Comparison dielectric and thermal properties of polyurethane/organoclay nanocomposites (original) (raw)
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Effect of nano-clay on di-electric and thermal properties of polyurethane/clay nanocomposites
The main object of this paper is to study the dielectric and thermal behavior of polyurethane/organoclay nanocomposites. Modification of Egyptian Bentonite (EB) was carried out using an organo-modifier namely; octadecyl amine (ODA). Polyurethane nanocomposites were synthesized with organically modified EB (Organo Bentonites OB) by in situ polymerization and compositions were prepared by a casting process. The morphology of the OB dispersion in polyurethane nanocomposites was investigated by transmission electron microscopy TEM. A thermogravimetric analyzer (TGA) was used to investigate the decomposition behavior and thermal stability of the cured nanocomposites. The thermal stability of the PNC films was significantly increased with the OB content increment. The complex dielectric permittivity, electrical conductivity, electric modulus, and impedance spectra of the PU/OB nanocomposites were investigated in the frequency range from 0.1 Hz to 10 MHz. The real and imaginary parts of the permittivity decrease with increasing frequency due to an increase in OB content. All the nanocomposites showed relatively low conductivity values and high impedance that could be used for nano-dielectrics.
Probing the dielectric response of polyurethane/alumina nanocomposites
Journal of Polymer Science Part B-polymer Physics, 2010
The dielectric properties of polyurethane (PUR) latexboehmite alumina nanocomposites were investigated by means of broadband dielectric spectroscopy in the temperature range À100 C to 70 C. The concentration of the filler (alumina) was kept constant at 10 phr for all specimens, whereas the mean particle diameter (namely 220, 90, and 25 nm) of the incorporated nanoparticles varied accordingly. For reasons of comparison, pure PUR was also examined. Four distinct relaxation modes were recorded in the spectra of all systems. They were attributed to interfacial polarization, glass transition (a-relaxation), local motions of polar side groups, and chain segments (b-relaxation and c-relaxation). All four relaxation processes exhibit a symmetric distribution of relaxation times, which in the case of interfacial polarization, becomes narrower. The intensity of interfacial polarization increases with the reduction of the mean particle diameter indicating enhanced interfacial area.
Journal of Polymer Research, 2010
Elastomeric polyurethane (PU) was mixed with 1, 3, 5, 7, and 10 wt% of Cloisite 30B to obtain PU-based nanocomposites. The thermal stabilities of the obtained products were characterized by thermal analysis using a thermogravimetric analyzer (TGA), which showed that the addition of 5 wt% of organoclay to the PU increased its stability, whereas thermal stabilization was less efficient at 10 wt%. The electrical conductivities of these composites were studied as a function of temperature, and it was found that the conductivity of PU was enhanced upon using 5 wt% of organoclay. The tensile strength, elongation (%), and Young’s modulus were considerably enhanced upon increasing the organoclay content to 5 wt%, but were then decreased to some extent upon further increasing the nanoparticle loading to 10 wt%. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study these nanocomposite structures, and it was found that the PU molecular chains were intercalated into the galleries of the silicate layers in all of the nanocomposites, and that this reached a maximum when 5 wt% of Cloisite 30B was used.
Polymer …, 2011
Ternary hybrid composites composed of polyoxymethylene (POM), polyurethane (PU) and boehmite alumina nanoparticles were produced by melt blending with and without latex pre-compounding. PU latex pre-compounding was employed for the fine dispersion of both the PU and alumina particles within the POM matrix. In this study the electrical properties of the POM/PU/boehmite alumina nanocomposites were examined by means of broadband dielectric spectroscopy over a wide temperature (−100 to 150 • C) and frequency (10 −1 to 10 6 Hz) range. Data were analysed by means of the electric modulus formalism. The recorded relaxations include contributions from both polymers and the inorganic reinforcing phase. In the ternary hybrid systems five distinct relaxation processes were detected. Relaxations were assigned and interpreted by considering the morphology of the corresponding composite. In particular, they were attributed to the γ -mode of POM and/or of PU, the α-mode of PU, the α-mode of POM and to the interfacial polarization process. Finally, the dynamics of all the recorded processes are examined and discussed.
European Polymer Journal, 2017
Polyoxymethylene/Polyurethane/Layered Silicates (POM/PU/LS) ternary hybrid nanocomposites were prepared by two methods: (a) direct melt compounding (DM) and (b) melt compounding using a latex-mediated masterbatch (MB) technique. The morphology of the produced specimens and the quality of the dispersion of LS (synthetic sodium fluorohectorite) were examined via Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Broadband dielectric spectroscopy (BDS) was employed in order to study the dielectric response of the two systems in a wide frequency and temperature range. Rich dielectric spectra are recorded, since dielectric relaxation mechanisms originate from POM matrix, PU latex as well as from interfacial phenomena between LS and the polymer matrix. Six different mechanisms were observed in the spectra of the examined
Development of polyurethane–titania nanocomposites as dielectric and piezoelectric material
RSC Advances, 2013
Flexible polyurethane (PU)-titania nanocomposites of different compositions are prepared by a meltmixing technique. Two different sequences of mixing method are adapted to prepare two different sets of composites. All these composites show composition-dependent dielectric properties, and composites with tunable dielectric properties can be obtained through judicial adjustment of composition. The morphology of these composites has been investigated by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and scanning probe microscopy (SPM). Dielectric properties at low frequency regions are found to depend on morphology. These composites show excellent piezoelectric behaviour, where the dielectric constant and conductivity of these flexible composites change appreciably with changes in applied stress. The dielectric breakdown strength of these composite is also measured. To understand the thermal stability of these composites, thermogravimetric analysis has been applied and it was found that a composite containing 12.49 vol% titania shows higher thermal stability, beyond which, stability decreases due to the photocatalytic effect of titania.
Electrophysical characteristics of polyurethane/organo-bentonite nanocomposites
Egyptian Journal of Petroleum, 2014
Modification of the Egyptian Bentonite (EB) was carried out using organo-modifier namely; octadecylamine ODA. Before the modification, the cation exchange capacity (CEC) of the EB was measured, also it was purified from different impurities using HCl and distilled water. The Organo-bentonite OB was characterized using IR, XRD, and TEM. PU/ODA-B nanocomposites were prepared by in situ polymerization then characterized by XRD and TEM. An amount of ODA-B ranging from 0.25% up to 5% by weight was added to the polyol component of the resin before mixing with toluene diisocynate TDI. TEM showed that the nanocomposites achieved good dispersion in the polyurethane matrix. The mechanical, swelling and electrical properties of the nanocomposites were measured. The results indicate that the tensile strength of all the nanocomposites enhanced with the addition of OB compared with the pure PU. The crosslink density of the nanocomposites increases with increasing the content of OB. The Pool-Frenckel conduction mechanism predominates for all the nanocomposite samples and the blank one.
Polymers for Advanced Technologies, 2009
Polymer nanocomposites based on thermoplastic polyurethane (TPU) containing organophilic montmorillonite (OMMT) were prepared by melt compounding method followed by compression molding. Different percentage of organically modified nanoclays (1, 3, 5, 7, and 9 wt%) was incorporated into the TPU matrix in order to examine the influence of the nanofillers on nanophase morphology and materials' properties. The microstructure morphology of the nanocomposites was examined by transmission electron microscopy (TEM), energy dispersion X-ray analysis (EDX), wide angle X-ray diffraction (WAXD), and atomic force microscope (AFM). The observation established that the organoclay is homogeneously dispersed and preferentially embedded in the TPU soft segment phase. Significant enhancement in the thermal stability of the nanocomposites was observed with the addition of the OMMT under thermogravimetric analysis (TGA). Dynamic mechanical properties of the TPU nanocomposites were analyzed using a dynamic mechanical thermal analyzer (DMTA), which confirms that the addition of OMMT has a strong influence on the storage and loss modulus of the TPU matrix. Copyright © 2009 John Wiley & Sons, Ltd.
International Journal of Green Nanotechnology, 2011
Elastomeric polyurethane (PU) was mixed with 1, 3, 5, 7, and 10 wt% of Cloisite 20A to obtain PU-based nanocomposites. The thermal stabilities of the obtained products were characterized by thermal analysis using a thermogravimetric analyzer (TGA), which showed that addition of 5 wt% of organoclay to the PU increased its stability, whereas thermal stabilization was less efficient at 10 wt%. The electrical conductivities of these composites were studied as a function of temperature, and it was found that the conductivity of PU was enhanced upon using 5 wt% of organoclay. The tensile strength, elongation (%), and Young's modulus were considerably enhanced upon increasing the organoclay content to 5 wt%, but were then decreased to some extent upon further increase of the nanoparticle loading to 10 wt%. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study these nanocomposite structures, and it was found that the organoclay is fully exfoliated in the PU matrix when 5 wt% of Cloisite 20A was used.
European Polymer Journal, 2007
Polylactide-based systems composed of an organoclay (Cloisite Ò 30B) and/or a compatibilizer (Exxelor VA1803) prepared by melt blending were investigated. Two types of not compatibilized nanocomposites containing 3 wt% or 10 wt% of the organoclay were studied to reveal the effect of the filler concentration on the nanostructure and physical properties of such systems. The 3 wt%-nanocomposite was also additionally compatibilized in order to improve the nanoclay dispersion. Neat polylactide and polylactide with the compatibilizer processed in similar conditions were used as reference samples. The X-ray investigations showed the presence of exfoliated nanostructure in 3 wt%-nanocomposite. Compatibilization of such system noticeably enhanced the degree of exfoliation of the organoclay. Viscoelastic spectra (DMTA) showed an increase of the storage and loss moduli with the increase of the organoclay content and dispersion. Dielectric properties of the nanocomposites show a weak influence of the nanoclay on segmental (a S) and local (b)-relaxations in PLA, except for the highest nanoclay content. Above T g a strong increase of dc conductivity related to ionic species in the clay is observed. It gives rise also to the Maxwell-Wagner-Sillars interfacial polarization and both real and imaginary parts of e strongly increase. In the temperature dependence of low frequency dielectric constant and mechanical moduli (at 1 Hz) an additional maximum around 80-90°C is observed due to cold crystallization of PLA.