ABSTRACT: I will present a nano-fibril composites technology that has been invented at the University of Toronto. This technology enhances the mechanical properties and the foaming ability of various resins.
In situ fibrillation of a variety of polymer blend systems, namely poly(lactic acid) (PLA)/ polyamide 6 (PA6), polypropylene (PP)/ polytetrafluoroethylene (PTFE), PP/ polyethylene terephthalate (PET), and metallocene polyethylene (mPE)/PP, was performed. High draw ratios which were experienced by the blends during the stretching process (via melt spinning or hot stretching of the as-extruded blends at the extruder’s die exit) transformed the dispersed phases from their initial spherical shapes into fully stretched micro/nano-fibrillar domains. Morphological characterizations of the compression molded in situ micro/nano-fibrillar composites confirmed that the dispersed phases were in the form of fully-stretched and well-dispersed fibrils. The inclusion of the in situ fibrillated dispersed phases substantially improved the matrices’ crystallization behaviors. In case of the PLA/PA6 composites, the improvements in the crystallization behaviors led to a significant increase in the PLA’s tensile properties. Crucially, it was observed that both the stiffness and the deformability of the PLA were improved which led to a significant increase in its tensile strength. Studying the linear viscoelastic behaviors and the extensional viscosities of the compounds showed that the physical entanglement of the long micro/nano-fibrils led to their rheological percolation (gelation), which substantially improved the matrices’ melt strengths and elasticity. The gelation occurred at a nano-fibril concentration of nearly 2-5 wt.% depending on the type of the dispersed phases. The improvements in the matrices’ melt elasticity and melt strengths led to significant improvements in their foaming behaviors. The facile and cost-effective processes which were used for the production of the micro/nano-fibrillar composite blends makes this approach ideal for the improvement of the properties of a wide variety of thermoplastics.
Bio-Sketch: Dr. Chul Park is Distinguished Professor of Microcellular Engineered Plastics at University of Toronto. He has an international recognition in the polymer foaming area. Prof Park has published more than 1000 papers, including over 300 journal papers and four books. Prof Park serves as the Editor-in-Chief of the Journal of Cellular Plastics, and sits on the Advisory Editorial Board of several international journals. He has chaired numerous conferences and workshops including Biofoams Conference and the PPS Americas Conference 2012. He has been inducted into 4 academies (the Royal Society of Canada, the Canadian Academy of Engineering, the Korean Academy of Science and Technology, and The National Academy of Engineering of Korea), and a fellow of 5 other professional societies. He has received over 70 awards.