MEDICAL | MATERIALS
addressing the customer’s primary needs, LSR Select also offered secondary benefits of increased productivity by not having to change out the material for each durometer change, less inventory required with all six durometers achieved through two bases, and more part production capability via the improved cycle times.” The company has also been involved in a
project related to low temperature cure for overmoulding printed circuit boards. “In this case, we had the challenge of overmoulding silicone to a printed circuit board for a wearable monitoring device,” says Goglia. “When moulding these circuit boards with standard two-component LSR at 135°C, the circuit boards were destroyed and non-functional. With LSR Select, we were able to bring the temperature down to 100°C and success- fully overmould the circuit boards with no damage to the boards and maintain full functionality of the device, with data successfully transmittable to the software after being moulded.” Teknor Apex has introduced a new series of Medalist medical-grade thermoplastic elastomer (TPE) compounds for overmoulding that exhibit strong adhesion to medical-grade polycarbonate and PC alloys and include formulations with enhanced resistance to chemicals encountered in wearable applications. Medalist MD-34900 series compounds, available in 50, 60, and 70 Shore A grades, are for general medical overmoulding applications, while the MD-36975 grade is a 75 Shore A TPE designed specifically for overmould- ing in wearable devices, with good resistance to the lotions and disinfectants that are typically encountered. In a joint project with Covestro, these materials
were overmoulded onto various medical grades of Makrolon PC, as well as Bayblend and Makroblend PC alloys, using both insert and multi-shot mould- ing. The project included tests to evaluate adhe- sion, processability and chemical resistance. Peel strength data showed the Medalist compounds exhibiting good adhesion to Covestro’s engineer- ing thermoplastics. Teknor Apex recommends the new Medalist compounds for wearable devices, where TPEs contribute comfort; soft-touch or cosmetic grips for medical device housings, handheld devices, and instruments; and seals and gaskets. The table on the previous page presents typical properties of representative grades from each series. “Medalist TPEs are excellent alternatives to liquid silicones used in overmoulding because they do not require the use of a primer, have a shorter cycle time (avoiding the lengthy curing process),
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and can be processed on conventional injection moulding equipment,” says Ross van Royen, Senior Market Manager for Teknor Apex. The new compounds for the medical device industry are an outgrowth of work carried out by Teknor Apex to develop overmoulding TPE formula- tions for consumer products. “We’ve made substan- tial investments in adhesion-modified technologies for TPEs, increasing our understanding of adhesion, developing more cost-effective formulations, and improving the bonding capabilities of these products in complex part designs,” says van Royen. The Medalist MD-34900 series and MD-36975 compounds are available worldwide. As medical- grade TPEs, they are subject to strict formulation controls, are made only with FDA-listed food-grade ingredients, are ISO 10993-5 compliant for biocompatibility, and are compliant with CONEG, RoHS, and California Proposition 65 requirements. Teknor Apex produces these compounds in multiple ISO-13485-certified facilities, ensuring security of supply. Covestro has supplied a tough and chemical-
resistant Makroblend M525 PC and polyester blend for the light and durable Apollo wearable. Developed by Apollo Neuroscience, the Apollo is the first wearable that helps the body beat stress by rapidly restoring its natural equilibrium, resulting in better sleep and energy, for example. Rather than just tracking your body, the company says that this device uses vibration to improve your recovery time from stress. Apollo claims that the device’s gentle vibration waves signal safety to the body and improve heart rate variability through the sense of touch.
It was originally developed by physicians and
neuroscientists at the University of Pittsburgh. Consumers can wear Apollo on the wrist or ankle, which exposes the device to personal care products, such as lotions, perfumes and detergents. The device is able to withstand these everyday products,
January/February 2020 | INJECTION WORLD 43
Above: Covestro Makroblend M525 PC and polyester blend lends toughness and chemical resistance to the Apollo wearable
IMAGE: APOLLO NEUROSCIENCE
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