MEDICAL TUBING | MATERIALS
A race towards miniaturisation and a widening scope of
alternative materials are some of the emerging themes in the medical tubing market
Life lines: latest in medical tubing
As surgery becomes more sophisticated, compo- nents such as medical tubing must move with it – be- coming both smaller and more mechanically stable. Delegates at AMI’s recent Medical Tubing
conference heard about a number of emerging applications, especially regarding alternative materials. Medical tubing requires materials with high mechanical properties – and few come higher than Peek. Jonathan Jurgeitis, senior extrusion engineer for vascular technologies at Apollo Medical Extru- sion, told delegates that crystallising Peek had a noticeable effect on extrusion performance The company carried out an experiment to test
Peek crystallinity in extruded tubing. The material was extruded to either its amorphous or crystalline state.
“Semi-crystalline tubes will be crystallised in-line, and some amorphous tubes will be crystallised sec- ondarily,” he said. The material used was Solvay’s KetaSpire KT-820
NT, and the tube had an outer diameter of 0.06in and an inner diameter of 0.05in. Extrusion was carried out on a 0.75in high heat extruder, at
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typical Peek processing temperatures. Amorphous tubes were quenched. Annealing was carried out at 175°C for 30 minutes. The tubes were tested for crystallinity, tensile
strength, elongation and flexural modulus. (Several properties that were not tested include density, thermal properties and chemical resistance.) For tensile strength, the in-line crystallised grade showed a far higher result than either the amor- phous or the secondary crystallised grades. Elongation at break was 192% – which was lower than for the other two samples. Maximum load was comparable with the secondary crystallised grade, but lower than the amorphous material. Tensile modules proved to be the highest. Overall, Jurgeitis said the in-line crystallised sample had much higher elongation at yield, lower elongation percentage and higher tensile modulus. “Inline crystallisation gives better tensile
properties than in the secondary process,” he said. Flexural results – such as flexural load modulus
– were similar for both crystallisation methods, and higher than for amorphous. Jurgeitis concluded that fully crystalline Peek
May 2020 | PIPE & PROFILE EXTRUSION 13
Main image: Medical tubing must keep pace with the latest advances in medicine
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