STUDIES ON EFFECTIVENESS OF ELECTROMAGNETIC-INTERFERENCE SHIELDING IN CARBON-FIBER FILLED POLYCHLOROPRENE COMPOSITES

The electromagnetic interference (EMI) shielding effectiveness (SE) and return loss (RL) of short carbon fiber filled polychloroprene composites, vulcanized by metal oxide and ethylene thiourea, have been studied in the two frequency ranges of 100 to 2000 MHz and 8 to 12 GHz with special reference to the effects of carbon fiber (CF) concentration, fiber aspect ratio, and composite thickness on SE and RL. It was found that SE increased and RL decreased with increase in fiber aspect ratio, fiber concentration, and composite thickness indicating that the loss was due to absorption (A). The correlation between the volume resistivity/CF concentration and SE of the composites at different CF concentrations and fiber aspect ratios indicates that at any particular frequency the SE depends not only on the electrical resistivity but also upon the thickness and fiber randomness.