Electrically conductive plastic for EMI shielding

Of particular note, at 2.5mm thick, the material has been designated 5VA, the highest flammability rating from UL 94, the Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances. This level of flame retardant performance is obviously essential when the application involves highly flammable fluids. A 5VA rating means burning stops inside 60 seconds on a vertical specimen without dripping (and without creating a hole in the specimen). For those who require a thinner EMI housing, PREMIER PBT-250FR carries a UL 94 rating of V-0 at 1.5mm thick.

“In ongoing discussions with our partners, one request we kept hearing over and over was how an electrically conductive plastic with a 5VA flammability rating would address a major gap in the marketplace,” said John Beswick, engineered plastics solutions Business Unit Manager, Parker Chomerics.

To provide an idea of shielding effectiveness with PREMIER PBT-250FR, values extend from 40-45 dB attenuation at 30 to 1,500MHz, up to 80-85 dB at 20,000 to 40,000MHz, ensuring the suitability of this semi-crystalline material in almost all automotive fuel/fluid-based applications. These performance levels are supported by good chemical resistance to substances such petroleum, motor oil, brake fluid and antifreeze, an attribute that is inherent in PBT grades.

Cost is a further advantage for designers and engineers working to a budget. PBT products use continuous stainless steel fibre as the filler content in lieu of nickel carbon plated fibre, which means that a product such as PREMIER PB-250FR is priced at around 65% less than PREMIER PC-ABS nickel-plated grades. The upshot is an economic price point supported by extremely stable performance.

It is also worth noting that PREMIER PB-250FR is the only single pellet material of its type on the market. As such, this resin system eliminates the mixing required with traditional electrically conductive plastic pellets. The principal benefit, therefore, is uniformity of conductive filler dispersion throughout the part, which results in consistent electrical properties and mechanical performance.

A further customer benefit is the ease with which PREMIER PBT-250FR can be manufactured; it will run in any injection moulding machine, while its easier processing capability allows for smaller barrel capacities. Here, typical reductions in injection pressure of 30 to 40% translate into smaller press tonnage requirements. The use of a single pellet material also eliminates any risk of improperly processed fibre pellets – which can be found in multi-pellet (cube blend) products – leading to agglomerates.

PREMIER PBT-250FR is manufactured by Parker Chomerics in the USA, and is available immediately.