Pore Structure and Properties of PEEK Hollow Fiber Membranes: Influence of the Phase Structure Evolution of PEEK/PEI Composite

Abstract

Poly(ether ether ketone) (PEEK) hollow fiber membranes were successfully prepared from miscible blends of PEEK and polyetherimide (PEI) via thermally-induced phase separation (TIPS) with subsequent extraction of the PEI diluent. The phase structure evolution, extraction kinetics, membrane morphology, pore size distribution and permeability for the hollow fiber membrane were studied in detail. Extraction experiments, differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMA) studies showed that the heat treatment had a significant influence on the two-phase structure of PEEK/PEI, and that it was controlled by the crystallization kinetic of PEEK and the diffusion kinetic of PEI. As the annealing temperature increased, the controlling factor of the phase separation changed from PEEK crystallization to PEI diffusion, and the main distribution of the amorphous PEI chains were changed from the interlamellar region to the interfibrillar or interspherulitic regions of PEEK crystallization. When the annealing temperature increased from 240 °C to 280 °C, the extracted amount of PEI increased from 85.19 to 96.24 wt %, and the pore diameter of PEEK membrane increased from 10.59 to 37.85 nm, while the surface area of the PEEK membrane decreased from 111.9 to 83.69 m2/g. Moreover, the water flux of the PEEK hollow fiber membranes increased from 1.91 × 10−2 to 1.65 × 10−1 L h−1 m−2 bar−1 as the annealing temperature increased from 240 °C to 270 °C. The structure and properties of the PEEK hollow fiber membrane can be effectively controlled by regulating heat treatment conditions.

Fabrication and Characterization of PEEK/PEI Multilayer Composites

“…Blends of PEEK/PEI have been studied due to their high miscibility, which can offer a chance to balance their properties, minimizing their respective drawbacks [1,2,[5][6][7][8][9][10][11][12][13]. Applications in membranes and welding processes [14][15][16], as well as in the aerospace industry, where good mechanical properties at high temperatures are required [17], has increased the interest in PEEK/PEI blends. Several studies have demonstrated the high miscibility of both polymers in all blend compositions due to the identification of a single glass transition [2,5,10,12,17], which varied nearly as predicted by the Fox equation [5,17,18].…”

The effect of grafting monomer charge on the antifouling performance of poly(ether ether ketone) hollow fiber membrane by ultraviolet irradiation polymerization

“…Then precursor fibers were annealed at 270 °C for 3 h and were immersed in extractants (80 vol% N ‐methylpyrrolidone, 10 vol% ethanolamine and 10 vol% water) for 1 h to remove PEI and obtain PEEK hollow fiber membrane. The specific preparation method of PEEK hollow fiber membrane has been demonstrated in detail in our previous work 16 …”

“…Poly(ether ether ketone) (PEEK) is a kind of semicrystalline aromatic engineering thermoplastic polymer with outstanding thermal resistance, chemical stability and comprehensive mechanical properties 14,15 . The continuous service temperature of PEEK is up to about 250 °C and it is almost insoluble in any common solvent at room temperature 16 . Therefore, PEEK is considered as a potential high performance membrane material which can be used in high‐temperature resistant ultrafiltration and microfiltration processes, 14 fuel cells 17–19 and gas separation 20 .…”

Optimization of Processing Conditions and Mechanical Properties for PEEK/PEI Multilayered Blends

“…Taking into account the comparative advantages of each thermoplastic (e.g., the thermal stability of PEI and the chemical resistance of PEEK), it is of great interest to combine their properties and minimize their respective drawbacks by means of a PEEK/PEI blend, whose molecular miscibility is a proven fact [ 13 , 14 , 15 , 16 ]. Until now, the melt blending process, which commonly uses a twin-screw extruder, has been the most widely used technique in manufacturing PEEK/PEI polymer blends [ 17 , 18 , 19 , 20 , 21 , 22 ]. Although full PEEK/PEI interpenetration has been shown to provide good thermal and mechanical properties, there are significant disadvantages in terms of the physical and chemical properties of these materials when both are found in a homogeneous mixture.…”