Boosting Polyurethane Conductivity Without Sacrificing Performance.(Brief Article)

High-performance semiconductive polyurethane (HP-SCPU) is ideal for tough business equipment and industrial applications.

Polyurethane (solid and foam) is frequently selected for manufacturing a wide range of elastomeric components. This is because polyurethane can provide excellent shock and vibration dampening, and many of the material's properties, such as hardness, chemical resistance, abrasion resistance, compression set, and tensile and tear strength, can be custom-formulated over a wide range of values to suit the requirements of specific applications.

Thermoset polyurethane can be formulated to be as hard as thermoplastics (50-85 Shore D) and as soft as thermoset rubber (1-95 Shore A). Both thermoset and thermoplastic urethane components are manufactured by a variety of processes including casting, injection molding, transfer molding, extrusion, and reaction injection molding (RIM). Additionally, after treatment by a peroxide or sulfur curing process, malleable gum urethane can be processed with standard rubber-industry molding equipment. Typical polyurethane components include wheels, belts, rollers, shock-absorbing parts, gears, housings, bumpers, and squeegees.

A less readily obtainable property of urethane, but one that OEMs are looking for with increasing frequency, is electrical semiconductivity. Semiconductive polyurethane components can enhance the performance of a wide range of business machines and other electronic products. These include printers, copiers, postal meters, ATM machines, and various medical charting and imaging devices.

In many instances, these semiconductive products are rollers designed to manage tribocharges and minimize static buildup, which, in turn, prevents wrinkling and inconsistent transfer of moving items such as ribbons and paper. Semiconductivity also minimizes the incidence and severity of ESD (electrostatic discharge). Aside from being potentially dangerous, ESD can degrade performance and shorten the life of critical components such as printheads and microprocessor chips. Semiconductive polyurethane components are also used widely in charge management to control and adjust the specific charge density and uniformity in electrophotographic applications (e.g., laser printers, thermal printers, and photocopiers).

Another important application of semiconductive urethane is in the automotive and truck manufacturing industry. RIM urethane components can be directly coated or painted without pre-applying conductive adhesives, eliminating the costs of conductive adhesive materials and the manufacturing steps of applying the adhesive for some car and truck fascias.

Conventional SCPU Problems

Like other elastomers and thermoplastic polymers, polyurethane is an insulator, not a conductor, by nature. It typically has a volume resistivity in the E15-E12 ohm-cm range. In order to achieve volume resistivity in the semiconductivity range from ES to …