Abstract

Defined quantities of the vegetable oil extracted from the seed of Neem tree were mixed with each of four commercial grades of Nigerian gum arabic exudates as hybrid binders for foundry sand cores. The cores which were made with silica sand were classified and oven baked at 200°C for 1 - 3 h, oven cooled and then tested for tensile strength using standard universal strength machine to ascertain their level of suitability for industrial casting. The specimens for tensile strength were shaped like figure eight. The result showed that grade 2 gum arabic hybrids with Neem oil offered best economic advantage as it attained required tensile strength after the shortest period of baking. It was followed by the grade 4, grade 1 and then grade 3 gum arabic based hybrids with Neem oil in that order. The benefit of hybridizing Nigerian gum arabic exudates with Neem oil was more pronounced when cores were baked at about the melting temperature of the grade of gum arabic involved. Baking cores below the melting point marginally improved bond strength while baking them at temperatures well above melting point depressed tensile strength.

Key words: Neem oil, gum Arabic, hybrid binder, tensile strength.