Abstract

Three different polymer lattices (latexes) derived from natural rubber (NR), Acrylic (Ac) and Vinyl Acetate/Veova (VA/Ve) copolymer emulsions were blended to yield ten compositions using the principle of simplex lattice design, after adjusting their TSCs solids to 30% (v/v) by dilution with distilled water. The blends were characterized for the determinations of pH, conductivity and refractive indexes, after which they were used in formulating corresponding number of water-based adhesives. Adhesive joints were prepared in pairs for every formulation by bonding two wood pieces with the adhesive. One set was for curing in sun and the second in oven temperature conditions, respectively. Bond strengths of the cured joints were evaluated using a locally improvised tool due to lack of standard testing device. It was observed that the highest value of bond strength was obtained after sun curing for the adhesive based on the blend which contained NR, Ac and VA/Ve in the ratio of 1/6:2/3:1/6, respectively. This blend was thus regarded as “optimum blend”. It was generally observed that the bond strengths obtained after sun-curing process were always higher than similar values obtained for oven dried conditions. This suggested that sun-curing conditions are more suitable for curing the prepared adhesives than oven-curing conditions. Bond strength measured from adhesive joint similarly prepared using a popular commercial wood based adhesive (Top Bond) in Nigeria was also compared to bond strength of the adhesive based on the optimum blend as mentioned above. Interestingly, it was observed that the value of bond strength from the latter was more promising.

Key words: Ternary blends, latexes, simplex lattice design, substrates, adhesive joints, adhesive formulations.