Effect of Preparation Methods on Electrical and Electromagnetic Interference Shielding Properties of PMMA/MWCNT Nanocomposites

Nanocomposites of polymethyl methacrylate/multiwalled carbon nanotubes (MWCNTs) were prepared via four different methods, namely, melt blending cum injection molding (MI), melt blending cum compression molding (MC), solution blending cum compression molding (SC), and solution blending cum melt compounding (SM). The effects of preparation methods on the microstructure, mechanical and electrical properties, and electromagnetic interference (EMI) shielding performance were investigated. The solution-based methods can disperse MWCNTs more uniformly without any significant agglomerates than the melt-based methods. The injection molding method led to significant alignment of MWCNTs, while the compression molding method allowed MWCNTs randomly distributed. Because of the uniform dispersion of MWCNTs, the SM nanocomposite exhibited the lowest percolation threshold (0.25 vol%), and the highest modulus and electrical conductivity among all the samples. Under a MWCNT concentration of 1.72 vol%, the SM nanocomposite showed a shielding effectiveness up to 68 dB. The MI and MC nanocomposite showed poor mechanical and electrical properties due to severe agglomerates and breakages of MWCNTs. The EMI shielding mechanism of the nanocomposites prepared by different methods was discussed by coupling the distribution, dispersion and microstructure of MWCNTs, and shielding theory. The findings are important for guiding the design and fabrication of high-efficient conductive polymer nanocomposites. (C) 2018 Society of Plastics Engineers