Kinzo Ishikawa

Mechanical properties of oriented polyvinylchloride composites filled with ultrafine particles

The tensile stress-strain behaviour of undrawn and drawn polyvinylchloride (PVC) composites filled with ultrafine SiO2 and micron sized glass particles were discussed as functions of filler content and size. For the undrawn PVC composites filled with ultrafine SiO2 particles, Youngs moduli, yield and breaking stresses increased with filler content and decreasing filler size. Whereas for the composites filled with micron sized glass particles, their Youngs moduli slightly increased with filler content but both the yield and breaking stresses decreased. Oriented PVC composites were made by uniaxially drawing to × 2.5 at 100 °C. Anisotropic mechanical properties of oriented specimens were discussed in terms of compliance tensor and yield stress measured in the direction of 0°, 45° and 90° to the original stretching direction at room temperature. In the case of 70A SiO2, all the compliance decreased with filler content, whereas those of 65μ glass, this relation was reversed. The yield stress of the oriented PVC composites showed filler size dependence similar to Youngs moduli. The anisotropic yield stress of oriented PVC composites were reasonably analysed by Hills yield criterion.

Reducible properties of draw temperature, rate of strain and filler content in tensile yield stress of polymethylmethacrylate filled with ultrafine particles

The yield stress of polymethylmethacrylate (PMMA) composites filled with ultrafine SiO2 particles was measured as a function of the draw temperature, rate of strain and filler content. The yield stress of the composites increased with increasing filler content and decreasing filler size. The tensile yield stress was found to be reducible with regard to draw temperature, rate of strain and filler content. At a given filler content, a master curve was obtained for the yield stress plotted versus the logarithm of the strain rate. The Arrhenius plot of the shift factors (aT) used to produce the strain rate-temperature master curve formed a single curve for all sizes and loadings of the filler. The master curves obtained for different loadings of a filler of given size could be further reduced into a master-master curve by shifting them along the axis of strain rate, with the logarithm of the second shift factors (logac) proportional to the 4/5th power of the filler volume fraction (Vf). The proportionality constant and the exponent represent the extent of the filler reinforcing effect in the polymer. These values were found to be correlated with the critical surface tension of the polymers.