Design and Characterization of Dual‐Layer Polypropylene–Polyurethane Composite Membranes

ABSTRACT The development of composite membranes with tunable surface properties and controlled fiber architecture is essential for improving membrane performance in advanced filtration systems. In this study, novel polypropylene–polyurethane (PP–PU) composite fiber membranes were fabricated and characterized using a two‐step fabrication strategy. The microfibrous PP bottom layer was modified with β‐zeolite, while the nanofibrous top layer was formed by electrospinning PU–oleic acid (OLE)–polyethylene glycol (PEG) copolymers with varying PEG content. The synthesized copolymers were characterized by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance ( 1 H NMR), while membrane morphology, wettability, and elemental composition were evaluated using scanning electron microscopy (SEM), contact angle measurements, and energy‐dispersive X‐ray spectroscopy (EDS). The electrospun membranes exhibited average fiber diameters of 0.307 ± 0.07, 0.309 ± 0.07, and 0.460 ± 0.10 μm for PEG1, PEG2, and PEG3, respectively. Morphological analyses confirmed uniform fiber structures and increased surface roughness with higher PEG ratios. The incorporation of β‐zeolite significantly enhanced the hydrophilicity of the membranes, reducing the water contact angle from 131.21° ± 2.4° to 115.33° ± 1.7°. Among the formulations, PU–OLE–PEG2 showed optimal performance, providing a balance between uniform morphology, controlled fiber diameter, and enhanced hydrophilicity. These findings demonstrate that the combined incorporation of PEG and β‐zeolite effectively tailors the structural and surface characteristics of dual‐layer PP–PU composite membranes, providing a promising platform for future membrane filtration applications.