Mechanical properties and electrical surface charges of microfibrillated cellulose/imidazole-modified polyketone composite membranes

• Published in: Polymer testing 2020-09, Vol.89, p.106710, Article 106710
• Main Authors: Gonzalez Cortes, Pablo, Araya-Hermosilla, Rodrigo, Araya-Hermosilla, Esteban, Acuña, Daniela, Mautner, Andreas, Caballero, Leonardo, Melo, Francisco, Moreno-Villoslada, Ignacio, Picchioni, Francesco, Rolleri, Aldo, Quero, Franck
• Format: Article
• Language: English
• Subjects: Composite membrane; Electrical surface charges; Mechanical properties; Microfibrillated cellulose; Paal-knorr reaction; Polyketone
• ISSN: 0142-9418; 1873-2348
• DOI: 10.1016/j.polymertesting.2020.106710

In the present work, microfibrillated cellulose (MFC) suspensions were produced by high-pressure homogenization and subsequently used to fabricate MFC membranes (C-1) by vacuum filtration followed by hot-pressing. A polyketone (PK50) was chemically modified by Paal-Knorr reaction to graft imidazole (IM) functional groups along its backbone structure. The resulting polymer is referred to as PK50IM80. By solution impregnation, C-1 was immersed in an aqueous solution of PK50IM80 and subsequently hot pressed, resulting in the fabrication of MFC/PK50IM80 composite membranes (C-IMP). Another method, referred to as solution mixing, consisted in adding MFC into an aqueous solution of PK50IM80 followed by vacuum filtration and hot-pressing to obtain MFC/PK50IM80 composite membranes (C-MEZC). C-IMP and C-MEZC were characterized by a wide range of analytical techniques including, X-ray photoelectron spectroscopy, Fourier-transform infrared chemical imaging, scanning electron microscopy, atomic force microscopy, dynamical mechanical analysis, tensile testing as well as streaming zeta potential, and compared to C-1 (reference material). The results suggested that C-IMP possess a more homogeneous distribution of PK50IM80 at their surface compared to C-MEZC. C-IMP was found to possess significantly enhanced Young's modulus compared to C-1 and C-MEZC. The tensile strength of C-IMP was found to improve significantly compared to C-1, whereas C-1 possessed significantly higher tensile index than C-IMP and C-MEZC. Furthermore, the presence of PK50IM80 at the surface of MFC was found to significantly shift the isoelectric point (IEP) of the membranes from pH 2.3 to a maximum value of 4.5 for C-IMP. Above the IEP, C-IMP and C-MEZC were found to possess significantly less negative electrical surface charges (plateau value of −25 mV at pH 10) when compared to C-1 (plateau value of −42 mV at pH 10). Our approach may have implication to broaden the range of filtration applications of MFC-based membranes. •Polyketone (PK50) was modified with imidazole (IM80) by Paal-Knorr reaction.•MFC/PK50IM80 composite membranes were produced by solution impregnation (SI).•FTIR 2D chemical imaging was used to assess PK50IM80 surface distribution.•Membranes with improved tensile mechanical properties were obtained by SI.•PK50IM80 affects the electrical surface charges of the composite membranes.