MEDICAL | TECHNOLOGY & MATERIALS
Right: Cushion- ing prosthetic sleeve
tion could offer a solution for a few short cycle exposures with Topas 8007X10 resin. “As devices become increasingly more
complex, combining medical devices and electronics over a wide temperature range from cold storage to steam sterilisation temperatures require the properties of Topas COC,” Canale adds. “A medical device needs to be functional without shrinkage variations to avoid leakers or a dimen- sional shift that can lead to field failures. Rigid grades of Topas COC are glassy at RT, and me- chanical properties do not change down to -80°C. Therefore, a broad temperature range is available to designers who want to stretch existing products for the next generation devices.” According to the company, replacement of the discontinued Barex material with Topas resin grades in both film and for injection moulded components have been very successful where moisture and chemical barrier is required, although not an oxygen barrier. Topas resin is claimed to work well for long term storage with aggressive chemistries and can be sterilised by all traditional methods successfully. As for future developments, Canale says that
Below:
Overmoulded seal on breast pump cup
Topas COC used as an additive in polyolefins, can enhance properties significantly. “This is widely used in medical film manufacturing, but is just becoming understood in injection moulding,” she says. “The properties of straight COC are not always needed, however, enhancing the properties of polyethylene can be a significant boost at low cost. For example, 10% COC in HDPE will approximately double the modulus in one mil nominal film. Therefore, in injection moulding, stiffer parts with better dimen- sional stability can be achieved with a minor component of Topas COC in the mix. Clarity is easy to maintain in thin film, but not in typical injection
moulded thicknesses. However, the Topas COC/ PE product will have excellent dimensional stability that does not warp and it will have the impact of an olefin.” Hexpol TPE believes that the medical device industry continues to be an interesting and growing market for TPE compounds. “We see a strong trend of customers exploring the possibilities to use TPE as alternatives to rubber, silicone and PVC in applications requiring soft touch aesthetics or sealing functionality,” says Niklas Ottosson, Techni- cal Manager – Medical. “In many applications the TPE is used in a single-component injection moulded part, but we see also two-component applications where the TPE is not only overmould- ed to polyolefins but also to transparent engineer- ing plastics such as MABS and PETG. Applications include seals, closures, grips and handles. “The majority of the compounds we supply are customised to a customer’s requirements or a specific application. These requirements can vary greatly; from a detailed list of property specifica- tions to more general features or product design concepts. The daily work for our sales and techni- cal teams is to translate these requirements into TPE compounds with the correct properties, processing, product safety and functional perfor- mance characteristics. “When developing solutions for the medical
market, we not only have to consider the character- istics of the TPE compound itself, it is also essential to have a deep understanding of specific regula- tory requirements and aspects. Our customers are looking for highly customisable materials, originat- ing from medical raw materials with high biocom- patibility status and compounded under clean and well-controlled conditions, thereby maximising the probability that their devices will pass relevant medical tests. That is why we continue to develop our Mediprene family, not only with regards to product development and performance, but also as a concept for how we work; encompassing raw-material selection, regulatory compliance, production controls, traceability, reproducibility and change management.” The company says that Mediprene TPEs are sterilisable with gamma, EtO and steam. Repre- sentative grades have passed cytotoxicity tests
28 INJECTION WORLD | September 2017
www.injectionworld.com
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