Originally Published MDDI August 2002
BULLETIN BOARD
Polyamide-imide material performs well in nonlubricated applications. A new material designed for nonlubricated applications reduces wear on moving parts. Polyamide-imide also provides a margin for continued operation of lubricated systems if lubrication is lost. Torlon 4435, designed by Solvay Advanced Polymers (Alpharetta, GA; 770/772-8200), exhibits wear resistance to both low-pressure and high-velocity conditions, and high-pressure and low-velocity conditions. Torlon's durability is due to its ability to maintain mechanical properties at high temperatures. The polyamide-imide material features a glass transition temperature that allows parts to operate at temperatures of up to 260ºC. The 4435 grade, a thermoplastic material, can be formed into a net shape by injection molding. Torlon is also available in grades applicable to moderate environments.
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Protein-based biomaterials offer an unusually high level of human compatibility. A team of scientists has developed biomaterials based on human keratin proteins. The research, funded by Southwest Research Institute (San Antonio, TX; 210/684-5111), focuses on chemical modification of human hair keratins to create keratin-based hydrogels, elastomers, and coatings. Keratins, proteins that make up structural elements of vertebrate tissues, feature homologs numbering more than 100. Human hair keratins provide a structural diversity ideal for biomaterials and are highly tolerated as implantable materials. Once the human keratins are modified, they are processed into biomaterials with tailored chemical, physical, and biological properties. Testing of the biomaterials has revealed the potential of keratins to enhance tissue growth and promote tissue repair. Applications include wound healing, coatings for medical implants, soft tissue augmentation, cellular and protein therapy delivery, and matrices and scaffolds for tissue engineering.
A company offers a wide variety of nitinol fabrication operations. Nitinol material is now available in both wire and tubular form from UTI Corp. (Collegeville, PA; 800/321-6285). Nitinol provides shape memory, high elasticity, biocompatibility, and MRI compatibility. Elastic properties give it rubberlike qualities; it can return to its preset shape after deformation. Uniform Tubes, a division of UTI, has developed a tube-drawing process that is compatible with nitinol fabrication. UTI's Star Guide division specializes in precision wire applications for the alloy. Potential applications include guidewires, stents, flexible needles, orthodontic wires, clamps, and sutures.
Silicone-coated base film joins a line of durable release films. A flexible, UV-stabilized polyolefin release liner has been added to the Clearsil line of release films by CPFilms (Martinsville, VA; 888/273-4567). Valeron film, produced by Valeron Strength Films of Houston, is a high-performance liner available on a 3-mil white base with CPFilms' cleanroom-coated UV10 silicone release. Valeron film is printable, convertible, tear-resistant, durable, and resistant to air, heat, vapor, water, and chemicals. The liner is compatible with pressure-sensitive adhesives (PSAs), ensuring consistency in release, and offers low silicone-transfer properties for backside printing. Valeron can be used in final applications such as top-printed, pressure-sensitive, self-wound labels. The side opposite the silcone can be coated with a PSA to provide linerless labels. The Clearsil line is produced in environmentally controlled facilities to ensure optical quality and contaminant-free products.
Materials catalog introduces a line of high-temperature polyimides. A series of polyimides can be processed by direct forming, a molding method similar to that used in powdered metallurgy. The Meldin 7000series polyimides are formed using high-pressure mold presses, automatic resin-feeding systems, and computer-controlled hydraulics. Complex shapes can be molded, reducing the need for secondary machining operations. The Meldin 7000series features operational temperatures of 600ºF for continuous operation and 900ºF for intermittent exposure, and tight tolerances of ±0.001 in. on both ODs and IDs. Manufactured by Saint-Gobain Performance Plastics (Bristol, RI; 401/253-2000), the polyimides are available in two grades: unfilled 7001 and 15% graphite-filled 7021. The 7001 grade is suitable for high-temperature structural, high-purity semiconductor, and welding component applications, while the 7021 grade is efficient in stable, low-weight bearing and guideway applications.
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