Physical Properties of PEEK

According to Boakye et al., PEEK has an elasticity that is similar to that of bones (2005). Unfilled PEEK biomaterials have an elastic modulus ranging from 3 to 4 GPa, which can be customized totally with the elasticity of the cortical bone (Kurtz 2012).

The melting point of PEEK is 334 ^oC. At temperatures of 700 ^oC and below PEEK undergoes a single-stage thermal decomposition (Krzysztof & Njuguna 2005). The thermal degradation is instigated by arbitrary homolytic scission of the carbonyl or ether bonds found in the polymer chains. The outcomes of the scission can volatilise if they display adequate mobility. Cyclisation to benzofuran derivatives can also take place. According to Krzysztof and Njuguna, oxidative environments greatly diminish the thermal stability of PEEK (2005).

The heating of most polymers leads to three key transitions, which are “the glass transition, melt temperature, and the flow temperature” (Kurtz 2012). However, PEEK undergoes an additional transition known as the recrystallisation transition. Polymer chains exhibit the behaviour of brittle glass at temperatures below the glass transition. At such temperatures, the polymer chains do not have adequate energy to slither beyond each other. The only way for the material to act in response to mechanical stress is by stretching the covalent bonds in the molecular chain (Kurtz 2012). The glass transition temperature for PEEK is about 143 ^oC. A fascinating fact about PEEK is that it remains ductile and flexible below its glass temperature.