Extrusion foaming of polyethylene/nanoclay composites with supercritical carbon dioxide
Kwek, Darien Yu De
Date of Issue2019-05-15
School of Materials Science and Engineering
Singapore Institute of Manufacturing Technology (SIMTech)
This study investigated the nucleation efficiency of Cloisite15 nanoclay in a nanocomposite based on a polyethylene matrix and the usage of supercritical carbon dioxide as the physical blowing agent in an extrusion foaming process. A Cloisite15 masterbatch was successfully produced and the structural and molecular stability of the organo-surfactant in Cloiste15 was evaluated using the thermogravimetric analyser. The degree of intercalation/exfoliation between the polyethylene chains and nanoclay platelets were characterized using X-Ray diffraction and scanning electron microscopy techniques. A bimodal cell structure was obtained upon the foaming of the nanocomposite which was likely due to the simultaneous occurrence of both homogeneous and heterogeneous nucleation as well as the contrasting CO2 affinity of polyethylene and Cloisite15 respectively. Lastly, the appearance of micro voids in the polyethylene/nanoclay nanocomposite foams was presumably due to the extensional stresses experienced by the melt during the extrusion process which could have detached intercalated polyethylene chains between the nanoclay platelets.
Final Year Project (FYP)
Nanyang Technological University