Medical Device Link.

Originally Published EMDM October 2001

PRODUCT UPDATE

SEPs combine traditionally conflicting properties.

Jamie Graham

Selectively enhanced polymers from Foster Corp. combine conductive properties with the toughness and flexibility of polyurethane.

Enhancing certain polymeric properties has often been considered a zero-sum game: selectively boosting certain properties in a material, the thinking went, would result in a trade-off in other areas. This phenomenon prompted Foster Corp. (Dayville, CT, USA) to develop a line of polymers that meld seemingly divergent attributes. The company's line of selectively enhanced polymers (SEPs) includes a urethane in which enhanced lubricity does not adversely affect the tensile strength or elongation of the material, and a nanocomposite with increased rigidity and minimal brittleness. Its newest product is a urethane with enhanced static dissipation properties.

Traditionally, the use of internally compounded additives such as carbon to dissipate static charges has affected the design and mechanical properties of urethane components. Foster's blend of structured carbon additives and its advanced compounding techniques reportedly result in enhanced dissipation properties that do not adversely affect the urethane.

According to company president Larry Acquarulo, the new urethanes are suited for a range of applications including tubing, film, sheet, and injection-moulded components. "Static charges can be an engineer's worst nightmare, since they jeopardize sensitive electrical components. Conductive materials give these charges a path to dissipate without destroying the product. Yet the sacrifice in toughness and flexibility when traditional carbon-filled polymers [are used] is unacceptable for belts, tubing, and other flexible components," he says. "Conductive urethanes provide a unique combination of properties that increases design flexibility and reduces overall product costs."

Foster Corp's SEP low-friction olefin elastomer was used in Visualization Technology's InstaTrak 3500 headset. The elastomer represents Foster's emerging family of low-friction polymers designed to enhance lubricity without affecting other key properties.

As technical requirements for polymers become more rigorous, a trade-off in properties is simply unacceptable to OEMs, adds marketing representative Dan Lazas. "Materials need to improve selectively, without carrying detrimental baggage," says Lazas. "Each SEP can meet the specific needs of OEMs."

The company's other enhanced families of polymers include lubricated SEPs and nanocomposites.

Lubricated SEPs can substantially reduce friction yet maintain flexibility. The key mechanical properties of urethanes can be affected when lubricity is increased by the use of internally compounded additives such as PTFE. The use of external lubricants as an alternative also has drawbacks, because the lubricants diminish with time and use, which hinders adhesive bonding. Foster's internal lubrication system maintains the physical properties of the material while reducing friction to levels comparable with those of PTFE. "Our low-friction urethane compounds have less than one-third the friction of unmodified urethanes in many cases, with virtually no change in tensile strength and elongation," says Acquarulo.

The company has also developed a nylon-12 nanocomposite for OEMs requiring a nonbrittle polymer with enhanced rigidity. The rigid material maintains its elongation properties, thus increasing the mechanical performance of thin-wall tubing, film, and similar products.

Selecting the Perfect Polymer

Selectively enhanced polymers helped Visualization Technology (Reinbek, Germany), a manufacturer of sinus and ENT image guidance systems, to solve a material dilemma while developing its InstaTrak 3500 headset. The headset is used for surgical navigation during endoscopic sinus procedures. When in use, the earpieces must maintain fixed points of contact in the ear, while also providing comfort to the patient. Because the earpieces touch the bone structure of the inner ear for long periods of time, the company needed a material with low frictional properties and high mechanical performance. Softer materials were too forgiving or were accompanied by a tackiness that led to discomfort when the earpieces were removed. Acetal, on the other hand, was too hard on the patient's ear. Foster's selectively enhanced elastomer met the requirements of the application by offering low friction without a reduction in other key properties.

Foster Corp. is not alone in its pursuit to develop optimal material solutions for OEMs. The following pages showcase the newest products and developments available from materials suppliers.

See more products

Copyright ©2001 European Medical Device Manufacturer