In this paper, a single-layer coated composite was prepared using PU2540 polyurethane as the matrix, nickel powder as the wave-absorbing functional particle, and coating technology on plain cotton fabric. The influence of the content of nickel powder on the dielectric properties (the real and imaginary parts and the loss tangent value), the shielding effectiveness and the mechanical properties was studied adopting the method of controlling variables. The result showed that when the content of nickel powder was 0~20% and that of nickel powder relative to that of polyurethane was 20%, the real and imaginary parts of the dielectric constant of the coating were the largest, and its polarising and loss ability with respect to electromagnetic waves were the strongest; when the content of nickel powder relative to that of polyurethane was 15%, the loss tangent value of the coating was the largest, and its absorption and attenuation ability with respect to electromagnetic waves was the strongest. When the values of the coating thickness were at 0.5~2 mm, the real and imaginary parts of the dielectric constant of the coating with a thickness of 1 mm were the largest, and the polarising and loss ability with respect to electromagnetic waves were the strongest. When the loss tangent value and the shielding-attenuation value of the coating with a thickness of 2 mm were the largest, the absorbing-attenuation and shielding-attenuation ability with respect to electromagnetic waves were the strongest.

With the rapid development of electronic technology and military techniques, electromagnetic protection materials are becoming more and more significant to people. Harmful electromagnetic radiation not only affects the normal operation of electronic equipments and military security, but also has a serious impact on human health. At present, using absorbing and shielding materials are effective means to reduce the harm of electromagnetic waves. In this project, graphite, graphene and silver-coated copper powder coated composites were prepared using PU-2540 polyurethane and adopting a coating process for the substrate on plain polyester/cotton fabric. The controlled variable method was used to prepare and study the electromagnetic properties of single-layer coating composites with different functional particle contents. The result showed that within the frequency range of 0.01GHz~1.0GHz, when the total mass of functional particles was 48% relative to that of the polyurethane, the value of the real part of the dielectric constant of the sample remained the largest and its polarization ability was the strongest. Within the frequency range of 0.08GHz~1.0GHz, when the content of functional particles was 24% relative to that of the polyurethane, the value of the imaginary part of the dielectric constant and the loss of the tangent value of the sample kept the maximum, and the loss and attenuation ability with respect to electromagnetic waves were both the strongest. Within the frequency range of 1.3GHz~2.0GHz, when the content of functional particles was 36% relative to that of the polyurethane, the value of the reflection loss of the sample was -26.93dB, and the minimum value of the reflection loss was obtained at a frequency of 1.6GHz, at the moment of which, the absorbing property of the sample was the best.

A coated composite was prepared on polyester-cotton plain weave fabric, using PU2540 polyurethane as the matrix. The influences of the content of nickel powders on the dielectric constant (the real and imaginary parts and loss tangent value), reflection loss and shielding effectiveness of single-layer coated composites were mainly investigated. The results showed that within the frequency range of 1–1000 MHz, the value of the real part of the dielectric constant of the coated composites was the largest, and the polarisation ability with regard to electromagnetic waves was the strongest when the content of nickel powders was 40%. Within the frequency range of 15–225 MHz, the value of the imaginary part of the dielectric constant of the coated composites was the largest and the loss ability with regard to electromagnetic waves was the strongest when the content of nickel powders was 40%. Within the frequency range of 250–800 MHz, the loss tangent value of the dielectric constant of coated composites was the largest, and the attenuation ability with regard to electromagnetic waves was the strongest when the content of nickel powders was 40%. Within the frequency range of 1220–3000 MHz, the reflection loss value was the smallest when the content of nickel powders was 40%, and its absorption ability with regard to electromagnetic waves was the strongest. Within the frequency range of 760–3000 MHz, the shielding effectiveness of the coated composite was the largest when the content of nickel powders was 40%.