Wide‐angle x‐ray scattering study of heat‐treated peek and peek composite

Abstract

We report the results of a study of poly(etheretherketone) (PEEK) neat resin and APC‐2 carbon fiber composite samples which were processed from the melt and then subjected to a variety of thermal treatments. Wide‐angle x‐ray scattering was used to study the effects of quenching and annealing treatments. For both neat resin and composite, annealing resulted in perfection of the crystalline microstructure. In addition to the crystalline and amorphous scattering usually observed, disorder is frozen‐in by fast cooling after heat treatment. The disordered component is detected as an additional low‐angle scattering peak at 14 degrees, well separated from the crystalline reflections, and is observed in low molecular weight material synthesized in our laboratory, and in commercially available neat resin PEEK and APC‐2 carbon fiber composite samples. When disordered material was subsequently heated above the glass transition, and then cooled very slowly, only the crystalline and amorphous scattering remained. Application of stress also resulted in formation of the disorder in the necked down regions of samples drawn in tension, suggesting that residual stresses may occur as a result of rapid cooling after heat treatment.