Effects of reinforcement grain size and concentration on the physicomechanical properties of green automotive brakepads from waste cowhorns and rockshells

This study presents the development and characterization of green automotive brakepads using cowhorn (CH) and Rockshell (Thias Coronata L.) (R) as reinforcement material in full factorial experiments. The brakepads were produced by compression moulding at 220.73N using epoxy resin binder, CaCO3 fillers, Diethylenetriamine hardener, colourless methyl-ethyl ketone peroxide (MEKP) catalyst, carbon black friction modifier, with copper and iron fillings as thermal conductivity additives. Three levels of particle grain sizes 125, 250, 500µm were produced from each material. Hybrid CHR samples were also produced with same grain sizes. The density, hardness, and compressive strength properties were observed to reduce with increase in grain size while liquid absorption increased with increase in grain size. Impregnating the reinforcement materials with increasing concentration of R-particles improved the hardness, compressive strength and liquid absorption but decreased the friction coefficient. The R-samples performed best among all in liquid absorption, except for oil absorption where the commercial (control) sample surpassed it. EDX spectroscopy results showed presence of antimony and vanadium toxic heavy metals in the control sample unlike the developed brakepads. All properties measured exhibited multivariate quadratic regression models with good fitness of R2-values, 0.8438 ≤ R2 ≤ 0.9976, and significance-F values, 0.000398 ≤ significance F. ≤ 0.18101. All response surfaces showed best performance with R-concentration of 80 – 100% and 125 – 250µm grain size ranges. Hence, reinforcements of cowhorn and rockshell particles with concentration and grain sizes above can be used to develop brakepads with properties superior to the toxic control brakepads.