Technology News

Polypropylene Resins Withstand Repeated High Doses of Gamma Radiation

A family of medical-grade resins exhibit virtually no degradation, deterioration, or discolouration after being exposed to multiple high doses of gamma radiation. According to Joseph Kopstein, president of Gamma-10 Plastics Inc. (Minneapolis, MN, USA), the resins his company has developed are unique.

"Products made from these polypropylene resins will last on the shelf for two to five years, even if they've been subjected to high levels of gamma or E-beam radiation," he says. If the polypropylenes routinely used today were sterilized in an equivalent manner, they would show signs of severe degradation possibly within days, according to Kopstein.

These properties make the resins especially attractive to manufacturers who would like to make the switch to gamma or E-beam sterilization but haven't done so because of the limitations of the materials they are currently using. "Syringes are an obvious candidate for the resins," says Kopstein, "but virtually any product made out of polypropylene or polyolefin would benefit."

The company also supplies film- and fibre-grade resins that are suited for medical pouches, surgical drapes and tapes for the operating theatre, "and any other application where ease of use and the capability to withstand high doses--or even multiple high doses--of radiation is desirable," says Kopstein. "In addition, these resins can withstand EtO, autoclave, and any other form of sterilization." Three of the resins created for operating-theatre applications feature a straight-line tearing capability, adds Kopstein, which precludes the need for perforations that could jeopardize sterility.

The resins are available in film, fibre, and injection grades with standard melt indices ranging from 1 to 35. "We can alter the melt indices and add gamma capabilities based upon customer requests," adds Kopstein. "In fact, we are willing and indeed eager to create new and different polypropylene and polyolefin formulations to meet the needs of our customers."

The resins can be heat sealed or joined by means of heat or sonic welding.

Small-Diameter Cables Developed for Catheter Applications

Ultrathin cables designed for catheter applications are composed of single or stranded microinsulated copper conductors. A jacket containing seven insulated wires can be produced in an outer diameter of only 0.26 mm. Manufactured by Axon' Cable (Montmirail, France), the components are especially well suited for electrophysiology, intravascular imaging, and electrical-based catheter therapy procedures.

Typically composed of AWG 43 wires, the conductors can be supplied with thin-walled outer jackets as well as in shielded versions. Because connectors are not available in such small sizes, the wires are soldered onto a transition flat printed circuit adapted to standard connector geometry. "The truly innovative feature of this product," says Véronique Faivre of Axon' Cable, "is the company's capability of assembling these very fine wires." The other end of the cable is fitted with a miniature ultrasound probe, blade, or other OEM-specified catheter attachment. The entire product, from the conductor to the terminated assembly, is manufactured in a cleanroom environment at the company's ISO 9001-compliant facility.

Axon' Cable designs and manufactures electronic cables and cable assemblies for a wide range of industries. In addition to its main facility in France, the company has subsidiaries in Germany, the UK, and the USA, and a sales office in Japan. The firm recently began construction of a new plant in France devoted to the high-volume production of flexible flat cables.

Cold-Plasma Treatment of PET Fabrics Enhances Wettability, Adhesion

Polyester mesh fabrics, particularly polyethyleneterephtalate (PET) formulations, are widely used in medical filtration applications because of their inert composition, calibrated and consistent openings, and mechanical resistance to tearing and fatigue. But there is always room for improvement, and product designers routinely modify the surface characteristics of materials to meet specific requirements. Of the surface treatments available, cold plasma is ideally suited to medical plastics, according to Paolo Canonico of Saatitech S.p.A. (Veniano, CO, Italy).

"Plasma-treated PET fabrics have the physical attributes of conventional fabrics but with restructured surface characteristics," says Canonico. One advantage is enhanced wettability of the treated area, resulting in faster and more uniform spreading and penetration of the liquid, he says. In addition, compared to other surface-modification methods, plasma treatment is a clean, dry process that does not require the use of additives. This represents a significant advantage for medical device manufacturers who are concerned about residue and low-molecular-weight leachables, notes Canonico.

In addition to filtration applications, plasma-treated PET also displays improved adhesive properties. The increased roughness and modified chemistry of the fabric's surface leads to a strong interfacial reaction between surface groups and chemical moieties within the adhesive, notes Canonico. "That creates a strong adhesive bond joining the treated fabrics and other liquid or solid products as well as plastic and metal parts," he says. "The enhanced bonding properties of treated fabrics is an advantage for product designers, who can exercise greater freedom in the design of innovative devices."

The company supplies plasma-treated PET as a raw material or in the form of custom mesh components.