CONICET | Buscador de Institutos y Recursos Humanos

The purpose of this work is to study the wear behavior of polyethylenes obtained by chemical modification of a low density ehtylene-octene copolymer. The study consists in determining the wear resistance of the material when sliding on steel and relating it to the molecular structure of the materials. A commercial ethylene-octene copolymer was modified by chemical attack using an organic peroxide to produce materials having different levels of molecular crosslinking. The modification process consisted in impregnate the copolymer with different amounts of dimethyl diterbutil peroxy hexane to give peroxide concentrations ranging between 0.08 and 3.5%wt. The materials were then compression molded between the hot plates of a hydraulic press to induce the modification reactions. The characterization of the polymers included the technique of solvent extraction to determine the gel fraction and calorimetric measurements to know the heat of fusion. The tribological properties were evaluated by performing block-on-ring wear tests. A block of the polymeric material is fixed with a known pressure to a curve surface of a steel ring that rotates at constant speed. The wear rate was estimated from the mass loss of the material. The friction force was measured during the wear test that allows determining the friction coefficient. It was observed that the gel content increases while the enthalpy of fusion does not present significant variation with the amount of peroxide added. The wear rate decreases with the peroxide added to the material, and this tendency is maintained with the two normal loads evaluated, of 3 and 5N. The wear rate increases with the normal load at a given peroxide concentration. The materials have similar coefficient of friction of about 1.1.

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