Carbon nano - tubes reinforced thermoplastics

The study of optimal manufacturing process of composites reinforced with carbon nanotubes has became a critical stage in the early phases of discovery of outstanding physical properties of carbon nanotubes. The increasing interest has been brought by rapid advancements in nanotechnology and composites manufacturing techniques. This master's thesis combines a study of two processes for manufacturing multiwall nanotubes reinforced polypropylene (PP) and characterization of physical properties of this composite. Shear mixing method and solution process are the techniques used to manufacture plates and thin films of composites containing different weight fractions of unpurified and purified multiwall nanotubes. The first method consists in processing the dry mixture of PP and nanotubes in a screw extruder and the second method uses ultrasound to improve dispersion of nanotubes in the matrix, through solvent medium. Solution process shows a better dispersion of the reinforcement in the matrix, but physical properties do not show significant improvements. With the purpose to investigate the addition of multi-functionality caused by carbon nanotubes, mechanical and electrical tests were performed. Mechanical properties, such as tensile strength, Young's modulus, fracture toughness, and Vickers hardness do not show relevant improvements. Electrical properties, such as shielding effectiveness and electrical conductivity, although are not so improved, show positive trends. The reason of this behavior is the poor adhesion at the interface carbon nanotube-matrix, caused by tendency of MWNTs to agglomerate in bundles, which create discontinuities in the final composite.Validerat; 20101217 (root