Shear‐induced migration of conductive fillers in injection molding

Abstract

The effect of shear‐induced conductive filler migration on surface and volume conductivity of injection molded articles of polystyrene and polypropylene with carbon black was investigated. It was found that the loss of conductivity was most significant when the mean particle concentration was at or slightly above the percolation threshold. The compounds with mean particle concentration well above the percolation threshold showed no loss at all. The conductivity decreased with the increase of shear rate used in molding. The removal of surface layers by excimer laser led to restoration of the conductivity to the value of well‐mixed, compression‐molded specimens. The thickness of surface layer removed before conductivity was restored was found to be a strong function of the shear rate and the nature of polymer used. Polym. Eng. Sci. 44:2101–2109, 2004. © 2004 Society of Plastics Engineers.

Production of electrically conductive networks in immiscible polymer blends by chaotic mixing

“…A Keithley picoammeter model No.487 attached to test fixture 8009 was used for the purpose. The concentration of CB particles in PPCB was well above the percolation threshold, 2% by volume, reported in a prior study [43]. Figure 1 presents shear viscosity of PP, PA6, and the PPCB compound measured by ARES rotational rheometer with plate-plate configuration at 250°C.…”

Electrical, thermal, and mechanical properties of polypropylene/multiwalled carbon nanotube micromoldings

“…The above suggests that there is a difficulty in building 3D conductive network pertain to the outer surface of microparts under intensive shearing conditions of μIM. In this scenario, shear‐induced migration of the added fillers is likely a contributing factor, which was commonly observed in an injection molding process . Meanwhile, the cooling effects are substantial due to the very high surface area to volume ratios of microparts .…”

“…In this scenario, shear-induced migration of the added fillers is likely a contributing factor, which was commonly observed in an injection molding process. [32,33] Meanwhile, the cooling effects are substantial due to the very high surface area to volume ratios of microparts. [12] As a result, it can be deduced that the very high shearing and cooling effects involved in μIM are unfavorable for the construction of 3D conductive pathways at lower filler loading concentrations.…”

Shrinkage alteration induced by segregation of glass beads in injection molded PA6: Experimental analysis and modeling

“…By milling the surface repeatedly, he showed that away from the specimen's wall towards the core layer the concentration of the conducting particles is increasing. Following Jana's [9] work, Hong et al [10] studied the conductivity of composites made by particles filled into PP and PS matrices (Ketjenblack, Akzo Nobel). They observed that by increasing the injection speed, the specimen's conductivity decreased.…”