Rheological, interfacial and morphological changes produced by fillers in immiscible blends

The work presented next is focused on the combination of two major polymer fields: polymer blends and composites. The goal was to use the established interphase concepts to obtain composites with desired properties to enhance the compatibility of immiscible blends. However, during the course of this work a new mechanism of property enhancement was established.; An extensive study of the effect of the particle size, filler concentration and filler surface treatment on the immiscible polymer blends at different ratios is described. Basically two polymer blends are studied, polypropylene-polystyrene and polystyrene-poly(methyl methacrylate) and two fillers, glass beads and fumed silica, are used.; The enhancement of the compatibility is achieved by two different mechanisms. The first mechanism is through interphase control by surface treatment of large particles, such as glass beads. The filler surface is treated in order to promote an interaction of both blend components with the filler surface. Through such interaction a new compatibilized interphase near the filler surface is originated. Therefore, the silane coupling agent selection is very important, since it should promote interaction of both polymers with the filler, as described in Chapter 2. The behavior of polypropylene-polystyrene and polystyrene-poly(methyl methacrylate) blends as a function of filler content and blend composition is extensively studied in Chapters 3, 4 and 5.; The second mechanism is not due to surface treatment but due to filler-filler interaction when the particle size is very small. As the filler concentration starts to increase a filler network is formed, when a polymer preferentially adsorbs onto the filler network the adsorbed polymer have the same pattern originating a polymer network superstructure. As one blend component forms a network the other one is left to fill the remaining space, resulting in a much more homogeneous and smaller phase separation system, as described in Chapter 6.; The properties are monitored in solid and melt state. The morphology is observed using scanning electronic microscopic technique. The glass transition is presented from the storage moduli of dynamic mechanical spectra, and its activation energy is also calculated. The complex viscosity behavior is discussed. The degree of crystallinity and the tensile strength of the systems are also considered.