Effects of fiber length on the reflection loss of electromagnetic wave absorbing polypropylene/carbon fiber composites prepared by injection molding and by screw extrusion process

The reflection loss (RL) performance and impedance matching characteristics of polypropylene (PP)/carbon fiber composite were studied according to two different composite preparation methods. For the PP/carbon fiber composite prepared by injection molding process, the RL value of -29.1 dB was achieved at low carbon fiber content (10 wt%), compared with the composite prepared by screw extrusion process (-15.6 dB). This good RL performance of the PP/carbon fiber composite prepared by the injection molding process was attributed to the impedance matching characteristic originating fi-om the longer fiber length in the composite, than in the composite prepared by screw extrusion. The results suggest that the carbon fiber length in the composite is an important factor to achieve PP/carbon fiber composites that have effective electromagnetic wave absorbing properties.