Impact of synthesis temperature on morphology, rheology and electromagnetic interference shielding of CVD-grown carbon nanotube/polyvinylidene fluoride nanocomposites

Electromagnetic interference (EMI) is undesirable and uncontrolled interference with the signal of intelligence. This is controlled by using either novel materials, or appropriate electronic design or a combination of both. In this context, functionalized multiwalled carbon nanotubes (FMWCNTs) have been proposed to use as EM shielding materials because of their promising electromagnetic properties, high flexibility, and high electrical conductivity. The non-functionalised MWCNTs does not demonstrate high shielding of electromagnetic waves but with acid functionalisation and further loading with optimized nanoparticles of Fe3O4, enhanced absorption (15.85 dB), enhanced reflection (9.43 dB), resulted in high total specific shielding effectiveness of around 49.56 dB (g cm−3)−1. All samples were light weight, flexible, thin and self-standing in the form of a buckypaper of thickness of 50 µm and density of 0.51 g cm−3. These buckypapers could be promising materials for electromagnetic shielding via both absorption and reflection. A fine amalgamated system of MWCNTs with half metallic Fe3O4, resulting in enhanced conductivity, in an extremely thin and flexible matrix, is considered to be the main contribution to these high shielding effectiveness values.

http://iopscience.iop.org/article/10.1088/2053-1591/aa69f4/pdf

Lightweight, flexible and thin Fe3O4-loaded, functionalized multi walled carbon nanotube buckypapers for enhanced X-band electromagnetic interference shielding

The need for electromagnetic interference (EMI) shields has risen over the years as the result of our digitally and highly connected lifestyle. This work reports on the development of one such shield based on vulcanized rubber foams. Nanocomposites of ethylene-propylene-diene monomer (EPDM) rubber and multiwall carbon nanotubes (MWCNTs) were prepared via hot compression molding using a chemical blowing agent as foaming agent. MWCNTs accelerated the cure and led to high shear-thinning behavior, indicative of the formation of a 3D interconnected physical network. Foamed nanocomposites exhibited lower electrical percolation threshold than their solid counterparts. Above percolation, foamed nanocomposites displayed EMI absorption values of 28-45 dB in the frequency range of the X-band. The total EMI shielding efficiency of the foams was insignificantly affected by repeated bending with high recovery behavior. Our results highlight the potential of cross-linked EPDM/MWCNT foams as a lightweight EM wave absorber with high flexibility and deformability.

https://digital.csic.es/bitstream/10261/209481/1/Highly_Bizhani_Art2020.pdf

Highly Deformable Porous Electromagnetic Wave Absorber Based on Ethylene-Propylene-Diene Monomer/Multiwall Carbon Nanotube Nanocomposites.

Polyvinylidene fluoride (PVDF)-graphite composites have been developed using solution mixing with uniform dispersion of micro-fillers within the PVDF polymer matrix for electromagnetic interference (EMI) shielding applications. A conductive network of flake shaped graphite particles is formed within the PVDF polymer layers which improved the electrical conductivity of the composite thus providing promising EMI shielding properties. Conductivity of the composite increased by several orders of magnitude on graphite (80 wt%) incorporation in the PVDF (i.e. from 3.41 × 10−13 S cm−1 to 120 S cm−1). A high effective dielectric constant ( at a frequency of 8.2 GHz) has also been obtained for the PVDF-graphite composite having 80 wt% graphite. A high absorption dominated total shielding effectiveness value of ~98 dB has also been achieved at a frequency of 8.2 GHz for the above mentioned composite. The results are promising for using the PVDF-graphite composite as EMI shielding material in the X-band frequency.

https://iopscience.iop.org/article/10.1088/2053-1591/ab13dd/pdf

Development of polyvinylidene fluoride-graphite composites as an alternate material for electromagnetic shielding applications

In this study, polydiacetylene (PDA) is embedded in electrospun polyvinylidene fluoride (PVDF) nanofibers for the preparation of mats with dual colorimetric and piezoelectric responses. The diacetylene monomers are self-assembled during the electrospinning process. The PDA-embedded PVDF nanofibers in the blue phase are obtained via photo-polymerization upon UV-light irradiation. The colorimetric transition of the nanofibers is studied as a function of temperature using a spectrophotometer. The morphology and crystal polymorphism of the nanofibers are investigated. The results show that the addition of PDA increases the diameter of the nanofibers due to the increase in the electrospinning solution viscosity. The results of Fourier transform infrared and wide angle X-ray diffraction demonstrate that PDA has the effect of inhibiting the growth of non-polar α-phase crystals, while promoting the growth of the polar β-phase. However, the red phase of PDA-embedded PVDF exhibits a lower intensity of the β-phase in comparison to that of the blue phase. In fact, the blue-to-red color transition of the PDA-embedded electrospun PVDF nanofibers is accompanied by the variation of piezoelectric signaling caused by variations in the β-phase. This phenomenon creates great potential in commercial detection sensors in addition to their colorimetric detection properties.

Crystal polymorphism in polydiacetylene-embedded electrospun polyvinylidene fluoride nanofibers.

Radar X-band electromagnetic interference shielding (EMS) is one of the prime requirements for any air vehicle coating; with limitations on the balance between strength and thickness of the EMS material. Nanocomposite of multiwalled-carbon-nanotubes (MWCNT) has been homogeneously integrated (0 – 9 wt%) with polymer, poly (vinylidene fluoride, PVDF) to yield 300 micron film. The PVDF + 9 wt% MWCNT sample of density 1.41 g/cm3 show specific shielding effectiveness (SSE) of 17.7 dB/(g/cm3) (99.6% EMS), with maintained hardness and improved conductivity. With multilayer stacking (900 microns) of these films of density 1.37 g/cm3, the sample showed increase in SSE to 23.3 dB/(g/cm3) (99.93% EMS). Uniform dispersion of MWCNTs in the PVDF matrix gives rise to increased conductivity in the sample beyond 5 wt% MWCNT reinforcement. The results are correlated to the hardness, reflection loss, absorption loss, percolation threshold, permittivity and the conductivity data. An extremely thin film with maximum EMS property is hence proposed.

Fabrication and evaluation of thin layer PVDF composites using MWCNT reinforcement: Mechanical, electrical and enhanced electromagnetic interference shielding properties

B. S. Kothavale

Papers

Fabrication and evaluation of thin layer PVDF composites using MWCNT reinforcement: Mechanical, electrical and enhanced electromagnetic interference shielding properties