S.C.S. Teixeira

Mechanical properties of polymer composites based on commercial epoxy vinyl ester resin and glass fiber

Abstract The effect of the addition of methyl ethyl ketone peroxide (MEKP) and cobalt naphthenate (CoNaph) on the mechanical behavior of epoxy vinyl ester resin (EVER) laminates has been investigated by using a factorial experimental design, in which the MEKP and NaphCo contents were varied. Previous results showed that there is an interaction effect between the process variables analysed on the mechanical properties evaluated. It was also observed that the MEKP/CoNaph ratio affected the tensile behavior of the EVER/glass fiber composites.

Polymers used as viscosity index improvers : a comparative study

Abstract Ethylene-propylene copolymers and hydrogenated styrene-diene copolymers were used for a comparative study aiming at their application as viscosity index improvers in multigrade engine oils. The variation of viscosity with temperature has been evaluated as a function of the polymer concentrations. The thickening effect of different viscosity index improvers and the dependence of reduced viscosities on temperature were determined. At concentrations lower than 3% (w/w) the viscosity/temperature characteristic suggested the occurrence of polymer coil expansion with temperature for hydrogenated styrene-diene copolymer. The direct dependence of mechanical stability on the copolymer molecular weight was observed.