Development of chitosan-nanocellulose composite fibres

Chitosan is the most well-known derivative of chitin, which is considered to be the second most abundant natural polymer in the world after cellulose. The main natural source of chitosan is crustacean shells (e.g. shells from crabs and shrimps), which are an abundant by-product of the food-processing industry. Chitosan has a range of attractive properties: it is renewable, biodegradable, biocompatible, non-allergenic and non-toxic material. Despite such unique properties, the use of this material is surprisingly limited, mostly targeting the biomedical area. Chitosan is thus considered to be one of the most underused biopolymers on Earth.

Recent developments in resource efficient technologies for isolating chitosan from crustacean shell wastes has opened up possibilities to use this raw material in new bio-based materials. Consequently, chitosan becomes a potential raw material for man-made fibres. From a chemical point of view, chitosan is a macromolecule very similar to cellulose, the predominant polymer of cotton, which envisions a future use in textiles.

Challenge

Regenerated chitosan fibres has previously been produced by using conventional wet spinning techniques. Usually chitosan is dissolved in acetic acid solution and then extruded through a spinneret into an alkaline coagulation bath to obtain the regenerated fibre. Chitosan fibres spun in this way reach a tenacity of 10–15 cN/tex, compared to cotton that has a tenacity of 15–40 cN/tex. Thus, non-sufficient fibre strength, both in dry and wet state, remains the main limitation for chitosan to be used in different areas, especially textiles.

To optimize the mechanical properties of spun fibres from chitosan, different strategies have been proposed lately, such as blending chitosan with synthetic polymers or introduction of inorganic nanofillers. However, such systems often have problems to meet requirements on sustainability. The development of fully bio-based fibres is of great importance and may open opportunities for industrialization of chitosan man-made fibres.

Aim

This project aims at developing a new generation of man-made fibres from chitosan with enhanced mechanical properties.

Solution

Incorporation of nanocellulose into a spinning solution of chitosan to produce composite fibres. Nanocellulose is the load-bearing material in trees. Today, it can be isolated and transferred into other materials to perform the same function. The introduction of nanocellulose into chitosan fibres is envisioned to provide enhancement of their mechanical properties.

Effect

Every year, 6–8 million tons of waste crustacean shells are produced globally. For instance, meat accounts for only around 40% of a crab's mass. The waste crustacean shells are rich in chitin. The potential value of chitin to the industries is being ignored. Therefore, sustainable ways to refine and valorise this material should be found. Given the increase of world population and growth of prosperity, which in turn prompts an increased demand for goods, the need in waste valorisation is very important.

This research has a potential of expanding Swedish circular and biobased economy by converting chitin wastes into useful raw materials, as well as by using abundant forest resources as a source of nanocellulose to produce new products.