Abstract
The purpose of adding cellulose nanocrystals (CNCs) into sodium alginate (SA) and Antarctic krill protein (AKP) system is to use the ionic cross-linking of SA and AKP and the dynamic hydrogen-bonding between them and CNCs to construct multiple cross-linking structures, to improve the water-resistance and strength of SA/AKP/CNCs composite fiber. Based on the structural viscosity index in rheological theory, the ratio of spinning solution and temperature were optimized by studying the structural viscosity index of the solution under different CNCs content and temperature, then the composite fiber was prepared by wet spinning. We found that when the content of CNCs is 0.8% and 1.2%, the temperature is 45 °C and 55 °C, the structural viscosity is relatively low. Under the optimal conditions, the intermolecular hydrogen bonds decrease with the increase of temperature. Some of the reduced hydrogen bonds convert into intramolecular hydrogen bonds. Some of them exist as free hydroxyl; increasing CNCs content increases intermolecular hydrogen bonds. With the increase of temperature, the crystallinity of composite fiber increases. The maximum crystallinity reaches 27%; the CNCs content increases from 0.8% to 1.2%, the breaking strength of composite fiber increases by 31%. The water resistance of composite fiber improves obviously, while the swelling rate is only 14%.
Highlights
Cellulose is one of the most abundant natural polymers globally that can be chemically treated to produce cellulose nanocrystals (CNCs) [1]
There are a large number of active hydroxyl groups on the surface of CNCs, which can participate in the formation of hydrogen bonds and various chemical cross-linking; CNCs has attracted increasing attention in the field of nanocomposites [3], and it’s considered as the best filler reinforcement material in the 21st century [4]
The apparent viscosity of the three groups of samples decreases with the increase of CNCs content, which is due to the rigidity of CNCs molecular chain, CNCs rigid molecular chains are inserted
Summary
Cellulose is one of the most abundant natural polymers globally that can be chemically treated to produce cellulose nanocrystals (CNCs) [1]. Ye et al [5], added CNCs to poly(butylene succinate) (PBA) and found that CNCs could promote the crystallization and lamellar thickening of PBA This mechanism attributes to the “memory effect” of CNCs/PBA composite in the molten state, namely the hydrogen bonding between CNCs and PBA chains. Due to loose cross-linking of the alginate system and the absorption of AKP crystal structure by composite system [14], SA/AKP composite fiber has low crystallinity and poor water resistance and mechanical properties. CNCs with a high aspect ratio was added into the SA/AKP composite system for the first time, aiming to use the hydroxyl group of CNCs to form dynamic hydrogen bonds with SA and AKP, and cross-link with the ions of SA and AKP to form multiple cross-linked structures, to improve the mechanical properties and water resistance of composite fiber. To improve the research efficiency, the relationship between the structural viscosity index and spinnability in rheology was used to select the spinning conditions, explored the influence of temperature and CNCs concentration on the structure and properties of composite fiber under the guidance of the structural viscosity index, designed to improve the mechanical properties and water-resistance of SA/AKP/CNCs composite fiber, the product is expected to be applied in biomedical and biomimetic materials
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