TECHNOLOGY & MATERIALS | MEDICAL
according to ISO 10993-5 and biocompatibility tests according to ISO 10993-10 (Intracutaneous Reactivity), ISO 10993-11 (Acute Systemic Toxicity) and USP Class VI. The Mediprene materials are latex free, which reduces the risk of allergic reactions. Mediprene TPEs are resistant to many fluids used in the healthcare environment. “A new development in our Mediprene family of TPEs for medical applications is the introduction of several grades for solvent bonding applications,” Ottosson says. “Many customers are today joining tubes with injection moulded components, such as connectors, by solvent bonding. Traditional TPS based formulations do not bond well with solvent – cyanoacrylate glue with or without primer is an alternative to achieve high bond strength in these situations. “However, in addition we have developed a
range of Mediprene TPE materials for extrusion and injection moulding for which we have achieved high bond strength when applying solvents such as cyclohexanone. Initially the solvent bondable materials for injection moulding will range from 70 Shore A to 45 Shore D in hardness and then be further expanded based on customer demand.” Teknor Apex has developed ultra-soft
medical TPE gels with low surface tack and enhanced adhesion to poplypropyl- ene in overmoulding. The company says that the Medalist MD-16100 and 10100 Series TPEs overcome limitations of standard gels and provide device makers with cost-effective alternatives to silicones. The company says that Medalist MD-16100 low-tack gels exhibit less surface friction than standard TPE gels, providing smooth surfaces and improved haptics. Grades are available with hardness levels from an exceedingly low 20 Shore OO to 65 Shore OO, or 10 Shore A. The compounds can provide padding, support, or cushioning in applica- tions like orthopedic devices and prosthetic liners and can serve in diabetes therapy as insoles, heel cushions and toe spacers. Medalist MD-10100 gels for overmoulding onto PP exhibit good adhesion to this substrate, providing the design flexibility of parts consolidation and yielding rigid components with built-in cushioning functionality. Grades range from 8 to 18 Shore A. These gels are used in respiratory masks to provide an air-tight, cushioning seal against the face. Other applications include orthopedic devices and grips for handles or hand-held devices. The new compounds are safe
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for skin contact, process and demould easily, and are available in clear and translucent grades that are ideal for custom colours.
Liquid silicone rubber As demands are placed on improving patient outcome from hospital-acquired infection (HAI), materials are becoming increasingly exposed to a variety of chemicals and conditions that are applied during the disinfecting or sterilisation of medical components, says Roger Hendrick, Application Engineering and Technical Service Specialist at Dow Food, Pharma & Medical. He adds that there are also similar demands being placed on polymers used in systems which deliver drugs for patient treatment such as with oncology drug delivery devices which can be negatively affected by exposure to these conditions. “New technical developments are also being driven by the need for more functionalised polymers such as self-bonding liquid silicone rubbers (LSRs) that can simplify processing and improve quality, thereby improving total cost when bringing together hard and soft materials,” Hendrick says. “Specific to self-bonding LSR technology, customers need an LSR that is durable, cures at low enough temperatures to not deflect the plastic and provide realistic moulding cycle times, and has suitable bioqualification to support its use in medical applica- tions. We are developing a self-bonding LSR targeting copolyester resin which is known for its clarity, chemical resistance, gamma stability and impact resistance. Dow is working to commercialise a medical, self-adhesive LSR suitable for insert and two-component injection moulding processes which is capable of
curing at low temperatures with reasonable cycle times. This capability will help provide BPA-free alternative plastics to be used with silicone in numerous medical applications.” In silicone injection moulding for medical
devices, Bob Waitt, Healthcare Market Manager for Elkem Silicones in North America, also sees connected health issues including at-home patient monitoring, diagnostics and care, as a major driving force at present. “We have seen a need for durable devices for at-home patient care and diagnostics,” he says. “Patients are spending less time in the hospital, primarily to reduce overall cost of health- care, prevent hospital born infections, and improve a patient’s overall quality of life. Today, physicians
September 2017 | INJECTION WORLD 31
Left: Solvay has introduced two new lubricated grades of Zeniva
polyethere- therketone (PEEK) to its portfolio of biocompatible polymers for use in implant- able devices
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