Abstract:This paper investigates the structure, length, and percentage of functional groups of multi-walled carbon nanotubes (CNT) depending on the time taken for functionalization in HNO3 and H2SO4 mixture. The carbon nanotube content and influence of functionalization time on mechanical properties of polymer composite materials based on epoxy matrix are studied. The extreme dependencies of mechanical properties of carbon nanotube functionalization time of polymer composites were established. The rise in tensile stren… Show more
“…Adding CNT into epoxy matrices to enhance its properties and obtain a multifunctional material has already been deeply studied in order to analyze the thermal [ 2–4 ] and mechanical [ 2–6 ] properties of its polymeric nanocomposites. Furthermore, several works in the literature [ 7,8 ] have devoted themselves to the study of the curing kinetics of these systems aiming a better understanding of their functioning mechanisms.…”
In this work, multiwalled carbon nanotubes (MWCNT) were oxidized in a mixture of sulfuric and nitric acid (3:1 v/v) using two distinct times (9 and 18 hours). The effects of different oxidation levels and concentrations of MWCNT on curing kinetics, thermal, and mechanical properties of bisphenol A diglycidyl ether nanocomposites were studied. The nanocomposites were produced using in situ polymerization technique at two different volume fractions (0.15% and 0.50% v/v) without using solvents. X-ray photoelectron spectroscopy results indicated that MWCNT were in fact oxidized and just 9 hours of acid treatment showed a greater amount of oxygen on the MWCNT surfaces. Results of differential scanning calorimetry and dynamic mechanical analysis showed small variations in the glass transition temperatures of the nanocomposites, indicating alterations in the quality of the interphase matrix/ carbon nanotubes. Concerning the thermogravimetric analysis results, the most thermally stable samples were those containing 0.15% v/v of pristine and 18 hours of oxidized MWCNT, which also had the highest stiffness of all nanocomposites. Finally, the cure kinetics of nanocomposites is fairly represented by Kamal and Sourour's semiempirical model with an autocatalytic behavior at 100 C and 120 C, but decelerated at 140 C.
“…Adding CNT into epoxy matrices to enhance its properties and obtain a multifunctional material has already been deeply studied in order to analyze the thermal [ 2–4 ] and mechanical [ 2–6 ] properties of its polymeric nanocomposites. Furthermore, several works in the literature [ 7,8 ] have devoted themselves to the study of the curing kinetics of these systems aiming a better understanding of their functioning mechanisms.…”
In this work, multiwalled carbon nanotubes (MWCNT) were oxidized in a mixture of sulfuric and nitric acid (3:1 v/v) using two distinct times (9 and 18 hours). The effects of different oxidation levels and concentrations of MWCNT on curing kinetics, thermal, and mechanical properties of bisphenol A diglycidyl ether nanocomposites were studied. The nanocomposites were produced using in situ polymerization technique at two different volume fractions (0.15% and 0.50% v/v) without using solvents. X-ray photoelectron spectroscopy results indicated that MWCNT were in fact oxidized and just 9 hours of acid treatment showed a greater amount of oxygen on the MWCNT surfaces. Results of differential scanning calorimetry and dynamic mechanical analysis showed small variations in the glass transition temperatures of the nanocomposites, indicating alterations in the quality of the interphase matrix/ carbon nanotubes. Concerning the thermogravimetric analysis results, the most thermally stable samples were those containing 0.15% v/v of pristine and 18 hours of oxidized MWCNT, which also had the highest stiffness of all nanocomposites. Finally, the cure kinetics of nanocomposites is fairly represented by Kamal and Sourour's semiempirical model with an autocatalytic behavior at 100 C and 120 C, but decelerated at 140 C.
“…The absorption peaks detected in this part are in good accordance with reports in other studies. 16,23 Figure 1.FTIR spectra of various MWCNTs.FTIR: Fourier transform infrared spectroscopy; MWCNTs: multi-walled carbon nanotubes.…”
Section: Resultsmentioning
confidence: 99%
“…The absorption peaks detected in this part are in good accordance with reports in other studies. 16,23 Figure 1 also indicates the FTIR spectra of aat-MWCNTs (i.e. aat-MWCNT-50).…”
Section: Titration Testmentioning
confidence: 99%
“…Nevertheless, none of these studies examined lesser durations. 23 Aviles et al. 24 focused on the concentration of the acid and concluded that a mixture of sulfuric acid and nitric acid at a concentration of 8 mol is the optimum concentration for the acid treatment of CNTs.…”
In this study, multi-walled carbon nanotubes (MWCNTs) were functionalized by both sulfuric/nitric acids and amino acids to form COOH and NH2/COOH/OH groups on their surface, respectively. The functionalized MWCNTs were characterized by Fourier Transform Infrared Spectroscopy, titration test, thermal gravimetric analysis, and solvent stability test. The results revealed that in each method, the functional groups were successfully attached to the surface of nanotubes. Acid treatment grafted more oxygen-containing groups compared to commercial carboxylated MWCNTs. The amino acid functionalized MWCNTs indicated improved stability in different solvents compared to raw and acid treated MWCNTs. These functionalized MWCNTs were incorporated into epoxy resin and the properties of the nanocomposites were evaluated by scanning electron microscopy, tensile test, dynamic mechanical thermal analysis, differential scanning calorimetry, and thermogravimetric analysis. The morphology of the nanocomposites revealed that acid and amino acid treated samples had better interaction with the epoxy resin. Compared to epoxy sample contained raw MWCNT (control) and commercial carboxylated MWCNTs, the addition of functionalized MWCNTs to the epoxy resin improved the tensile strength by 39% and 25% (for acid treated) and 46% and 33% (for amino acid treated), respectively. The best tensile properties for acid and amino acid treated samples were reached by MWCNTs acid treated at 110℃ for 15 min and MWCNTs treated in a 50 g/L aqueous solution of amino acid, respectively. Storage modulus of the epoxy samples which contained acid and amino acid treated MWCNTs were 1560 and 1900 MPa, respectively. The glass rubber transition temperature ( Tg) of the epoxy samples containing acid and amino acid treated nanotubes were increased by 1.1℃ and 5.9℃, respectively, compared to the control sample. Therefore, based on these mechanical properties, the epoxy samples containing nanotubes functionalized by amino acid exhibited the highest performance in the epoxy nanocomposite. Incorporating acid and amino acid treated MWCNTs accelerated the curing process of epoxy where the curing temperature decreased by 9.1℃ and 13.3℃, respectively. Because of the reaction between amine groups grafted on MWCNTs in the amino acid treatment and epoxide groups of the epoxy resin, this acceleration was more significant in the case of amino acid sample. Note that addition of functionalized MWCNTs to epoxy resin did not lead to increased thermal stability.
“…It has been found that high temperature destroys the internal structure of the resin and weakens the intermolecular interaction. At the same time, the structure of CNTs can also support the mechanical properties of resin matrix . Effects of NPs on the thermal stability of resin matrix are shown in Table .…”
Section: Effect Of Nanoparticles On the Thermal Stability Of Resin Mamentioning
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