Effect of poly(ether ether ketone) degradation on commingled fabrics consolidation

Abstract The effects of poly(ether ether ketone) (PEEK) degradation on consolidation of commingled preforms have been investigated. Contrary to what could be expected, under the same processing conditions, consolidation of the preforms systematically results in a high porosity content, above 10%. Fourier Transform Infrared spectrophotometry (FTIR) and Gel Permeation Chromatography (GPC) have shown small molecular structure modifications of PEEK yarns compared to the raw material. These modifications have been attributed to sizing of PEEK filament. Calorimetric (DSC) and rheological analyses have demonstrated that the presence of sizing in the preforms have huge consequences on the degradation kinetics. The crystallization temperature decreases and the viscosity increases significantly. This acceleration of the degradation kinetics is the reason of the poor consolidation behavior during composite manufacturing. The conditions of melt-spinning under which the neat PEEK is transformed into filament are therefore a key factor of PEEK degradation.