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Light cure adhesive proves to be reliable and inexpensive
In adhesive technology terms, the medical device sector is like no other. Seldom is it simply a case of specifying an off-the-shelf adhesive to do the job. A total solution from the adhesive manufacturer is considered essential, one that takes the customer stage by stage through process design, product specification, testing and beyond.
This may include providing expert help on joint design and support through initial trials. The development of adhesives with specific characteristics is often needed. And then the optimum dispensing and curing system must be identified. It is a complex process and typically time-to-production can take six months to five years. Henkel has considerable experience in this field.
One application proved uncharacteristically uncomplicated however thanks to Henkel's wide ranging applications experience and its medically approved products. When the Medical Packaging Corporation (MPC) developed an innovative new product, Henkel was able to recommend a Loctite light curing adhesive that was available off-the-shelf. It could also be automatically dispensed directly on MPC's existing equipment.
Swab devices with glass ampoules containing a reagent had been used in medical testing for many years. However a variety of problems presented themselves when the ampoule was broken to release the reagent. Glass shards could clog the dropper tube or combine with the reagent affecting the variability in the volume dispensed.
They could also cause injury or infection and it was the need to address these health and safety issues that prompted the MPC to produce a new design of swab package. Snap Swab was the result, a Dacron swab tip on a polystyrene shaft encased in a polyethylene tube. When the shaft is broken, it releases the reagent and the swab is ready for use. With no glass to puncture the skin or prevent the reagent from flowing, it is quick and easy to use.
To manufacture this new product economically yet ensure its dependability, MPC realised that the swab had to be reliably bonded to the inside of the tube. In addition, the interface of the swab shaft, the protective tube and the reagent bulb had to be leak-proof.
The tolerance of the swab extrusion and the blow-moulded tube were incompatible for an interference fit but Henkel had ready a Loctite solution. It recommended a single product to bond both surfaces - Loctite Light Cure 3311, a one-component, low viscosity adhesive. It cures rapidly to form a flexible transparent bond when exposed to ultraviolet radiation and/or visible light sources.
Since patenting the Snap Swab the product was introduced for other applications. For example they are now used for applying antibiotics to burns or wounds, mixing solutions at the point of use in general industry, single-use cosmetic sampling and for home testing kits.
Loctite Light-Curing Acrylic 3311 has enabled MPC to produce a product that is safe, convenient and inexpensive. Despite being low cost however, the market expects the product to work every time. Frederic Nason, President of Medical Packaging Corporation confirmed: "The Loctite product made our Snap Swab reliable. It wouldn't have been possible without it."
Henkel took four major factors into account when considering the application of this light-curing adhesive. These are the emissions spectrum of the curing system, the light intensity required, the transmittance of the material being bonded and the requisite curing properties. The co-ordination of these tools with the chosen Loctite 3311 adhesive was critical to the quality of the join.
For most bonding applications in medical device assembly, Henkel provides both adhesive technology and the necessary hardware for curing and monitoring. Modular equipment in the Loctite range guarantees bubble-free flow metering in accordance with the high standard of reliability required from medical products. Various light curing systems are also available for both blanket and focused light irradiation.
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