event review | Conductive Plastics 2016
conductivity. Some carbon blacks are more shear sensi- tive than others, and there is an optimal compounding screw speed for each system. Split feeding—introduc- ing the carbon black into the already molten polymer downstream in a compounding twin-screw extruder using a side feeder—produces more consistent electrical conductivity properties than either feeding the carbon black with the polymer into the feed throat of the compounder or using a carbon black masterbatch at the processing machine, said Van Bellingen. Stainless steel fibers (SSF) are highly effective for EMI applications, but moulders often question whether they will damage their tools, said Ned Bryant, Senior Product Development Engineer at RTP Company. He presented data, however, that showed this is an unnecessary concern. He said RTP has simulated long-term wear resistance using a thrust washer wear test and has found that SSF caused lower mould wear than glass fibre reinforcements.
Below: This multi-meter chassis is injection
moulded in an EMI shielding grade from RTP Company
Conductive novelties Innovative additives, including nanomaterials, are being tested for making plastics electrically and/or thermally conductive. Tushar Shah, Chief Technology Officer at US-based Applied Nanostructured Solutions (ANS), described the company’s Carbon Nanostructured Solution (CNS), polymers of carbon nanotubes designed to produce electrical and thermal conductivity. ANS grows the carbon nanostructures on a continuous glass fibre substrate, roll to roll, in open atmosphere, and the fibres are then chopped. CNS flake is harvested from the continuous fibre and extruded into pellets or made into granules for improved handling. CNS is unique among carbon nanotube technologies, said Shah, in that it is easy to disperse. Like other carbon nanotubes, however, it requires only low concentrations to create conductivity. Shah said the EMI shielding effectiveness of CNS compounds exceeds that of compounds with carbon nanotubes or carbon fibres and meets or
exceeds the capability of aluminum or copper at some
frequencies. ANS worked closely with US regulators to be sure that
environmental, health, and safety aspects of the nanomaterials could be assured and the company now has
approval to produce unlimited quantities. Netherlands-based CarbonX, a spin-off from the Delft University of Technology, has developed a new material that is an aggregate of carbon nanofi-
62 INJECTION WORLD | January/February 2017
Typical electrical resistance values of conductive plastic compounds compared to metal Source: Premix Group
bres chemically linked to create a porous three-dimen- sional network. One specific grade of CarbonX present- ed at the conference enables isotropic improvements in a polymer compound’s strength and conductivity. The material, which is thermally stable, offers a recyclable alternative to glass fibres for mechanical enhancement, as well as improving conductivity, said Chief Technology Officer Daniela Sordi. OCSiAl Group, which launched industrial-scale
production of its TUBALL single wall carbon nanotubes (SWCNTs) in 2013, has now developed advanced conductivity solutions for polyolefins based on master- batches in PP and PE. It also has a developmental- grade concentrate for PVC. The company is currently registered in the EU (REACH) for production of up to 10 tonnes/year; US EPA registration is also underway. The SWCNTs can be melt compounded to produce conduc- tivity at low loadings, said Christian Maus, Development Leader at OCSiAl. This technology was discussed in detail in the September issue of Compounding World. Josef Krivanek, Senior Researcher at the Czech Republic Polymer Institute Brno, now part of Unipetrol, described the company’s high-structure conductive carbon black, Chezacarb. He discussed the influence of impurities on the stability of compounds and noted that metal deactivators can be used to improve this. He also noted the “skin effect” that frequently occurs in injection moulding applications, where the core of the part is more conductive than the exterior surface layer. Rick Cahill, Senior Technical Account Manager at
Milliken, presented the company’s Zelec electrocon- ductive powders for electrostatic dissipation (ESD) applications. The powders offer a number of benefits
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