Physical, Mechanical and Chemical Aging of Polyurea Nanocomposites

Two component polyurea systems, on one hand, are gaining popularity as corrosion and abrasion resistant coatings and linings while on the other hand there are a few polyurea compositions being used as barrier against blast and ballistic threats to protect nation\u27s critical infrastructure. Physical properties of polymer composites can be tailored with appropriate choice of type, size and amount of reinforcement. In general, nano-sized reinforcements provide better reinforcing over conventional reinforcements due to higher surface to volume ratio. In this dissertation, the first aim is to study effect of nanoreinforcement addition on the overall character (mechanical, chemical and microstructural) of different polyurea systems. Control tensile strength, dynamic mechanical and nanoindentation properties of these composites are used as parameters to rank the mechanical performance of these composites. Evaluation of synergistic effects of various environmental factors such as temperature, humidity, light, etc. on the performance of composite materials is the second challenge addressed in this research work. Selective composites are subject to hygrothermal cycling and ultraviolet (UV) radiation and stabilities studies for long durations. The severity of the effect of these exposures are measured in terms of the tensile strength of composites at predetermined time intervals. Change in the chemical makeup of these composites due to hygrothermal and UV exposures is studied using Fourier transformed infrared (FTIR) spectroscopy. Atomic force microscopy (AFM) is used to study the changes in polyurea microstructure due to addition of nanoreinforcements and subsequent aging. Long term mechanical performance of polyurea nanocomposites is evaluated using time temperature superposition (TTS) principle. Effects of different amounts of nano reinforcement on the elastic properties in polyurea nanocomposites are studied using molecular dynamics (MD) simulations