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The possibility of obtaining relatively high dielectric constant polymer-ceramic composite by incorporating the giant dielectric constant material, CaCu 3 Ti 4 O 12 (CCTO) in a Poly(vinylidene fluoride) (PVDF) polymer matrix by melt mixing and hot pressing process was demonstrated. The structure, morphology and dielectric properties of the composites were characterized using X-ray diffraction, Thermal analysis, Scanning Electron Microscope, and Impedance analyzer. The effective dielectric constant ( eff ) of the composite increased with increase in the volume fraction of CCTO at all the frequencies (100 Hz to 1MHz) under study. The dielectric loss did not show any variation upto 40 % loading of CCTO, but showed an increasing trend beyond 40%. The room temperature dielectric constant as high as 95 at 100Hz has been realized for the composite with 55 Vol % of CCTO, which has increased to about 190 at 150 o C. Theoretical models like Maxwell's, Clausius-Mossotti, Effective medium theory, logarithmic law and Yamada were employed to rationalize the dielectric behaviour of the composite and discussed.

Natural rubber was reinforced with sisal and oil palm fibers and was subjected to dynamic mechanical analysis to determine the dynamic properties as a function of temperature. The storage modulus E was found to increase with weight fraction of fiber. This is due to the increased stiffness imparted by the natural fibers. Loss modulus increased with loading while the damping property was found to decrease. The fibers were subjected to alkali treatment of different concentrations namely 0.5, 1, 2, and 4% and the dynamic properties were studied. In the case of composites containing chemically modified fibers, storage modulus and loss modulus were found to increase. Scanning electron micrographs of tensile fracture surfaces of treated and untreated composites demonstrated better fiber-matrix bonding in the case of the former. POLYM. COMPOS., 27:671-680, 2006. a 2,2,4 trimethyl-1,2-dihydro quinoline. b N-cyclohexylbenzothiazyl sulphenamide.

Abstract. The dynamic mechanical properties such as storage modulus, loss modulus and damping properties of blends of nylon copolymer (PA6,66) with ethylene propylene diene (EPDM) rubber was investigated with special reference to the effect of blend ratio and compatibilisation over a temperature range -100°C to 150°C at different frequencies. The effect of change in the composition of the polymer blends on tanδ was studied to understand the extent of polymer miscibility and damping characteristics. The loss tangent curve of the blends exhibited two transition peaks, corresponding to the glass transition temperature (Tg) of individual components indicating incompatibility of the blend systems. The morphology of the blends has been examined by using scanning electron microscopy. The Arrhenius relationship was used to calculate the activation energy for the glass transition of the blends. Finally, attempts have been made to compare the experimental data with theoretical models.

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