ENGINEERING DESIGNMAY 2011

Innovative design solutions using DuPont high performance polymersin the industrial, consumer and energy sectors

If you are the kind of reader whojust homes in on one article, we’dlike to challenge you to read the others as well. It may seem at firstglance that there is little relevance toyour project or industry. However,what we continually find is thatsome of the best products , as well asthe most apparently novel designs,are a direct result of taking ideasfrom one industry and transplantingthem into another, sometimes with

just a small tweak to make them fit perfectly. Inside DuPontwe call this “industrial cross-fertilization.” Each industry hasdifferent ideas, needs and applications for the use of rawmaterials, but those same ideas and solutions often have somuch broader potential which can often go unnoticed. Ourown engineers and development support team are doing justthis – working with customers in many different fields andapplying technologies or solutions from one industry tobring advantages to another.

Take some of the stories in this issue of Engineering Design,for example. The Onzo Smart Energy Kit and the Autopen 2both use DuPont™ Delrin® acetal resin for small mechanisms –the characteristics of Delrin® homopolymer give it significantadvantages over copolymer, or any other polymer for thatmatter. When molded into small components, it provides

reliable mechanical performance – spring performance andcreep resistance, low wear and low friction, quiet operation,precision and strength all in the smallest space possible. It’sall the kind of stuff that the consumer expects performance-wise, but equally doesn’t want to have to think about. Relia-bility should be a given. Make the parts a bit bigger and theyhave the same reliable, accurate, low friction performance inthe large molded bearings you will read about in the photo-voltaic bearing article.

As for another example, take the use of DuPont™ Zytel®HTN high performance polyamide in laptop covers. Itreplaces PC/ABS blends where a step change in perform-ance is required. Unsurprisingly, the underlying require-ments are familiar to many different industries – higherstrength, higher stiffness, and lower weight to meet thedemands of the next generation of product.

So, in short, as you read through the magazine, we’d like tochallenge you to read the articles in a new light. How canthe solutions you see in these different industries be appliedto your own industry and design problem? We’d also bevery happy if we could work together with you on some ofyour challenges – by “cross fertilizing” the solutions we seefrom other industries to help solve your design and develop-ment material requirements.

You can reach us on: plastics@dupont.com

WHERE ARE THE DESIGN ANSWERS?BY MARK YOUNG, EUROPEAN MANAGER FOR INDUSTRIAL, CONSUMER ANDENERGY APPLICATIONS

Many times we ask ourselves how you, our customers, industry engineers, designers and managers, readEngineering Design magazine. Feedback we receive reassures us that it is appreciated, and read by a broad crosssection of the engineering and design community. Yet we suspect it is valued very differently at an individuallevel – sometimes read in chunks during coffee breaks, sometimes from cover to cover, or sometimes it may justbe a specific article that grabs your attention with the hope of providing a solution to your real and currentdesign challenges.

Mark Young

• DuPont™ Delrin® in the Onzo Smart Energy Kit (page 3)

• DuPont™ Delrin in the Autopen® insulin deliverydevice (page 4)

• DuPont™ Zytel® HTN in handheld devices (page 6)

• DuPont™ Delrin® in drivetrain transmission systems (page 8)

• DuPont™ Zytel® in the SonarBell® sonar responder (page 9)

• DuPont™ Hytrel® and DuPont™ Crastin® in the Generation byKnoll® work chair (page 10)

• DuPont™ Zytel® and DuPont™ Delrin® in photovoltaicapplications (page 11)

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The Onzo Smart Energy Kit is designed to put householdsin control of their energy use. It gives consumers real-timeinformation about how much electricity they are using intheir home and how much it is costing. By delivering action-able information that is easy to understand it helps them tolearn how to manage their consumption, saving both energyand money.

It works in three simple steps: 1) the sensor clips onto thelive wire of the electricity meter, 2) it sends the amount ofelectricity being used in the home wirelessly to the display,3) the display is connected to a computer to upload data, viaUSB, to a personalized website.

The display shows users how much energy their home isusing in real time, as well as contextualizing this informa-tion with targets and tools that help consumers understandtheir usage at a glance. The website allows users to digdeeper into how they use electricity and learn how they canreduce or change their consumption over time.

It’s as part of the sensor’s unique clamp design that compo-nents molded from Delrin® acetal resin play an integral rolein its attachment to the electricity meter and its ability toaccurately read energy consumption. “The gray clip is fun-damental to the simple and easy-to-use lock and releasemechanism, which we purposely designed for single-handeduse,” explains Jeremy Stimson, product design manager atOnzo Ltd, “while the spring inner ensures the constant con-tact between the two sections of the current transformer,the component that senses electricity consumption and con-verts it to a digital signal, which fits tightly around the elec-

tricity cable.” Indeed, it is the ability of the Delrin®spring to generate a con-

sistently reliable forceon the current trans-

former overtime that is key

to the long-termaccuracy of the

sensor. “DuPont

produced a stress analysis of the spring mechanism whichshowed that Delrin® acetal is able to outperform its competi-tors in terms of resistance to creep and stress relaxation,thereby extending the clamping force for this particularapplication,” confirms Stimson.

A further quality of the Delrin® spring is its ability to caterfor variations in size of the current transformer (CT). “TheCT is a rough, metal component with wide tolerances. Bychoosing Delrin® we could be sure that there was enoughflexural behavior in the springs to accommodate these dif-ferences in sizes,” continues Stimson. The integration ofdesign features such as snap fits, hooks and catches in theDelrin® components helped Onzo eliminate the use of metalclips or hinges that would otherwise interfere with the wire-less communication between the sensor and the display. Theexclusion of metal components also means that the sensor,as well as the display, can be more easily recycled at the endof their useful lives.

Launched in the UK in 2009 and a winner of the presti-gious red dot award in the same year, the Onzo SmartEnergy Kit is available free of charge to Scottish & SouthernEnergy (SSE) customers that sign up for its iplan energyscheme, or can be bought from Amazon in the UK.

A SMART MATERIAL FOR A SMARTDEVICEBY IAN WANDS AND MARK HAZEL, DUPONT PERFORMANCE POLYMERS UK

DuPont™ Delrin® acetal resin used for key components of the sensor included in the award-winning Onzo SmartEnergy Kit, ensuring high accuracy, reliability and consistent operation.

Onzo Ltd.

6 Great Newport Street, London WC2H 7JBTel.: +44 (0) 20 3051 3270hello@onzo.com, www.onzo.comCO

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Introduced during 2010, the Autopen® 2 constitutes a newgeneration of reusable pen injectors launched by OwenMumford (Oxfordshire, England) under the Autopen®trademark that benefit from an automatic delivery systemproviding greater patient comfort and control. Its principalenhancement, beyond the ability to deliver a dose of up to72 units of insulin in steps of one unit, is the integration of apatented mechanism that allows the user to correct the doseif it has been over dialed.

“The original Autopen® incorporated a dose meteringdevice, provided by a dose knob, that is rotatable to a posi-tion related to the dose of medication to be injected,”explains Mark Eaton, product designer at Owen Mumford.

“However once a dose had been set by the user, it could notbe reduced by winding the knob in the reverse direction andthe user had to expel the set dose and redial. The design ofthe Autopen® 2 resolves this problem.”

“Essentially a torsion spring is arranged within the housingto provide the drive force for ejecting medication from theinsulin cartridge,” continues Mark Eaton. “The dose settingknob is coupled to both the spring and the housing in sucha way that rotation of the knob relative to the housingresults in compression of the spring. When the user appliesa downward force on the trigger at the side of the pen, itreleases the spring and a drive member is driven through thehousing, expelling the required dose of insulin from the car-tridge. In the event that a user oversets a dose, the button atthe top of the dose setting knob, which is also coupled tothe torsion spring, is used to unwind the spring in discretesteps with each press of the button.”

Delrin® key to successful developmentThe principal components behind the sophisticated mecha-nism used within the Autopen® 2 are molded from a rangeof grades of Delrin®. Required properties of the DuPontacetal resins include strength and stiffness, dimensional sta-bility, fatigue resistance, low coefficient of friction andresistance to wear when used in intricate, geometricallyadvanced parts that, in many cases, move against each otheror are required to snap fit together.

For instance the locking bush, which is used to prevent therotational movement of the leadscrew until delivery of themedication is triggered, is molded from a toughened gradeof Delrin® due to the high torsional forces it must withstand,particularly during dose setting. It comprises a pair of fingersthat engage with a corresponding channel within the lead-screw to prevent rotation during delivery. They are requiredto be flexible enough to flex outwards over ramps on theleadscrew when it is passed through the centre of the lockingbush before snapping back to engage with the channels.

EFFORTLESS DELIVERYBY IAN WANDS, EUROPEAN HEALTH CARE SEGMENT LEADER AT DUPONT PERFORMANCE POLYMERS

Specific grades of DuPont high performance polymers that meet demanding requirements for use in medicalequipment enable the design and manufacture of reliable and durable products. This is illustrated by the recentlaunch of the Autopen® 2 insulin delivery device from Owen Mumford. It includes several functionalcomponents made of DuPont™ Delrin® acetal resin that are fundamental to its use for the effortless and accuratedelivery of insulin to diabetes patients.

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EFFORTLESS DELIVERY

Alternatively, the dose knob is molded in a laser-markablegrade of Delrin® for incorporation of the insulin measure-ments. It must also provide a robust surface for two sets ofgear teeth within the part which works with the clutch col-let and rewind button to allow the spring to unwind (as partof the dose correction procedure). A further five parts aremolded from Delrin®, including the drive gear, rewind but-ton, dose knob cover, ratchet drive shaft and cartridge com-pression cup.

“Of all the plastic parts used within the Autopen® 2, sevenare molded from Delrin® and they represent all of themechanical and robust components fundamental to itsoperation,” confirms Mark Eaton. “We would not have beenable to produce the Autopen® 2 without DuPont materials,the strength, dimensional stability and low wear/low fric-tion of which are key to ensuring simple, reliable and accu-

rate dose delivery.” Rigorous and comprehensive testingconfirmed the compliance of Autopen® 2 with the interna-

tional standard ISO 11608 for pen-injectors.

The Delrin® products were supplied to Owen Mumford byDistrupol, DuPont’s authorized distributor of its perform-ance polymers in the UK. Both Distrupol and DuPont pro-vided additional technical assistance with regard to reduc-ing friction within the dose setting and delivery mechanism.

DuPont: the material supplier of choice to thehealth care segmentDuPont offers one of the broadest portfolios of engineeringplastics and thermoplastic elastomers for medical devices,surgical devices and for diagnostic or pharmaceutical manu-facturing equipment. The DuPont health care productoffering provides food agency compliance (EMSA andFDA), ISO 10993-5 and -11 compliance as well as USPClass VI compliance. Specialty health care products aremanufactured following GMP.

The specialty health care grades with regulatory support areavailable in two versions, each reflecting different levels ofmanufacturing control and material testing. Customerswork with DuPont to identify the version that meets theneeds of their specific application. Sixteen of the productsare available as “special control” grades that meet very highstandards of manufacturing consistency important for awide range of non-implantable medical products. Twelve ofthe grades are available in “premium control” versions meet-ing requirements for even more demanding manufacturingcontrols, broader regulatory support, more testing, DMFaccess and the highest level of inspection.

http://healthcare.dupont.com

Autopen® is a registered trademark of Owen Mumford Ltd.

Owen Mumford Ltd.

Brook Hill, Woodstock, Oxfordshire, OX20 1TU, United KingdomTel.: +44 (0)1993 812021 info@owenmumford.co.ukwww.owenmumford.com

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Special Control grade of DuPont™Zytel® nylon for collagen implantdelivery device

The ChondroMimetic™ fromTiGenix NV is marketed as aprocedure pack with the collagenimplant preloaded in an accurate,easy-to-use arthroscopic deliverydevice. A Special Control (SC)grade of DuPont™ Zytel® nylonwas adopted for two of itscomponent – the plunger andcompressor fingers – each ofwhich come into directcontact with the implant andare key to holding it in placeand inserting it smoothly andaccurately into the defectsite. The DuPont materialwas specifically chosen forthe stiffness and low-friction behaviour of theplunger as well asproviding the preciseflexibility of thecompressor fingers.

ChondroMimetic™ is a trademark of TiGenix NV

With built-in shielding, excellent flow, dimensional stabil-ity, toughness and strength, Zytel® HTN can reduce thetotal system cost of thinner and lighter housings for laptopcomputers, tablet PCs, cell phones and other devices. Zytel®HTN also delivers the right property set for the many elec-tronic connectors, relays, light-emitting diode componentsand various other electrical and electronic parts containedwithin these devices. It can withstand high-temperature cir-cuit assembly methods, including those using lead-free sol-der, has good strength, stiffness and toughness over a widetemperature and humidity range, and is now also availableas a halogen-free grade providing conformity with recyclingprograms for discarded electronic products.

A thinner, lighter laptop housing A recent testimonial of the design flexibility afforded byZytel® HTN in handheld devices is provided by theredesigned housing of the Lenovo IdeaPad U550. Weighingin at just 5.3 lbs (2.4 kgs) and measuring just over one inch(2.5 cm) in height, it is remarkably thin and light for a 15.6-inch (40 cm) multimedia notebook. This is partly due tothe use of a non-halogen, flame retardant grade of Zytel®HTN for the LCD rear cover assembly (the so-called Acover) and the bottom cover assembly (the D cover). Bothcovers had been previously produced using a polycarbonate(PC)/ acrylonitrile butadiene styrene (ABS) blend, but bychanging to Zytel® HTN it has been possible to reduce theirwall thickness from 1.8 mm – the thinnest thickness possi-ble with PC/ABS – to 1.3 mm, a reduction of more than 25percent.

“Material stiffness is one of the critical requirements for themechanical stability of a laptop’s A cover, which has to pro-tect the sensitive electrical components inside the laptop aswell as the LCD screen,” explains Aric Dai (Huafeng),research and development director of the IdeaPad productgroup at Lenovo. “The improved flexural modulus (approxi-

mately 17 GPa) and flexural strength (approximately300 MPa) of Zytel® HTN makes it the material of choicefor the production of these thinner, lighter and more cost-effective covers.”

Drop and pressure tests were used to confirm the protectiveattributes of the laptop housing, including the placing ofloads of up to 25 kg (55 pounds) on the A cover. Duringhands-on consumer reviews, the laptop chassis and lid aredescribed as exhibiting only mild flex when grabbed by thecorners and twisted, whilst pushing on the back of the liddoes not yield any ripples in the LCD screen – an impres-sive performance considering its reduced thickness. As wellas improved strength, stiffness and impact resistance, thespecified Zytel HTN® grade also demonstrates excellentflame retardancy. Whereas a UL-94 V0 rating at 0.8 mmwas specified by Lenovo for the application, the halogen-free, flame retardant grade of Zytel® HTN achieves this atjust 0.4 mm.

The switch to Zytel® HTN also saw Lenovo adopt RapidHeat Cycle Molding (RHCM) technology for the produc-tion of the highly visible covers. This process can be used tomaximize the surface appearance of injection molded partswith a minimal effect on cycle time. Part costs can bereduced using this technology by eliminating the need forsecondary operations to hide surface defects, whilst it can

ZYTEL® HTN: A MATERIAL OF CHOICEFOR HANDHELD DEVICES BY JERRY TSAI AND RUI ZHANG, DUPONT PERFORMANCE POLYMERS ASIA

Engineering thermoplastics play an increasingly vital role in the production of electronic components anddevices. Rather than seeking a one-size-fits-all solution, polymer producers such as DuPont are tailoring materialsto the specific application with the goal of increasing performance and processing efficiency while lowering costs.One such product group is the DuPont™ Zytel® HTN family of semi-aromatic polyamides, which offers a combi-nation of properties that make them ideal materials for use in handheld devices.

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ZYTEL® HTN: A MATERIAL OF CHOICE FOR HANDHELD DEVICES

also be used to obtain glossy surfaces even with glass-filledmaterials. The adoption of RHCM technology was madepossible by the higher glass transition temperature (around115 °C or 240 °F) of Zytel® HTN than that of the previ-ously used PC/ABS blend.

Support in line with the customer's needsComprehensive technical support by DuPont assistedLenovo in its switch to the higher performance and morecost effective material solution, as Aric Dai of Lenovo recalls:“DuPont was able to offer a unique business package includ-ing access to its CAE capability during the design phase, on-site technical support, tool and customized gate design andmold-flow simulation, as well as a decoration solution whichwas in line with our design needs.” Indeed, patterns and tex-ture are a defining element of the Lenovo IdeaPad aesthetic,and the U550 is no exception. An extremely fine checker-board pattern molded onto the A cover makes it feel almostlike the texture of knurled metal to the touch. The covers arepainted and subsequent adhesion and warpage tests ensureconformity with production standards.

The Lenovo IdeaPad U550 with A and D covers moldedfrom Zytel® HTN was developed in Asia at the end of 2009and went into commercial production in China during May2010. Further laptops within the Lenovo range are pro-duced with either an A or D cover made with Zytel® HTNdepending on design requirements. Members of the Design& User Experience team for the IdeaPad Product Group atLenovo include Bulin Chen (designer), Zhensheng Wu(designer) and Detao You (material designer).

Dr. Ning Hao

Designer, IdeaPad R&D, LenovoNo. 6 Shang Di West Road, Haidian District, Beijing, China Tel.: +86-10-58862089 haoning@lenovo.com

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As part of its technical assistance, DuPont provided recommendations on gate location in order to achieve lower filling pressureand improved cover flatness

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The Ultra Light Urban Vehicle Project is the brainchild ofMartin Morris, professor of mechanical engineering atBradley University, Peoria, Illinois (US). The challenge todesign and manufacture a zero-emissions vehicle began in2006 and has evolved into a 3-wheeled vehicle licensed as amotorcycle that carries two people, baggage and weighs 430lbs (195 kgs). It offers regenerative braking, a top speed of45 mph (72 kmph) and a range of 40 miles (64 km) – theBradley design team claims it costs 0.6 cents per mile tooperate.

Several gears used within the vehicle’s drivetrain transmis-sion have been intricately produced using Delrin® acetal(POM) from DuPont Performance Polymers. Design andmanufacturing support for the project was provided byWinzeler Gear, Harwood Heights, Illinois. The gears faceconditions that traditional engineers may have previouslyconsidered off limits for standard acetal material, as MikeCassata, design engineer at Winzeler Gear confirms: “Thehigh-performance nature of a homopolymer acetal can man-age the torque and load while delivering low friction andreduced noise.” He added that the planetary transmissiongears of Delrin® POM must withstand the torque producedby a 25 horsepower motor @ 6,000 rpm.

The gears can be machined from Delrin® bar or plate stock,significantly cutting cost and time while delivering

mechanical properties comparable to the injection moldedgears. “We can proceed from design to machined modelsin weeks, with a small tooling investment,” said Cassata.

The successful use of Delrin® for gears in the Ultra LightUrban Vehicle goes some way to challenging the traditionalpreconception that POM is unable to withstand the harshconditions associated with transmission applications. It isnot difficult to imagine such gears being used in smallengine transmissions such as those found in riding lawnmowers and golf carts. Indeed this will be the focus of thenext generation of student design, where the young design-ers will be challenged to take even more weight and noisefrom the vehicle by using more Delrin® POM in the gearsand housings.

“As the world changes, we need to challenge many of ourpreconceived notions. We also need more whole brain,especially right brain, thinking to innovate,” concluded JohnWinzeler, president of Winzeler Gears and a fervent sup-porter of student challenges and art programs. “Studentdesign challenges, such as the one initiated by Martin Mor-ris at Bradley University, are great ways to challenge ourprejudices and stimulate new ideas.”

DRIVE YOUR IMAGINATIONBY TIM BROGLA, PROGRAM DEVELOPER AT DUPONT PERFORMANCE POLYMERS

An Ultra Light Urban Vehicle project at Bradley University shows how acetal gears – specifically gears made ofDuPont™ Delrin® POM – offer strength, toughness and low-friction attributes needed to take the load, stressgenerated in drivetrain transmission systems while significantly damping noise and reducing weight inherent inmetal gears.

The drivetrain transmission uses several intricately machinedgears that face conditions that traditional engineers mayconsider off limits for standard acetal material

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To find equipment in anything but clear shallow waterrequires the use of sonar. Even with sonar, visualising thewater column or sea bed is difficult and the industrial usersof the ocean use powered transponders to locate key equip-ment. Such transponders are not only expensive but requireregular routine maintenance depending on use and batterylife.

It is against this background that Subsea Asset LocationTechnologies (SALT) Ltd. of Salisbury (England) devisedthe concept for the SonarBell®, a passive sonar reflectorwhich acts much as a ‘cats-eye’ does in the road. It takes inexternal energy and provides a strong ‘reflection’ in return,magnifying the original signal back to the searchers. This isachieved without the SonarBell® requiring an internal powersource itself.

How it works is largely down to the elegant use of materialstechnology for its construction. Looking very much like abowling ball with diameters up to 200 mm, the SonarBell®has an outer shell made of DuPont™ Zytel® nylon and a coremade of very soft silicon-based gel. The different acousticqualities of the two materials used means that the soundwaves from the received sonar signal travel faster round theZytel® shell than through the silicon. This creates a construc-tive interference that delivers a return signal significantlyhigher than a hard reflecting sphere might otherwise deliver.It is omni-directional and is detectable by sonar in excess of2 kilometers (1.2 miles) away depending on frequency ofoperation.

The shell consists of two hemispherical parts, molded fromZytel®, that are currently joined by an adhesive, althoughspin welding is being investigated. The specific grade ofmaterial used was determined by the particularly demand-ing requirements of the design. As well as being able towithstand pressures of around 410 bars at depths of up to4,100 meters (4,484 yards) the material also has to beimpervious to moisture and possess specific sonar frequencyproperties. Providing ongoing support to SALT and its pro-

duction partners from its technical resources in the UK andGeneva, DuPont accompanied the development of theSonarBell® from its earliest prototype to the current produc-tion design. This included the provision of test samples andmaterial data as well as guidance on mold and gate design.DuPont experts also recommended suitable spin weldingdesigns and specific operating parameters to achieve opti-mum weld quality with Zytel®.

The SonarBell® can be used in many market sectors: besidesmilitary use, the units can also be used to provide navigationlanes on the seabed or for keeping track of expensive subseaequipment. They can also mean fewer dolphins get caughtin fishing nets, as Mr Tiltman, Chief Technical Office atSALT explains: “We can make the SonarBell® respond at aneffective frequency that will allow the mammal to see thenet much better using its sonar.”

SonarBell® is a registered trademark of Subsea Asset LocationTechnologies Ltd.

.Subsea Asset Location Technologies (SALT) Ltd.

Upper Courtyard 2, Renshaw Barns, Upper Woodford, Salisbury, Wiltshire, SP4 6FATel.: +44(0) 1722 782856Fax: +44(0) 1722 782856info@cesalt.co.uk, www.cesalt.co.uk

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SONAR TRANSPONDER RELIES ON DUPONT™ ZYTEL®

BY IAN WELSH, SENIOR DEVELOPMENT SPECIALIST AT DUPONT PERFORMANCE POLYMERS UK

The elegant use of materials, including DuPont™ Zytel® nylon, has helped revolutionize underwater subsea asset location andprevent marine mammals getting caught in nets.

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DuPont involvement in the Generation by Knoll® chair projectfrom an early stage was fundamental to its award winningdesign. DuPont provided key input to Formway Design andKnoll that allowed them to envision the use of its materials in away that had not been seen before in the furniture industry.The chair design leverages DuPont Performance Polymers forsignificant functional and structural components of the chair.

Material flexibility and durabilityKey to the chair’s flexing and supportive features is the useof the DuPont high performance thermoplastics DuPont™Hytrel® TPC-ET and DuPont™ Crastin® PBT for key com-ponents of its design, the Flex Back and the Dynamic Sus-pension control.

The frameless Flex Back design flexes as you move, with theFlex Back Net cradling your back and the unique figure 8structure enabling multidimensional movement. “The FlexBack Net is fused to the figure 8 structure, yet to identify onecomponent as the skin and the other as the skeleton would bemisleading, as they are inextricably intertwined,” explains Ben-jamin Pardo, Knoll design director.

The chair’s streamlined and innovative Dynamic Suspensioncontrol, which also uses Hytrel® and Crastin®, is a simple, non-mechanical control that provides a weight-compensated,smooth ride. Without the complexity of metal links orsprings, the control uses one-third the number of parts of a tra-ditional chair mechanism. The inherent properties of thematerials – flexibility and durability – enable a range of ener-gizing, multidirectional movements.

“The materials give the Flex Back Net and the Dynamic Sus-pension control their elasticity and durability – so theyessentially provide form and function, in one,” describesPardo. With the materials providing both movement andstructure, fewer parts and less energy are required to makethe chair. As a result, at 37 lbs (17 kg), Generation is lighterthan most high performance task chairs.

It is the first chair to be rated SMaRT© Sustainable Platinum,an achievement that reflects the Knoll commitment to inte-grating performance, quality and sustainability into its designs.This commitment is also reflected by ongoing developmentwork between Knoll and DuPont on the use of renewably-sourced materials in the chair. This year, the Flex Back Net willtransition to Hytrel® that contains at least 50% renewablysourced ingredients by weight. Hytrel® RS grades create asmaller environmental footprint than the entirely petrochemi-cally-based materials they replace without compromising per-formance.

Overall, the Generation by Knoll® chair project constitutes aprime example of what we at DuPont call inclusive innova-tion, and it is a highly successful design story that is yet to beconcluded.

Generation by Knoll® is a registered trademark of Knoll, Inc.

Knoll, Inc.

1235 Water Street, East Greenville, PA 18041Tel.: +1 215 679-7991info@knoll.com, www.sithowyouwant.comCO

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A FLEXIBLE APPROACH TO WORKBY RICK TOBAR, GLOBAL FURNISHINGS SEGMENT LEADER AT DUPONT PERFORMANCE POLYMERS

Designed by Formway Design of New Zealand, the Generation by Knoll® work chair offers a new level of comfortand unrestrained movement, supporting the range of postures and work styles typical of today’s dynamicworkplace. The Generation chair takes the idea of elastic design – where a product rearranges itself in response toits user – to a new level. Using the inherent properties of DuPont™ high performance thermoplastics, Generationliterally flexes as you change position, responding to your movements.

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The inverter module is at the heart of a photovoltaic system:it converts direct current produced by the solar modules intoalternating current, which is subsequently fed into thenational grid. Its housing is usually made of metal due to thehigh requirements in terms of dielectric strength and firesafety that apply to such an application. However, in the latestgeneration of ‘Sunny Boy’ inverters from SMA Solar Tech-nology AG, Niestetal (Germany), a Bluetooth interface isused to enable wireless communication with the photovoltaicsystem. Because metal is impenetrable for radio waves, thecompany sought to develop a polymer cover for the lower sec-tion of the housing where the switch disconnector, the elec-tronic display unit and the radio module are located.

The material used to produce the cover (see image right,black section of inverter module cover) is a special, flame-retardant grade of DuPont™ Zytel® PA66/6 copolymer witha 25 wt. % glass fiber reinforcement. With a CTI value(CTI = Comparative Tracking Index) of 325 V, a GWFIvalue (GWFI = Glow Wire Flammability Index) of 906 °Cand classified with the UL94 V-0 flammability standard, itmeets high dielectric strength and fire safety requirement.The specified Zytel® grade also provides very high mechani-cal strength and stiffness as well as high dimensional stabil-ity. The material’s low tendency for warpage or shrinkageduring injection molding, combined with structuralenhancements such as reinforcing ribs, enable compliancewith even the tightest of manufacturing tolerances. Thisensures a high accuracy of fit with the other housing sectionmade of cast aluminum. Moreover, the use of Zytel® ensuresa high surface quality for the visible component.

Low friction and low maintenance polymerbearingsIn Majadas de Tiétar, Spain, bearings made from a particu-larly low wear/low friction grade of DuPont™ Delrin® acetalresin support a total of 192,000 parabolic mirrors at a solarthermal power plant belonging to ACCIONA Energía S.A.

The material possesses a very low dynamic coefficient of fric-tion of 0.13 (standard grade: 0.35), enabling the reliable,smooth and millimetre-precise positioning of the hydrauli-cally-operated mirrors in accordance with the sun’s move-ment. Consequently, this helps further improve the plant’soverall effectiveness. Thanks to the high wear resistance ofthe material, maintenance costs over the entire lifetime ofthe plant are reduced when compared to steel bearings. Thisultimately helps reduce total operating costs and thereby thecost of energy production.

ACCIONA Energía is one of the global leaders in the pro-duction of solar thermal power plants. The company cur-rently operates three plants in Spain and one in Nevada/USAwith an overall capacity of 214 MW. The 50 MW solar thermal power plant in Majadas de Tiétar supplies 32,000households with environmentally-friendly power. Whencompared to a traditional coal-fired power station, the solarthermal power plant contributes to an annual saving ofapproximately 100,000 t CO2.

http://photovoltaics.dupont.com

NEW DEVELOPMENTS FOR THEPHOTOVOLTAIC INDUSTRYBY ORVAR OTTERSTEDT, PV MARKET DEVELOPMENT MANAGER AT DUPONT PERFORMANCE POLYMERS

DuPont materials have been used in the photovoltaic industry for more than 30 years. Amongst recent applica-tions are the development of a cover for an inverter module, made from a special, flame-retardant grade ofDuPont™ Zytel® PA66/6 copolymer, and bearings used solar tracking systems, made from a particularly lowwear/low friction grade of DuPont™ Delrin® acetal resin.

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Engineering Design is published in English, French, German, Italian, Russian and Spanish byDu Pont de Nemours International S.A. P.O.Box 50, CH-1218 Le Grand-Saconnex, Geneva,Switzerland.

The information set forth herein is furnished free of charge and is based on technical data thatDuPont believes to be reliable. It is intended for use by persons having technical skill at their own discretion and risk. DuPont makes no warranties, express or implied, and assumesno liability in connection with any use of this information.

© 2011 E.I. du Pont de Nemours and CompanyThe DuPont Oval Logo, DuPont™, The miracles of science™ and all products denoted with ® or ™ are registered trademarks or trademarks of E. I. du Pont de Nemours and Company or its affiliates.

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Publisher: Du Pont International Operations Sarl DuPont Performance Polymers2, ch. du Pavillon, CH-1218 Le Grand-Saconnex, Geneva SwitzerlandTel.: +41 22 717 51 11, Fax: +41 22 580 22 35

Contact: Rémi Daneyroleremi.daneyrole@dupont.com

Editor: Andrew Wilkins PRandrew.wilkins@btconnect.com

Layout: Konsens PR GmbH & Co. KGmail@konsens.de

http://plastics.dupont.com

EUROPE/MIDDLE EAST/AFRICA

Belgique / BelgiëDu Pont de Nemours (Belgium)Antoon Spinoystraat 6, B-2800 MechelenTel. +32 15 44 14 11, Fax +32 15 44 14 09

BulgariaServiced by Biesterfeld Interowa GmbH & Co. KG.See under Österreich.

Ceská Republika aSlovenská RepublikaDu Pont CZ s.r.o., Pekarska 14/628CZ-155 00 Praha 5 – JinoniceTel. +420 257 41 41 11, Fax +420 257 41 41 50 51

Danmark DuPont Danmark ApS Skojtevej 26, P.O. Box 3000, DK-2770 Kastrup Tel. +45 32 47 98 00, Fax +45 32 47 98 05

DeutschlandDuPont de Nemours (Deutschland) GmbHHugenottenallee 173-175, D-63263 Neu-Isenburg Tel. +49 6102 18-0, Fax +49 6102 18-4400

EgyptDu Pont Products S.A.48, El-Nasr St. New Maadi, 10th Floor, ET-CairoTel. +202 75 465 80, Fax +202 75 465 83

EspañaDu Pont Ibérica S.L., Edificio L’IllaAvda. Diagonal 561, E-08029 BarcelonaTel. +34 93 227 60 00, Fax +34 93 227 62 00

FranceDu Pont de Nemours (France) S.A.S. Défense Plaza, 23/25, rue Delarivière-Lefoullon La Défense 9, F-92800 Puteaux Tel. +33 1 41 97 44 00, Fax +33 1 47 53 09 67

HellasBiesterfeld Hellas Intralink S.A.Trading Establishmen149, AG. Triados Menidi AcharnesGR-13671 AthensTel. +30 210 24 02 900, Fax +30 210 24 02 141

IsraëlGadot Chemical Terminals (1985) Ltd. 16 Habonim Street, Netanya - South Ind. Zone IL-42504 Netanya Tel. +972 9 892 95 52, Fax +972 9 865 33 81

ItaliaDuPont de Nemours Italiana S.r.L.Centro Direzionale “Villa Fiorita”Via Piero Gobetti, 2/C, I-20063 Cernusco s/N (MI)Tel. +39 02 92629.1 (switchboard)Fax +39 02 92107755

MagyarországDuPont Magyarország Kft.Neuman Janos u.1, HU-2040 BudaörsTel. +36 23 509 400, Fax +36 23 509 432

MarocServiced by Biesterfeld Iberica S.L.see under Portugal

Norway / NorgeDistrupol NordicOstenssjoveien 36, N-0677 OsloTel. +47 23 16 80 62, Fax +47 23 16 80 62

Österreich Biesterfeld Interowa GmbH & Co. KGBräuhausgasse 3-5, P.O. Box 19, A-1051 WienTel. +43 1 512 35 71-0, Fax +43 1 512 35 72-100info@interowa.at, www.interowa.at

PolskaDu Pont Poland Sp. z o.o.ul. Powazkowska 44C, PL-01-797 WarsawTel. +48 22 320 0900, Fax +48 22 320 0910

PortugalBIESTERFELD IBÉRICA, S.L.U. Praça Dr. Francisco Sá Carneiro, 219 Galeria Direita 4200-313 Oporto (Portugal) Tel: +351 229 698 760, Fax: +351 229 698 769

RomaniaDu Pont Romania SRL Sos. Bucuresti PloiestiNo. 42 - 44 Baneasa Business & Technology Park Building B, 2nd floor, Sector 1, Bucharest 013696, Romania Tel. + 4031 620 4118, Fax + 4031 620 4101

RussiaDuPont Science and Technologies LLC. Krylatskaya str., 17, kor.3 121614 Moscow Tel. +7 495 797 22 00, Fax +7 495 797 22 01

Schweiz / Suisse / SvizzeraBiesterfeld Plastic Suisse GmbHDufourstrasse 21, Postfach 14695CH-4010 BaselTel. +41 61 201 31 50, Fax +41 61 201 31 69

SlovenijaServiced by Biesterfeld InterowaGmbH & Co. KG.See under Österreich.

Suomi / FinlandDu Pont Suomi Oy PO Box 54 (Keilaranta 12)FIN-02150 EspooTel. +358 207 890 500, Fax +358 207 890 501

SverigeServiced by Du Pont Danmark ApS.See under Danmark.

TürkiyeDu Pont Products S.A.Buyukdere Caddesi No. 122Ozsezen Ismerkezi,A block, Kat: 3Esentepe, 34394 Istanbul, TurkeyTel. +90 212 340 0400, Fax +90 212 340 0430

UkraineDuPont Ukraine LLC Representative Office Business center "Podil Plaza" 30a, Spaska Street, Kyiv 04070 Tel. +380 44 4952670, Fax +380 44 4952671

United KingdomDu Pont (U.K.) LimitedWedgwood WayStevenageHerts, SG1 4QNTel. +44 14 38 73 40 00, Fax +44 14 38 73 41 09

South AfricaDuPont de NemoursSociété AnonymeSouth African Branch Office4th floor Outspan House1006 Lenchen Avenue NorthCenturion, Pretoria 0046Tel. +27 12 683 5600, Fax +27 12 683 5661

Requests for further informationfrom countries not listed aboveshould be sent to:

Du Pont de NemoursInternational S.A.2, chemin du PavillonCH-1218 Le Grand-Saconnex/GenevaTel. +41 22 717 51 11, Fax +41 22 717 52 00

NORTH AMERICA

USADuPont Performance Polymers Chestnut Run Plaza, Bldg. 713, P O Box 800713, Wilmington, Delaware 19880-0713 Tel. +1 302-999-4592

DuPont Automotive950 Stephenson Highway, P.O. Box 7013Troy, Michigan 48007-7013Tel. +1 248 583 8000

CanadaE.I. du Pont Canada CompanyBox 2200, StreetsvilleMississauga, Ontario, L5M 2H3Tel. +1 905-821-5193, +1-800-387-2122 Fax +1 905 821 5057Information@can.dupont.com

MexicoDuPont S.A. de C.V. Homero 206 Col. Chapultepec Morales 11570 Mexico D.F. Tel. +525 722 1208, Fax +525 722 1454

SOUTH AMERICA

ArgentinaDu Pont Argentina S.A., Avda. Mitre y Calle 5 (B1880EED) Berazategui-Bs.As. Tel. +54 11 4239 3865, Fax +54 11 4239 3817

BrasilDuPont do Brasil S.A.Al. Itapecuru, 506 Alphaville06454-080 Barueri-Sao PauloTel. +55 11 4166 8299, Fax +55 11 4166 8513

ASIA-PACIFIC

AustraliaDuPont (Australia) Ltd.Level 16, 168 Walker Street, North Sydney NSW 2060, AustraliaTel. +61 2 9923 6111, Fax +61 2 9923 6011

China BeijingDu Pont China Holding Co., Ltd. 18/F, Tower A, Gemdale Plaza No. 91 Jianguo Road, Chaoyang District, Beijing 100022, P.R. China Tel. +86-10-8557-1000, Fax +86-10-8557-1888, 8557-1999

China ShanghaiDuPont (China) Research & Development and Man-agement Co., Ltd. No. 600, Cailun Road, Zhangjiang Hi-Tech Park, Pudong New District, Shanghai 201210, P.R. China Tel. +86-21-2892-1000, Fax +86-21-2892-1234

DuPont China Holding Co. Ltd.,Shanghai Branch 399 Keyuan Road, Bldg. 11 Zhangjiang Hi-Tech Park Pudong New District, Shanghai 201203, P.R. China Tel. +86-21-3862-2888, Fax +86-21-3862-2889

China ShenzhenDu Pont China Holding Co., Ltd. Chegongmiao Industrial Area, District No. 5 Shenzhen, Guangdong 518040, P.R. China Tel. +86-755-8330-7848, Fax +86-755-8340-0760

JapanDuPont Kabushiki KaishaSanno Park Tower, 11-1Nagata-cho 2-chomeChiyoda-ku, Tokyo 100-6111, JapanTel. +81-3 5521 8500, Fax +81-3 5521 2595

Hong KongDu Pont China Ltd.26th Floor, The Gateway, Tower 69 Canton Road, TsimshatsuiKowloon, Hong KongTel. +852 2734 5345, Fax +852-2724 4458

IndiaE I DuPont India Private LimitedElnet Software City,TS140, Block 2 & 93rd Floor, Module 31Rajiv Gandhi RoadTaramani, Chennai 600 113Tel. +91-44 22542701, Fax +91-44 22542710

IndonesiaDuPont Far East Inc.Menara Mulia, Suite 501Jl. Jend. Gatot Subroto Kav 9 - 11Jakarta 12930, IndonesiaTel. +62-21 522 2555, Fax +62-21 522 2565

Korea DuPont (Korea) Inc. 3-5th Floor, Asia Tower #726, Yeoksam-dong, Kangnam-Ku Seoul 135-082, Korea Tel. +82-2-2222 5200, Fax. +82-2-2222 5470

New ZealandDuPont (New Zealand) Ltd.98 Kerrs Road, Manukau CityAuckland, New ZealandTel. +64-9 268 5500, Fax +64-9 268 5490

MalaysiaDuPont Far East Inc.6th Floor, Wisma Samudra,No. 1, Jln. Kontraktor U1/14,Hicom-Glenmarie Ind. Park,40150 Shah Alam, Selangor,MalaysiaTel. +60-3-5569-3006, Fax +60-3-5569-3001

PakistanDuPont Pakistan Operations (Pvt) Ltd.Bahria Complex I, 2nd FloorMT Khan RoadKarachi 74000, PakistanTel. +92-21 561 1110, Fax +92-21 561 1430

PhilippinesDuPont Far East Inc.8/F., Solid Bank Building777 Paseo de Roxas1226 Makati City, PhilippinesTel. +63-2 818 9911, Fax +63-2 818 9659

SingaporeDuPont Company (S) Pte Ltd1 HarbourFront Place #11-01HarbourFront Tower One, Singapore 098633Tel. +65 6586 3688, Fax +65 6272 7494

TaiwanDuPont Taiwan Ltd.13/F., No. 167, Tun Hua North RoadTaipei 10590, TaiwanTel. +886-2 2719 1999, Fax +886-2 2719 0852

ThailandDuPont (Thailand) Limited6-7th Floor, M. Thai TowerAll Seasons Place, 87 Wireless RoadLumpini, PhatumwanBangkok 10330, ThailandTel. +66-2 659 4000, Fax +66-2 659 4001

VietnamDuPont Far East Inc.12th Floor, Central Plaza Building, 17 Le Duan Blvd., District 1, Ho Chi Minh City, VietnamTel. +84-8 824 3192, Fax +84-8 824 3191

CONTACT INFORMATION