A Method of Distinguishing Degree of Dispersion and Filler-Rubber Interaction in Silica- Filled Polyethylacrylate

Both the degree of dispersion and filler-rubber interaction affect mechanical properties of uncured compounds. Because the better dispersion offers a possibility of developing the enhanced interaction, the two effects are difficult to separate. However, under certain conditions of mechanical measurements, one effect dominates the other. This study seeks such conditions. The silica-polyethylacrylate system was selected for two reasons: 1. The same partical-size silicas are available in forms that give different degrees of dispersion after the same mixing procedure is followed. 2. In some of the samples, a heat treatment significantly enhances the filler-rubber interaction. Dynamic mechanical measurements are, in general, ineffective for separating the two effects. In tensile stress-strain measurements, the effect of dispersion dominates the behavior at relatively small strains and the effect of interaction dominates at larger strains. Qualitatively speaking, the above observation has been recognized, and the approaches in this study offer quantitative means. Direct comparisons of tensile stress-strain curves are not easy; however, the conversion of the data into strain amplification makes it more lucid.