Abstract
The route for the preparation of cellulose nanofiber dispersions from bacterial cellulose using ethylene glycol- or glycerol-based deep eutectic solvents (DES) is demonstrated. Choline chloride was used as a hydrogen bond acceptor and the effect of the combined influence of DES treatment and ultrasound on the thermal and mechanical properties of bacterial cellulose nanofibers (BC-NFs) is demonstrated. It was found that the maximal Young’s modulus (9.2 GPa) is achieved for samples prepared using a combination of ethylene glycol-based DES and ultrasound treatment. Samples prepared with glycerol-based DES combined with ultrasound exhibit the maximal strength (132 MPa). Results on the mechanical properties are discussed based on the structural investigations that were performed using FTIR, Raman, WAXD, SEM and AFM measurements, as well as the determination of the degree of polymerization and the density of BC-NF packing during drying with the formation of paper. We propose that the disordering of the BC-NF surface structure along with the preservation of high crystallinity bulk are the key factors leading to the improved mechanical and thermal characteristics of prepared BC-NF-based papers.
Highlights
Environmental pollution and the excessive depletion of fossil fuel resources [1] have generated increased interest in renewable and sustainable polymers [2,3]
All further tests were performed on bacterial cellulose nanofibers (BC-NFs) films
Bacterial cellulose (BC)-NF films obtained from dispersions prepared through the treating of lyophilized bacterial cellulose with deep eutectic solvents (DES) systems (ChCl/ethylene glycol (EG) and Choline chloride (ChCl)/Gly) both with or without the application of ultrasound were investigated
Summary
Environmental pollution and the excessive depletion of fossil fuel resources [1] have generated increased interest in renewable and sustainable polymers [2,3]. The outstanding mechanical properties of cellulose crystallites have promoted a growing interest in cellulose nanomaterials with high degrees of crystallinity, such as cellulose nanocrystals [9,10] and nanofibers (CNFs) [11,12] These materials, known as nanocellulose or nanocrystalline cellulose, are intensively studied for applications that include composite reinforcement [13,14], biomedicine applications [15,16]. Among nanocellulose-based materials, nanopaper has attracted increased attention This material is defined as a sheet prepared from CNF [57] and it has been proposed to be a material in which the high mechanical properties of nanocellulose can potentially be transferred to the macroscopic level [58]. Glycerol (Gly), and their effect on the structure, morphology, mechanical and thermal properties of prepared BC-NFs. The interest in polyatomic alcohols for the pretreatment of cellulose is due to their ability to form strong hydrogen bonds with this polymer, which makes such alcohols effective plasticizers for the disintegration of intramolecular hydrogen bonds in cellulose [71]. The cellulose nanopaper based on BC-NFs was prepared and its thermal and mechanical properties were characterized
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