Study On The Filled Composite Electromagnetic Shielding Materials

With the development of information technology, electromagnetic radiation has attracted people's attention widely. Electromagnetic waves shielding also become a hot research. In order to achieve better shielding effect, many countries have done a lot of research in the theory of the electromagnetic shielding and the development of new shielding materials. Amongst the various methods of electromagnetic shielding, filler type electromagnetic shielding materials becomes one of the important areas of research because of its characteristics that can be made into complex products, processes simple, without special equipment, low cost, wide application. Our country get behind other countries in this field, the majority of this kind of materials depends on imports. Therefore, the researches on the electromagnetic shielding composite materials are necessary.Common shielding composition blending with carbon black has many shortcomings. Such as great filling amount, difficult dispersion and low shielding efficiency. In this paper, we derived PP/sisal fiber shielding composition by blending PP with chemical treated sisal fiber that as a carrier to adsorb electric carbon black. Effect of length of sisal fiber and addition on shielding efficiency and mechanical properties of shielding composition in 100MHz to 1GHz range had been studied based on the theory presented by material science and electromagnetism.Results showed that shielding efficiency first increased then decreased as the addition of sisal fiber/carbon black accreted with the same length of sisal fiber. Shielding efficiency reached to maximum when the concentration of sisal fiber/carbon black was 20wt% ~ 30wt%. However, shielding efficiency decreased as the length of sisal fiber grew with the same concentration of sisal fiber/carbon black. To conclude, the max shielding efficiency reached 28dB when the length of sisal fiber was 2mm and the concentration of sisal fiber/carbon black was 20wt% in 400M~600M frequency. Compare with the same amount of pure carbon black carbon black / polypropylene, the shielding effectiveness improved about 10 dB .Meanwhile, tensile stress of the composition decreased slowly as the addition of sisal fiber/carbon black grew.