Valorization of Thermoplastic Polyurethane and Styrofoam Waste for Development of Improved Sustainable Blend Membranes

This study aimed to improve the mechanical integrity of Styrofoam membranes fabricated from post-consumer food packaging. To this end, 3D-printing byproduct—thermoplastic polyurethane (TPU) waste—was blended with polyimide (PI) in the membrane dope solution. The synthesized flat-sheet upcycled membranes were evaluated via scanning electron microscopy (SEM), water contact angle (WCA), and tensile testing, while separation efficiency was determined through bovine serum albumin (BSA) rejection and permeation trials. Findings indicate that incorporating TPU into the Styrofoam/PI matrix increased tensile strength by 50%, BSA rejection by 12.4%, and permeation by 33%. Compared with pristine Styrofoam membranes, tensile strength and BSA rejection improved by 240% and 46%, respectively. Although the blend membranes exhibited a reduction in water flux (from 214 to 162.5 LMH/bar) due to pore contraction, they maintained high rejection rates (~86%) for large macromolecules like PVP (1300 kDa). Furthermore, while all membranes remained hydrophilic, hydrophobicity scaled with TPU concentration.