Electromagnetic and mechanical properties of conductive polyethylene composite antennas for utility location

Abstract

Location of polyethylene utility pipes is improved by installing electromagnetic targets with the pipe. A new electromagnetic target could be created by impregnating polyethylene with conductive materials to impart it with electromagnetic properties necessary for use in utility location. Antennas created from this conductive polyethylene composite could be molded directly to the pipe during fabrication. The addition of high concentrations of conductive fillers into the material alters the mechanical performance of the material in addition to the electromagnetic properties, resulting in a material which displays brittle behavior, unlike neat polyethylene. Both electromagnetic and mechanical properties of the material are characterized to predict the behavior of the conductive polyethylene in service. In a layered composite with unmodified polyethylene and conductive polyethylene layers, the brittle behavior of the conductive polyethylene limits the strain to failure of the overall composite.

Remendable conductive polyethylene composite with simultaneous restoration of electrical and mechanical behavior

“…Previous work has indicated that when large aluminum flakes are used as conductive filler, the flakes can act as crack initiation points, leading to premature failure relative to polyethylene with no fillers. [ 8 ]…”

“…This fracture surface shows short tendrils typical to a brittle fracture surface of polyethylene compounded with carbon black. [ 8,53 ] A higher magnification image of tendrils formed during typical brittle fracture is shown in Figure 6C. A specimen with a healed fracture is shown in Figure 6E, and a higher magnification image of the same area is shown in Figure 6F.…”

“…Previous work has indicated that when large aluminum flakes are used as conductive filler, the flakes can act as crack initiation points, leading to premature failure tive to polyethylene with no fillers. [8] This fracture area after healing is shown in Figure 5B. Figure 5C shows the fracture surface of this same specimen after secondary testing.…”

“…Previous work indicated that maximum conductivity in this composite occurred at concentrations of carbon black above 15% by volume and concentrations of aluminum flake above 10%. [ 8 ] Though the composite also exhibited electrical conductivity at loadings below 15% carbon black, induction heating efficiency depends on the conductivity of the material, so electrical conductivity was maximized for this study. At concentrations of filler above these thresholds, no additional decrease in electrical resistance of the composite was measured and 15% carbon black was chosen as the baseline composition.…”

“…Conductive polymers have been previously developed for such applications as flame retardant materials, [1] electrical conductors, [2] self-regulating heaters, [3] electromagnetic interference shielding, [4] sensors for damage and deformation, [5][6][7] and antennas for utility location. [8] To create conductive polymers, conductive fillers are compounded into the polymer matrix. These fillers are commonly carbon-based, such as carbon black or carbon nanotubes.…”