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Innovative medication injector uses rugged, low-friction DuPont Polymers

Du Pont Engineering Polymers : 08 July, 2002  (New Product)
An award-winning device for self-injection of an arthritis medication meets stringent requirements for reliability and ease of use thanks to key components made of DuPont Zytel nylon resin and Delrin acetal resin. The SimpleJect auto-injector system is designed for self-administration of Amgen Inc.'s Kineret (anakinra) drug for rheumatoid arthritis. The injector's manufacturer, Owen Mumford Ltd., Woodstock, England, worked closely with Amgen in developing it. SimpleJect has earned the Arthritis Foundation's Ease of Use commendation and has received two prestigious awards this year. Canon Communications gave it a Medical Design Excellence Award in June, and the Healthcare Compliance Packaging Council presented it with its Compliance Package of the Year Award in May.
Steven Rolfe, industrial designer and phase project leader for Owen Mumford, said, 'Because SimpleJect is so easy and safe to use, it promotes self-reliance and compliance among arthritis sufferers who need to administer their own injections on a daily basis. The guesswork is taken out of self-injection, in that SimpleJect sets the correct penetration level every time.'

The device is also designed to assuage the fears of needle-phobic patients, according to Owen Mumford. The colorful and robust design does not resemble in any way a classic syringe; patients never see the needle of the syringe, before or during the injection.

SimpleJect consists of a carrying case and two main assemblies, a handle containing an actuating mechanism and a housing assembly that holds the syringe during injection. To use it, the patient places a syringe in the housing, cocks the actuating mechanism, screws the handle into the housing, places the end of the housing on the injection site and pushes down on the handle to inject the drug.

The syringe housing and a needle shroud assembled to one end of it are injection molded from a special low-friction nylon resin, DuPont Zytel 7335F. The same resin is also used for the body of the actuating mechanism located in the handle assembly. Low friction is very helpful for this part when the patient screws it into the syringe housing made of the same resin.

In addition to meeting low-friction requirements, Zytel 7335F also fulfills requirements for mechanical strength and the right balance of stiffness and toughness. Its mechanical strength enables the parts to withstand repeated injection forces.

Devices were thoroughly tested by Owen Mumford, including extended life cycle and resistance to extreme heat (+70C at 90 percent humidity) and cold (-40C). In drop tests, they also performed faultlessly with a 100 percent pass rate and no damage to the syringe or to the SimpleJect.

Another part of the syringe housing, the syringe carrier, is molded from a standard acetal grade, Delrin 500. It is snap-assembled inside the housing, snapping perfectly into place and remaining firmly in place for thousands of injections. In addition to its eminent suitability for snap-fit assembly, Delrin was selected for its strength, impact resistance and dimensional stability, all key factors in long-term delivery accuracy.

Owen Mumford and DuPont worked closely together to select materials for optimal performance of SimpleJect. DuPont specialists also assisted Owen Mumford with full mold flow analyses and help in rapid prototyping and production tool design.

Amgen senior packaging engineer Jean-Michel Guirado, based in the company's European logistics center in The Netherlands, said: 'The use of DuPont engineering polymers means that SimpleJect has an attractive and ergonomic, robust design that is easy to use, even for severely disabled patients with impaired dexterity. This was proven when we received a message of thanks from a blind RA sufferer in the United States whose life has been made infinitely easier since SimpleJect has been made available for her daily Kineret injections.'
30 May 2002

Truck transmissions rely on Hot Oil Resistance of DuPont Zytel HTN

A rugged electrical coil encapsulated in DuPont Zytel HTN high performance polyamide resin helps assure smooth, reliable shifting of automatic six-speed truck transmissions from Eaton Corporation. The coil, made by Tri-Tech, LLC, Mishawaka, Ind., actuates an inertia brake that slows engine speed during shifting of Eaton's Fuller AutoShift transmissions.

'The coil is performing very well in our six-speed transmissions for medium trucks, and we plan to use it later in our 10 and 18-speed transmissions for larger vehicles,' says Tom Riley, chief engineer at Eaton's Heavy-Duty Transmission Division.

Tri-Tech recommended to Eaton both an encapsulated design and Zytel HTN as the material of construction to withstand an aggressive service environment. The encapsulated coil is exposed to synthetic transmission oil at typical operating temperatures of 275F (135C), but with peaks up to 350F (177C).

The coil's design underscores the benefits of thermoplastic encapsulation over thermoset technology. Integrally molded lugs around the perimeter of the part snap into a groove in a metal clutch plate housing. This approach both simplifies assembly and provides secure, vibration-tolerant mounting, according to Bill Everett, director - engineering and sales at Tri-Tech, LLC. 'The toughness and resilience of Zytel HTN are crucial for snap-fit assembly,' says Everett.

The coil is manufactured in just three steps. The first step is to injection mold a bobbin using a 35 percent glass-reinforced grade of Zytel HTN. The next is to wind magnet wire around the bobbin and install terminations and lead wires. The wound, terminated unit is then placed in the mold of an injection molding machine and a 15 percent glass-reinforced grade of Zytel HTN is injected to fully encapsulate it. The encapsulated coil comes out of the tool ready for use with no secondary finishing steps required.

Tri-Tech, LLC's design and molding technology provide maximum protection against penetration of oil to the coil's windings. The bobbin's flanges have thin, feathered edges, which, during overmolding, soften and bond with the encapsulation material, according to Everett.
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