Characterization and tensile modulus modeling of conductive resins

Engineering thermoplastics are being increasingly used in the electronic/electrical market. This market calls for materials that are electrically and thermally conductive, as well as having shielding properties. Polymers are inherently nonconducting materials; and therefore, conductive fillers must be added to the polymer. Single-filler and multiple-filler composites have been introduced to increase the conductivity and shielding of thermoplastics. Previous studies have been conducted concerning conductive resins, but these studies were mainly concerned with the electrical, thermal, and shielding properties of the composites. This project is focused on examining the mechanical properties of these materials. The conductive resins must be easy to process and possess reasonable mechanical strength properties if they are to be a useful composite.; The main objective of this project is to develop a model to predict the tensile modulus of short fiber and particle-filled thermoplastics. Single-filler and multiple-filler composites will be modeled so that not only will the model predict the single-filler composites' tensile modulus, but will also predict the synergistic effects of the multiple-filler composites' tensile modulus. Three different types of thermally and electrically conductive fillers (carbon black, synthetic graphite, and carbon fiber) in nylon 6,6 and polycarbonate matrices were produced and tested. A 23 factorial design was created with these filler in order to efficiently examine the synergistic effects of the fillers. Current models were first examined to determine their deficiencies.; For this work, numerous mechanical property test were performed, including tensile testing, notched Izod impact testing, and melt flow index measurement. In addition, characterization of the fillers was performed. Using optical microscopy and image analysis software, the length, aspect ratio, and orientation of the fillers was examined. Also, a vibrated bulk density test was performed, which indicates the filler packing.; The results of the factorial design analysis showed that combinations of conductive fillers produced a significant synergistic effect on all measurements. Additionally, the multiple-filler tensile modulus results were modeled using a newly formulated model based on the Nielsen single-filler model. This new model accounts for the difference between the actual packing fraction and a theoretical value using the ratio between the experimental and theoretical vibrated bulk densities of multiple-filler combinations.