COMPOUNDS | ELECTRICALLY CONDUCTIVE
electrical charge or that dissipate them before they accumulate to dangerous levels. Generally thermoplastic polymers have a surface resistivity of 1012
-1016 ohms/sq, the com-
pany says. It has developed a range of compounds offering surface resistivity in the range 103
-1012
are suitable for extrusion or injection moulding. The highest conductivities are achieved using
combinations of carbon additives, including carbon blacks and carbon fibres of various sizes. Tisoplen D UNR K17 R02 (an unreinforced antistatic PP), Tisapet L 30D11 K07 R02 (a 30% carbon fibre reinforced anti-static PET), and Tisren K UNR K17 R02 (an unreinforced anti-static PS) all offer resistivity between 103
and 104 ohms/sq. Where
Figure 3: The effect of carbon black surface area and dosage on compound resistivity. The black curve represents super conductive black performance; the other curves depict more conventional conductive black performance. Source: Orion Engineered Carbons
Right: Premix’s electrically conductive Pre-Elec plastics
compounds incorporate carbon black and offer good mechanicals and flexibilty
difficult to disperse than conventional conductive blacks. “Conventional conductive blacks are not well suited for EMI applications. Super conductive blacks, such as Orion’s Printex XE2B, can enable EMI applications, and we are actively working with compounders to optimise black dosage, com- pounding conditions, and mechanical properties,” Narayanan says. The Pre-Elec line of electrically conductive plastic compounds from Finland’s Premix incorpo- rate carbon black, which the company says is the most reliable and cost-efficient choice for produc- ing conductive plastics. As an example of how they can be applied, it cites flexible conduit and tubes that retain strength and flexibility. “Using our conductive compounds you guarantee conductivity, high abrasion resistance, high flex-life, durability, easy processability, and flexibility even at low temperatures,” says Senior Product Manager Anssi Aarnio.
Uncontrolled electrostatic discharge (ESD) can destroy electronic components or cause explosions in flammable environments. For such applications, Tisan Engineering Plastics has developed a range of conductive polymer com- pounds that either prevent generation of high
50 COMPOUNDING WORLD | February 2022
colour is a priority, it can offer a number of carbon- free formulations. Tisetilen N UNR K17 R10, for example, is an anti-static unreinforced PE with a resistivity of 108 tive applications.
-1010 ohms/sq suitable for dissipa- IMAGE: PREMIX
Nano-opportunities Conductivity in plastics can also serve to improve paintability in the automotive industry. Non-con- ductive plastics parts cannot be painted using the electrostatic spray painting systems used for metal elements of cars, and so have to be painted offline. This adds to costs and slows down the whole painting process. “To overcome this, manufacturers of automotive parts should wisely choose tempera- ture-stable thermoplastic grades and modify these systems with electrically conductive additives. Carbon black is frequently used, but high addition rates may be required, negatively affecting mechanical properties and processability,” accord- ing to single wall carbon nanotube producer OCSiAl. The company has launched a new single-wall carbon nanotube (it uses the term graphene nanotube) concentrate for use with PA, filled PPS, ABS, TPU, and PC. It says the new product
provides targeted conductivity in thermo- plastics produced by injection molding at working loadings
starting from 0.1 wt% of nanotubes in the final system.
“This approach allows makers to optimise
the painting process and reduce the final produc- tion cost,” the company says. Incorporation of Tuball Matrix 822 creates a permanent and homogeneous electrical conduc-
www.compoundingworld.com that
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