Development of PVC based polymer nanocomposites

This thesis investigates the development of polyvinyl chloride (PVC) materials reinforced with nano-scale calcium carbonate particulates (PVC/CaC03). The research primarily focuses on the effect of nanoparticle addition on the mechanical properties of the composite. In addition, the thesis also investigates the use of titanate coupling agent to improve nanoparticle dispersion and its subsequent effect on the mechanical properties of the composites.PVC nanocomposites of varying nano-sized calcium carbonate particulate fractions were processed using several different techniques, and both with and without a titanate coupling agent. TEM images indicated that good particle dispersions were obtained when the PVC nanocomposites were processed with the two-roll mill. Particle agglomerations were observed when the nano-CaC03 particles were directly incorporated during PVC processing using an extruder. However, when titanate was used, the level of agglomeration can be reduced in composites processing using extruder or two-roll mill.Tensile tests, dynamic mechanical analysis, Charpy impact tests and fracture toughness tests were used to determine the static and dynamic properties of PVC nanocomposites. The presence of nanometersized CaC03 particles slightly decreased the tensile strength but improved the impact energy, modulus and fracture toughness. PVC matrix cavitations around the particles can be seen in the fracture surface of the test specimens, which is believed to be responsible for the enhanced toughness. The addition of titanate coupling agent improved tensile strength slightly but decreased the composite modulus and fracture toughness. Fracture surface examinations also showed that the use of titanate coupling agent improves the particle-matrix bonding which suppresses cavity formation; this confirmed the significance of cavitation in the deformation mechanism of the PVC nanocomposites. A microstructure-based finite element modelling of elastoplastic deformations around a weakly-, moderately- and strongly-bonded particle were conducted to investigate the deformation mechanisms.In summary, the study clarifies the benefits of using nano-CaC03 particles to improve the mechanical properties of PVC for engineering applications. Specific formulations produced improved properties over m-PVC without the use of expensive impact modifiers. Furthermore, the study outlined a commercially viable method using a titanate based coupling agent to resolve the agglomeration issues