Functional fibres by Wet-spinning of Bio-based Colloids

Abstract

Chitin nanofibrils (ChNF), TEMPO-oxidized cellulose nanofibrils (TOCNF), lignocellulose nanofibrils (LCNF), and lignin were isolated from marine and plant biomass. Microfibres were synthesized by wet spinning of aqueous suspensions of the respective bio-based colloid. The influence of coagulant type in wet spinning as well as the properties of the microfibers obtained from TOCNF and ChNF were studied. In general, fibres coagulated via ion exchange demonstrated better mechanical properties and water/moisture stability. Meanwhile, a clear difference was found in thermal properties: TOCNF microfibres coagulated in aqueous electrolyte presented better thermal stability compared to those coagulated in organic solvents. All the TOCNF and ChNF microfibres were biocompatible as shown by in vitro tests, which indicate prospective applications in the biomedical fields.

Lignin-based fibres were manufactured from either LCNF or aqueous lignin suspensions in the presence of TOCNF. An increased lignin loading resulted in microfibres of lower mechanical strength and better thermostability. Carbon microfibres were obtained by one-step carbonization. The higher lignin content in the precursor led to carbon microfibres at higher mass yields and displaying smoother surfaces and higher electroconductivity. The measured electroconductivity (up to 103 S/cm) make them suitable for microelectrodes and wearable electronics. Moreover, the carbon microfibres developed from LCNF suspensions were demonstrated in uses as fibre-shaped supercapacitors, which showed a promising performance.

A prototype system for continuous wet-spinning was developed to increase the spinning rate and to optimize the process. This work highlights the use of renewable bioresources in the production of microfibers with no need for molecular dissolution. Thus, the wet-spinning technique is shown as a feasible and versatile approach to produce microfibres, furthering their potential in functional materials. Biobased colloids are suitable alternatives for adoption in fibre production, replacing petroleum-based precursors and opening new opportunities for green processing.