Originally Published October 2000
Resins & Compounds
A line of customizable expanded polytetrafluoroethylene materials is available for medical and laboratory uses. The Poro-Tex materials support a wide variety of applications, from venting media and microfiltration to analytical equipment. Poro-Tex membranes are available in pore sizes from 5 to 0.05 µm and have uniform pore size and pore-size distribution. They are especially suited to high-performance liquid chromatography, microfiltration, venting media, test-strip blotters, and other uses in which the filtering of gases and liquids or wicking of liquids is required. DeWal Industries Inc., 15 Ray Trainor Dr., Saunderstown, RI 02874.
A type of polyaryletherketone, marketed under the name of PEEK, can withstand up to 3000 autoclave cycles. The semicrystalline biocompatible material maintains high mechanical strength and resists stress cracking in the presence of hot water, steam, solvents, and chemicals. Because of its properties, the polymer was selected by device manufacturer Surgical Innovations to replace metal in several applications. For example, PEEK was specified for a cannula that is inserted into the patient's abdomen to provide a working channel during minimally invasive surgical procedures. It was also used in a medical valve assembly. A worldwide network of specialist extruders and stockists provides a wide range of PEEK stock shapes including sheet, plates, rods, and tubes. Victrex, Hillhouse International, Thornton Cleveleys, Lancs FY5 4QD, UK.
Five families of polyurethane resin can be utilized for extrusion or injection molding applications. Tecoflex, Tecothane, and Carbothane are available in a durometer range from Shore 75A to 75D. Tecophilic is a hydrophilic polyurethane designed to produce rugged injection-molded components. The resins are designated medical-grade biomaterials and have passed USP Class VI, MEM elution, or other necessary tests to establish biocompatibility and biostability. Thermedics Inc., 470 Wildwood St., Woburn, MA 01801.
Porous plastics are manufactured for use in venting, filtering, controlled release, diffusion, wicking, and membrane support. The materials are made from thermoplastic polymers, primarily high-density polyethylene, ultrahigh-molecular-weight polyethylene, polypropylene, and various combinations of these thermoplastics. The porous products have an intricate network of open-celled omnidirectional pores. Controlled particle-size distribution produces a wide range of interconnected cell structures and specific pore size ranges. M.A. Industries Inc., 303 Dividend Dr., Peachtree City, GA 30269.
Silicone rubber dispersions
Color charts, consisting of molded silicone rubber buttons in various colors, can assist OEMs and silicone fabricators in selecting a suitable color for their applications. The color samples are derived from the company's pigment and additive dispersions for both liquid and high-consistency silicone rubber. The Healthcare binder features a collection of pastel, translucent, and primary colors for liquid silicone. All are based on FDA-listed ingredients. Gayson SDI, 30 Second St. SW, Barberton, OH 44203.
An acrylic-based multipolymer compound has been designed for medical applications requiring a high degree of chemical resistance to lipids and PVC plasticizers. Transparent Cyrolite CG-97 is an easy-to-process impact-modified compound suitable for injection molding. Good processability at low temperatures makes it ideal for use in thin-walled devices, multicavity parts, and other difficult-to-fill molded products. It exhibits good initial light transmission and 85% clarity after radiation, showing no deterioration of properties following gamma sterilization at typical irradiation levels. The material does not yellow but rather shifts to a permanent blue-green tint. Sterilization of medical parts made from the substance by EtO gas causes no adverse effects. CYRO Industries, 100 Enterprise Dr., Rockaway, NJ 07866.
A family of high-consistency elastomers has been developed for users that desire high-volume production with flexibility. VersaSil3 30, 50, and 70 can be used to produce extruded, molded, and calendered silicone parts. The cure rate and table life can be adjusted for specific fabricating requirements in this three-part system. The system also includes three base stocks, which can be vulcanized by a peroxide or a platinum addition- cure master batch. Additionally, the base stocks may be blended to produce elastomers of intermediate durometer and other physical properties. NuSil Technology, 1050 Cindy Lane, Carpinteria, CA 93013.
A company specializes in manufacturing biodegradable polymers from lactide, glycolide and caprolactone. The Lactel line is used in medical devices such as sutures, suture anchors, screws, pins, and rods. Physical properties can be tailored to produce semicrystalline, high-strength materials for sutures, and degradation times can be varied from weeks to years to meet specific applications. Materials may be fabricated into devices or fibers by extrusion, injection or compression molding, and melt pressing. Birmingham Polymers Inc., 756 Tom Martin Dr., Birmingham, AL 35211.
PVC, EVA Lay-Flat Tubing
A medical-grade extruded lay-flat tube, now manufactured in the United States, has been developed for hemodialysis, CAPD, IV, TPN, drug-delivery, and other solution applications. Solmed Medipak is a closed, airtight system that reduces contamination from microorganisms, pyrogens, and other particulates. The tubing is available in PVC, with non-DEHP formulations available, and EVA, and can be RF or heat sealed. Solvay Draka Inc., 6900 Elm St., Commerce, CA 90050.
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