technology | Medical
Right: Covestro worked with Pentracor to develop this blood treat- ment chamber, injection moulded in Apec high heat PC
cytotoxicity tests according to ISO 10993-5 and biocom- patibility tests according to USP Class VI. The materials are also latex free, which reduces the risk of allergic reactions, and are resistant to many fluids used in the healthcare environment.
tions to be either one- or two-component mouldings where the TPE is overmoulded onto a substrate such as PP, PE, ABS, PC, PETG and SMMA. Overmoulding is a powerful technique that allows the production of finished parts in soft and hard material combinations without trimming or assembly. It offers many design and product advantages, allowing designers to differen- tiate products while meeting important user and patient demands, including soft-touch and cushioning for greater comfort and non-slip surfaces with improved grip for safety,” Ottosson says.
Improved bonding “We have developed the 500M Mediprene TPE range to bond very well to polyolefins like polyethylene (PE) and polypropylene (PP). However, in several medical applica- tions transparent engineering plastics like ABS, PC and PETG are utilised. The Mediprene A2 series has been developed to address demands for medical grade TPEs that bond well to these substrates. We see Mediprene TPE overmoulding grades being used in applications such as seals, membranes, closures, friction grips and soft-touch handles. Mediprene TPEs also provide enhanced sealing capabilities in fluid environments.” Ottosson says that another current trend involves
customers replacing rubber parts that are sourced externally with in-house moulding of TPE parts. An example is the replacement of butyl rubber with TPE for plunger seals in single-use syringes. He says that Elasto has developed a range of Mediprene TPE compounds specifically for this application. The Mediprene grades are available in a range of hardnesses from 43 to 73 Shore A. The TPE seal, which is mounted on the end of the plunger, needs to provide a leak-proof seal with the syringe barrel. The Mediprene TPEs offer low compres- sion set helping to maintain seal integrity. Mediprene grades are sterilisable with gamma, EtO and steam and representative grades have passed
22 INJECTION WORLD | September 2016
Versatile LSRs According to Bluestar Silicones, key application areas for Liquid Silicone Rubber (LSR) for injection moulding in medical applications include at-home patient care and diagnostics. “We have seen a need for durable devices for at-home patient care and diagnostics,” says a company spokesperson. “Patients are spending less time in the hospital to reduce overall cost of healthcare as well as to prevent hospital born infections. Today, physicians are able to monitor patients remotely thanks to smartphones and wearable devices. As a result, consumers are handling and caring for the devices they are using for at-home care. These devices need to be durable from a consumer standpoint, able to withstand cleaning and a more active lifestyle. So moulders are looking for strong tear and high elongation materials to meet these needs. Bluestar Silicones offers a range of low durometer high performance soft LSRs that offer exceptional tear and stretch and return features for durability, flexibility and patient comfort. We offer a 01 ShA material that delivers exceptional high tear strength and elongation for soft cushioning and vibration dampening applications, combined with the ease of processing and improved productivity advantages.” The company also reports an increased interest in
the market for low temperature cure materials. This trend is driven by the increasing usage of electronics in medical devices and plastics with low melt points. Devices with electronic components or low melt plastics cannot withstand the standard 177°C (350°F) curing temperature of traditional two component LSRs. Bluestar also cites cost pressures in healthcare as a major driving force at present. Among the latest additions to the BlueStar Silicones
range is LSR Select. The company says that it gives moulders flexibility and control related to cure kinetics rather than depending entirely on the LSR chemistry. Moulders can adjust and optimise the cure speed for the part size and dimension of a specific part to increase output and decrease cycle time and reject rates. This is accomplished by changing the inhibitor levels in the process and metering the platinum just before moulding. Cycle time improvement rates of up to 60% are reported. For low temperature cure applica- tions, LSR Select is claimed to offer benefits to productivity, enabling moulders to improve cure speed rate even at low temperatures.
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