Polysulfone

Polysulfone, or PSU, is a polymer thermoplastic material. It is tough, rigid, high-strength, and transparent, retaining its properties between &minus;100 °C and +150 °C. It has very high dimensional stability; the size change when exposed to boiling water or +150 °C air or steam generally falls below 0.1%. Its glass transition temperature is 185 °C.

Chemically, polysulfone consists of repeating units of C27H22O4S. It is produced by step polymerization of bisphenol-A and bis(4-chlorophenyl)sulfone, forming a polyether by elimination of hydrogen chloride. The chemical structure can be written as: H-[O-C6 H4 –C(CH3)2 –C6 H4 –O–C6 H4 –SO2 –C6 H4]x -Cl.

Polysulfone is highly resistant to mineral acids, alkali, and electrolytes, in pH ranging from 2 to 13. It is resistant to oxidizing agents, therefore it can be cleaned by bleaches. It is also resistant to surfactants and hydrocarbon oils. It is not resistant to low-polar organic solvents (eg. ketones and chlorinated hydrocarbons), and aromatic hydrocarbons.

Due to its excellent electrical properties, polysulfone is used as a dielectric in capacitors.

Mechanically, polysulfone has fairly high compaction resistance, allowing its use under high pressures.

Polysulfone allows easy manufacturing of membranes, with reproducible properties and controllable size of pores. Such membranes can be used in applications like hemodialysis, waste water recovery, food and beverage processing, and gas separation.

Polysulfone can be reinforced with glass fibers. The resulting composite material has twice the tensile strength and three time increase of its modulus.

Polysulfone can be used in Food and Drug Administration (FDA)-recognized devices. It is used in medical devices, food processing, feeding systems, and automotive and electronic industry.

Polysulfone has the highest service temperature of all melt-processable thermoplastics. Its resistance to high temperatures gives it a role of a flame retardant, without compromising its strength that usually results from addition of flame retardants. Its high hydrolysis stability allows its use in medical applications requiring autoclave and steam sterilization. However, it has low resistance to some solvents and undergoes weathering; however the weathering instability can be offset by adding other materials into the polymer.

Polysulfone was introduced in 1965 by Union Carbide. It is a specialty material with very small share of the total plastics market. It is very expensive both as raw material and to process, therefore it is generally not used in applications that do not call for its special properties. In such applications, it is often a superior replacement for polycarbonates.

It is supplied eg. by Solvay Advanced Polymers, BASF, and PolyOne.

Polysulfone is also used as a copolymer.

Polysulfone is resistant to compression and temperature induced deformation (boiling water). It is also stable in aqueous acids and bases and many non-polar solvents; however it is soluble in strong polar solvents such as dichloromethane and N-methylpyrrolidinone.