More skillful solutions from DuPont. Engineering Polymers for High Performance Gears To satisfy the demand for lighter, faster, products, including windshield wipers, quieter, more durable, cost-effective windowlifts, speedometers, rotary pumps, products, innovative designs increasingly appliances, power tools, clocks, and office include the use of high-performance automation equipment. plastics. In applications ranging from No other supplier today offers more high- automotive components to office performance polymers for gears and more automation equipment, engineering expertise—from design consultation to polymers successfully replace metals— molding assistance—to streamline mate- even in fine critical gears—and contribute rial selection. With the recent introduc- superior performance. As design engineers tion of additional grades to many product worldwide discover the remarkable families, DuPont offers a wider range of benefits of polymers for gears, they also solutions than ever before. discover that identifying the right product Delrin® acetal resin for the job can sometimes be a difficult DuPont Polymers: The Right proposition. Choice, Right from the Start Gear trains used in Lexmark’s Optra By involving DuPont early in the develop- laser printers have 11 gears molded from DuPont Can Help You Hit the Mark ment process, along with an experienced Delrin®. The gears drive the printer’s DuPont has been helping to solve tough team of gear molders and designers, toner drum, fuser rollers, and other gear design problems almost as long as DuPont can help you select the ideal prod- media transport rollers or in ink transfer we’ve been making polymers. In fact, uct to meet your exact needs and help you and fusion operations to an output tray. the earliest plastic gears were made with enjoy the following benefits of plastics: In the spur gears, Delrin® 500P offers the industry’s first engineering polymer, dimensional stability, high strength, DuPont™ Zytel® nylon resin. Lubricity. A low coefficient of friction low friction and wear, and high molding provides gears of Delrin®, Zytel®, and other DuPont™ Delrin® acetal resins and Zytel® productivity. In the helical gears, Delrin® DuPont engineering polymers with a dis- nylon resins have been used in gears for 500CL satisfies additional requirements tinct performance advantage over metals more than 40 years in hundreds of diverse for low wear and friction at high PV in applications that do not permit external conditions. lubrication or where lubrication is limited to initial installation. DuPont offers a variety of internally lubricated polymer compositions to further improve wear resistance and reduce friction without the expense or assembly complication and inconvenience of external lubricants. Shock Resistance. The intrinsic resilience of plastic gears provides superior damp- ing of moderate shock or impact loads. Toughened grades of Delrin® and Zytel® as well as unmodified Hytrel® thermoplastic polyester elastomer are available for high-shock applications. DuPont polymers for gears at a glance. Delrin® acetal resin (POM) Hytrel® thermoplastic polyester The most widely used DuPont resin for gears, Delrin® elastomer (TPC-ET) provides strength and stiffness without the need for Hytrel® provides extra tough teeth for gears subject to glass fiber reinforcement. In addition, Delrin® offers a extreme shock or when mesh noise reduction is required. superior combination of performance benefits: excellent Often, just one gear made of Hytrel® is enough to reduce mechanical properties—strength, toughness, fatigue noise in an entire gear train. endurance, and surface hardness—good lubricity, and resistance to wear, moisture, and chemicals. Crastin® PBT, Rynite® PET, and Thermx® PCT thermoplastic polyester resins ® Zytel nylon resin (PA) Crastin® PBT, Rynite® PET, and Thermx® PCT are selected The first engineering polymer for gears, Zytel® offers for strong, stiff gears in environments where a high exceptional strength, toughness, temperature resistance, degree of dimensional stability is required. The broad and excellent moldability. It can be modified in a number thermoplastic polyester product offering allows a range of ways to optimize performance, and is frequently used of service temperature requirements to be met. in conjunction with Delrin® to reduce gear noise and wear. Zenite® LCP liquid crystal polymer resin ® Zytel HTN high performance polyamide Zenite® LCP may be the best solution in applications resin requiring any or all of the following: extremely thin Compared with other nylons, Zytel® HTN exhibits or small gears, exact tool replications, ultra-high enhanced retention of mechanical properties with temperature resistance, superior chemical resistance, exposure to moisture, chemicals, and elevated exceptional dimensional stability. temperatures. Zytel® HTN grades are available in both PPA and PA types. Vespel® parts and shapes Vespel® tackles high-performance gear applications. ® Minlon mineral-reinforced nylon resin DuPont offers finished gears of Vespel® manufactured to (PA) your specific requirements. Minlon® offers better strength and stiffness than unreinforced nylon. Compared with glass reinforced nylon, Minlon® exhibits less potential for part warpage. Noise Reduction. Pliable plastic gears properties which can be enhanced by offer smoother, quieter operation than modifications. Selection of modifications metal gears. When designed with ad- should be based on the expected failure equate clearance, plastic gear teeth will mode, such as wear, fatigue, tooth shear, deflect slightly under loading. This deflec- or bending. Unlike metal gears, plastic tion makes small differences in pitch and gears should be designed to allow for profile less critical, thus helping to reduce tooth deflection, which is a result of the noise from meshing teeth. DuPont’s flexural modulus of the polymer. Gear life toughened resins are more flexible and can be maximized by selecting a polymer, help to enhance this effect. For highly family and modification that balances sliding meshes, like those found in worm friction and wear properties, strength, or helical gear arrangements, potential and fatigue resistance all at operating plastic squeak can be prevented by temperature. selecting one of DuPont’s many internally Chemical Resistance. Compared with lubricated polymers. most metals, plastics offer superior Cost Efficiency. Gears made with DuPont resistance to the corrosive effects of a polymers can be a cost-effective alterna- wide range of chemicals. Gears made of tive to metal. The nature of molded plastic Delrin®, Zytel®, Zytel® HTN and other semi- permits parts consolidation and therefore crystalline DuPont polymers resist most reduces costly manufacturing and assem- oils and lubricants, solvents, and more. bly operations. Cams, bearings, ratchets, Weight Reduction. Plastics have lower and gear shafts can be designed as an density than metals even when reinforced integral part of an injection molded plastic with glass and other materials. Gears gear. Multiple gear clusters also may be made with DuPont polymers can signifi- molded as a unit, decreasing part count cantly reduce inertia and total assembly and significantly increasing costs savings. weight. Durability. In low-stress environments, plastic gears typically offer longer lasting performance than their metal counterparts. Unmodified Delrin® and Zytel® both exhibit excellent friction, wear, and mechanical Zenite® LCP liquid crystal polymer resin Two mating oval gears molded from Zenite® LCP precisely meter motor oil or other automotive fluids flowing through a hand- held electronic meter. Zenite® 6330, a 0% mineral reinforced formulation, fulfills Graco’s demanding requirements for molding accuracy, exceptional dimensional stability, and resistance to attack by automotive lubricants, brake fluid, and antifreeze. What a Few Pages Can Do for You More Products, More Solutions This brochure is designed to introduce you In addition to our widely specified to DuPont’s wide selection of polymers resins for gears—Delrin® and Zytel®— for gears and to offer some general DuPont offers the broadest assortment material selection guidelines. We hope of engineering polymers in the business. you’ll use this information as just one With so many high-performance products part of a material selection process that to choose from, it would be difficult to includes technical support from DuPont. list every available resin grade. Table 1 presents the DuPont polymer families for gears along with applicable modifications, reinforcements, and lubricants. Recently introduced compositions are highlighted. Table 1. DuPont Engineering Polymers for Gears Reinforced/Modified Lubricated PTFE Aramid ® Product Composition ® Glass Mineral Silicone Nucleated Toughened Unmodified, Teflon Finished Gears Kevlar General Purpose Internal Chemical Multiple Flow Grades Enhanced Crystallinity/ Product Family Delrin® acetal resin ▲ ▲ ▲ ■ ■ ■ ▲ ■ ■ Zytel® nylon resin/Minlon® ■ ■ ■ ■ ■ ■ ■ ■ ▲ mineral-reinforced nylon resin Zytel® HTN high performance ■ ▲ ▲ ▲ ▲ polyamide resin Hytrel® thermoplastic polyester ■ ■ elastomer Crastin® PBT thermoplastic ■ ■ ■ ■ ■ ■ ▲ polyester resin Rynite® PET thermoplastic ■ ■ ■ polyester resin Thermx® PCT polyester resin ▲ ▲ ▲ Zenite® LCP liquid crystal ■ ■ polymer resin Vespel® parts and shapes1 ▲ Key: ■ = available grades 1 Vespel® is the only polymer made into finished gears by DuPont. ▲ = new composition since 2000 Vespel® is not available