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Vegetable Nanofibers

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Introduction

In the last years, the fast development of the society went hand in hand with the increase in the consumption of all kind of commodities. Today, we are all more or less conscious about the impact that the human activities have on the Earth’s ecosystem. And being responsible for the climate change that is occurring, we are looking for alternative solutions in order to start a more respectful and sustainable lifestyle.

This solution comes right from the Nature that, thanks to its infinite resources, offers us nutrition and renewable materials with whom we can tailor all our activities and satisfy our needs.

The secret is to look with the right intent.

Cellulose

The right intent is the one that brough in the last decades many researchers and industries to study in an analytical and extended way the most abundant biopolymer presents on Earth: the cellulose.

Cellulose is a polymer, so a macromolecule formed by many glucose units linked all together. It can be obtained from any type of vegetal material, being the principal structural component of the plant walls.

So, it is possible to obtain cellulose from plants, for example from agricultural wastes, from flax, from hemp, cellulose from bamboo, but also from some marine animals such as tunicates and microorganisms, like bacteria and some algae.

Cellulose potential

Cellulose potential is the fact that, more than being a completely natural material that potentially could be obtained from waste biomass, it can have different final characteristics, based on the original material it came from and on the type of process used.

Indeed, the structural basis that constitutes the macromolecule can be broken down into smaller fragments, until obtaining the cellulose nanofibers.

Cellulose nanofibers

It is important to underline that the nanocellulose can be obtained also in the form of nanocrystals, depending on the method used for the degradation of the starting vegetal matrix.

In particular, the main types of processing methods for the cellulose are: chemical, mechanic, enzymatic or a combination of them. Finally, nanocellulose could also be obtained directly from bacteria that synthesize it inside their cells, making of it a biotechnological process.

Thanks to their microscopic dimensions – we are talking about nanometers, so one billionth of the meter – the cellulose nanofibers acquire particular mechanical, optical and thermal properties, that make them the principal constituents for various applications.

For example, they have a high rigidity: with an elastic modulus that can reach 220 GPa, they overtake Kevlar fibers. These nanofibers also preset a high tensile strength, until 10 GPa, so even higher than cast iron. But also: their strength to weight ratio results to be 8 times higher than the stainless-steel one.

Therefore, they can be used as filler inside other materials, in order to improve their properties.

The new frontier for the nanofiber

Nanofibers are completely biodegradable, biocompatible and bioderived and so they constitute the new frontier for bio-based materials, in contrast with the classical ones derived from oil. In addition to this, the high surface area and the abundant presence of hydroxyl groups – molecular endings formed by one oxygen and one hydrogen atom – cellulose nanofibers can be superficially modified depending on the type of application for which they are intended.

Therefore, it is easy to see how cellulose nanofibers find various applications ranging from biomedical engineering and drug delivery systems, to batteries and biosensors, to the paper and bioplastics industry for packaging, to wastewater purification treatments, where it is an excellent candidate for the removal of heavy metals thanks to its special absorbing properties.

Other sectors in which cellulose nanofibers are studied and used as an important alternative to environmentally unsustainable materials are, for example, the food, pharmaceutical, cosmetic, automotive and construction ones.

Nanofibers and bamboo

Within this rich and varied landscape, cellulose nanofibers derived from bamboo become an interesting object of study, thanks to a different crystalline structure that differentiates them from nanofibers obtained from wood pulp, thus suggesting the possibility of getting different properties that open the way for further applications of this versatile material.

In fact, bamboo is considered an important alternative resource for a biorefinery process. For this reason, we are trying to reduce the costs of obtaining nanofibers by developing processes that take into account different parts of the plant.

Author: Sara Casalini – Chemical & Biochemical Engineer

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