Resistance gradient polymeric electromagnetic shielding composites: Preparation and Characterization

Based on the principle of Stokes’ law, a series of polyvinyl butyral (PVB)/nickel (Ni) composite films with a resistance gradient were successfully prepared using a suspension casting method with the aid of gravity. Gradient distribution structure, conductive and mechanical properties, and electromagnetic shielding effectiveness (SE) were investigated. Scanning electron microscopy (SEM) observations and energy‐dispersive spectrometer (EDS) detection show that the gradient distribution of Ni particles in the PVB matrix was formed along the thickness‐direction. A surface resistivity difference of 10 orders of magnitude appears between the top surface (PVB‐rich side) and the bottom surface (Ni‐rich side). Percolation transformation occurs in the range of Ni content of 3.0∼4.5 vol% at the Ni‐rich side, which is much lower than that of PVB/Ni composites with homogeneous Ni distribution. The gradient distribution structure grants the composite both good electromagnetic shielding performance and good mechanical properties. When the Ni loading reaches 10.5 vol% in the film, its SE value rises to 30 dB, which is 15 dB higher than that of a homogenous film with the same filler content. It is believed that electrically conductive gradient polymeric composites have potential application value in the field of electromagnetic shielding. POLYM. COMPOS., 40:1842–1849, 2019. © 2018 Society of Plastics Engineers