Copolymers that resist stress cracking despite aggressive disinfectants
February 11, 2020
The use of highly aggressive chemical disinfectants is a common approach to preventing hospital-acquired infections (HAIs) in hospitals and clinics. However, these disinfectants can produce side effects in the polymers used in medical device components and equipment housings.
Repeated cleanings can cause environmental stress cracking (ESC) that can lead to part failure. To address this issue, SABIC is introducing here at MD&M West 2020 its new family of LNP ELCRES CRX polycarbonate (PC) copolymers featuring improved chemical resistance over existing materials.
Compared to traditional PC, acrylonitrile-butadiene-styrene (ABS), and polyester and co-polyester resins and blends — which are potentially incompatible with highly aggressive disinfectants such as quaternary ammonium compounds — the new LNP ELCRES CRX copolymers can help prevent stress cracking and mitigate crack propagation. Adding to their value, these amorphous and semi-crystalline blends can potentially serve as offset solutions in existing injection mold tools for a variety of materials.
“Our new LNP ELCRES CRX copolymers offer device manufacturers an easier, drop-in alternative to conventional resins that experience challenges in withstanding repeated cleanings with extremely harsh disinfectants,” said Darpan Parikh, global product management leader, LNP Specialty Compounds at SABIC. “By adopting our new copolymers, which offer robust resistance to crazing, cracking and discolouration, customers can help enable longer device life and avoid premature replacement. Based on the exceptional performance of these new materials in healthcare applications, SABIC is actively exploring additional grades for other industry sectors where chemical exposure is a challenge.”
Balance of Chemical Resistance and Mechanical Performance
SABIC’s LNP ELCRES CRX copolymers leverage unique copolymer technology to advance beyond the performance of existing materials used in healthcare devices and equipment, such as PC/ABS and PC/PBT (polybutylene terephthalate) blends. Not only do the new SABIC products demonstrate compatibility with the most aggressive disinfectants on the market — alcohols, peroxides and quaternary ammonium compounds — they also deliver good mechanical performance (impact and flow).
Specifically, LNP ELCRES CRX grades show excellent property retention after exposure to PDI Healthcare’s Sani-Cloth AF3 wipes and other aggressive healthcare cleaners, combined with excellent impact performance (ductile notched Izod at 23°C) and mitigation of crack propagation.
“To measure a polymer’s potential compatibility with chemical disinfectants, SABIC devised a quantitative ESC test that evaluates retention of both tensile stress at yield and tensile elongation at break,” said Ashir Thakore, global segment leader, Healthcare at SABIC. “Our efforts to develop materials with improved chemical resistance that meet these standards can help extend the useful life of plastic medical devices and support repeated application of strong disinfectants aimed at preventing HAIs.”
In addition to their chemical resistance and impact strength, the LNP ELCRES CRX resin portfolio offer specialized properties. The initial portfolio includes both amorphous blends of PC copolymer and PC resin, as well as a semi-crystalline blend of PC copolymer and PBT resin. The material building blocks of these grades have been pre-screened for limited biocompatibility (e.g., cytotoxicity). The portfolio contains flame-retardant versions with UL V0 performance up to 1.5 mm. All grades are opaque and can be custom coloured. Lastly, the portfolio can be tailored further to deliver additional features, such as inclusion under SABIC’s Healthcare Product Policy in which the material is subject to formulation lock and management of change process.
Potential applications for these materials include non-powered and powered medical devices such as hand-held diagnostics and drug/infusion pumps, and housings for diagnostic equipment like X-ray, ultrasound and MRI machines, as well as certain surgical devices.
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