Despite of the great interest carbon nanotubes (CNTs) have aroused in engineering fields since their official discovery more than two decades ago, composite (polymer/CNT) applications are far beyond their potential spread. Due to their mechanical and physical properties, CNTs can work as reinforcement, thermal stabilizer and conductive network in a polymeric matrix. However, they are difficult to disperse since they easily form stable aggregates or bundles. Many research efforts went in the production of CNT composites for functional and structural applications and many processing methodologies have been experimented. Twin-screw extrusion appears to be the most realistic from the perspective of production scale up and commercialization of these composites. Nevertheless, despite of the massive literature about nanocomposites, few papers focus on the interaction between the compounding process and the following microinjection moulding transformation processes to obtain a final micro-device. This paper aims at analyzing the extrusion process configuration and correlated parameters in order to assess some characteristic and technological properties of resulting nanocomposites for micro-injection. Taking advantage of the modularity of a laboratory-scale twin screw extruder, two different combinations of screw elements have been tested to incorporate CNTs in a Polyoxymethylene (POM) grade typically used in micro-injection moulding. Indeed, the design of screw profile strongly affects the flow within the extruder and, consequently, the dispersion and distribution of the fillers within the matrix. The effects of the process set up and conditions have been observed studying the rheology and the electrical properties of the nano-composites as well as the mouldability of compound, evaluated in microinjected ribs characterized by very high aspect ratio. Moreover, the mechanical properties have been evaluated in miniaturized components obtained via microinjection moulding.
Effect of extrusion configuration on the properties of MWCNT/POM composites
BALDI, Francesco;Fassi I.
2014-01-01
Abstract
Despite of the great interest carbon nanotubes (CNTs) have aroused in engineering fields since their official discovery more than two decades ago, composite (polymer/CNT) applications are far beyond their potential spread. Due to their mechanical and physical properties, CNTs can work as reinforcement, thermal stabilizer and conductive network in a polymeric matrix. However, they are difficult to disperse since they easily form stable aggregates or bundles. Many research efforts went in the production of CNT composites for functional and structural applications and many processing methodologies have been experimented. Twin-screw extrusion appears to be the most realistic from the perspective of production scale up and commercialization of these composites. Nevertheless, despite of the massive literature about nanocomposites, few papers focus on the interaction between the compounding process and the following microinjection moulding transformation processes to obtain a final micro-device. This paper aims at analyzing the extrusion process configuration and correlated parameters in order to assess some characteristic and technological properties of resulting nanocomposites for micro-injection. Taking advantage of the modularity of a laboratory-scale twin screw extruder, two different combinations of screw elements have been tested to incorporate CNTs in a Polyoxymethylene (POM) grade typically used in micro-injection moulding. Indeed, the design of screw profile strongly affects the flow within the extruder and, consequently, the dispersion and distribution of the fillers within the matrix. The effects of the process set up and conditions have been observed studying the rheology and the electrical properties of the nano-composites as well as the mouldability of compound, evaluated in microinjected ribs characterized by very high aspect ratio. Moreover, the mechanical properties have been evaluated in miniaturized components obtained via microinjection moulding.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
