MATERIALS | MEDICAL TUBING
Right: Ineos Styrolution’s Styroflex 4G80 TPE imbues tubing with rubber-like mechanical properties, plus high puncture resistance
two separate materials in an extruded product like a catheter tube. However, the integration between the two is smoother, he said, and avoids the traditional ‘stepped’ approach. “The goal of this technology is meant to generate a para- digm shift around the way catheters are de- signed,” he said. Part of the approach is to understand – and manipulate – the flow behaviour of the two different materials, he said. In Exgineer- ing’s case, it was using two different grades of Pebax. The ability to make the catheter tube in a single
operation has several advantages, including: a wider variety in Shore D hardness between the materials; simpler production; greater bond strength between the two materials; and better pushability and kink resistance. Davis said one advantage of this method included was that it allowed direct extrusion through the braid. “It’s an enabler of complex design – optimising device performance based on material properties required rather than assembly limitations,” he said. The company has collaborated with a number of others in the development, including Gimac, Arkema and Optinova.
Tube selection Ruediger Gall, general manager of Freudenberg Medical Europe, explained the key steps behind designing medical tubing – including correct material selection and determining which features to include. This is partly to avoid a host of potential pitfalls,
including burst failure, gels and black spots, structural failure (such as delamination). As well as communi-
cation, he said that correct specification was critical. This includes defining the right material, assessing
regulatory requirements and considering factors such as post-curing and UV-absorption. The wide variety of medical tubes
and catheters means that many approach-
es are needed. He cited a number of case studies: a venous access port catheter had to be of customised length, and pad printed; a cardio-vas- cular catheter was produced by micro-extrusion, from an implant-grade material with increased torquability and kind resistance; and, a percutane- ous endoscopic gastrostomy (PEG) tube needed a modified surface in order to reduce friction.
Silicone supply Dan Sanchez, product manager at Trelleborg Healthcare & Medical, explained how silicones are finding wider use in medical tubing, due to their stability in harsh environments, plus attributes such as customisability, permeability and biocom- patibility. He cited several case studies, in which silicone had proved an effective base material. In layered micro extrusion, a large medical OEM
requested a component for a long-term implant. A silicone extrusion with a diameter below 0.38mm was required. Using two-component extrusion – involving a core with a special additive, and custom tooling to produce a thin outer layer that controlled elusion rate – Trelleborg made a tube with a diameter below 0.3mm. In a separate example, a customer required reinforced tubing – with improved kink resistance
Xaloy®
Screw & Barrel Technology for Medical Tubing Applications
Produce high-quality medical tubing products that meet the highest standards with customized plasticizing solutions from Nordson.
Hall 11 Booth A26
WWW.NORDSONPOLYMERPROCESSING.COM
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