Polymer Based Composites for Electromagnetic Interference Shielding

Dear Colleagues,

The topic of electromagnetic interference shielding is becoming a very important issue in the modern world. In fact, the wireless world of mobile and satellite telecommunication and radar observation and the electronic war systems have nowadays to coexist and operate simultaneously. In such a scenario, the paradigm is reducing electromagnetic interference (EMI) and intentional electromagnetic interference (IEMI) as much as possible. Electromagnetic compatibility (EMC) is the ability of different electronic devices and components to work correctly even in the presence of other devices that emit electromagnetic waves.

For example, in modern automobiles, the growing number of onboard electronics and microprocessor-controlled systems requires that the electronic sub-assemblies (ESA) in the vehicle meet EMC requirements. If airbag, cruise control, anti-lock braking, or other electronically controlled assemblies are adversely affected by EMI, the vehicle’s operation or its critical safety systems could be compromised. As mandated by safety and reliability requirements, the automotive onboard ESAs must not emit EMI signals and must be immune to external EMI signals.

One of the approaches to reduce the effect of electromagnetic interference consists in designing and developing materials and structures able to effectively shield electromagnetic interference.

As a function of the frequency of the electromagnetic field and depending on the system to shield, different approaches can be applied. This Special Issue is devoted to carbon-based composites for electromagnetic interference shielding.

Metal, in the form of thin sheets or sheathing, is an effective EMI shielding material, common, for example, in automotive applications. However, metal is expensive, heavy, and prone to corrosion, which adds to the complexity and cost of the manufacturing processes. Moreover, because of their high electrical conductivity, metals play a role in scattering the electromagnetic interference on other parts. Conductive polymer composites offer a potentially cost-effective and process-friendly alternative to metal. The embedded thin metal foils of aluminum, copper, or silver in the polymer matrix are in vogue with suitable provision for grounding. Conventional conductive fillers such as metal flakes, stainless steel fibers, or carbon-based fillers can be dispersed in a polymer matrix creating an electrically conductive network that improves electromagnetic absorption and shielding as a function of the frequency of EMI.

Recently, conductive polymer nano-composites have attracted a great deal of academic and industrial interest due to their potential applications in many areas, including EMI shielding.

Plastic housings are natural insulators and do not reflect or absorb EMI. Most of the energy waves are not obstructed by thermoplastics and enter or leave the housings readily, which causes interference problems. A prompt solution is, therefore, to increase their electrical conductivity by incorporating electro-conducting fillers.

To shield EMI, technical approaches have been extensively considered, aimed at modifying the electrical conductivity of the plastics:

1. Conductive Coating on Plastics
2. Compounding with Conductive Fillers
3. Intrinsically Conductive Polymers (ICP)

For what concerns compounding with conductive fillers, nano-composite fillers, in contrast with larger conventional composite fillers, have at least one dimension in the nanometer range and include materials such as carbon nanotubes (CNT), graphite nanoplatelets (GNP), and metal oxides. These high-aspect-ratio nano-scale fillers form conductive networks much more readily than the conventional conductive fillers. Because of their larger filler–matrix interface, their mechanical and thermal properties may also be enhanced or improved. Furthermore, conductive polymeric nano-composites are lighter and more easily processed.

Some studies reported how composites of very high specific strength and stiffness were produced by incorporating continuous aligned filaments of glass and carbon into matrices of thermosetting plastics like epoxy or polyester.

By incorporating different types of particles into polymeric matrices, improved performance of different types of composites can be achieved.

Currently, many researches are focused on optimizing the dispersion of conductive nano-fillers in the matrix of polymers of different types, such as polypropylene (PP), ABS, conductive rubber composites based on Ethylene–Propylene–Diene Rubber (EPDM), Acrylonitrile butadiene rubber (NBR), polyphenylene oxide polystyrene blend, nylon, polyphenylene sulfide (PPS), PET, and PPO.

Because of the strong tendency of nanoparticles to agglomerate, uniform dispersion of conductive nano-fillers in the polymer matrix is a considerable challenge. Yet, this is essential to the formation of an effective conductive network at low filler loading. Advancements have been made in this area through the use of a proprietary compounding technique.

We look forward to your submission

Dr. Davide Micheli
Guest Editor

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• Electromagnetic Interference
• Electromagnetic Shielding
• Electromagnetic Absorption
• Electric Conductive Polymers
• Conductive Nano-Fillers
• Conductive Fillers