Veli Deniz

Effect of gamma irradiation conditions on the radiation-induced degradation of isobutylene–isoprene rubber

Abstract The effect of gamma irradiation conditions on the radiation-induced degradation of uncrosslinked, commercial isobutylene–isoprene rubbers has been investigated in this study. Influence of dose rate and irradiation atmosphere on the degradation of butyl rubber has been followed by viscosimetric and chromatographic analyses. Limiting viscosity number of all butyl rubbers decreased sharply up to 100 kGy and leveled off at around the same molecular weight, independent of dose rate. Slightly higher decrease in viscosity was observed for samples irradiated in air than in nitrogen especially at low dose rate irradiation. Cross-linking G(X), and chain scission G(S) yields of butyl rubbers were calculated by using weight- and number-average molecular weights of irradiated rubber determined by Size Exclusion Chromatography analyses. G-value results showed that chain scission reactions in isobutylene–isoprene rubber in air atmosphere are more favorable than in nitrogen atmosphere, and that lower dose rate enhances chain scission over cross-linking.

Effects of initial fiber length and fiber length distribution on the properties of carbon-fiber-reinforced-polypropylene composites

In this study, short carbon fiber-reinforced polypropylene composites with three different initial carbon fiber lengths were prepared by using extrusion compounding and injection molding techniques. The physical and morphological properties of the prepared short carbon fiber-reinforced composites were investigated by means of tensile test, differential scanning calorimetry and scanning electron microscopy. Final fiber length distributions of composites were also determined by using an image analyzing program. It was found that the maximum number of fibers was observed in the range from 51 to 100 µm. Number average final fiber lengths were calculated between 230 and 280 µm. Regardless of the used initial carbon fiber length, tensile strength and modulus values of the composites increased with the increasing carbon fiber content. It has been concluded that the initial fiber length at the studied range did not have any significant effect on the properties of composites.

Interphase Modification and Compatibilization of Rubber Based Blends

Blending of two or more elastomers is carried out for several purposes. The properties of an elastomer blend depend strongly on its state of compatibility and miscibility. In this chapter, recent advances on development of interphase modification and compatibilization of rubber-based blends are summarized. Current trends in compatibilization of rubber/rubber blends, TPEs and other rubber/thermoplastic blends, natural polymer blends, rubber-based blends with and without filler modification are discussed in detail. Finally, new challenges and opportunities of rubber-based blends are given.

FATIGUE PROPERTIES OF NYLON 66/POLYESTER HYBRID CORDS

Abstract In this study, the fatigue and mechanical properties of Nylon 66/Polyester (Ny 66/PET) hybrid cords and Ny 66 and polyester reference cords which are being used in tire industry were studied. The most effective parameters and the optimum twist levels were determined for the fatigue performance of Ny 66/PET hybrid cords. Taguchi design of experiment method is used to minimize the required number of experiments. Different sets of nylon and PET reference cords were prepared in order to make a comparison of fatigue performance. The selected process parameters for Taguchi experimental analysis were Ny 66, PET, and cable ply twist levels. The effects of the selected parameters were investigated. It was found that the most effective factor was cable twist level and better fatigue resistance for hybrid cords with high cable and PET ply twist level can be obtained.