Abstract
Cellulose films regenerated from aqueous alkali–urea solution possess different properties depending on coagulation conditions. However, the correlation between coagulant species and properties of regenerated cellulose (RC) films has not been clarified yet. In this study, RC films were prepared from cellulose nanofiber (CNF) and microcrystalline cellulose (MCC) under several coagulation conditions. Cellulose dissolved in aqueous LiOH–urea solution was regenerated using various solvents at ambient temperature to investigate the effects of their dielectric constant on the properties of RC film. The crystal structure, mechanical properties, and surface morphology of prepared RC films were analyzed using X-ray diffraction (XRD), tensile tester, and atomic probe microscopy (AFM), respectively. It is revealed that the preferential orientation of (110) and (020) crystal planes, which are formed by inter- and intramolecular hydrogen bonding in cellulose crystal regions, changed depending on coagulant species. Furthermore, we found out that tensile strength, elongation at break, and crystal structure properties of RC films strongly correlate to the dielectric constant of solvents used for the coagulation process. This work, therefore, would be able to provide an indicator to control the mechanical performance of RC film depending on its application and to develop detailed researches on controlling the crystal structure of cellulose.
Highlights
The development of a replacement for petroleum-based plastics is becoming more necessary in the face of global warming and plastic pollution
Coagulation–regeneration of cellulose from alkali–urea solution is carried out with an acidic aqueous solution or polar organic solvents, and it has been discovered that the properties of regenerated cellulose (RC) materials, such as crystal structure, mechanical properties, and surface wettability, can widely vary with types of coagulant and coagulation conditions [34,35,36,37]
This study suggests the detailed researches on tuning the performance of films of RC films through its crystal structure, and provide an indicator to control the properties through its crystal structure, and provide an indicator to control the properties of film of RC film depending on its application
Summary
The development of a replacement for petroleum-based plastics is becoming more necessary in the face of global warming and plastic pollution. Coagulation–regeneration of cellulose from alkali–urea solution is carried out with an acidic aqueous solution or polar organic solvents, and it has been discovered that the properties of RC materials, such as crystal structure, mechanical properties, and surface wettability, can widely vary with types of coagulant and coagulation conditions [34,35,36,37]. Yamane et al revealed that (110) and (020) were formed by the arrangement of the glucan chains via inter-and intrahydrogen bonding, while the planar glucan chains were arranged through weak hydrophobic interactions in (1–10) plane Based on this knowledge, we presumed the polarity of coagulant would affect the interactions among cellulose during the regeneration process, and so the composition of crystal planes, leading to the changes in mechanical properties of RC films, the composition of these three crystal planes, and, the mechanical strength of RC films.
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