Part of the polysulfone family of polymers, polyphenylsulfone (PPSU) has a number of properties that make it an increasingly popular metal-replacement material in medical applications. Particularly noteworthy is its heat resistance — PPSU can withstand continuous-use temperatures up to 260°C — and its resistance to chemicals and harsh disinfectants commonly used in hospitals.
“High flexural modulus, impact resistance, and durability make PPSU an excellent candidate for metal replacement in applications such as single- and multi-use surgical instruments because it imparts mechanical properties [similar to metal] but at a much lighter weight,” Larry Johnson, Vice President of Business Development at Foster Corp., told PlasticsToday. “Additionally, its high temperature resistance makes PPSU an excellent alternative for multi-use medical devices that are repeatedly steam sterilized,” says Johnson, while its resistance to “acids, bases, disinfectants, and organic solvents such as alcohol makes PPSU an excellent choice for medical housings. This material is EtO, gamma, and steam sterilizable, which is crucial for medical device applications. PPSU also is toxicologically inert which makes it an excellent candidate for Class II and Class III medical applications,” adds Johnson. His company, Foster Corp., is a compounder serving the medical technology industry.
Anna Maria Bertasa, Global Marketing Manager – Healthcare Specialty Polymers at Solvay, also points to PPSU’s wide-ranging sterilizability and chemical resistance as key properties for medical applications. “Tests show that PPSU can withstand over 1,000 cycles of steam sterilization, which is quite remarkable for a thermoplastic,” says Bertasa. “This property supports PPSU’s use in reusable medical devices. Moreover, it has good chemical resistance, making it suitable for medical applications exposed to aggressive disinfectants and cleaners that may be used in healthcare environments,” says Bertasa. In fact, she adds, Solvay has seen a rise in the use of PPSU for applications such as “housings for patient monitoring devices and barcode readers due to their repeated exposure to harsh chemicals and frequent drops.”
PPSU vs. PC
PPSU competes with a handful of other polymers in medical applications, but it is finding increasing purchase with medical device design engineers. “Polycarbonate (PC) is used extensively in the medical industry for applications similar to those where PPSU is used,” explains Bertasa. “However, PPSU is increasingly replacing PC because of its capability to improve the lifetime of medical devices and their components. Compared with PC, PPSU offers better sterilization and heat resistance, combined with hydrolytic stability and chemical resistance to disinfectants and sanitizers. That is a significant benefit during the current COVID-19 pandemic," adds Bertasa.