Author: Christine Versluijs

Wittenburg Group company Witcom Engineering Plastics specialises in development and production of electrically conductive compounds based on a wide range of polymers. It says conductive POM (acetal) is gaining a lot of attention for semi-finished materials used during manufacturing and assembly of electronic components.

“We can produce conductive POM that our customers can extrude safely up to more than 200 mm thick slabs and rod stocks without any stress cracking or gas bubbles on cross sections during further machining,” says Christine Van Bellingen, Business Development Manager for Conductive Materials at the company.

“In another direction, motivated by the corona pandemic, our conductive TPE grades offer touch-free solutions as well as tight profiles and sealing solutions,” she says.

Witcom has customers in the automotive industry already using its radar absorption compounds in the latest radar systems for blind spot detection, cross-traffic alert and more. Opportunities are also seen across the broader EV sector. “While electrifica­tion and digitalisation of cars generate more electro-magnetic interferences, the trend for lower energy consumption and light weighting calls for more plastics. Our latest generation of cost-effective EMI shielding plastics compounds clearly opens new perspectives for metal replacement as well as for metal coating alternatives,” says Udo Schwestka, Business Development Manager for Radar Absorbing Materials.

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Witcom Engineering Plastics has developed a broad range of lubricated engineering plastic compounds for such applications with what it describes as outstanding wear and friction proper­ties. “We see an increasing demand of low wear and friction compounds. In automobiles, buzzing, squeaks and rattles need to be kept to a minimum, as nowadays they are very noticeable, especially in electric vehicles,” says Bram Willemen, the com­pany’s Business Development Manager for Lubricated Compounds.

PPS 2014 316

Wear resistance has to be considered alongside other mechanical requirements, according to the company. A recent project for a metal/plastic bearing/shaft combination assembly incorporating a component in its Witcom PPS-2014/316 grade illustrates this. The compound contains a proprietary high-performance lubricant system in which the coefficient of linear thermal expansion is adjusted to be in the same range as the metal elements. As a result, the bearing/shaft combination remains within the required tight tolerance field over a temperature range from -40°C to over +200°C.

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Witcom Engineering Plastics, part of Wittenburg Group, worked closely with injection moulder Miki-Plastik in a project to make new PCB magazines, which house and transport PCBs during their automated assembly process. For its high temperature magazine, Witcom needed an electrically conductive high temperature plastic.

Witcom Miki Conductive PES

Marcus Weiland, Managing Director at Miki-Plastik, says: “The vertical guide rack is a large, flat part that needs to be moulded within tight tolerances without any warpage. It also needs to be electrically conductive for ESD protection, and withstand impact loads, and, for our high temperature range, temperatures in excess of 130°C. We consulted with a large number of suppliers for a suitable raw material; Witcom Engineering Plastics was the only one to pick up this challenge.”

Witcom selected PES as the base polymer, as it can withstand temperatures of up 180°C, is inherently flame retardant and can be moulded within tight tolerances. Piotr Zgnilec, Lead Engineer in conductive thermoplastics at Witcom, says: “To achieve the conductivity needed for the ESD protection and some reinforcement, we could not use carbon fibre, because that would cause the parts to warp. Using conductive carbon black however, causes PES to become rather brittle. In close co-operation with Miki-Plastik we developed a new formulation based on a unique conductive carbon black, which did not show brittleness and had enough flow to fill these large tools. Witcom PES-EC is a multi-purpose grade which can be injection moulded as well as extruded.” Christine Van Bellingen, Business Development Manager for conductive applications, adds: “Other potential market areas we are looking at include conductive high temperature sheet and other components for electronics manufacturing.”

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