Synergistic Optimization of Toughness and EMI Shielding Properties in Rigid Polyurethane Composites by Designing Ring Structures on the Surface of Carbon Fibers

How to achieve both toughness and enhanced electromagnetic interference shielding effectiveness(EMI SE)of carbon fibers(CFs)reinforced rigid polyurethane(RPU)composites is a significative challenge at present.In this work,a ring-shaped zinc coating was deposited on the short CFs by electrodeposition technique.It is expected to improve the interfacial properties between the fibers and the resin matrix as well as enhance the EMI shielding properties of the composites by changing the surface morphology and roughness of the fibers.Results showed that the surface free energy of the ring-shaped zinc modified carbon fibers(RS-CFs)increased from 49.0 mJ/m^(2) to 53.2 mJ/m^(2),indicating that the surface roughness and wettability of the CFs were effectively improved.In comparison with the pristine short carbon fibers/rigid polyurethane(CFs/RPU)composites,tensile strength and tensile toughness of RS-CFs modified composites were increased by 27.1% and 121.4%,respectively.In addition,the bending and impact strengths of RS-CFs reinforced RPU composites were also improved.Notably,the electrical conductivity of RS-CFs/RPU composites reached 1.2×10^(-5) S/m,which was much higher than that of CFs/RPU composites at 1.4×10^(-10) S/m.Moreover,the EMI SE of the modified composites reached 22 dB,which was 152.9% higher than that of CFs/RPU composites.The enhanced electrical conductivity and EMI shielding properties of the composites could be attributed to the synergistic effect of the porous structure in the RPU matrix and the CFs modified by the metal coating.