Comparison of Cellulose Dissolution Behavior by Alkaline and Sulfuric Acid Solvents and Their Films' Physical Properties.

Jungsoo Han,Yungbum Seo

doi:10.3390/ma14185273

Abstract

Three alkaline mixtures (NaOH/thiourea, NaOH/urea/thiourea, NaOH/urea/ZnO) and sulfuric acid were used at low temperatures as cellulose solvents, and their cellulose solubility and films’ physical properties for bleached chemical wood pulps and cotton linter were compared. Their degree of polymerization (DP) was controlled to 600–800 before dissolution. Among the alkaline solvents, NaOH/urea/ZnO gave the film the highest tensile strength and stretch. When compared to sulfuric acid, NaOH/urea/ZnO gave lower strength properties but higher crystallinity indices in the films. While alkaline solvents could not dissolve the high DP cellulose (DP ~ 2000), sulfuric acid could dissolve the high DP cellulose at below zero Celsius temperature, and the strength properties of the films were not much different from that of the low DP one. It appeared that the low-temperature sulfuric acid treatment did away with the cellulose’s DP controlling stage; it decreased cellulose DP very quickly for the high-DP cellulose at the initial stage, and as soon as the cellulose DP reached a DP low enough for dissolution, it began to dissolve the cellulose to result in stable cellulose solution.

Highlights

Bio-polymers from natural resources have gained much attention as an alternative to petroleum-based polymers due to their equivalent or better functionality, renewability, and biodegradability
The physical properties of cellulose films from alkaline solvents were compared for the low degree of polymerization (DP) cotton linter
Yang et al reported that the thermal stability and the tensile strength of cellulose films prepared from the NaOH/urea/ZnO solvent were higher than those prepared from the NaOH/urea solvent without ZnO, and explained that it was due to better solubility and miscibility of the cellulose in the solvent of the

Summary

Introduction

Bio-polymers from natural resources have gained much attention as an alternative to petroleum-based polymers due to their equivalent or better functionality, renewability, and biodegradability. Cellulose is one of the most abundant glucose-based bio-polymers available on the planet, representing about 1.5 × 1012 tons of the total annual biomass production [1]. It has excellent physical properties such as high elastic modulus and low coefficient of thermal expansion, as well as biodegradability and renewability [2]. Besides many practical utilization methods such as making pulp and paper, one way of using cellulose is by its dissolved form. Dissolved cellulose can be used to make a variety of products from regenerated textile fibers, packaging films, and cellulose derivatives, which are commercially produced for manufacturing advanced materials, such as separation membrane, hydrogel for bio-medical engineering, electronic devices, and various regenerated nano-fibers depending on their shapes and regeneration methods [3,4,5].

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