Good Dispersion State Research Articles

Electrical and dynamic mechanical behavior of carbon black filled polymer composites

The effect of processing conditions on the electrical and dynamic behavior of carbon black (CB) filled ethylene/ethylacrylate copolymer (EEA) composites was investigated. The compounds were prepared by two methods, solution blending and mechanical mixing. Compared with the solution counterpart, the mechanical composites have a strong positive temperature coefficient (PTC) effect and a high dynamic elastic modulus, which results from the good dispersion state of carbon black in EEA, i.e. the strong interaction between carbon black and EEA. It can be concluded that the strong interaction between polymer and carbon black is essential for composites to have a high PTC intensity, good electrical reproducibility and high dynamic elastic modulus.

Synthesis of hydrous SnO2 and SnO2-coated TiO2 powders by the homogeneous precipitation method and their characterization

Hydrous SnO2 and SnO2-coated TiO2 powders were synthesized by the homogeneous precipitation method using urea and the products were characterized by X-ray diffraction, thermogravimetry, differential thermal analysis, scanning electron microscopy and energy- dispersive X-ray microanalysis. Electrical conductivities were measured with an impedance analyser. Hydrous SnO2 powder prepared under conditions without SO42− ions was a bulky product containing 75 wt% of water. The addition of SO42− ions to the solution changed bulky hydrous SnO2 to a dense product; approximately spherical particles were obtained with an average particle size of 0.14 ± 0.03 μm. with 13.5 wt % of absorbed water. Antimony-doped hydrous SnO2 prepared under conditions with SO42− ions consisted of approximately spherical particles with an average particle size of 0.17 ± 0.04 μm with 15.0 wt % of absorbed water. Hydrous SnO2-coated TiO2 powders with a good dispersion state and with various Sn/Ti ratios were prepared under conditions with SO42− ions. All the as-prepared coated powders were white, but the products doped with Sb3+ ions were turned to pale blue by heat treatment at 600° C for 1 h and their electrical conductivities increased by orders of about 3.0 in comparison with those of the other two.