K. Moriam: Modification of Ioncell spinning technology to increase fiber toughness and create a water-repellent surface

Abstract:

This thesis work presents an eco-friendly way of hydrophobizing the Ioncell fibers and strategies to improve the mechanical properties (especially toughness) of the Ioncell fibers. In the first part of this thesis, hydrophobization of the Ioncell fibers was achieved by incorporating plant-based hydrophobic agents Betulin (BE) and Betulinic acid (BA) into the spun fibers during dry-jet wet spinning. 10 wt% BE and BA incorporated cellulose solution showed excellent spinnabilities, and the mechanical properties of the spun Ioncell fibers. Both BE and BA introduced hydrophobicity (defined by water contact angle >90 degree) into the spun staple fibers, and the hydrophobicity was transferred to the nonwovens and yarns. However, BA showed better compatibility with cellulose than BE, which was evident from the surface morphologies of the fibers and the yarn spinnability of the staple fibers.

To improve the toughness of the Ioncell fibers, the effects of the spinneret aspect ratio (L/D) and the high molecular weight containing pulp on the mechanical properties of spun fibers were investigated in the second part of the thesis. Combining high molecular weight pulp and the spinneret with L/D 2, the highest toughness (83.3 MPa) and tensile strength (61.5 cN/tex) of the Ioncell fibers were achieved. Numeric simulations revealed that the combined effect of the longer molecular cellulose chains and the longer capillary length foster the cellulose chain alignment inside the spinneret capillary resulted in simultaneous improvement of elongation and tensile strength. Furthermore, as a continuation of this research, a wide variety of spinneret geometries was applied to observe the effect of spinneret geometries on fiber toughness. Optimization of spinneret geometrical parameters significantly improved fiber mechanical properties. Interestingly, the fiber toughness was improved up to 93 MPa (12% more than the initial study) using a spinneret with optimized geometries (hole diameter 100 μm, L/D 1 and entrance cone 8°) and high molecular weight pulp. The structural properties such as longer periodicity of the lamellar plane, wider tilt angle, and lower microvoid orientation were presumably attributed to the high toughness of the fibers.

In summary, this thesis work has developed eco-friendly approaches for fiber hydrophobization and improvement of the mechanical properties of the Ioncell fibers – a step forward for building a sustainable textile industry by reducing harmful impacts on the environment.

Follow the remote defence: https://aalto.zoom.us/j/69366355816

Opponents: Professor Christian Muller, Chalmers University of Technology, Sweden

Supervisor: Professor Herbert Sixta, Aalto University, Department of Chemical Engineering

Link to electronic thesis: Modification of Ioncell spinning technology to increase fiber toughness and create a water-repellent surface