Sulfones

Sulfones are amorphous engineering thermoplastics noted for high heat deflection temperature and outstanding dimensional stability. The sulfone polymers usually contain ether oxygen which is a necessary component of the polymers as in the diphenyl sulfone moiety.

Three commercially sulfone based resins are: Polysulfone (PSU), Polyethersulfone (PES), and polyphenylsulfone (PPSU). Nature color of the sulfone resins is transparent light amber.

Sulfones are inherently transparent and flame resistant. They often have a slight amber hue. For purely optical applications, polycarbonates and acrylics have greater clarity and are often preferred.

Creep of sulfones, compared with that of other thermoplastics is exceptionally low at elevated temperatures and under continuous load. This excellent dimensional stability qualifies the sulfone resins for precision molded parts.

For medical applications, Steam sterilization of reusable medical devices requires materials that are resistant to degradation from water at temperatures ranging from 121℃ to 134℃ for about 30 minutes. In general, acrylics do not have sufficient temperature resistance for steam sterilization. Polycarbonate has a glass-transition and heat-deflection temperature high enough to withstand normal steam sterilization; however, it quickly loses ductility and impact properties following repeated sterilization cycles. Polysulfones and polyetherimide (PEI) are the only amorphous thermoplastics that can withstand repeated steam sterilization without substantial degradation of properties.

( PEI)

Polysulfones typically compete with PEI for rigid, transparent components that are exposed to frequent sterilization. PEI is considerably stronger and more rigid than polysulfones. PEI also has nearly twice the dielectric strength, a measure of insulation and beneficial for electrical applications.

However, a major weakness of PEI is impact strength. PSU offers better impact resistance and is a more economical alternative to PEI. PPSU is generally priced similar to PEI but offers substantially better impact resistance.

The sulfones also share a common draw-back: They absorb ultraviolet rays, giving them poor weather resistance. Thus. they are not recommended for outdoor service unless they are painted, plated, or UV stabilized.