Large-scale control of morphology and tensile strength enhancement of PEEK fibers after post-treatment

In this study, a post-treatment method was carried out to increase the tensile strength of poly ether ketone (PEEK) fibers, with a maximum increase of 69%. The effects of the post-treatment process parameters on the diameter shrinkage ratio, mechanical properties of PEEK fibers, and the aggregated state structure were also quantitatively investigated by optical measurements, uniaxial tensile tests, differential scanning calorimetry, and two-dimensional-wide angle X-ray diffraction. These studies revealed that the enhanced orientation of PEEK fibers with increasing post-treatment temperature and constant tensile force is the major reason for the significant increase in uniaxial tensile strength. The diameter shrinkage ratio can be used as an indicator of the degree of fiber orientation. More critically, this study also presented mathematical models that described the high linearity of the increase in diameter shrinkage ratio and uniaxial tensile strength of fibers with post-treatment temperature and constant tensile force, respectively. That also revealed the equivalence of temperature and constant tensile force in the post-treatment process and obtained the conversion factor. These in-depth understandings provided positive guidance for improving the strength of PEEK fibers and achieving controllable morphology and mechanical properties in PEEK fiber production.