Clariant has introduced new polymer compounds specially formulated to limit or even eliminate hydrolytic degradation, which is known to effect certain materials commonly used in catheters.
The resins are offered under the Mevopur brand name, and will be presented at the MD&M West tradeshow in Anaheim from February 5th to 7th.
In PEBAs and TPUs, absorbed moisture can cause a breakdown of the polymer chains and reduce the mechanical properties, rendering the materials brittle.
Even with careful pre-drying of the ingredients prior to compounding and tube extrusion, hydrolysis remains a risk, as moisture can also condense from the atmosphere, even inside foil-lined packaging, due to changes in temperature during transition or storage.
Eric Rohr, Medical and Pharmaceutical Segment Manager in North America for Clariant, said: “This hydrolysis effect is variable and difficult to predict. Uncontrolled it creates quality and reliability risks, increasingly the need for vigilance in QA procedures.”
“In addition, the shelf-life of the polymer compounds is less predictable and may be shortened to only a few months. After several years of research and testing, we are pleased to be able to limit the risk of hydrolysis and breakage in these materials, thereby helping device manufacturers improve the reliability of catheters.”
One of the first indications of chain scission is an increased melt-flow index (MFI), so Clariant researchers compared the MFI of a standard, unmodified tungsten-filled PEBA 35 Shore A compound against a sample of the new Mevopur.
After ten weeks storage under humid conditions, the unmodified compound showed more than double the original MFI values and a wider spread, indicating chain scission and reduction in molecular weight, and in comparison, the Mevopur compound maintained its MFI values in the same range as before the test began.
Tensile strength and elongation properties in standard test bars moulded from the test materials were similarly unaffected in Mevopur compounds, while the standard material showed signification degradation in these critical properties.