Dynamic electrical thermal analysis on zinc oxide/epoxy resin nanodielectrics

The dielectric response of ZnO/epoxy resin nanocomposites was studied by means of dynamic electrical thermal analysis in the frequency range of 10^?1 to 10⁷ Hz, and over the temperature range of 30–160 °C, varying the content of the reinforcing phase. Scanning electron microscopy pictures were used for assessing the composites morphology and for examining the particles’ dispersion. The thermal properties of nanocomposites were examined by differential scanning calorimetry in the temperature range of 0–170 °C. Dielectric data were analyzed via dielectric permittivity and electric modulus formalisms. Recorded relaxation phenomena include contributions from both the polymeric matrix and the presence of the reinforcing phase. Processes related to the polymer matrix are attributed to the glass to rubber transition (α-relaxation) of the epoxy resin and local motions of polar side groups of the main polymer chain (β-relaxation). Finally, the slower process appearing at low frequencies and high temperatures, originates from interfacial phenomena due to the accumulation of unbounded charges at the system’s interface.     

Probing the multifunctional behaviour of barium zirconate/barium titanate/epoxy resin hybrid nanodielectrics

Journal of Thermal Analysis and Calorimetry - In this study, thermodynamic analysis of a supercritical closed Brayton cycle integrated with parabolic trough solar collectors operating with various...     

Ansa bis(fluorenyl) complexes as homogeneous catalysts for propylene polymerization

Preparation and characterization of new ansa-metallocene complexes containing two substituted fluorenyl ligands connected by an R₂E bridge (R = Me, Ph; E = Si, Sn) are reported. The complexes, activated with methylaluminoxane (MAO), polymerize propylene. The degree of stereospecifity of the propylene polymerization depends on the size of the hetero atom in the bridge and the position of the substituents.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2334–2339, September, 1996.     

Graphite nanoplatelets/polymer nanocomposites: thermomechanical,dielectric, and functional behavior

Exfoliated graphite nanoplatelets (GNP)/epoxy resin nanocomposites were prepared and tested, varying the amount of the filler content. Systems’ morphology was investigated by means of scanning electron microscopy, while their thermal response was examined via differential scanning calorimetry (DSC). Broadband dielectric spectroscopy and dynamic mechanical thermal analysis were employed in order to characterize the produced systems. Static mechanical tests were also conducted at ambient. Reinforced systems exhibit improved performance under mechanical and electrical excitation. In particular, storage modulus increases systematically with GNP content. DSC results imply that glass transition temperature is not affected by the presence of GNP. Flexural modulus and storage modulus, as determined by static and dynamic mechanical tests, respectively, increased with filler content. Dielectric permittivity increases also systematically with GNP content. Recorded relaxation processes arise from the glass to rubber transition of the polymer matrix (α-mode), re-orientation of polar side groups of the polymer chains (β-mode), and interfacial polarization because of the accumulation of charges at the systems’ interface. Finally, the energy storing efficiency of the nanocomposites enhances with reinforcing phase in the examined frequency and temperature range. Optimum performance corresponds to the nanocomposite with maximum GNP loading.     

Boron nitride/epoxy resin nanocomposites: development,characterization and functionality

Journal of Thermal Analysis and Calorimetry - Polymer matrix composites with embedded ceramic nanoparticles receive not only enhanced scientific but also technological interest, due to their...