Abstract
In this work, the effects of blend ratio and mixing time on the migration of multi-walled carbon nanotubes (MWCNTs) within poly(vinylidene fluoride) (PVDF)/polyethylene (PE) blends are studied. A novel two-step mixing approach was used to pre-localize MWCNTs within the PE phase, and subsequently allow them to migrate into the thermodynamically favored PVDF phase. Light microscopy images confirm that MWCNTs migrate from PE to PVDF, and transmission electron microscopy (TEM) images show individual MWCNTs migrating fully into PVDF, while agglomerates remained trapped at the PVDF/PE interface. PVDF:PE 50:50 and 20:80 polymer blend nanocomposites with 2 vol% MWCNTs exhibit exceptional electromagnetic interference shielding effectiveness (EMI SE) at 10 min of mixing (13 and 16 dB, respectively-at a thickness of 0.45 mm), when compared to 30 s of mixing (11 and 12 dB, respectively), suggesting the formation of more interconnected MWCNT networks over time. TEM images show that these improved microstructures are concentrated on the PE side of the PVDF/PE interface. A modified version of the “Slim-Fast-Mechanism” is proposed to explain the migration behavior of MWCNTs within the PVDF/PE blend. In this theory, MWCNTs approaching perpendicular to the interface penetrate the PVDF/PE interface, while those approaching in parallel or as MWCNT agglomerates remain trapped. Trapped MWCNTs act as barriers to additional MWCNTs, regardless of geometry. This mechanism is verified via TEM and scanning electron microscopy and suggests the feasibility of localizing MWCNTs at the interface of PVDF/PE blends.
Highlights
Wireless electronic devices have become a staple in our everyday lives which has led to a surge in electromagnetic (EM) radiation being emitted into the environment
Polymer nanocomposites (PNCs) with multiwalled carbon nanotubes (MWCNTs) have attracted great interest as conductive materials that can be used as electromagnetic interference (EMI) shields that attenuate incident EMI by absorbing it, reducing the amount of EM smog in the environment [12,13,14]
Light microscopy (LM) imaging was first performed on poly(vinylidene fluoride) (PVDF) and PE nanocomposites, to identify how MWCNTs disperse within each polymer
Summary
Wireless electronic devices have become a staple in our everyday lives which has led to a surge in electromagnetic (EM) radiation being emitted into the environment. Ji et al in particular [9] made use of Cu-Ni-carbon nanotube (CNT) open-celled foams, which relied on multiple reflections to attenuate incident EMI. These methods are limited by the need to use high concentrations of nanofiller and require expensive solution-based methods to synthesize. Polymer nanocomposites (PNCs) with multiwalled carbon nanotubes (MWCNTs) have attracted great interest as conductive materials that can be used as EMI shields that attenuate incident EMI by absorbing it, reducing the amount of EM smog in the environment [12,13,14]. Due to this prohibitively high cost, researchers have been investigating ways of reducing the amount of MWCNTs needed to create low-cost and high conductive PNCs
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