The linear viscoelastic behavior and electrical conductivity of highdensity polyethylene (HDPE) filled with stainless steel fibers (SSF) were investigated and compared with those of carbon black (CB) filled HDPE composites system.It is found that CB/HDPE composites show two electrical conductivity percolation values (φc1 and φc2) and a wide percolation range.However

SSF/HDPE composites present an extremely low threshold of the electrical conductivity percolation (only 0.3 vol%) and a narrow percolation range.Only one conductivity percolation value (φc) was observed.The speciality of conductivity percolation behavior of SSF/HDPE composites owes to the formation of conducting channels of SSF/HDPE composites.It is well recognized that the rheological percolation threshold is identical to the percolation threshold of electrical conductivity for CB/HDPE composites.Whereas

for SSF/HDPE composites

dynamics storage modulus (G′) becomes almost independent of frequency in the low frequency region as the SSF loading increases up to 4.8 vol%

suggesting an onset of solidlike behavior in SSF/HDPE composites.By plotting G′ versus SSF loading

the rheological threshold is determined as 4.8 vol%

which is much lower than the percolation threshold of electrical conductivity

i.e. 0.3 vol%.Additionally

the positive temperature coefficient (PTC) effect was measured for SSF/HDPE and CB/HDPE composites.It reveals that the conductivity channels formed by SSF show a higher stability than those formed by CB particles in HDPE matrix.The difference in the percolation threshold and the stability of conductivity channels are understood in terms of the larger L/D of SSF and the particular conductive mechanism of SSF/HDPE composites.