Mechanical properties of poly(vinyl chloride) filled with silica particles
In general, the yield stress of a ductile polymer is decreased by incorporating filler particles. The effects of particle shape, size, content and changes in the adhesion of particle/matrix interfaces on the yield stress were investigated qualitatively in silica particle-filled poly(vinyl chloride). For this purpose, spherical and irregular-shaped silica particles having different mean sizes, ranging from 2 - 50 μm, were incorporated. The particle contents were 6 and 16% by volume. In the untreated silica-filled resins, the yield stress decreased with increasing particle content and size. The yield stress was higher in the irregular-shaped than in the spherical particle silica-filled resins. The particles were treated with y-aminopropyl methyldiethoxysilane as a silane coupling agent to improve the adhesion of the particle/matrix interfaces. The yield stress was increased by the treatment and the tendency was more noticeable in the irregular-shaped than in the spherical systems. That is, the yield stresses of the treated irregular-shaped silica systems were higher than that of unfilled poly(vinyl chloride) and they were independent of particle content within the measured range. It was confirmed that the yield stress of the particle-filled composite was affected by the above factors and the importance of particle shape and the adhesion of particle/matrix interface were particularly noteworthy.