Medical Device Link.

Originally Published EMDM September 2003

Product Update

A new antimicrobial material from the Specialty Elastomers business unit of Milliken Chemical is suited for the manufacture of gaskets, seals, O-rings, and other components used in medical equipment.

A new antimicrobial technology and thermoplastics with enhanced breathability are launched at the Chicago plastics show.

Hammered by rising oil prices and knee-deep in a soggy economy, the plastics industry did not anticipate a blockbuster NPE show in Chicago this year. Some openly wondered how bad it was going to be. Although attendance fell almost 30% compared to the record set in 2000, the number of exhibitors, down only 4%, barely took a hit. More importantly, the exhibitors I spoke with were fairly upbeat. Of course, most of my appointments were with suppliers for whom the device industry is a key customer. They have good reason to be optimistic.
According to a recent report on the medical device plastics market, demand for resins will grow by more than 4% annually over the next five years. By 2008, medical technology companies will consume almost 2.9 billion lb of resin annually, according to Business Communications Company, Inc. With growth industries hard to come by, it should come as no surprise that NPE exhibitors were eager to highlight products with medical applications.

A sampling of product introductions relevant to device OEMs are featured in this article. Suppliers of medical-grade polymers and alloys are profiled in the accompanying company descriptions.

Building a Better Antimicrobial

The Specialty Elastomers business of Milliken Chemical (Middleton, Lancs, UK) chose NPE for the global launch of its nonleaching antimicrobial heat-cured rubber compounds. The Elastoguard materials reportedly address some of the deficiencies of “traditional antimicrobial materials that come from an organic base,” according to Scott McDowell, marketing analyst and planner for Milliken’s coated products and elastomers business in the United States. These drawbacks include the chemicals’ tendency to leach from the matrix material and to degrade at processing temperatures above 250°C, says McDowell.

The patented biocide—Alphasan silver-sodium-zirconium-phosphate ion-exchange resin—used in Elastoguard compounds reportedly provides skin-to-core protection. Thermally stable at temperatures above 800°C, the materials slowly release silver ions, which are exchanged for other common, positively charged ions in the environment. Scientists theorize that the absorption of silver ions by microbes interrupts the formation of vital enzymes used in energy production. As a result, the microorganisms quickly lose their ability to grow and reproduce.

Considered to be safe, nontoxic, and nonirritating, the biocide requires no special handling. Once vulcanized, the silver antimicrobial is encapsulated in the rubber matrix. It has been approved for use in medical devices by numerous regulatory bodies worldwide.

Elastoguard antimicrobial rubber compounds are supplied in standard formulations ranging from natural rubber to EPDM grades to high-performance fluoroelastomers. They are available in 40 to 90 Shore A hardness ranges, and can be offered in slab, strip, calendered sheet, or pellet form. The materials can also be preformed into specific shapes for OEM use. The compounds can be formulated for moulding, extrusion, autoclave, or coating applications.

Potential uses for the antimicrobial rubber include numerous components in medical and pharmaceutical processing and packaging equipment and filtration and fluid-handling equipment, according to Milliken. To learn more about this product, see the company profile in this section.

Thermoplastics News

Some grades of thermoplastics also made their debut at NPE. Star Thermoplastic Elastomers (Chicago, IL, USA) unveiled its Mediflex compounds suited for a variety of medical tubing and other applications. The materials’ properties are detailed in the company profile in this section.

A supplier of thermoplastic polyurethanes, Noveon Inc. (Cleveland, OH, USA), introduced two Estane formulations. The high-heat and ultra-HMVT materials are suited for a number of breathable medical apparel and wound-care applications.
The company’s breathable TPU technology reportedly achieves a moisture-vapour transmission rate that is six times greater than traditional TPU materials. The new ultra-HMVT formulation takes the technology a step further, notes new business development manager Susan Hemphill. “It creates a monolithic barrier in film or coated form,” she says, keeping out water and other fluids while allowing moisture vapour to move about freely. The chemistry of the Estane HMVT grades allows manufacturers to specify the breathability required for a specific application. This technology is profiled in the company description that appears on the following pages.

The company also featured its Estane Easy to Extrude (ETE) TPUs at NPE, which are now available globally in grades up to 80 Shore D. These materials overcome the shortcomings typically associated with TPUs in the 50 Shore D range and higher. TPU’s narrow melt range, rapid crystallization and setup, and tendency to freeze within the extruder can lead to line stoppages and reduced productivity. Estane ETE TPU pellets, on the other hand, are melted and maintained at a usable viscosity without the appearance of crystallized chunks or gels. Extrusion can be interrupted with material in the barrel for as long as 25 minutes with no restart problems or product defects.

These properties allow engineers to design thinner profiles and cross sections into products without substantially affecting their end-use physical properties or performance. By using less material, overall production costs are reduced.

PPS Formulator Eyes Medical Market

Polyphenylene sulphide (PPS) is a heat- and chemical-resistant engineering plastic that can be moulded to tight tolerances. Often used in electronics applications, notably connectors, Ryton PPS from Chevron Phillips Chemicals International NV (Kallo, Belgium) may have some desirable properties for medical applications. At least that’s what Bryan Fox, market development leader at the company’s US operations, is currently researching.

“The material’s resistance to chemicals and the fact that it can withstand sterilization by autoclave would make it suitable for use in thermoformed medical trays,” says Fox. It is also lower in cost than the materials that are typically used in this application, he adds. Fox is currently researching the market for thermoplastic medical trays and evaluating how Ryton PPS can add value to the process. To learn more, contact Fox at 1540 Turnberry Ct., Geneva, IL 60134, USA; phone: +1 630 2087343; fax: +1 630 2087410; e-mail: foxbr@cpchem.com. 

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