▼ Conducting polymer composites (CPCs) have been studied since the 1950’s and till date remain the focus of theoretical and experimental studies. With CPCs, the need often arises to preserve particular inherent properties of matrix and / or filler phase, such as mechanical, thermal or electrical properties in the final composite. Unfortunately, commonly used dispersion techniques fall short of assuring these goals because they alter the original polymer structure and require high filler loadings thereby compromising cohesive strengths, as is commonly observed with melt and solution mixing techniques. Even when component properties can be preserved and filler requirements are low, as in dry mixed systems, mechanical properties still remain poor. Therefore, a major challenge in processing CPCs is the need to balance high electrical conductivity with an acceptable mechanical performance, which sets the tone for this study. In this work, three commonly used blending techniques (dry, wet and complete solution methods) were optimized and the property results compared against a novel partial solubility mixing model based on the standard solubility parameter concept. The experimental design required a controlled swelling of the polymer particles, avoiding actual dissolution, such that filler particles of much smaller particle size can be embedded within the swelled polymer structure. The swelling parameter, developed as a function of mixing time, polymer particle size and solubility parameter, served as a useful tool for process control and property development. Powder compositions of poly(acrylonitrile butadiene styrene) and poly(styrene butadiene styrene) block copolymers were first classified into narrow size ranges. Using developed solvent solubility parameters (linked to swelling ratios), a controlled coating of conductive (graphite, polyaniline) and non-conductive fillers (alumina) was deployed over the polymer particles. These were dried and compression molded at 120-130°C and 110 MPa pressure for 5 minutes. Characterization was done by SEM (after fine polishing), compression testing and XRD analysis. A significantly low percolation concentration of 0.047 vol. % was obtained for a dry mixed composite when the mean polymer matrix/filler particle size ratio was ~90. As a result of the narrow particle size classification of blend components and the application of a novel dispersion technique, percent standard deviation was reduced to single digits. In the absence of particle size classification, the standard deviation was higher by a factor of 3 and 7. A percolation concentration of 0.23 vol. % was achieved for partial solution mixing, which value is a decade lower than that for solution mixing. Compressive yield strength, used as a measure of composite cohesion, was much improved under partial solution mixing, and at ~32 MPa, it was about 25 - 60 % higher than for other three mixing methods tested. The use of inert filler and the development of solubility parameter as processing aid in partial solution mixing were also effective tools in the reproducible control of electrical percolation and resulted in composites with high temperature coefficient of resistivity (TCR) of up to 5000 ppm/°C. High piezoresistive coefficients of up to -2.5 MPa-1 were also obtained for 5 wt. % graphite filled composites. Advisors/Committee Members: Buchanan, Relva.