Effect of Alfa fiber mechanical separation on dielectric properties of hybrid unsaturated polyester composites

An exhaustive study of dielectric and impedance analysis on two Alfa‐fiber‐reinforced unsaturated polyester hybrid composites was performed. Alfa fiber reinforcements were hybridized by wool and PE/PET fibers in the relative volume fraction ratio 17:2:1. However, these reinforcements differ by the number of mechanical separation of Alfa fibers in the Shirley analyzer. For Composite (1), Alfa fibers were separated mechanically once in the Shirley analyzer whereas for the Composite (2), they were separated mechanically twice in the Shirley analyzer. Dielectric parameters analysis (ɛ′, ɛ″) revealed the presence of the α‐relaxation process at intermediate temperature range for the matrix and the water dipoles polarization at low temperatures for the Composite (1). No dynamic dielectric relaxation was observed for the Composite (2) at low temperatures. However, dielectric properties were controlled by the dc conductivity effect at higher temperatures. The Kramers‐Kronig relation was used to eliminate its effect. Hence, α mode relaxation was observed for the matrix and the interfacial polarization effect was observed for its composites. The attenuated effect of this latter for the Composite (2) was attributed to its homogeneous structure. Electrical conductivity analysis using the Jonscher law allowed determining the transport mechanism for all studied materials and confirmed such result. Complex impedance analysis supported the homogeneous structure for the Composite (2). POLYM. COMPOS., 40:1774–1785, 2019. © 2018 Society of Plastics Engineers