New nanopaper is transparent and UV-blocking

A new type of paper made from cellulose fibres with a thickness of just a few nanometers has the potential to become a sustainable alternative for plastic packaging materials. Physicists from Utrecht University developed the fully biobased material together with Unilever and the University of Amsterdam. The work is published in the scientific journal ACS Applied Polymer Materials.

Lots of fresh food produce is packaged in transparent plastic. That material has two main advantages: it keeps the food fresh and you can see the food inside the packaging. But, it is not sustainable. Directly after opening it is thrown away.

Cellulose from orange peel

Douglas Hayden is a PhD candidate from the Debye Institute for Nanomaterials at Utrecht University. Together with colleague Srivatssan Mohan, he developed a potential sustainable alternative for this type of plastic food packaging. “It is made from a waste source of cellulose from the inside of orange peels. Cellulose is the main component of paper and fully biodegradable, but our ‘nanopaper’ is made from cellulose fibres which are a thousand times thinner than the fibres in normal paper. This makes it transparent.

Simple production process

In order to be a good food packaging material, the paper should also be able to keep food fresh. Therefore, it must also be able to block UV light. “Our nanopaper contains UV-absorbing nanoparticles. These are easy to make from cellulose with help from ethanol, a.k.a. alcohol, and water.” The rest of the production process is also impressively simple. Hayden: “We added the nanoparticles to a cellulose fibre mixture and filtered this. Afterwards, we put the substance in an oven for ten minutes at 50 degrees Celsius and this resulted in the transparent, UV-blocking nanopaper. The process is also completely upscalable.”

The fact that this transparent nanopaper is biodegradable could help with the acceptance of nanomaterials in everyday applications.

Still too thin and not waterproof

Arnout Imhof, the supervisor of Hayden in the research group Soft Condensed Matter at the UU, hopes that this research result will make sure that nanomaterials become more accepted for everyday applications. “The fact that this nanopaper is biodegradable could help with that.” There are still some challenges to overcome in order to make this paper commercially viable. To prevent food drying-out, the material needs to be more waterproof. “This material is more so than normal paper, but not yet good enough to keep fruit and vegetables fresh”, according to Imhof. Hayden also sees another point for development: “The paper we made is still ten times thinner than normal paper which you would put into your printer, it’s just a few micrometers thick. At this thickness it is not strong enough for the supermarket. However, we know that it is possible to make strong transparent paper”.

Publication

Fully Biobased Highly Transparent Nanopaper with UV-Blocking Functionality
Douglas R. Hayden, Srivatssan Mohan, Arnout Imhof, Krassimir P. Velikov, ACS Appl. Polym. Mater. 2019, 1 (4), pp 641–646
All researchers are affiliated to Utrecht University.

This research is part of the strategic theme Pathways to Sustainability of Utrecht University.