A facile route for the synthesis of mechanically strong MWCNTs/NDs nanobifiller filled polyacrylate composites

ABSTRACT

We present here the synthesis of novel Nano-Bifiller filled composites with extremely promising material properties. To achieve this goal, initially, poly (methyl methacrylate) (PMMA) and poly (ethylene glycol) (PEG) blend were formed. Later, the matrix was reinforced with purified carbon (P-CNT), amino modified carbon nanotube (PDA-CNT) and amino modified carbon nanotube nanodiamond (PDA-CNT-ND). In this way, three series of nanocomposites, i.e. PMMA/PEG/P-CNT, PMMA/PEG/PDA-CNT, and PMMA/PEG/PDA-CNT-ND were synthesized with varying P-CNT, PDA-CNT and PDA-CNT-ND loading (i.e., 1 wt.%, 3 wt.%, 5 wt.%, 10 wt.%, 30 wt.% and 50 wt.%) by a solution blending route. The reinforcement and loading effect of these three types of nanofillers on the matrix was studied. Studies were performed using Fourier transform infrared spectroscopy (FTIR), mechanical testing, thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM) and X-ray powder diffraction (XRD) to explore the structural, morphological, mechanical and thermal properties of nanocomposites prepared. The inter-association of poly (methyl methacrylate) and poly (ethylene glycol) (PMMA/PEG) due to hydrogen bonding and covalent attachment of matrix to the sidewalls of nanotubes was confirmed by FTIR spectra. The experimental results showed that a loading of 5 wt. % filler in matrix produced a tensile strength and modulus of 26.4 (MPa) and 1255.75 (MPa) in PMMA/PEG/P-CNT nanocomposites, while 28.8 (MPa) and 1411.04 (MPa) in PMMA/PEG/PDA-CNT nanocomposites and 29.4 (MPa) and 1419.41 (MPa) in PMMA/PEG/PDA-CNT-ND nanocomposites as compared to neat PMMA which has tensile strength and modulus of 21.79 (MPa) and 1083.84 (MPa) respectively. These results depict that bifiller nanocomposites showed better mechanical properties as compared to pristine and amine functionalized MWCNT. Scanning electron microscopy revealed granular morphology with few protruding out carbon nanotubes. Thermal stability of PMMA/PEG/PDA-CNT-ND nanocomposites was found higher than PMMA/PEG/PDA-CNT and PMMA/PEG/P-CNT nanocomposites. The T_o (369^°C) and T₁₀ (515^°C) values for PMMA/PEG/PDA-CNT-ND composites was higher than PMMA/PEG/PDA-CNT [T_o (354^°C) and T₁₀ (420^°C)] and PMMA/PEG/P-CNT composites [T_o (312^°C) and T₁₀ (390^°C)]. These results suggest that the bifiller nanocomposites were thermally more stable. The XRD spectra showed a pronounced XRD peak at 25.9^°, corresponding to (002) reflection of the nanotubes indicating that MWCNT structure was not destroyed during composite formation. The peak appeared at 75.3^° were indexed to (220) reflections due to nanodiamond structure.

GRAPHICAL IMAGE

KEYWORDS:

• Poly (methyl methacrylate)
• poly (ethylene glycol)
• field emission scanning electron microscopy
• X-ray powder diffraction
• carbon nanotubes
• nanodiamond

Summary

In this article we have studied the synthesis and characterization of PMMA/PEG blends reinforced by three different of fillers, i.e., pristine MWCNT (P-CNT), p-Phenylenediamine modified carbon nanotube (PDA-CNT) and p-Phenylenediamine modified carbon nanotube nanodiamond (PDA-CNT-ND). In this way, three series of nanocomposites, i.e. PMMA/PEG/P- CNT, PMMA/PEG/PDA-CNT and PMMA/PEG/PDA-CNT-ND were synthesized with varying P-CNT, PDA-CNT and PDA-CNT-ND loading (i.e., 1 wt.%, 3 wt.%, 5 wt.%, 10 wt.%, 30wt.% and 50 wt.%) by a solution casting route. The reinforcement and loading effect of these three types of nanofillers on the properties of the matrix was studied. FTIR analysis confirmed the functionalization of CNT with amine and nanodiamond. The inter-association of poly (methyl methacrylate) and poly (ethylene glycol) (PMMA/PEG) due to hydrogen bonding and covalent attachment of matrix to the sidewalls of nanotubes was confirmed by FTIR spectra. SEM studies showed granular morphology for P-CNT with few carbon nanotubes protruding out. The amino functionalized nanocomposites reveal a non-uniform glazing of polymer matrix on the surface of functionalized MWCNT. This wrapping of polymer layers on MWCNT results in globular morphology of functionalized MWCNT compared to pristine MWCNT. The nanobifiller also exhibited smooth and uniform morphology with homogeneously dispersed nanofiller. Thermal stability of PMMA/PEG/PDA-CNT-ND nanocomposites was found higher than PMMA/PEG/PDA-CNT and PMMA/PEG/P-CNT nanocomposites. This improvement in thermal stability is attributed to the excellent dispersion of the functionalized CNT in the polymeric matrix, which in turn has reinforced the interfacial interactions between the MWCNT and the matrix. With the addition of nanofillers, an appreciable improvement in the mechanical properties of the composites was recorded as compared to the neat polymer. The composites having CNT as filler show increase in mechanical properties up to a certain loading of CNT and after that it shows a declining trend. This may be due to higher CNT loading causes increase in viscosity of polymers and also because of some surface of CNT may not be completely covered by matrix because of a large specific area of CNT. The XRD spectra showed a pronounced XRD peak at 25.9^°, corresponding to (002) reflection of the nanotubes indicating that MWCNT structure was not destroyed during composite formation. The peak appeared at 75.3^° were indexed to (220) reflections due to nanodiamond structure.