DuPont engineering polymers contribute to convenient diabetes care

New disposable and reusable insulin pens, designed by Industrial Design Consultancy Ltd (IDC) in the UK, contain a number of components moulded from DuPont (www.dupont.com) engineering thermoplastics, selected for their quality and performance, and involved the cooperation of DuPont in both Europe and Asia during their production. The resulting products are expected to dramatically advance diabetes treatment in India, by offering a portable, discreet, quick and easy insulin dosage system for users on the move.

The insulin pen design is the size of a marker pen and is manufactured entirely from plastic, whereby a number of the key components, required for the accurate dose setting and delivery of the insulin, are moulded from engineering thermoplastics from DuPont. DuPont™ Delrin® acetal homopolymer resin, a common choice for safety components to obtain highest device reliability, is used for the clutch tube and locking sleeve. DuPont™ Zytel® nylon resin has been selected for the drive shaft, inner housing, thumb pad and piston rod cap.

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“For the intricate system of ratchets and gears used within the pen’s delivery mechanism, we needed a material such as Delrin® that could deliver excellent dimensional stability in combination with resistance to creep and a certain level of natural lubricity,” explains IDC’s Managing Director, Stephen Knowles. “Moreover, where many mechanical movements must occur in an exact sequence, there are components that need the combination of very high impact strength, elastic modulus and tensile strength. For these we chose Zytel®.”

A further DuPont material, DuPont™ Crastin® PBT polyester resin, is used for the pen’s dose dial and clip. These parts had initially been specified in Zytel®, however testing revealed that the nylon would absorb moisture in the extremely humid conditions prevalent in India, which in turn would have a detrimental effect on dose accuracy. “We quickly needed an alternative material with the same functional properties and that could be used in the same tools,” explains Knowles. “Fortunately, DuPont was able to ship us samples of Crastin® to Thailand for testing within a week, and we found it to be the perfect alternative!” The polyester resin’s visual appeal and suitability for printing were further benefits to be gained from the change of material.

The overall project was coordinated across Europe and Asia by IDC: the production of high-precision tooling was carried out in Taiwan, testing to ISO standards was conducted in Holland, while the Indian moulder, Shaily Engineering Plastics Limited were responsible for production manufacturing. DuPont representatives in each continent were heavily involved in the project’s completion and ultimate success, as Stephen Knowles acknowledges: “The breadth of material offering from a single source, plus the readily available, local technical support were the greatest benefits of working with DuPont. Familiar with their products from previous projects, we knew what to expect in terms of material performance and quality. But when a problem does occur, they had the back-up and resources to solve it quickly!”

DuPont de Nemours (Deutschland) GmbH, Neu-Isenburg, Germany

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