Development of carbon-based polymer nanocomposite powder for selective laser sintering

• Main Author: Sim, Derek Jia Shu
• Other Authors: Zhou Kun
• Format: Final Year Project
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/65214
• Institution: Nanyang Technological University

The works of additive manufacture (AM), most commonly known as 3D printing, have gain much attention in the recent decade and selective laser sintering (SLS) is one of the most established additive manufacturing process. SLS is a free-form additive powder-based process that utilizes an infrared laser to fuse polymer powder layer by layer into three-dimensional parts. This method of manufacturing allows greater flexibility in design and the applications are boundless. However, materials available for SLS are limited and those that are available are unable to meet to property requirements of a variety of applications. There is need to look into polymeric nanocomposites to produce laser sintered parts that meets the property requirements and to develop a method to prepare PNC powder for SLS process. It is important to understand the functionalization of carbon nanotubes (CNTs) and the effects it has during the laser sintering process. However, the potential of CNTs application is limited by the difficulties associated with entanglement due to its high aspect ratio. This poses a problem as the performance of PNCs depends greatly on the uniformity of dispersion of CNTs across the polymeric matrix and the adhesion between the polymer and the added nanofillers. In previous studies, surfactant has been used in the application of thin film transistor to disperse nanoparticle. Thus, similar application could be used to reduce the CNTs agglomeration. If uniform dispersion of CNTs is achieved on the polymeric matrix, laser-sintered component will be able to attain higher density due to increased thermal conductivity of PNCs as compared to neat polymer. This is because the increased thermal conductivity would distribute heat from the laser more evenly resulting in thorough melting and the reduction in voids cause by non-melted polymer powder. The presence of CNTs bundles also translates to hot spots that cause more voids and distortion. Voids in laser-sintered part are undesirable as they are stress concentrators that weaken the part. Thus, a laser-sintered part with no voids has an absence of critical points, resulting in superior mechanical properties.