Nano-carbons and other nanomaterials have been long studied for their potential to provide exceptional enhancements and multifunctional properties in composites. However, these promised composite improvements have remained far below theoretical predictions. Prior work has shown that the limitations primarily come from the poor dispersion during processing and weak polymer-nano interactions, which lead to defective structures in the composite.
In this research work, the fundamental issue of dispersing CNTs within a polymer matrix is addressed by studying a non-solvent induced liquid-solid phase separation process in polymer/CNT composite systems. By employing phase separation, uniform dispersion of CNT in the polymer was achieved and the interacting polymer-CNT phase was separated as a blend. Experimental, theoretical, and computational studies were performed to show the fundamental mechanism behind blend formation and to understand the specificity of preferential polymer-CNT interactions. A geometric dependence described by a “cylinder-in-sphere” model was established between the critical CNT bundle size and polymer radius of gyration, which dictates preferential polymer-CNT interactions. This model represents the interactive relationship required to form a blended polymer-CNT phase in the system under the phase separation conditions used.
Understanding the use of phase separation as well as this geometrical dependence between filler and polymer is important to resolve CNT dispersion issue. The harvested polymer-CNT blended phase was further incorporated into high-performance composite fibers with a customized spinning dope preparation procedure. Detailed analyses regarding the fabricated composite microstructures were performed to fundamentally understand the structure-process-property relationship. The contributions of this research work provides new insights into fabrication of high-performance polymer/CNT composites.
Prof. Marilyn Minus is currently a professor and associate chair for Graduate Studies and Research in the Department of Mechanical and Industrial Engineering at Northeastern University in Boston. She is also the director of the Macromolecular Innovation in Nano-materials Utilizing Systems Laboratory otherwise known as the MINUS-lab. She received her B.S. and Ph.D. from the Georgia Institute of Technology in the area of polymer, textile, and fiber engineering. Prof. Minus’ research is focused on addressing sustainability issues with the goal of producing energy-efficient lightweight materials. Another focus of her research is toward understanding natural hierarchical systems in order to design and fabricate structural materials. These materials are based on bio-polymer and high-polymer nanocomposites. The fundamental aim for Prof. Minus’ research is to understand phenomena associated with polymer/nano-filler structural development in the composites during processing procedures. This research work expands the scientific and technological base for understanding the manipulation of nano-scale matter during composite fabrication as it pertains to building mechanically superior materials. Her research interests also include structure-property relationships in polymer-based nano-composites, control of interfacial morphology and molecular interactions between the polymer and carbon nano-materials, as well as control of interphase structures and morphology in polymer-based hybrid materials. Both the technical and education research work in the MINUS lab has been supported by ~$9M in funding to date from agencies including NSF, AFOSR, ARO, and DARPA. Prof. Minus has published more than 40 scientific publications and presented over 30 conference papers in the area of polymer-based nano-composites. She is also the recipient of the NSF CAREER award. She is currently a member of the American Chemical Society (ACS), Materials Research Society (MRS), Society for the Advancement of Material and Process Engineering (SAMPE), and the Society of Plastics Engineers (SPE).
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Sponsored by the Department of Aerospace and Mechanical Engineering