Originally Published MPMN January/February 2002
Originally Published MPMN January/February 2002
PRODUCT UPDATEK 2001: Living in a Material World
Polymers that promise device OEMs cost and performance benefits debuted at the international plastics and rubber show
Every three years, the K show occupies the massive fairgrounds in Düsseldorf, Germany, turning the city into the de facto plastics capital of the world. From raw materials and processing equipment to contract manufacturers, exhibitors cover the spectrum of activities directly or peripherally related to the plastics and rubber industry. Although visitor attendance at the 2001 show took an understandable dip for the first time in decades, exhibitors were not deterred and squeezed into every nook and cranny of the 17 halls. In fact, if the show organizers had not announced that attendance was down by 12% compared to the 1998 show, it's doubtful that anyone would have noticed.
Although automotive products and consumer goods were among the most visible applications on display, numerous suppliers of materials, equipment, and services that cater to the device industry were present. Several of them chose K 2001 as a platform to introduce products suited for the medical market; they will be profiled in MPMN as the technologies become available to North American customers. In this section, we focus on exhibitors who introduced materials that may lower production costs or improve the performance of medical products.
Nova presents a clear alternative to premium-priced materials
|A clear impact-modified SMMA copolymer from Nova Chemicals, Zylar delivers toughness and clarity at a lower total molding cost than polycarbonate.|
Designing and manufacturing a new device is a little like bringing up your first child. You coddle it, sparing no effort or expense to ensure its safety. After a couple of panicked visits to the emergency room that prompt the physician to chuckle and comment, "first-time parents, eh?" you learn that you might be trying too hard. In the product design world, that's called overengineering. According to Greg Wilkinson, business director for the NAS and Zylar families of materials at Nova Chemicals Inc., it's quite common, and often unnecessary.
"In the early stages of a product's life cycle, the tendency is to overengineer the device. Later on, OEMs often will take a second look at their devices and realize they don't need all of that strength . . . that they're using aerospace technology where it really isn't required," says Wilkinson. When they reach that point, Wilkinson hopes they will keep Zylar in mind.
A clear, impact-modified SMMA copolymer with enhanced stiffness and heat-deflection temperature, Zylar reportedly delivers toughness and clarity at a lower total molding cost than acrylic, polycarbonate, or clear ABS resins. The Zylar 94-568 formulation was introduced during the K 2001 show by Nova at an off-site location.
"Zylar 94-568 is designed for applications where impact resistance and elongation strength are needed and stiffness is essential," says Wilkinson. It represents an attractive alternative material for manufacturers of mature products seeking cost-efficiencies, he adds. "It doesn't have all of the strength of polycarbonate, but it may have enough to satisfy your needs."
Because it processes like a styrenic, Zylar is easier to work with than polycarbonate and thus reduces utility costs and cycle times, according to Wilkinson. The material is alcohol resistant and withstands gamma and EtO sterilization. Parts made of the material can be solvent welded. Current applications include Yankauer suction wands and IV components.
The company also announced during the show that the material had successfully completed ISO 10993 testing. "By meeting the ISO standard, Nova can help OEMs accelerate the approval process," stresses Wilkinson.
Nylon's flow qualities ease processing
|Orthopedic devices may benefit from a semicrystalline nylon introduced by Rhodia Inc. The material's performance characteristics match those of other polyamides but it is easier to process, according to the firm.|
The core applications of a semicrystalline nylon introduced by Rhodia Inc. are in the automotive sector, but it may also have a bright future in medical devices. Orthopedic devices, in particular, are under serious consideration, according to Philippe Guinot, strategy and business development director at Rhodia Engineering Plastics.
"The Technyl Star material's flow characteristics result in substantial processing advantages," says Guinot, who cites reduced mold-fill times, lower processing temperatures, and the ability to use smaller presses as some of the benefits. This family of polymers is based on a proprietary polymerization and compounding technology that engenders a nonlinear structure in the polymeric chain.
In addition to its processing characteristics, Technyl Star achieves high mechanical and thermal properties at room and elevated temperatures. "The performance characteristics match other polyamides and high-performance polymers," points out Guinot, "but it is much easier to process." The material's chemical and physical properties, he adds, minimize roughness in the surface finish even with highly filled grades. Consequently, Technyl Star is well positioned for applications in which strength and surface aesthetics are required.
The device sector shows promise, says Guinot, who nevertheless cautions that "Rhodia will only consider nonimplantable products that do not come in contact with body fluids." A device manufacturer is evaluating the material, he adds, but it is too early in the process to mention any specifics.
"As with any new application, we are exploring how we can bring a functional value to our customers and, ultimately, to the end-user. In this case, we can bring down the overall production costs and reduce the weight of the final device," says Guinot.
Interest heats up for thermally conductive TPEs
As power densities increase, conventional plastic products become prone to overheating, thus causing component failure. Thermally conductive plastics can solve this problem while enhancing design flexibility. Cool Polymers Inc. introduced some recent medical applications of the materials at K 2001.
Among other products, the company exhibited a temperature monitor the size of a watch battery that incorporates a thermally conductive liquid crystalline polymer. The monitor acts like a heat pipe, conducting body heat at rates up to 50 W/meter Kelvin to a sensor that sends the data via a wireless connection to a computerized monitoring system.
The company also showed an integrated high-torque motor and driver suited for use in medical equipment. The component is aimed at designers who want the simplicity of onboard electronics without the expense of an indexer on each axis. The part uses a thermally conductive polycarbonate to draw heat away from the controller and dissipate it into the surrounding air.
Thermally conductive materials can be formulated with most base thermoplastics. They feature a low coefficient of thermal expansion and contribute to a reduction or elimination of additional parts and assembly processes. The materials are available in electrically insulative and conductive grades and meet UL flammability requirements; some grades are also suitable for EMI and RFI shielding applications.
New TPE exhibits array of benefits
Based on proprietary technology, a new thermoplastic elastomer combines the high-temperature performance of silicone rubber with the melt reprocessing characteristics and thermal and chemical resistance of engineering thermoplastics. At K 2001, Dow Corning Corp. announced that it is in the early stages of commercializing the thermoplastic silicone vulcanizate (TPSiV) material. "We have begun sampling limited quantities to customers who contributed in the development of TPSiV," says Kevin Murphy, Dow Corning's global portfolio leader for thermoplastics.
In addition to the attributes mentioned above, the material's benefits include its compatibility with injection molding, extrusion, and blow molding processes and its ability to bond with a variety of substrates. Its silky feel is achieved without the use of plasticizers, and the material is available in durometers ranging from 50 Shore A to 60 Shore D.
"Initially, we will be going into automotive applications," notes Murphy, "but we are seriously looking at the medical market as well." The material's properties, along with its cost, make it "a natural for this sector," he adds.
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