| PEEK | |
|---|---|
| Density | 1300 kg/m3 |
| Young's modulus (E) | 3700 MPa |
| Tensile strength (σt) | 90 MPa |
| Elongation @ break | 50% |
| notch test | 55 kJ/m2 |
| Glass temperature | 130-150 °C and 260-290 ºC |
| melting point | ~350 °C |
| Vicat B[citation needed] | - |
| heat transfer coefficient (λ) | 0.25 W/m.K |
| linear expansion coefficient (α) | 1.7 10-5 /K |
| Specific heat (c) | - kJ/kg.K |
| Water absorption (ASTM) | - |
| Price | 25-50 €/kg |
| source: [1] | |
Polyetheretherketones (PEEK), also referred to as polyketones, are obtained from aromatic dihalides and bisphenolate salts by nucleophilic substitution. The bisphenolate salt is formed in situ from bisphenol and either added sodium or added alkali metal carbonate or hydroxide.
PEEK is a thermoplastic with extraordinary mechanical properties. The Young's modulus is 3.6 GPa and its tensile strength 170 MPa.
PEEK is partially crystalline, and is highly unusual in exhibiting two glass transition temperatures at around 140 °C and around 275 ºC, depending on cure cycle and precise formulation. PEEK melts at around 350 °C and is highly resistant to thermal degradation. The material is also resistant to both organic and aqueous environments, and is used in bearings, piston parts, pumps, compressor plate valves, and cable insulation applications.
PEEK is considered an advanced biomaterial used in medical implants, often in reinforced format using biocompatable fibre fillers such as carbon. Also in carbon fibre reinforced form, PEEK has come under consideration as an aerospace structural material due to its high strength-to-weight ratio.
Chemical resistance
PEEK also exhibits good chemical resistance in many environments, including alkalis (i.e. sodium, potassium and ammonium hydroxides), aromatic hydrocarbons, alcohols (i.e. ethanol, propanol), greases, oils and halegonated hydrocarbons.
However, its performance in acids is very dependent on the type of acid - PEEK shows poor resistance in concentrated sulfuric, nitric, hydrochloric, hydrobromic and other mineral acids (though performance may be adequate for short term use with these acids in very dilute form). Its resistance to hydrofluoric acid and oleum is very poor. PEEK shows good resistance to phosphoric acid and organic acids (acetic, citric, oxalic, tataric etc.), but varying resistance in the presence of halogens. PEEK is resistant to dissolution by some formaldehydes and ketones such as acetone, but not (at higher temperature) methylethyl ketone.
References
- ^ A.K. vam der Vegt & L.E. Govaert, Polymeren, van keten tot kunstof, ISBN 90-407-2388-5