High-Performance Acetylated Ioncell-F Fibers with Low Degree of Substitution.

Shirin Asaadi,Herbert Sixta,Alistair W.T King,Tia Kakko,Michael Hummel,Ilkka Kilpeläinen

doi:10.1021/acssuschemeng.8b01768

Shirin Asaadi, Herbert Sixta + Show 4 more

Open Access

https://doi.org/10.1021/acssuschemeng.8b01768

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Abstract

Cellulose acetate is one of the most important cellulose derivatives. Herein we present a method to access cellulose acetate with a low degree of substitution through a homogeneous reaction in the ionic liquid 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc]). This ionic liquid has also been identified as an excellent cellulose solvent for dry-jet wet fiber spinning. Cellulose was dissolved in [DBNH][OAc] and esterified in situ to be immediately spun into modified cellulose filaments with a degree of substitution (DS) value of 0.05–0.75. The structural properties of the resulting fibers, which are characterized by particularly high tensile strength values (525–750 MPa conditioned and 315–615 MPa wet) and elastic moduli between 10–26 GPa, were investigated by birefringence measurements, wide-angle X-ray scattering, and molar mass distribution techniques while their unique interactions with water have been studied through dynamic vapor sorption. Thus, an understanding of the novel process is gained, and the advantages are demonstrated for producing high-value products such as textiles, biocomposites, filters, and membranes.

Highlights

The global popularity of man-made cellulose fibers (MMCFs) is rising, and the manufacturing processes are incessantly modernized
For the first time we report about the effect of a low degree of acetylation (DS < 1) on the spinnability and mechanical properties of the newly developed Ioncell-F fibers
Among different reagents for cellulose acetylation in ionic liquids studied by Kakko et al, isopropenyl acetate (IpeAc) has been identified as a fast and efficient acetylation reagent which does not require the addition of a catalyst or an additional base for achieving degree of substitution (DS) values ranging from 0.25 to 2.97.13

Summary

■ INTRODUCTION

The global popularity of man-made cellulose fibers (MMCFs) is rising, and the manufacturing processes are incessantly modernized. The viscoelastic properties of the spinning solutions must be in a defined range to reach an optimum spinnability.[53−55] The acetylated spinning dopes showed zero-shear viscosities that were outside the optimum range found in our previous studies using pure cellulose solutions.[25,56] The dope corresponding to DS 0.75 had a very low dynamic modulus at the COP, which is indicative for both broadening the molecular mass distribution and lowering the stiffness/hardness or resistance to deformation. The development of orientation is mainly from the amorphous regions, calculated from the total (birefringence) and crystalline orientation (WAXS) It seems that the cellulose molecules substituted with a low degree of acetyl group can be easier. By decrease of the surface area and hydroxyl groups at higher DS, fibers develop hydrophobicity

■ CONCLUSION

■ ACKNOWLEDGMENTS

■ REFERENCES