Materials: Resin power

The past year saw the release of many new engineering resins as materials manufacturers geared up for the K Show. The new or upgraded resin selections covers the entire spectrum of engineering plastics applications. Presented here is a selection of these recently introduced materials and applications with the most significance for the Canadian market.

COPOLYMERS/ALLOYS ADD DASH OF EXCITEMENT

GE Plastics has launched a new line of aliphatic polyester/polycarbonate alloy resins which combine good chemical resistance, ductility and high flow along with superior transparency. Xylex was developed after the company researched the market needs of customers.

“Our customers wanted a resin that could maintain its performance properties and transparency when special effects additives were used,” says Francois de Ble, European product manager.

Xylex is targeted for telecommunications and consumer electronics products, primarily mobile phone covers, PC monitors and PDAs. The resin’s strong chemical resistance reduces cracking and crazing, while its high flow allows for thinner walls and in-mold decoration. It is available in GE’s Visualfx light diffusion special effects portfolio of materials.

One commercial application is a line of sports sunglasses in which a grade of Xylex replaced nylon. In addition to equal UV and chemical resistance, the material allowed the manufacturer to add translucent blue and black to the line. Xylex can be extruded into film and used as the substrate for cell phone keypads. While more expensive than PC, the material doesn’t have to be coated to achieve weather or scratch resistance.

Bayer Corporation says it has developed a new grade of its ABS/polyamide Triax resins that may solve the problem that has prevented wider use of plastic in the exteriors of cars and trucks. The company says it has raised the temperature resistance of Triax grade LP3155 so that it can now withstand the high temperature (185C or higher) usually found in the paint line areas of automotive assembly plants.

“We think this is a real breakthrough in the area of automotive body panel manufacturing,” says Mark Matsco, manager, process technology, Bayer Plastics Division.

Matsco says that in addition to high heat resistance, Triax LP3155 has an extremely low coefficient of expansion and can meet the Class A surface requirements of OEMs.

HIGH PERFORMANCE RESINS

DaimlerChrysler chose Ticona’s Fortron 1140L4 linear polyphenylene sulfide (PPS) when it switched from steel to plastic fuel rails in its 2.7 L V-6 engines. The new rails weigh 25 percent less and cost 30 percent less than the steel rails they replaced. As well, additional savings were realized by consolidating the seven components in the metal rail into a single molded component.

Mark Cerny, engineering supervisor at DaimlerChrysler, says the company also considered polyphthalamide and nylon, but picked PPS because of its better dimensional stability. PPS also had better permeation resistance and flex fuel compatibility than nylon, according to Cerny.

Bayer Corporation reports that the world’s first plastic oil sump for transmission systems has been made from glass fibre-reinforced nylon 6-6 Durethan AKV 35 H2.0. The part will be used in the new BMW 7-Series. The part has to be able to meet extreme performance requirements for impact, tightness of flanges and structural rigidity. Bayer believes the project has demonstrated the basic feasibility of making engine oil sumps from thermoplastic.

Cars will be equipped with a 42-volt electrical system in the near future. Responding to this change, DuPont Engineering Polymers has developed special grades of materials designed to meet higher demands for electrical performance. The flame-retardant Rynite FR531 PET was developed to meet stringent heat and electrical requirements. The material’s high temperature resistance and excellent insulation properties permit engineers to design small components such as electrical switches with densely spaced contact pins. Cherry GmbH of Aurebach, Germany used this grade of Rynite for its D-4 series of snap-action switches. The switches have a PTI (proof Tracking Index) rating of 300 V, which practically excludes the possibility that the switch will burn; allowing conventional, less costly plastic types to be used adjacent to it.

DuPont has also developed a grade of its PBT Crastin with significantly improved hydrolysis resistance. Low hydrolysis resistance has often limited PBT use in automotive and electrical applications. Grades HR5115HF and HR5130HF are 15 and 30 percent glass-reinforced products which also exhibit enhanced flow properties in comparison to traditional grades.

The new weatherable Solix film builds on GE Plastics’ first generation of molded-in color Xenoy PC/PBT resin developed as a thermoplastic replacement for metal exterior automotive parts. Solix film can be applied over a variety of thermoplastic and thermoset substrates through an in-mold decoration process, thus eliminating expensive paint processes.

When exposed to the equivalent of 10 years of Florida ultraviolet radiation, Solix film retained 95 percent of its gloss. When backmolded with a PC/PBT resin and subjected to various OEM paint specification tests, Solix film was found in most cases to perform better than or equal to exterior paint systems.

NYLON GETS NEW PLAYERS, GRADES, APPLICATIONS

Rhodia Engineering Plastics announced several new applications for the TechnylStar polyamide grades it launched at last year’s NPE. When it was launched at the show, Rhodia characterized the resin as not just another nylon but a whole new polymer architecture. In comparison to a conventional PA 6, TechnylStar has a lower viscosity, and improved flow properties which provide molders with enhanced productivity.

The polymer is offered in two families: S grade, which is 20 to 45 percent glass-filled; and SX grade, which is 50 to 65 percent glass-filled. According to North American automotive director Chad Waldschmidt, TechnylStar shows two-times the spiral flow length, compared with a standard PA 6 with identical levels of glass-fill, in standard spiral flow tests. This means that molders can successfully injection mold parts with higher levels of glass than previously possible using conventional PA, says Waldschmidt.

Recently, automotive Tier 1 supplier Mark IV replaced a standard 35 percent glass-reinforced PA 6 used in an air-intake manifold with a grade of TechnylStar. The material was used without modification to the current machine or molds. The material substitution resulted in a 10 percent improvement in cycle time, a reduction in injection pressure and a reduction in clamping force, according to Waldschmidt. Sample quantities of the material can be purchased from Rhodia’s Mississauga, ON compounding facility.

The Japanese firm Ube has formed a division, Ube Engineering Plastics, to market nylon 6, 6-6 and 12 in North America. One particular application being touted by the company is the use of its Ube nylon 6 (grade 1013 WX 50) and Ubesta nylon 12 (grade 3020 UX 1) in components going into a HDPE fuel tank. The nylon is used to make valves and inlet and outlet connectors previously made of HPDE. Nylon 6 is 50 times less permeable to fuel than HDPE and nylon 12 is five times less permeable. The components are mounted on the fuel tank with adhesive. New U.S. fuel regulations will require lower fuel permeation values from plastic gas tanks, which presently contribute to about 25 percent of the total hydrocarbon vehicle emission.

DuPont has broadened the performance range of its Zytel HTN line of nylon with the introduction of the new 53 and 54 series. The materials have been engineered for structural applications requiring high stiffness and impact resistance with low moisture absorption. As well, the new offering Zytel EFE 1166 can provide fast crystallization and cycle time reductions of up to 20 percent. Zytel ST ‘Advantage’ is a new range of super tough nylon resin with significantly improved flow characteristics, resulting in productivity improvement
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