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

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 similar to 78 dB cm(3)/g was achieved in foams, which was more than 70 times higher than that of the unfoamed polymer (1.1 dB cm(3)/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. (C) 2015 Elsevier B.V. All rights reserved.