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Epoxy resin based on diglycidyl ether of bisphenol A and varying content of hydroxyl terminated polybutadiene (HTPB) were cured using a polyamide curing agent. The ultimate aim of the study was to modify the epoxy matrix by liquid rubber so as to improve its toughness. Tensile, flexural, and impact properties were evaluated. The morphological evolution of the toughened networks was examined by scanning electron microscope, and the observations were used effectively to explain the obtained impact properties.

Epoxy resins are widely utilized as high performance thermosetting adhesives. Polyamide cured epoxies provide improved flexibility, moisture resistance, and adhesion. Moreover, Versamid could provide lower viscosity, better compatibility, and better cure profiles under adverse conditions. Thus, the use of polyamide (Versamid 125) as a curing agent and HTPB as an elastomeric rubbery modifier give this study an importance in formulating adhesives to be used in high temperature applications. A systematic study has been conducted to investigate the modification of DGEBA-based epoxy systems by the incorporation of hydroxyl-terminated polybutadiene (HTPB) as an elastomeric rubbery modifier in different proportions (0.75, 1.5, 2.5, 5, and 10% by weight) into an epoxy resin. Mechanical mixing process, accompanied with vacuum to get rid of cavitations, was employed to disperse the particles homogeneously into the resin system. Thermal and mechanical properties of the composite and the neat resin were measured with DSC, Zwick universal test machine, and Zwick durometer hardness tester. The composite shows an improvement in stress, strain, shore D hardness, flexural and compressive values. Nearly 2.5% of HTPB was quite enough to obtain a compromise of the desired mechanical and thermal properties. The detected decrease in T g as the rubber content increases means that this modifier can enhance plasticity of the matrix. Reduction in the cross-linking density of the thermoset because of the added modifier has been confirmed and explained. KeywordsEpoxy resins/ Adhesives/ Modifiers/ Thermal and mechanical properties / HTPB.  Egyptian Armed Forces

Six copolymers based on acrylates were used as viscosity index improvers [1]. The effect of these copolymers on the rheological behavior such as viscosity thinning or thickening has been studied. A rheological study was carried out to SAE 30 base oil before and after adding the viscosity index improvers with different concentrations (1, 2, 3% wt). Brookfield rheometer model (DV-III+) was used with different shear rates and at different temperatures (40, 60, 100 ˚C), for characterization of the enhanced lubricant. It was noticed that Freeadditives Base oil exhibits a Newtonian behavior at all temperatures, on the other hand; all enhanced samples exhibit a weak non-Newtonian behavior that disappears with increasing either temperature or shear rate or both of them. The effect of temperature on specific viscosities of the blends under different shear rates was studied to determine the efficiency of viscosity index improvers and record its mechanism of action at different shear rates and temperatures.

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