Tailoring the properties of nanocellulose-sepiolite hybrid nanopapers by varying the nanocellulose type and clay content

Abstract

The development of nanocellulose-clay materials resulted of great relevance, as it opened up the applications of nanocellulose, but it still requires new approaches that could contribute to improve the preparation procedures and the features of this type of biohybrid materials. In this context, nanocellulose-sepiolite (NC-S) biocomposite foams and films have already been successfully tested for some applications. However, the influence of the nanocellulose properties on sepiolite-cellulose interactions, and consequently on the final properties and potential applications of NC-S biohybrid materials, has not been previously studied. To address this knowledge gap, four kinds of nanocelluloses produced from elm biomass (non-chemically pretreated lignocellulose and bleached cellulose nanofibers (LCNFs and CNFs, respectively), TEMPO-oxidized cellulose nanofibers (TOCNFs) and cellulose nanocrystals (CNCs)) were characterized and used to develop NC-S nanopapers. A stronger interaction was found between sepiolite and negatively charged nanocelluloses (TOCNFs and CNCs), improving their thermal stability and mechanical properties by increasing the sepiolite content. Furthermore, the type of nanocellulose and the sepiolite content could be adjusted to tune the flammability, water permeability and mechanical and optical properties of the NC-S nanopapers. Graphical abstract

Effect of the dispersion state of minerals on the properties of cellulose nanofiber-based composite films

“…However, the ultrasonication of sepiolite suspension, beyond an additional trend to a slight improvement in the tensile strength, allowed to keep the transparency of the film containing 20% of sepiolite with a value close to that of the neat TEMPO CNF film. The mechanical properties of the composite films obtained in the present work are in line to those of related films reported in the literature (González del Campo et al, 2018;Martín-Sampedro et al, 2022). For example, Martín-Sampedro et al reported the preparation of hybrid nanopapers of TEMPO-oxidised CNF and sepiolite (20%) with a tensile strength of 79.0 MPa and Young's modulus of 4.7 GPa; our composite films presented comparable values for these properties (74.8 MPa and…”

“…S3) showed a remarkable decrease of the intensity of all the bands in the mentioned region and, in particular, the very weak band due to the OH stretching in Si-O-H bonds at 3717 cm − 1 disappeared. The latter observation is an indication of the existence of interactions by hydrogen bonding between the silanol groups of the mineral surface and the hydroxyl groups of the CMC (Martín-Sampedro et al, 2022). Breaking of Mg-O bonds in the octahedral layer on the surface of the sepiolite crystals may also have occurred.…”

“…In the literature, most of the reported works deal with planar minerals (Alves et al, 2019). Few studies reporting composites using fibrous minerals, such as sepiolite, are available (Ghanadpour et al, 2018;González del Campo et al, 2018;Martín-Sampedro et al, 2022). Additionally, to the best of our knowledge, no study in literature reports the effect of different dispersing equipment on the CNF-mineral composite film properties.…”

Micro Nanofibrillated Cellulose as Functional Additive Supporting Processability of Surface-Active Mineral Suspensions: Exemplified by Pixel Coating of an NOx-Sorbent Layer

“…The ancillary minerals exhibit a strong effect on the rheology of the suspension, relating to their individual morphology and lower particle density compared with GCC, hence exhibiting high volume concentration per unit weight in the formulation, especially under shear [ 7 , 26 ]. In considering the properties defined above ((i)–(iv)) we studied the stress-related viscoelastic and dilatant structure behavior of the complex material suspension.…”

“…Therefore, the rheological behavior of suspension coatings that contain such minerals affects the end-point coating structure, including pore morphology, uniformity, and porosity, which, in turn, influence the surface sorption properties. Furthermore, due to the high surface area and/or aspect ratio of such ancillary minerals in the coating color matrix, once dried, and depending on orientation, they exhibit extensive volume fraction occupancy in the coating, and this feature can aid coverage of rough substrate surfaces [ 7 , 8 ].…”