Influence of rheological properties of bimodal PEEK blends on melt spinnability

Low molecular weight (70 kg/mol) Polyether-ether-ketone (PEEK) is blended in different ratios with two different high molecular weight (105 kg/mol and 130 kg/mol) PEEK materials. Blending is carried out on a technical scale using a double screw extruder at a mass throughput range of 2 – 3.5 kg/h. The influence of the blends on crystallinity and viscoelasticity (complex viscosity and loss factor) is investigated. A reference to PEEK with medium molecular weight (85 kg/mol) is made. This material has ideal viscoelastic properties for melt spinning fibers with technical strengths of more than 60 cN/tex (792 MPa). A higher molecular weight theoretically leads to higher strength. However, processing becomes more difficult as complex viscosity increases and loss factor decreases. With the bimodal PEEK blends presented in this study spinnability can be customized regarding complex viscosity (100 to 1000 Pa∙s) and loss factor (greater than 5). With the available number of bimodal blends, PEEK fibers with higher strength can be developed on a technical scale.