The mixture was de-gassed in a vacuumoven at 760 mm Hg for 30 min and hardened in anoven at 120 C for 4 h The fabricated nanocompositeplates were machined as tensile specimens and the dimen-sions of the gauge section were 5 mm thicktimes 80 mm

(a)

(b)

(c)

Fig 2 TEM images of dispersion states (a) unmodified MWCNTs(b) oxidized MWCNTs (c) Gum treated MWCNTs

7370 J Nanosci Nanotechnol 11 7369ndash7373 2011

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Kim et al CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites

longtimes15 mm wide Tensile tests were performed in a uni-versal test machine according to the ASTM D 6387 Atleast three tensile tests were performed for the three typesof nanocomposites

3 RESULTS AND DISCUSSION

Unmodified Acid-treated and Gum-treated MWCNTs(U-MWCNTs O-MWCNTs and G- MWCNTs) were dis-persed in distilled water via ultrasonication to determinethe effect of Gum treatment on dispersion in the aque-ous solution Figure 1 shows the dispersion states of theU-MWCNTs O-MWCNTs and G-MWCNTs observed attimes of 10 min and 240 h As shown in Figure 1(a)U-MWCNTs O-MWCNTs and G-MWCNTs showedgood dispersion in distilled water after 10 min of ultrasoni-cation However the U-MWCNTs gradually settled due totheir agglomeration and hydrophobic nature whereas theO-MWCNTs and G-MWCNTs exhibited good suspensionstability even after 240 h of sonicationThis agrees well with the results in the Ref [8] Accord-

ing to Bagheri et al Gum Arabic adsorbs to the aggre-gated MWCNTs and works as a repulsive force Thus theoverall potential of the intertubes becomes repulsive andthe dispersion of the MWCNTS becomes thermodynami-cally stableThe microscopic structures of MWCNTs with dif-

ferent surface modifications were investigated usingTEM Figure 2 presents TEM images of U-MWCNTsO-MWCNTs and G-MWCNTs As shown in Figure 2(a)the U-MWCNTs were severely agglomerated and their endtips were closed which are the features of unmodifiedMWCNTsFor O-MWCNTs as shown in Figure 2(b) the agglom-

eration of the carbon nanotubes was reduced and the endtips of many carbon nanotubes were open which enablesthe generation of functional groups at the open endsSimilar dispersion results were obtained for Gum-treatedMWCNTS As shown in Figure 2(c) the dispersion of thenanotubes was significantly improved compared to that ofthe U-MWCNTs Figure 2 also shows that the MWCNTsretained their external average diameter of 10ndash15 nm afteroxidation and Gum treatment which is in good agree-ment with the suspension stabilities described in Figure 1Figure 3 shows the comparison of the tensile strengths ofuntreated acid-treated and Gum-treated MWCNTepoxynanocomposites The tensile strength was on the orderof the G-MWCNT O-MWCNT and U-MWCNTepoxynanocomposites Specifically the tensile strength of theG-MWCNTepoxy nanocomposites was 22 higher andthat of the O-MWCNTepoxy nanocomposites was 15higher than that of the U-MWCNTepoxy nanocompos-ites Figure 4 shows the comparison of the three nanocom-posites Similar to the tensile strength results the elasticmodulus was improved by the Gum treatment with the

Fig 3 Comparison of tensile strength of unmodified oxidized andGum treated MWCNTepoxy nanocomposites

elastic modulus of the G-MWCNTepoxy nanocompositesbeing higher than that of the O-MWCNTepoxy nanocom-posites The elastic modulus of the G-MWCNTepoxynanocomposites was 29 higher and that of theO-MWCNTepoxy nanocomposites was 13 higher thanthat of the U-MWCNTepoxy nanocomposites Thefracture surfaces of the U-MWCNT O-MWCNT andG-MWCNTepoxy nanocomposites were examined bySEM Figure 5 shows the comparison of the fracturesurfaces of the MWCNTepoxy nanocomposites In theU-MWCNTepoxy nanocomposites (Fig 5(a)) the car-bon nanotubes curled entangled and pulled out fromthe epoxy matrix which indicates poor dispersibility andweak interfacial bonding between the U-MWCNTs andthe epoxy matrix However as can be observed fromFigures 5(b) and (c) the oxidation and Gum treatment ofthe MWCNTs increased the dispersibility In both casesthe MWCNTs were tightly held to the epoxy matrix and

Fig 4 Comparison of elastic modulus of unmodified oxidized andGum treated MWCNTepoxy nanocomposites

J Nanosci Nanotechnol 11 7369ndash7373 2011 7371

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CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites Kim et al

Fig 5 SEM photographs of fracture surfaces of (a) unmodified (c) oxidized and (e) Gum treated MWCNTepoxy nanocomposites (b) (d) (f) aremagnified images of boxed region in (a) (c) (e) respectively

many surface cleavages were observed which indicates animprovement in the interfacial bonding between function-alized MWCNTs and the epoxy matrix However it canbe observed in the O-MWCNTepoxy nanocomposites thatsome nanotubes were pulled out from the matrix whichshows that the stress transfer from the matrix to theO-MWCNTs was lower than to the G-MWCNTs The uni-form dispersion of nanotubes restricted the mobility ofpolymer chains under loading and improved the modulusand strength of the MWCNTepoxy nanocomposites

4 CONCLUSION

It was found that Gum-treated MWCNTs showed gooddispersion stability even after 240 h of ultrasonica-tion but exhibited little difference in dispersion fromthe acid-treated MWCNTs The improved dispersionstability of Gum-treated MWCNTs was due to theirenhanced negative ion abilities due to the functional-ization effect on their surfaces TEM analysis showedthat little damage occurred on Gum-treated MWCNTscompared to acid-treated MWCNTs The tensile strength

7372 J Nanosci Nanotechnol 11 7369ndash7373 2011

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Kim et al CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites

and modulus of G-MWCNTepoxy nanocomposites wereimproved by 22 and 29 respectively comparedto the U-MWCNTepoxy nanocomposites whereas theimprovements were 15 and 13 respectively overO-MWCNTepoxy nanocomposites This enhancement isattributed to the good dispersibility and strong interfacialbonding energy between the functionalized MWCNTs andthe epoxy matrix

Acknowledgment This research was supported by theCenter for Science amp Technology Research (CSTR) grant(CSTR-002-100701-03) and Basic Science Research Pro-gram through the National Research Foundation of Korea(NRF) funded by the Ministry of Education Science andTechnology (2010-0023106)

References and Notes

1 M S P Shaffer X Fan and A H Windle Carbon 36 1603(1998)

2 J Sandler M S P Shaffer T Prasse W Bauhofer K Schulte andA H Windle Polymer 40 5967 (1999)

3 F H Gojny J Nastalczyk Z Roslaniec and K Schulte Chem PhysLetters 370 820 (2003)

4 P C Ma J K Kim and B Z Tang Compos Sci Technol 67 2965(2007)

5 J Kathi K Y Rhee and J H Lee Composites Part A 40 800(2009)

6 R Bandyopadhyaya E Nativ-Roth O Regev and R Yerushlmi-Rozen Nano Lett 2 25 (2002)

7 ASTM D 638 Standard test method of tensile properties of plasticsASTM International USA (2003)

8 B Bagheri M Abdouss and A M Shoushtari Mat Wiss U Werk-stofftech 41 234 (2010)

Received 20 November 2010 Accepted 28 February 2011

J Nanosci Nanotechnol 11 7369ndash7373 2011 7373

Delivered by Ingenta toKYUNG HEE UNIVERSITY SUWON CAMPUS LIBRARY

IP 163180125177Mon 19 Nov 2012 062509

RESEARCH

ARTIC

LE

Kim et al CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites

longtimes15 mm wide Tensile tests were performed in a uni-versal test machine according to the ASTM D 6387 Atleast three tensile tests were performed for the three typesof nanocomposites

3 RESULTS AND DISCUSSION

Unmodified Acid-treated and Gum-treated MWCNTs(U-MWCNTs O-MWCNTs and G- MWCNTs) were dis-persed in distilled water via ultrasonication to determinethe effect of Gum treatment on dispersion in the aque-ous solution Figure 1 shows the dispersion states of theU-MWCNTs O-MWCNTs and G-MWCNTs observed attimes of 10 min and 240 h As shown in Figure 1(a)U-MWCNTs O-MWCNTs and G-MWCNTs showedgood dispersion in distilled water after 10 min of ultrasoni-cation However the U-MWCNTs gradually settled due totheir agglomeration and hydrophobic nature whereas theO-MWCNTs and G-MWCNTs exhibited good suspensionstability even after 240 h of sonicationThis agrees well with the results in the Ref [8] Accord-

ing to Bagheri et al Gum Arabic adsorbs to the aggre-gated MWCNTs and works as a repulsive force Thus theoverall potential of the intertubes becomes repulsive andthe dispersion of the MWCNTS becomes thermodynami-cally stableThe microscopic structures of MWCNTs with dif-

ferent surface modifications were investigated usingTEM Figure 2 presents TEM images of U-MWCNTsO-MWCNTs and G-MWCNTs As shown in Figure 2(a)the U-MWCNTs were severely agglomerated and their endtips were closed which are the features of unmodifiedMWCNTsFor O-MWCNTs as shown in Figure 2(b) the agglom-

eration of the carbon nanotubes was reduced and the endtips of many carbon nanotubes were open which enablesthe generation of functional groups at the open endsSimilar dispersion results were obtained for Gum-treatedMWCNTS As shown in Figure 2(c) the dispersion of thenanotubes was significantly improved compared to that ofthe U-MWCNTs Figure 2 also shows that the MWCNTsretained their external average diameter of 10ndash15 nm afteroxidation and Gum treatment which is in good agree-ment with the suspension stabilities described in Figure 1Figure 3 shows the comparison of the tensile strengths ofuntreated acid-treated and Gum-treated MWCNTepoxynanocomposites The tensile strength was on the orderof the G-MWCNT O-MWCNT and U-MWCNTepoxynanocomposites Specifically the tensile strength of theG-MWCNTepoxy nanocomposites was 22 higher andthat of the O-MWCNTepoxy nanocomposites was 15higher than that of the U-MWCNTepoxy nanocompos-ites Figure 4 shows the comparison of the three nanocom-posites Similar to the tensile strength results the elasticmodulus was improved by the Gum treatment with the

Fig 3 Comparison of tensile strength of unmodified oxidized andGum treated MWCNTepoxy nanocomposites

elastic modulus of the G-MWCNTepoxy nanocompositesbeing higher than that of the O-MWCNTepoxy nanocom-posites The elastic modulus of the G-MWCNTepoxynanocomposites was 29 higher and that of theO-MWCNTepoxy nanocomposites was 13 higher thanthat of the U-MWCNTepoxy nanocomposites Thefracture surfaces of the U-MWCNT O-MWCNT andG-MWCNTepoxy nanocomposites were examined bySEM Figure 5 shows the comparison of the fracturesurfaces of the MWCNTepoxy nanocomposites In theU-MWCNTepoxy nanocomposites (Fig 5(a)) the car-bon nanotubes curled entangled and pulled out fromthe epoxy matrix which indicates poor dispersibility andweak interfacial bonding between the U-MWCNTs andthe epoxy matrix However as can be observed fromFigures 5(b) and (c) the oxidation and Gum treatment ofthe MWCNTs increased the dispersibility In both casesthe MWCNTs were tightly held to the epoxy matrix and

Fig 4 Comparison of elastic modulus of unmodified oxidized andGum treated MWCNTepoxy nanocomposites

J Nanosci Nanotechnol 11 7369ndash7373 2011 7371

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CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites Kim et al

Fig 5 SEM photographs of fracture surfaces of (a) unmodified (c) oxidized and (e) Gum treated MWCNTepoxy nanocomposites (b) (d) (f) aremagnified images of boxed region in (a) (c) (e) respectively

many surface cleavages were observed which indicates animprovement in the interfacial bonding between function-alized MWCNTs and the epoxy matrix However it canbe observed in the O-MWCNTepoxy nanocomposites thatsome nanotubes were pulled out from the matrix whichshows that the stress transfer from the matrix to theO-MWCNTs was lower than to the G-MWCNTs The uni-form dispersion of nanotubes restricted the mobility ofpolymer chains under loading and improved the modulusand strength of the MWCNTepoxy nanocomposites

4 CONCLUSION

It was found that Gum-treated MWCNTs showed gooddispersion stability even after 240 h of ultrasonica-tion but exhibited little difference in dispersion fromthe acid-treated MWCNTs The improved dispersionstability of Gum-treated MWCNTs was due to theirenhanced negative ion abilities due to the functional-ization effect on their surfaces TEM analysis showedthat little damage occurred on Gum-treated MWCNTscompared to acid-treated MWCNTs The tensile strength

7372 J Nanosci Nanotechnol 11 7369ndash7373 2011

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IP 163180125177Mon 19 Nov 2012 062509

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ARTIC

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Kim et al CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites

and modulus of G-MWCNTepoxy nanocomposites wereimproved by 22 and 29 respectively comparedto the U-MWCNTepoxy nanocomposites whereas theimprovements were 15 and 13 respectively overO-MWCNTepoxy nanocomposites This enhancement isattributed to the good dispersibility and strong interfacialbonding energy between the functionalized MWCNTs andthe epoxy matrix

Acknowledgment This research was supported by theCenter for Science amp Technology Research (CSTR) grant(CSTR-002-100701-03) and Basic Science Research Pro-gram through the National Research Foundation of Korea(NRF) funded by the Ministry of Education Science andTechnology (2010-0023106)

References and Notes

1 M S P Shaffer X Fan and A H Windle Carbon 36 1603(1998)

2 J Sandler M S P Shaffer T Prasse W Bauhofer K Schulte andA H Windle Polymer 40 5967 (1999)

3 F H Gojny J Nastalczyk Z Roslaniec and K Schulte Chem PhysLetters 370 820 (2003)

4 P C Ma J K Kim and B Z Tang Compos Sci Technol 67 2965(2007)

5 J Kathi K Y Rhee and J H Lee Composites Part A 40 800(2009)

6 R Bandyopadhyaya E Nativ-Roth O Regev and R Yerushlmi-Rozen Nano Lett 2 25 (2002)

7 ASTM D 638 Standard test method of tensile properties of plasticsASTM International USA (2003)

8 B Bagheri M Abdouss and A M Shoushtari Mat Wiss U Werk-stofftech 41 234 (2010)

Received 20 November 2010 Accepted 28 February 2011

J Nanosci Nanotechnol 11 7369ndash7373 2011 7373

Delivered by Ingenta toKYUNG HEE UNIVERSITY SUWON CAMPUS LIBRARY

IP 163180125177Mon 19 Nov 2012 062509

RESEARCH

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LE

CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites Kim et al

Fig 5 SEM photographs of fracture surfaces of (a) unmodified (c) oxidized and (e) Gum treated MWCNTepoxy nanocomposites (b) (d) (f) aremagnified images of boxed region in (a) (c) (e) respectively

many surface cleavages were observed which indicates animprovement in the interfacial bonding between function-alized MWCNTs and the epoxy matrix However it canbe observed in the O-MWCNTepoxy nanocomposites thatsome nanotubes were pulled out from the matrix whichshows that the stress transfer from the matrix to theO-MWCNTs was lower than to the G-MWCNTs The uni-form dispersion of nanotubes restricted the mobility ofpolymer chains under loading and improved the modulusand strength of the MWCNTepoxy nanocomposites

4 CONCLUSION

It was found that Gum-treated MWCNTs showed gooddispersion stability even after 240 h of ultrasonica-tion but exhibited little difference in dispersion fromthe acid-treated MWCNTs The improved dispersionstability of Gum-treated MWCNTs was due to theirenhanced negative ion abilities due to the functional-ization effect on their surfaces TEM analysis showedthat little damage occurred on Gum-treated MWCNTscompared to acid-treated MWCNTs The tensile strength

7372 J Nanosci Nanotechnol 11 7369ndash7373 2011

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IP 163180125177Mon 19 Nov 2012 062509

RESEARCH

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Kim et al CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites

and modulus of G-MWCNTepoxy nanocomposites wereimproved by 22 and 29 respectively comparedto the U-MWCNTepoxy nanocomposites whereas theimprovements were 15 and 13 respectively overO-MWCNTepoxy nanocomposites This enhancement isattributed to the good dispersibility and strong interfacialbonding energy between the functionalized MWCNTs andthe epoxy matrix

Acknowledgment This research was supported by theCenter for Science amp Technology Research (CSTR) grant(CSTR-002-100701-03) and Basic Science Research Pro-gram through the National Research Foundation of Korea(NRF) funded by the Ministry of Education Science andTechnology (2010-0023106)

References and Notes

1 M S P Shaffer X Fan and A H Windle Carbon 36 1603(1998)

2 J Sandler M S P Shaffer T Prasse W Bauhofer K Schulte andA H Windle Polymer 40 5967 (1999)

3 F H Gojny J Nastalczyk Z Roslaniec and K Schulte Chem PhysLetters 370 820 (2003)

4 P C Ma J K Kim and B Z Tang Compos Sci Technol 67 2965(2007)

5 J Kathi K Y Rhee and J H Lee Composites Part A 40 800(2009)

6 R Bandyopadhyaya E Nativ-Roth O Regev and R Yerushlmi-Rozen Nano Lett 2 25 (2002)

7 ASTM D 638 Standard test method of tensile properties of plasticsASTM International USA (2003)

8 B Bagheri M Abdouss and A M Shoushtari Mat Wiss U Werk-stofftech 41 234 (2010)

Received 20 November 2010 Accepted 28 February 2011

J Nanosci Nanotechnol 11 7369ndash7373 2011 7373

Delivered by Ingenta toKYUNG HEE UNIVERSITY SUWON CAMPUS LIBRARY

IP 163180125177Mon 19 Nov 2012 062509

RESEARCH

ARTIC

LE

Kim et al CNT Modification Using GA and Its Effect on the Dispersion and Tensile Properties of CNTsEpoxy Nanocomposites

and modulus of G-MWCNTepoxy nanocomposites wereimproved by 22 and 29 respectively comparedto the U-MWCNTepoxy nanocomposites whereas theimprovements were 15 and 13 respectively overO-MWCNTepoxy nanocomposites This enhancement isattributed to the good dispersibility and strong interfacialbonding energy between the functionalized MWCNTs andthe epoxy matrix

Acknowledgment This research was supported by theCenter for Science amp Technology Research (CSTR) grant(CSTR-002-100701-03) and Basic Science Research Pro-gram through the National Research Foundation of Korea(NRF) funded by the Ministry of Education Science andTechnology (2010-0023106)

References and Notes

1 M S P Shaffer X Fan and A H Windle Carbon 36 1603(1998)

2 J Sandler M S P Shaffer T Prasse W Bauhofer K Schulte andA H Windle Polymer 40 5967 (1999)

3 F H Gojny J Nastalczyk Z Roslaniec and K Schulte Chem PhysLetters 370 820 (2003)

4 P C Ma J K Kim and B Z Tang Compos Sci Technol 67 2965(2007)

5 J Kathi K Y Rhee and J H Lee Composites Part A 40 800(2009)

6 R Bandyopadhyaya E Nativ-Roth O Regev and R Yerushlmi-Rozen Nano Lett 2 25 (2002)

7 ASTM D 638 Standard test method of tensile properties of plasticsASTM International USA (2003)

8 B Bagheri M Abdouss and A M Shoushtari Mat Wiss U Werk-stofftech 41 234 (2010)

Received 20 November 2010 Accepted 28 February 2011

J Nanosci Nanotechnol 11 7369ndash7373 2011 7373