Browsing by Author "Lencar, Calin Constantin"

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    Phase Migration of Carbon Nanotubes in Melt-Mixed Immiscible Polymer Blend Nanocomposites
    (2022-10-27) Lencar, Calin Constantin; Sundararaj, Uttandaraman; Sathish, Ponnurangam; Egberts, Philip
    The growing demand for inexpensive and sophisticated electronics (e.g., sensors, medical devices, electromagnetic interference shields, etc.), has led to a need to develop robust commodity materials. Though metals have traditionally been used in electrical applications, polymer blend nanocomposites (PBNs) offer numerous benefits over metals, making them strong candidates for use as conductive materials. PBNs are typically immiscible and possess a phase-separated structure, which can have a significant impact on the final properties of the material. The main limitation facing the widespread application of polymer nanocomposites (PNCs) is the difficulty if effectively dispersing conductive nanofillers within polymeric systems. Multiwalled carbon nanotubes (MWCNTs) are a high aspect ratio nanoparticle with exceptional conductivity, thermal resistance, and tensile properties. and the dispersion of MWCNTs within polymeric systems is needed to achieve improvements in electrical and mechanical properties. In this thesis, the final localization of MWCNTs within immiscible polymer blends prepared via melt-compounding was tuned by controlling the migration of MWCNTs from one polymer phase to another. The goal was to achieve localization of MWCNTs at the polymer/polymer interface, and thereby greatly reducing the percolation threshold for MWCNTs within the PBN system. Two systems were studied to better understand the migration of MWCNTs within polymer blends: 1) effect of blend composition and mixing time on polyvinylidene difluoride/polyethylene (PVDF/PE) blends containing 2vol% MWCNTs, and 2) effect of MWCNT concentration and mixing time on co-continuous 40:60 blends of polyethylene oxide (PEO)/PE. Light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to study the blend morphology and MWCNT localization at the end of mixing. In both systems, MWCNTs were pre-localized in the PE phase, and migrated towards either PVDF or PEO with during subsequent melt-mixing, due to MWCNTs higher thermodynamic affinity for PVDF and PEO over PE. The premixing of MWCNTs within PE and their subsequent melt-mixing with the second polymer phase resulted in significantly different results between either study.