Effect of melt spinning on the integrity of poly(ether ether ketone) for commingled yarn based composite preforms

PEEK yarns are used for commingled yarn based preforms in order to manufacture high performance thermoplastic composites. In a previous work, characterizations of PEEK commingled yarns revealed degradation, causing poor consolidation of final composites. The sizing applied onto the yarn surface in the melt spinning was identified as a degradation factor. Thus, the aim of this work is to assess the effect of different melt spinning parameters: extrusion, sizing and draw ratio, on PEEK integrity and its degradation process. Yarns at different stages of melt spinning were characterized through various techniques. For all yarns, degradation was identified during further transformation, in the molten state, inducing a decrease of the crystallization temperature and an increase of viscosity due to crosslinking. Extrusion initiates degradation earlier without changing the PEEK decomposition process. Sizing is responsible for an acceleration and modifications of degradation steps.