epoxy nanocomposites

epoxy nanocomposites

Available online at www.sciencedirect.com ScienceDirect Materials Today: Proceedings 4 (2017) 4061–4064 www.materialstoday.com/proceedings 5th Inte...

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Available online at www.sciencedirect.com

ScienceDirect Materials Today: Proceedings 4 (2017) 4061–4064

www.materialstoday.com/proceedings

5th International Conference of Materials Processing and Characterization (ICMPC 2016)

Mechanical properties of functionalized multiwalled carbon nanotube/epoxy nanocomposites Subhra Gantayata*, Dibyaranjan Routa, Sarat K. Swainb b

a School of Applied Sciences, KIIT University, Bhubaneswar-751024, Odisha, India Department of Chemistry, Veer Surendra Sai University of Technology, Burla, Sambalpur- 768018, Odisha, India

Abstract Nanocomposites were synthesized by dispersing multiwalled carbon nanotube (MWCNT) of different weight percentages (0.4, 0.6 and 1.0 wt %) into epoxy resin polymer matrix. Prior to the MWCNTs were functionalized by a mixed acid chemical treatment. The composites were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction. The morphology of the composites was studied by field emission scanning microscope (FESEM). The tensile strength and modulus of elasticity of epoxy were substantially improved due to well dispersion of f-MWCNT in epoxy polymer and firm interfacial adhesion between epoxy and MWCNTs. ©2017 Published by Elsevier Ltd. Selection and peer-review under responsibility of Conference Committee Members of 5th International Conference of Materials Processing and Characterization (ICMPC 2016). Keywords: Epoxy resin, MWCNT, Tensile strength

1. Introduction Recently the development of polymer composites with nanosized fillers has become an attractive subject in material science [1]. Particularly carbon nanotubes (CNTs)/polymer composites have given lot of attention because of its unparallel thermal, electrical and mechanical properties. CNT is elongated fullerene graphite like sheet arranged in a tube shape by the sp2 hybridized carbon atom. Because of their graphitic structure, they posses large thermal conductivity and semiconducting or metal like electrical conductivity [2]. * Corresponding author. Subhra Gantayat; Tel.: +91-9437091109; E-mail address:[email protected] 2214-7853©2017 Published by Elsevier Ltd. Selection and peer-review under responsibility of Conference Committee Members of 5th International Conference of Materials Processing and Characterization (ICMPC 2016).

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They possess a unique structural arrangement of atom with high aspect ratio, strength (~102 times stronger than steel), modulus (~1TPa), electrical capacity (~103 times higher than Cu) and thermal stability [3] along with low density and high flexibility. Owing to its unique properties CNTs have emerged as highly desirable filler candidates in polymeric materials to yield the next generation nanocomposites [4]. However, developing advanced polymer nanocomposites with CNTs as reinforcement, two main problems have to be solved i.e. (i) poor interfacial adhesion between polymer matrix and CNT limits the transfer of stress during load effectively and (ii) poor dispersion of CNTs into polymer matrix [5]. In order to overcome these problems and improve the interfacial property between CNTs and polymer matrix, chemical functionalization of CNTs can be employed [6]. Furthermore, epoxy resin is one of the widely used as polymer matrix amongst other polymers in fabricating nanocomposites. These epoxy based composites receive potential applications in aircraft, space shuttle, electronic products etc. due to their interesting characteristic properties i.e. good stiffness, specific strength, low weight, high adhesion etc. Therefore, nanotube reinforced epoxy system have attracted a great attention by developing advanced composites with adequate features for various applications. Guo et al. [7] reported gradual increase of tensile strength of the epoxy composites as the MWCNT content increases and they obtained a maximum value of 69.7MPa at 8wt% of MWCNTs loading. Similarly, Allaoui et al. [8] reported significant increase in Young’s modulus and strength of the composites with addition of MWCNTs in a rubbery epoxy matrix. Montazeri et al. [9-10] also showed improvement of mechanical strength of MWCNT/epoxy nanocomposites. In this paper, an attempt has been made to functionalize MWCNT by a mixed acid chemical treatment to enhance the interfacial interaction substantially between MWCNT filler and epoxy matrix. Then mechanical properties of the samples were measured and discussed as a function of different weight percentages of f-MWCNT. 2. Experimental details Multiwalled carbon nanotubes with purity ≥ 95%, dia. 20-30 nm and length 10-30 µm (SRL, Mumbai, India), Epoxy resin; LY 556, Bisphenol Diglycidyl ether (Merck India), Curing agent; HY 951, Aliphatic amine (Merck, India), Concentrated H2SO4 and HNO3 (analytical grade chemicals) were used as starting reagents. MWCNTs were added to a mixture of conc. H2SO4 and HNO3 in 3:1 volume ratio and sonicated for 24h at 400C. Using distilled water the mixture was diluted and filtered. The residue was washed with distilled water and then further polished by H2O2 and H2SO4 in 1:4 volume ratio with constant stirring at 70oC for 30 min. The solution was then centrifuged for many times in distilled water medium to remove the excess acid and to get functionalized MWCNTs.The fMWCNT of different wt% (0.4, 0.6 & 1.0) was mixed with epoxy resin and sonicated for 2h. Then Curing agent was added in 1:10 ratio to it and stirred at 150rpm for 10min. The mixture was then cast on a mold and cured at 60110oC for 1-2h. A Shimadzu IR Affinity-1 Fourier infrared spectrophotometer was used to record the FTIR spectra of the samples. X-Ray diffraction pattern were taken using Rigaku X-Ray diffractometer. The surface morphology of nanocomposites was observed by FESEM. Mechanical properties of those samples were measured by ASTM (D638-00), Instron testing machine. 3. Result and Discussion The FTIR spectra of the nanocomposites were carried out to realize the nature of interactions between functional groups present in the constituting components, i.e. epoxy resin and f- MWCNT. Fig-1 shows a comparative FTIR spectrum of epoxy and epoxy/f- MWCNT. The appearance of –OH stretching band at 3200-3600 cm-1 gives an indication of adhesion of polar functional (-OH) groups on f- MWCNT surface after chemical modification, which improves the f-MWCNT/epoxy resin effective interfacial interaction. The figure revealed no extra band, which indicates the presence of hydrogen bond at the interface between hydroxyl groups of functionalized nanotubes and epoxy. Similar type of cooperative interfacial interaction through hydrogen bonding between -OH functional groups of acid treated f-MWCNT and epoxy has been reported by Montazeri et al. [11]. Fig. 2(a) shows a representative figure of the XRD pattern of epoxy and epoxy/f-MWCNT (1 wt %) nanocomposite. The XRD pattern of composite indicates a sharp diffraction peak at 25.90 revealing the crystalline nature of the MWCNTs. On the other hand, XRD pattern of epoxy resin represents a broad peak at 2ϴ value of 450. Nevertheless, the f-MWCNT/epoxy nanocomposites exhibit peaks corresponding to the epoxy and f-MWCNT. The intensity of the peak increases with increasing wt% of f-MWCNT and a slight shifting in peak positions is also observed.

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Fig.1 FTIR spectra of f-MWCNT (inset), epoxy and epoxy/f-MWCNT samples

The simultaneous presence of epoxy and f-MWCNT characteristic peaks in the nanocomposite gives the evidence of the formation of epoxy/f- MWCNT nanocomposites. Further, uniform dispersion of the f-MWCNTs in to the epoxy has been confirmed from FESEM picture of f-MWCNT (1wt %) /epoxy composites as shown in a representative figure [Fig. 2(b)]. Besides good dispersion, this figure also shows good adhesion of epoxy matrix with f-MWCNT [12].

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Fig. 2 (a) XRD patterns of Epoxy and 1% f-MWCNT nanocomposites, (b) FESEM image of 1wt% f-MWCNT/epoxy nanocomposite

Fig. 3 shows the variation of tensile strength and Young’s modulus of epoxy/f-MWCNT nanocomposites at different f-MWCNT loading. The tensile strength exhibits a gradual increase to a maximum of 27% at 0.6wt%. Similarly the addition of f-MWCNT produces an increase in the Young’s modulus. The maximum increase of 14% was exhibited at a concentration of 0.6wt%. However both the properties begin to degrade with further increasing fMWCNT content. Probably, it is due to poor dispersion of f-MWCNT at higher concentration and their reagglomeration. Besides, addition of more f-MWCNTs gives f-MWCNT much easier to be aggregated after the certain content. Similar results are reported by Montazeri et al. [11,13,14].

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Fig. 3 (a)Tensile strength (b) Young’s Modulus with variation of f-MWCNT loading

4. Conclusion MWCNTs were functionalized by a mixed acid treatment and epoxy/f-MWCNT nanocomposites were prepared with different wt% of f-MWCNT. Functionalization of MWCNT interrupts the firm vander Waals force between nanotubes preventing them to agglomerate. FTIR and XRD data clearly indicated that the dispersion of MWCNTs in the polymer matrix was homoheneous leading to the increase of interfacial interaction between the nanotubes and the epoxy resin. The uniform dispersion of MWCNT within the matrix was also observed from the FESEM image. Substantial enhancement of Young's modulus and tensile strength was observed with incorporation of f-MWCNT into epoxy resin. Maximum increases in both the properties were achieved at 0.6% of f-MWCNT loading. References [1] K. Yang, G. Mingyuan, G. Yiping, P. Xifeng, M. Guohong, Carbon. 47(2009) 1723-1737. [2]H. Chen, O. Jacobs, W. Wu, G. Rudiger, B. Schadel, Polym. Test. 26 (2007) 351–360. [3]Y-H. Liao, O. Marietta-Tondin, Z-Y. Liang, C. Zhang, B. Wang, Mater. Sci. Engg. Part A: Struc. Mater. 385(2004) 175–181. [4]J.M. Wernik, S. A. Meguid, Mater. Desig. 59(2014)19-32. [5]X. Chen, J. Wang, M. Lin, W. Zhong, T. Feng, X. Chen, J. Chen, F. Xue, Mater. Sci. Engg. 492 (2008) 236–242. [6] V.K. Srivastava, Mater. Desig. 39(2012) 432-436. [7]P. Guo, X. Chen, X. Gao, H. Song, H. Shen, Compos. Sci. Technol. 67 (2007) 3331–3337. [8]A. Allaoui, S. Bai, H. M. Cheng, J. B. Bai, Compos. Sci. Technol. 62(2002) 1933-1998. [9]A. Montazeri, A. Khavandi, J. Javadpur, A. Tcharkhtchi, Mater. Desig. 31(2010) 3383-3388. [10]D. Dash, S. Samanta, S.S. Gautam, M. Murlidhar, Adv. Mater Manufac & Charact 3(2013)275-279. [11]A. Montazeri., J. Jafar, K. Alireza, T. Abbas, M. Ali, Mater. Desig. 31(2010) 4202-4208. [12]C.M. Damian, S.A. Garea, E. Vasile, H. Iovu, Composites: Part B 43 (2012) 3507–3515. [13]A. K. Gupta, S.P. Harsha, Procedia Mater. Sci. 6 (2014)18 – 2. [14] A. K. Parida, B. C. Routara, R. K. Bhuyan, Materials Today: Proceedings 2 (2015) 3065–3074.