Structure development in silicate-layered polymer nanocomposites

Abstract

The demands made of materials have resulted in the formation of complex composite structures; one such example of these is nanocomposites. This study is primarily devoted to the preparation and characterisation of nanocomposites. Reactively cast and reactively extruded nanocomposite strategies for the preparation of polyamide-6 composites were compared. The catalyst and activator system selected was based on an industrially successful combination. The extruder screw and barrel configuration used had previously been proven effective for the reactive polymerisation of polyamide-6. The principal objectives were the investigation of the influence of layered-silicates on both the microstructure and the physical properties of the composites. As well as the analysis of the mechanisms that influence the physical performance of the materials produced. The characterisation of the filler-matrix microstructure and its effect on physical properties of the composites were investigated using a range of chromatographic, microscopic, thermal and X-ray analytical techniques. Selected mechanical properties were measured using standard test procedures. Therefore results obtained and subsequent trends observed in reaction cast and reaction extruded nanocomposites could be compared and contrasted. The influence of the polymerisation conditions, residual monomer content and the nature of the composite structure produced were considered. It was observed that the nature of the matrix crystalline structure could be greatly influenced by the material composition, method of preparation and processing technique. The crystal form of the spherulites present appeared to be the key factor in influencing mechanical strength. The treatment of the silicate-layered clay successfully increased the inter-layer spacings, which was further increased by the presence of high shear forces.