Filler particle size and mechanical properties of polymers



Literature data for the effect of mineral fillers on the mechanical properties of polyethylene at two temperatures, styrene–butadiene rubber, and natural rubber were examined. The data for modulus, tensile strength, elongation at yield, and ultimate elongation could be well represented by linear plots of the relative mechanical property (ratio of the values for the filled to the unfilled) as functions of the reciprocal of the filler particle size. A plot of one of these properties versus reciprocal filler size shows a family of lines, one line for each concentration of filler, and independent from the chemical nature of the filler. The dependence of the mechanical properties on reciprocal particle size may express a dependence on the surface-to-volume ratio of the filler, a balance between the effective cross-linking due to the large surface area of the filler, and the dilution of the polymer by the volume of filler present.