Electromagnetic shielding effectiveness of polycarbonate/graphene nanocomposite foams processed in 2-steps with supercritical carbon dioxide

• Random orientation of graphene particles improved electromagnetic shielding.
• Larger cells promoted better graphene dispersion/distribution and hence, better EMI shielding.
• Maximum specific shielding effectiveness of foamed composites was 14 dB (78 dB cm3/g).
• Reflection was found to be the dominant EMI shielding mechanism.
• Shielding effectiveness increased +10 times after foaming.

The electromagnetic interference (EMI) shielding properties of polycarbonate/graphene composites foamed with supercritical carbon dioxide were investigated as a function of cellular morphology and graphene particle dispersion. The 2-step foaming method used was found to improve graphene dispersion and led to a different cellular structure compared to traditional 1-step foaming. Reflection was found to be the dominant EMI shielding mechanism and EMI shielding effectiveness was improved with large cell morphology that promoted isotropic/random orientation of graphene particles. A maximum EMI specific shielding effectiveness of ~78 dB cm3/g was achieved in foams, which was more than 70 times higher than that of the unfoamed polymer (1.1 dB cm3/g). The study shows that by controlling foaming process conditions and nanoparticle characteristics, it is possible to improve multiple properties while achieving lightweight materials suitable for various applications.

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