Recently, the development of high-performance thermoplastic polymer composites has been a focus for the polymer engineering field. These polymer composites are formulated with polymer blends and alloys and various fillers. Twin-screw extruders can provide excellent mixing for these composites. The filler dispersion depends on processing conditions such as processing temperature, residence time, screw speed and screw profile. The physical properties of these polymer composites are also strongly dominated by the dispersion conditions of the filler.In this study, conductive carbon-nanotube (CCNT) was used as a filler and polycarbonate (PC) as the matrix polymer. The conductivity of these composites was measured and related to the dispersion of CCNT under different processing conditions. The dispersion was characterized by the dispersion ratio. The total shear strain [r • t ] , the product of shear rate [11 and residence time distribution [t ] , was used as a dispersion parameter.We can conclude that the filler dispersion depends on the processing parameters of the twin screw extruder. Moreover the filler dispersion can be related to the total shear strain [r • t ] which is one of the dispersion parameters. An optimized condition for conductivity in these carbonnanotube (CCNT) filled polymer composites can be determined by this correlation.
Clay nanocomposites of amorphous polymers with ester groups were prepared by twin screw extrusion and injection molding. Although, in general, an organophilic clay is required to form good nanocomposites, we succeeded in preparing nanocomposites with good clay dispersion by using natural clay without organophilic agents. In this study, PETG, an amorphous polymer with excellent clarity, was used as the matrix polymer. The resultant nanocomposites retained high transparency and clarity despite the 5% clay content. Flammability properties were measured using a cone-calorimeter. The heat release rate decreased 54% for the PETG/clay nanocomposites compared to the neat PETG resin and the phenomenon of molten droplets (dripping) does not appear during the combustion. Therefore, high flame retardancy has been achieved. Furthermore, the tensile modulus of the nanocomposites increased by 50% over the neat PETG modulus. The evaluation of WAXD patterns and TEM observations indicated that the silicate layers of the clay were not intercalated nor individually exfoliated. Partial exfoliation and a decrease in the number of layers were, however, indicated.
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