“We know there's a problem in the healthcare market with infections,” says Kevin Dunay, market segment leader for the consumer and medical segment, BMS. “Infections are costly, dangerous, and deadly, and BMS is trying to address this problem with new products such as antimicrobial Makrolon polycarbonate resin that can help inhibit the growth of bacteria.”

Two developmental grades of antimicrobial Makrolon polycarbonate — grades DP1-1868 and DP1-1869 — have different levels of efficacy. Stain testing shows that bacteria on untreated polycarbonate grows unabated, while bacteria growth on the antimicrobial Makrolon polycarbonate is almost nonexistent.

Potential applications for antimicrobial Makrolon polycarbonate resin include intravenous (IV) access systems, urological devices, and housings for diagnostic and hospital equipment.

Another polymeric solid antimicrobial is said to be a nontoxic, environmentally sustainable means of permanent protection for plastic products and costs less than silver-based antimicrobials.

Biosafe HM-4100 from Biosafe Inc., Pittsburgh, (biosafe.com) is a cationic quaternary ammonium salt. Until now, this type of antimicrobial was not used in plastics because it was available only in liquid form, which made it difficult to incorporate. Biosafe HM-4100 is a crystalline powder based on patented polymer technology that is thermally stable in injection molding and extrusion. It reportedly will not discolor or leach out of a wide range of thermoplastics.

Biosafe chemistry is FDA listed as a modifier for medical devices and has received EPA approval. It is said to protect plastics from staining and degradation caused by bacteria, mold, mildew, and fungi, yet does not compromise transparency in clear resins. Biosafe is effective at levels as low as 0.25% to 0.50%, whereas other antimicrobials require up to 1%. Biosafe also works faster. For example, Biosafe in TPU suppressed E-coli bacteria in under 4 hr, while a silver-based antimicrobial took the typical 24 hr. Biosafe HM 4100 costs at least 33% less than competitive silver necessary to protect the plastic. HM-4100 is aimed at medical devices and surfaces in healthcare environments.

Spotlight on radiation shielding

While medical devices are currently not included within the scope of RoHS regulations, the European Commission plans to present proposals for including them. Industry sources indicate they could be regulated as early as 2010. “Many of our customers are looking for lead replacements where possible in advance of the possibility that the EU will strengthen the directive to a complete ban by 2010,” says Matt Hlavin, cofounder, Green Shielding Solutions, which is a joint venture between Thogus Products, Avon Lake, Ohio, and Vulcan GMS, Milwaukee.

“RoHS exemptions are reviewed on a regular basis, and the outcome of the upcoming review will depend on the commercial success of lead-free alternatives,” says Green Shielding Solutions cofounder Tom Ray. If the European Commission deems lead-free products as viable, they will be more inclined to remove the exemption for medical devices.”

Tungsten and lead are the two most commonly used elements for cost effective radiation shielding. Tungsten is a non-toxic, environmentally friendly material. Testing, both on prototypes and actual products already in use, has proven that Green Shielding Solutions' tungsten-filled polymer products in varying densities provide radiation shielding and attenuation up to and including a one-to-one equivalency to lead.

Another line of thermoplastic materials with high specific gravity (HSG) may replace lead in many healthcare applications that call for radiation shielding. High-density compounds such as LNP Thermocomp HSG radiation shielding from Sabic Innovative Plastics'(www.sabic-ip.com) allows injection molding X-ray shields without the use of known toxic substances, while providing greater design freedom and higher-volume manufacturing with lower total-part cost.

The X-ray shielding compounds have been shown to shield radiation up to the effectiveness of lead without leakage or hot spots. They are also based on tungsten. LNP Thermocomp HSG X-ray shielding compounds can be made with enhanced stiffness, strength, and impact resistance for demanding injection-molding applications.

“Replacing lead with LNP Thermocomp HSG compound in our X-ray equipment may help us provide a higher level of safety for patients and caregivers,” says David Barker, engineering manager, GE Healthcare. “Part-to-part consistency made possible by injection molding facilitates uniform shielding, and gives designers precise control over the amount of radiation filtered through their devices. The fact that this compound is environmentally responsible and reduces overall system costs was a welcome bonus.”

LNP Thermocomp HSG compound offers the potential to replace other shielding materials for similar cost and performance advantages. Applications include X-ray shielding devices and containers, housings, X-ray tubing components, dental X-ray equipment, and nuclear medicine containers.

Spotlight on TPEs

Global demand for thermoplastic elastomers will grow 6.2% annually through 2009, driven by direct displacement of competitive materials and by over-molds onto rigid plastic and metal, according to the Freedonia Group, Cleveland, Ohio. Part of the growth is attributable to eight grades of Versaflex and Versollan TPEs from PolyOne Corp., Avon Lake, Ohio, (www.polyone.com), all suitable for overmolding applications and FDA compliant. “The materials are a part of the GLS (www.glscorporation.com) brand and are used in overmolding and soft-touch applications,” says Michael Rademacher, senior vice president and general manager, PolyOne Distribution.

The company says its Versaflex elastomer alloys are next generation TPEs intended to deliver high performance in demanding applications. They come in clear, sterilizable, medical grades, high performance overmolding alloys, and an easy-to-process general purpose series.

Versollan elastomer alloys contain BASF Corporation's high-performance thermoplastic polyurethane (TPU), and are a new class of soft TPU elastomers with improved processability and cycle times. These products have the enhanced performance characteristics of TPUs with the rubbery grip and a matte finish.

Other TPEs, Monprene from Teknor Apex, Pawtucket, RI, (www.teknorapex.com), are composed of saturated styrene block copolymer rubbers and thermoplastic olefin resins. Compounds are within the complete Shore A hardness range (0 to 90), specific gravities range from 0.89 to 2.0, and optical properties range from transparent to opaque. Monprene compounds exhibit a rubber-like feel and the company says they are easily processed on conventional thermoplastic equipment. The surface characteristics and feel of the elastomers range from high coefficient of friction (high tack) to low coefficient of friction with a dry feel. Grades with higher tack are generally clearer than equivalent grades with less tack.

Monprene FDA compliant grades are available for a variety of applications. The company says most FDA grades are in compliance with FDA c.21 CFR 177.1810 and ISO 10993. The material comes in injection molding and extrusion grades. It can be custom compounded into a range of viscosity characteristics to fit the required processing parameters.