SOME MICROWAVE AND MECHANICAL-PROPERTIES OF CARBON FIBER-POLYPROPYLENE AND CARBON BLACK-POLYPROPYLENE COMPOSITES

The insertion loss, return loss and electromagnetic shielding effectiv eness of carbon-black and carbon-fiber-filled polypropylene composites were studied in the 8 to 12 GHz frequency range. Both electromagnetic and mechanical measurements were performed at various filler concentr ations. The maximum shielding values obtained for carbon-fiber-filled composites was over 40 dB for 35 wt% concentration. Young's modulus, u ltimate strength and elongation at break with respect to filler concen tration were also determined. The stiffness and brittleness of the com posites increased with increasing filler concentration. The ultimate s trength of the carbon-black-filled composites increased whereas the ul timate strength of carbon-fiber-filled composites decreased with the f iller content. Elongation at break values for all composites dropped s harply with the filler concentration.