Processing and rheology in thermoplastic and thermoplastic composites
Abstract
Polymer process design methodologies using design of experiments and simple empirical relationships between important process parameters and process performance criteria were developed. Thermoplastic pultrusion, single screw extrusion, and injection molding were studied to illustrate the application of the developed methodologies. The three processes considered represent different shear rate regimes. A model based on the power law viscosity-shear rate relationship was developed to predict the pulling force as a function of the pulling speed and temperature in pultrusion of the thermoplastic powder impregnated tows. Shear rate-temperature superposition principle was shown to be applicable for pulling force as a function of pulling speed and temperature in pultrusion of the thermoplastic powder impregnated towpregs made using the wet slurry process. The effects of the important process parameters on the process performance criteria were studied using statistical design of experiments in single screw extrusion and injection molding. In single screw extrusion, screw RPM and the three zone temperatures were the selected process parameters, while extruder output, melt temperature, and mechanical energy input were the selected performance criteria. In injection molding, injection speed, packing pressure, back pressure, and screw RPM were the selected process parameters, while tensile strength and impact strength were the selected performance criteria. Zone-3 temperature and screw RPM were observed to be the most important process parameters influencing the extruder output, melt temperature, and energy input in single screw extrusion. Packing pressure and injection speed were the most significant parameters affecting the tensile properties, while no process parameters affected the impact properties. Microstructural studies on the fracture surfaces of the long fiber injection molded tensile and impact specimen revealed that the number and location of the long fiber bundles with well coated individual fibers were the primary microstructural features affecting the tensile and impact behavior.
Degree
Ph.D.
Advisors
Ramani, Purdue University.
Subject Area
Mechanical engineering|Plastics
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