Faruk Öksüzömer

Effects of various polyolefin copolymers on the interfacial interaction, microstructure and physical properties of cyclic olefin copolymer(COC)/graphite composites

In this study, effects of various types of functional polyolefin copolymers (FPOCs), poly(isobutylene-alt-maleic anhydride), poly(maleic anhydride-alt-1-octadecene) and poly(ethylene-graft-maleic anhydride), on the microstructure formation, interfacial interaction and physical properties of cyclic olefin copolymer (COC)/graphite composites were investigated. The COC/graphite composites were prepared in a lab. scale twin screw extruder. Microstructural features of samples were studied in a field emission scanning electron microscopy (FESEM). Viscoelastic properties of samples, obtained from the rheology tests in melt state and the dynamic mechanical analysis in solid state were used to quantify interfacial interactions between the COC and graphite depending on the types of FPOC. The average aspect ratio (Af) values of graphite flakes in the COC phase were determined about 40–65 by SEM observation and image analysis study on the samples prepared with different types of FPOC. Based on the gas permeability measurements, tortuous diffusion model suggested that the Af values of graphite flakes varied between 40 and 80 depending on the amount of graphite. It was shown that the poly(isobutylene-alt-maleic anhydride) copolymer provided relatively higher interfacial interaction between the COC and graphite flakes than the other FPOCs.

Preparation of MgAl2O4 by Modified Sol-Gel Method

Magnesium aluminate spinel (MgAl2O4) has refractory and structural applications since it has high melting temperature (2135°C), high resistance to chemical attack and mechanical properties [1, 2]. Magnesium aluminate spinel is also used as catalyst support. Especially promoted platinum and platinum-tin catalysts supported on magnesium aluminate spinel have good activity and stability for light alkane conversion reactions [3]. Thus, the synthesis of high purity MgAl2O4 is an important issue. Magnesium aluminate spinels have been prepared by methods including precipitation, coprecipitation, spray drying, freeze drying, hydrothermal synthesis, spray pyrolysis, alkoxide (solgel) method. In this respect, sol-gel synthesis provides an alternative route to the conventional solid state reaction method. This method of preparation allows the use of low temperatures, a high degree of homogeneity and purity and thus improves the ceramic powders sinterability properties.