Abstract
AbstractIn this study, poly(methyl methacrylate) (PMMA)/graphene nanoplatelets (GNPs) conductive composite films with different morphologies were fabricated from the same constituent materials using four fabrication techniques, solution casting (SC), SC followed by hot pressing (SCP), melt mixing followed by SC (MSC), and melt mixing followed by hot pressing (MP). Morphologies of dispersed GNPs and electrical properties in both in‐plane and perpendicular direction were investigated and compared systematically. The corresponding percolation thresholds (Φc) of the composites varied from 0.42 ± 0.13 vol% to 3.26 ± 0.48 vol%. The conductivities varied up to two orders of magnitude and decreased in the sequence of SC > MSC > SCP > MP. These variations were explained in terms of GNPs size, GNPs orientation, distribution and dispersion state of fillers. The contribution of the above factors in each procedure were discerned individually, the results were discussed and compared with other experimental studies and simulations as well.
Highlights
The incorporation of conductive fillers into nonconductive polymer matrices allows to obtain a new class of electrically conductive polymer composites (CPCs)
The size of graphene nanoplatelets (GNP) in solution casting (SC) 2.0 sample (Figure 3(b')) was comparable while that in mixing followed by SC (MSC) 1.9, SC followed by hot pressing (SCP) 2.0, and melt mixing followed by hot pressing (MP) 1.9 sample (Figure 3(d'), (e')) showed obvious smaller size. This indicates that SC method preserved the GNPs better while the GNPs could be efficiently broken up during melt compounding with the poly(methyl methacrylate) (PMMA) matrix or during the hot pressing
Simple mechanical shearing at molten state can facilitate the exfoliation of the GNPs into smaller dimension.[28,57]
Summary
The incorporation of conductive fillers into nonconductive polymer matrices allows to obtain a new class of electrically conductive polymer composites (CPCs). This is due to strong π–π bonding between graphene layers without solvent-aided dispersion, as a result, large parts of PMMA matrix can be seen from the image.[63,64] From the findings, it is considered that SC process had the best exfoliation of GNPs. It should be noted that the distribution, dispersion and exfoliation are different terms to describe graphene states.
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