Characterization, processing, and properties of an aromatic poly (ether ketone)

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Abstract
Poly(oxy‐1,3‐phenylenecarbonyl‐1,4‐phenylene), mPEK, was synthesized in a methane sulfonic acid/phosphorus pentoxide medium through the polycondensation of 3‐phenoxybenzoic acid. The polymer was soluble at room temperature in strong acids and common organic solvents. Differential scanning calorimetry on mPEK indicated a glass transition temperature of 132°C and no detectable crystal melting behavior. The polymer was thermo‐oxidatively stable up to 420°C in air as determined by thermogravimetric analysis. Thermal degradation resulted in a crosslinked polymer. Compression molding was successfully applied to consolidate mPEK powder into bulk specimens without causing degradation. Tensilefractured surfaces of the consolidated specimens were examined by scanning electron microscopy which strongly indicated adequate fusion of mPEK powder but also disclosed microvoids of uniform size, shape, and distribution. X‐ray scattering revealed that mPEK powder was amorphous and that the consolidated mPEK specimens were structurally isotropic as well as amorphous. The bulk specimen density was determined to be 1.29 ± 0.01 g/cm3 and the three‐dimensionally isotropic bulk tensile properties were shown to be 4.10 ± 0.10 GPa (modulus), 0.07 ± 0.01 GPa (strength), and 0.021 ± 0.006 (elongation at break). Tensile properties of the amorphous mPEK specimens compared favourably with literature values of state‐of‐the‐art semicrystalline thermoplastics. Crystaline phases could be realized for mPEK by melt‐processing, or precipitating from a solvent.