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K P Pramoda - One of the best experts on this subject based on the ideXlab platform.
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microstructure crystallization and dynamic mechanical behaviour of poly vinylidene fluoride composites containing poly methyl methacrylate grafted multiwalled carbon nanotubes
Nanotechnology, 2007Co-Authors: Mian Wang, K P PramodaAbstract:Composites of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA)-grafted MWNTs were prepared by melt mixing. The miscibility between PVDF and PMMA helps improve the dispersion of PMMA-grafted MWNTs in the PVDF matrix and also the load transfer from the PVDF matrix to the nanotubes. MWNTs act as nucleation agents to increase the crystallization and melting temperatures of PVDF, but the nucleation effect is suppressed when PMMA is grafted onto the nanotubes. X-ray diffraction and infrared spectroscopic studies showed that MWNTs induce the formation of β-form PVDF crystallites. The Storage Modulus of PVDF is increased by nearly 150% at 20 °C upon the incorporation of PMMA-grafted MWNTs with MWNT content of 1.93 wt%. PMMA-grafted MWNTs are more effective than organoclay in increasing the Storage Modulus of PVDF.
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enhancement of interfacial adhesion and dynamic mechanical properties of poly methyl methacrylate multiwalled carbon nanotube composites with amine terminated poly ethylene oxide
Carbon, 2006Co-Authors: Mian Wang, K P Pramoda, S H GohAbstract:Abstract We have studied the dynamic mechanical behavior of poly(methyl methacrylate) (PMMA)/acidified multiwalled carbon nanotube (MWNT) composites compatibilized with amine-terminated poly(ethylene oxide) (PEO-NH2). PEO-NH2 is ionically associated with acidified MWNTs via ionic interaction as shown by XPS and FTIR. The miscibility between PEO and PMMA improves the interfacial adhesion between polymer matrix and MWNTs, leading to an increase in the Storage Modulus values of the composites. The effects of PEO-NH2 on Storage Modulus and glass transition temperature are discussed.
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crystallization and dynamic mechanical behavior of double c60 end capped poly ethylene oxide multi walled carbon nanotube composites
Chemical Physics Letters, 2003Co-Authors: H W Goh, K P Pramoda, S H Goh, W D ZhangAbstract:Abstract Double-C 60 -end-capped poly(ethylene oxide) (FPEOF) was reinforced with acid-treated multi-walled carbon nanotubes (MWNTs). The Storage Modulus of FPEOF was significantly enhanced, whereas the crystallization behavior was not significantly affected upon the incorporation of MWNTs. Fourier transform infrared spectroscopy showed the existence of hydrogen-bonding interactions between the ether oxygen atoms on FPEOF and proton-donating functionalities on the MWNTs, leading to a strong matrix-filler interfacial adhesion. The low-temperature Storage Modulus of a FPEOF/MWNT composite (6.0 GPa) is more than twice that of a poly(ethylene oxide)/fluorinated single-walled carbon nanotube composite (2.5 GPa) with the same nanotube loading of 4 wt%. The thermal stability of FPEOF is also improved by the addition of MWNTs.
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poly vinylidene fluoride assisted melt blending of multi walled carbon nanotube poly methyl methacrylate composites
Materials Research Bulletin, 2002Co-Authors: K P Pramoda, Guo Qin XuAbstract:Multi-walled carbon nanotubes (MWNTs) were sonicated in the dimethylformamide solution of poly(vinylidene fluoride) (PVDF). The PVDF-covered MWNTs were then melt-blended with poly(methyl methacrylate) (PMMA). The dynamic mechanical behavior of various composites was studied. The presence of a small amount of PVDF leads to a significant improvement in the Storage moduli of the MWNT/PMMA composites at low temperatures. The Storage Modulus of a PVDF/MWNT/PMMA composite containing 0.5 wt.% PVDF is almost twice as that of a MWNT/PMMA composite at 50°C. However, a further increase in the PVDF content leads to a reduction of the Storage Modulus. The beneficial effect of PVDF diminishes at higher temperatures.
Nikhil Gupta - One of the best experts on this subject based on the ideXlab platform.
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dynamic properties of alumina hollow particle filled aluminum alloy a356 matrix syntactic foams
Materials & Design, 2015Co-Authors: Luca Licitra, Dung D Luong, Oliver M Strbik, Nikhil GuptaAbstract:Abstract Dynamic properties of two aluminum alloy A356/alumina hollow particle syntactic foams that have densities of 1.61 and 2.11 g/cc are studied. The materials are characterized for quasi-static (10−3 s−1) and high strain rate (445–910 s−1) compression. The results show that the lower density syntactic foam has lower Modulus, compressive strength and plateau stress, but the lower density provides better specific properties than either the A356 alloy and higher density syntactic foam. The fracture mechanism of the syntactic foams was investigated by using high speed cameras. The particle failure is found to initiate the failure in the specimen, followed by shear failure of the matrix and particles. The A356 alloy and syntactic foams are also characterized for their dynamic mechanical properties to understand the effect of temperature and loading frequency on the Storage and loss moduli and damping parameter. The Storage Modulus of A356 matrix and syntactic foams decreases but the loss Modulus and damping parameter increase as the temperature increases. At the same temperature, the lower density material has lower Storage Modulus and loss Modulus. The Storage Modulus of A356 alloy decreases steeply as the temperature is increased above 375 °C, whereas syntactic foams demonstrate better thermal stability.
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viscoelastic properties of hollow glass particle filled vinyl ester matrix syntactic foams effect of temperature and loading frequency
Journal of Materials Science, 2013Co-Authors: Vasanth Chakravarthy Shunmugasamy, Dinesh Pinisetty, Nikhil GuptaAbstract:Viscoelastic properties of hollow particle-reinforced composites called syntactic foams are studied using a dynamic mechanical analyzer. Glass hollow particles of three different wall thicknesses are incorporated in the volume fraction range of 0.3–0.6 in vinyl ester resin matrix to fabricate twelve compositions of syntactic foams. Storage Modulus, loss Modulus, and glass transition temperature are measured and related to the microstructural parameters of syntactic foams. In the first step, a temperature sweep from −75 to 195 °C is applied at a fixed loading frequency of 1 Hz to obtain temperature dependent properties of syntactic foams. In the next step, selected four compositions of syntactic foams are studied for combined effect of temperature and loading frequency. A frequency sweep is applied in the range 1–100 Hz and the temperature is varied in the range 30–140 °C. Time–temperature superposition (TTS) principle is used to generate master curves for Storage Modulus over a wide frequency range. The room temperature loss Modulus and maximum damping parameter, Tanδ, are found to have a linear relationship with the syntactic foam density. Increasing volume fraction of particles helps in improving the retention of Storage Modulus at high temperature in syntactic foams. Cole–Cole plot and William–Landel–Ferry equation are used to interpret the trends obtained from TTS. The correlations developed between the viscoelastic properties and material parameters help in tailoring the properties of syntactic foams as per requirements of an application.
Mian Wang - One of the best experts on this subject based on the ideXlab platform.
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microstructure crystallization and dynamic mechanical behaviour of poly vinylidene fluoride composites containing poly methyl methacrylate grafted multiwalled carbon nanotubes
Nanotechnology, 2007Co-Authors: Mian Wang, K P PramodaAbstract:Composites of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA)-grafted MWNTs were prepared by melt mixing. The miscibility between PVDF and PMMA helps improve the dispersion of PMMA-grafted MWNTs in the PVDF matrix and also the load transfer from the PVDF matrix to the nanotubes. MWNTs act as nucleation agents to increase the crystallization and melting temperatures of PVDF, but the nucleation effect is suppressed when PMMA is grafted onto the nanotubes. X-ray diffraction and infrared spectroscopic studies showed that MWNTs induce the formation of β-form PVDF crystallites. The Storage Modulus of PVDF is increased by nearly 150% at 20 °C upon the incorporation of PMMA-grafted MWNTs with MWNT content of 1.93 wt%. PMMA-grafted MWNTs are more effective than organoclay in increasing the Storage Modulus of PVDF.
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enhancement of interfacial adhesion and dynamic mechanical properties of poly methyl methacrylate multiwalled carbon nanotube composites with amine terminated poly ethylene oxide
Carbon, 2006Co-Authors: Mian Wang, K P Pramoda, S H GohAbstract:Abstract We have studied the dynamic mechanical behavior of poly(methyl methacrylate) (PMMA)/acidified multiwalled carbon nanotube (MWNT) composites compatibilized with amine-terminated poly(ethylene oxide) (PEO-NH2). PEO-NH2 is ionically associated with acidified MWNTs via ionic interaction as shown by XPS and FTIR. The miscibility between PEO and PMMA improves the interfacial adhesion between polymer matrix and MWNTs, leading to an increase in the Storage Modulus values of the composites. The effects of PEO-NH2 on Storage Modulus and glass transition temperature are discussed.
Charles C Han - One of the best experts on this subject based on the ideXlab platform.
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rheological properties of polybutadiene polyisoprene blend in the unstable and metastable regions under oscillatory shear
Polymer, 2014Co-Authors: Wei Liu, Xia Dong, Fasheng Zou, Jian Yang, Dujin Wang, Charles C HanAbstract:The rheological properties of polybutadiene (PB)/polyisoprene (PI) in the unstable and metastable regions under oscillatory shear flow has been studied. Based on the shear quench experiment, it showed that the time dependent Storage Modulus G′ initially increased and then decreased with time in the unstable region. The concentration fluctuation led to the increasing part and the coarsening of the bicontinuous structure led to the decreasing of the Storage Modulus. The rheological response of the nucleation/growth in the metastable region was similar to that of spinodal decomposition. The fluctuation-assisted nucleation theory proposed by Balsara et al. was similar to the spinodal decomposition mechanism, which led to the similar rheological response. However, the continuous nucleation led to the slow growth and the almost linear decayed rheological curve, which was different from that in the unstable region. According to this theory, the relative nucleation rate on the early stage of nucleation could be calculated, which increased exponentially with the reciprocal of quench temperature in the metastable region. The spinodal point under oscillatory shear was also determined by the difference of maximum value of the Storage Modulus and the bulk Modulus.
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phase behavior actuating morphology and rheological response of polybutadiene polyisoprene blends under small amplitude oscillatory shear
Chinese Journal of Polymer Science, 2014Co-Authors: Fasheng Zou, Xia Dong, Wei Liu, Dujin Wang, Charles C HanAbstract:The morphology evolution and the corresponding linear viscoelastic behavior of the phase-separating polybutadiene (PB)/low vinyl content polyisoprene (LPI) blend have been investigated by phase contrast optical microscopy (PCOM), small-angle light scattering (SALS) and rheometry. Two kinds of structure evolutions and rheological responses have been observed. It is found that the co-continuous structure generally gives a power law behavior of the dynamic Storage Modulus versus frequency and the coarsening of co-continuous structure leads to a decrease of the Storage Modulus. For the droplet-matrix structure, a platform Modulus is observed at the mediate frequencies, followed by the typical terminal relaxation behavior of Storage Modulus at the extremely low frequencies. The decreasing platform Modulus and increasing terminal Modulus with the growth of droplets are observed and can be well interpreted by the simplified Palierne model. The platform Modulus and terminal Modulus at a given frequency are found to be scalable with the phase separation time. Besides, the characteristic relaxation time and domain size of the droplets have been obtained by rheology. And it seems that the rheologically determined droplet dimensions are consistent with the ones determined by PCOM and SALS.
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melt rheology of lower critical solution temperature polybutadiene polyisoprene blends
Macromolecules, 2000Co-Authors: H S Jeon, And A I Nakatani, Charles C Han, R H ColbyAbstract:The viscoelastic properties of near critical entangled polybutadiene (PB)/polyisoprene (PI) blends were investigated in oscillatory shear above and below the lower critical solution temperature (LCST). The terminal loss Modulus of a near critical PB/PI blend above and below the LCST is well described by means of a log additive mixing rule. A single master curve in the loss Modulus of the critical blend exhibiting WLF behavior was obtained above and below the LCST by using the empirical time−temperature superposition (tTS) principle. However, the Storage Modulus above the LCST deviates from both the tTS principle and the log additive mixing rule. The phase-separated PB/PI blends within the linear viscoelastic regime display higher than expected values of Storage Modulus at low frequencies, due to the interfacial tension between the two phases of the blend. This increase causes a discontinuity in the temperature dependence of the Storage Modulus at low frequencies. The discontinuity occurs at a frequency-de...
Guo Qin Xu - One of the best experts on this subject based on the ideXlab platform.
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poly vinylidene fluoride assisted melt blending of multi walled carbon nanotube poly methyl methacrylate composites
Materials Research Bulletin, 2002Co-Authors: K P Pramoda, Guo Qin XuAbstract:Multi-walled carbon nanotubes (MWNTs) were sonicated in the dimethylformamide solution of poly(vinylidene fluoride) (PVDF). The PVDF-covered MWNTs were then melt-blended with poly(methyl methacrylate) (PMMA). The dynamic mechanical behavior of various composites was studied. The presence of a small amount of PVDF leads to a significant improvement in the Storage moduli of the MWNT/PMMA composites at low temperatures. The Storage Modulus of a PVDF/MWNT/PMMA composite containing 0.5 wt.% PVDF is almost twice as that of a MWNT/PMMA composite at 50°C. However, a further increase in the PVDF content leads to a reduction of the Storage Modulus. The beneficial effect of PVDF diminishes at higher temperatures.
