Tesis: Mechanical and Structural Properties of Highly Loaded Carbon Nanotubes/Polyamide 6 Composites

Abstract: Recently, carbon-based (e.g. carbon fibers) materials have been attractive to many industries and agencies such as automotive, aerospace, industries where sport equipment is manufactured, Department of Defense, and Department of Energy. These materials can show greater mechanicals properties and also can be lighter than steel and many other alloys. Carbon nanotubes are carbon-based materials that present unique chemical and mechanical properties, such has a sp2 hybridization and an elastic modulus of about 1 TPa, which make them a good prospective to replace the carbon fibers. Reported studies have shown how carbon nanotubes can be used as fillers in different polymeric matrices such as epoxy, polyether ether ketone, polycarbonate, polyamides, and others. However, obtaining a good dispersion of carbon nanotubes in the matrix is quite challenging because their electrostatics forces make them to form agglomerations between them. In order to get a better bonding between the carbon nanotubes and the polymer matrix, many researchers have tried to functionalize the carbon nanotubes surfaces. However, functionalization of the carbon nanotube surfaces might end in reduction of their chemical and mechanical properties. In this study, non-functionalized carbon nanotubes/polyamide 6 composites were fabricated using an innovative type of solid-state method. Higher concentrations of carbon nanotubes (40-65 wt%) than the previously reported were used to create the composites. In addition, reaching higher temperatures than the melting point of the polymer and applying some pressure during the processing was found to have an effect on their final structure. For this reason, two different temperatures (280-300 oC), and two different pressures (5 and 10 MPa) were studied. Higher polyamide 6 degradation was found for the samples processed at 300 oC and under air atmosphere than for the samples processed at 280 oC and under nitrogen atmosphere. Furthermore, higher number of defects was found for those composites that a pressure of 5 MPa was applied, in comparison to the ones that were processed applying a pressure of 10 MPa. An improvement in the polyamide 6 mechanical properties, such as the hardness and the elastic modulus, was found after adding some amount of carbon nanotubes.