An alternative to plastic packaging thanks to the combination of cellulose and ceramics

As a result of the work of two research laboratories, the start-up Cilkoa is developing a process that consists of the deposition of a nanometric layer of ceramic on a sheet of cellulose. The new material obtained has barrier properties similar to those of plastics, being fully biodegradable and recyclable. Meeting with the company’s co-founders.

Packaging, bottles, labels… single-use plastics are very present in our daily lives. They are noted for their harmful effects on the environment, because they do not disintegrate after use, but decompose into microparticles that are found everywhere, especially in the oceans. Reducing these wastes is therefore a major environmental challenge. In Grenoble, researchers have developed a material that has the flexibility and biodegradability of paper, but has the barrier properties of plastic, that is, it is resistant to water and impermeable to gases. Their recipe? They deposited a nanometric layer of ceramic onto a sheet of cellulose. This process is the result of the research work of two laboratories, which combined their knowledge, each in its own area: SIMAP (Science and Engineering of Materials and Processes) specialized in ceramic materials, and LGP2 (Process Engineering Laboratory Papermakers) which, as as its name suggests, specializes in papermaking. A start-up has just been created to promote this new technology. Interview with Frédéric Mercier and Erwan Gicquel, two of Cilkoa’s four co-founders. The first is also a CNRS researcher at SIMAP and the second is a former doctoral student at LGP2.

Engineering Techniques: How do you manage to deposit a thin layer of ceramic on top of cellulose?

Frédéric Mercier (left) and Erwan Gicquel (right), two of the four co-founders of Cilkoa. Credit: Cilkoa

Frederico Mercier: Cellulosic materials have interesting chemical bonds on their surface, called OH groups (or hydroxyl groups), which are capable of reacting with an organometallic compound, which has the particularity of being a precursor of ceramics. It comes in the form of a gas and will interact with the OH bonds to form a very thin ceramic coating (less than 50 nanometers) over the entire surface of the paper. Some ceramic atoms will thus be grafted onto each cellulose fiber. It’s like putting a ceramic shell around each fiber.

What difficulties did you have to overcome to develop this process?

Erwan Gicquel: Normally, this process, called ALD (Atomic layer deposition), is used in a clean room, with smooth, non-rough materials and in a dust-free environment. It is particularly used in the field of microelectronics. This technology is therefore light years away from the world of papermaking, where there is dust everywhere, the materials are rough, massive…

This method of deposition of a nanometric layer of ceramic on cellulose already existed in the literature, but it was only suitable for surfaces of a few cm². All our research work, which started in 2018, consisted of making it compatible with the volumes of the packaging industry, whose needs reach several hundred million m². We performed several experiments to test different operating points, on different sheets of paper. We couple this work with simulation to understand how this gas is introduced into each cellulose fiber. We have also developed methods to very accurately characterize the presence of these few nanometers of ceramic across the entire surface of the papers.

How is your new material performing?

FM: Cellulose has many interesting properties, but it cannot withstand water. At the slightest trace of moisture, it disintegrates and there is no longer any mechanical resistance on this support. Thanks to the deposition of a nanometric layer of ceramic, cellulose becomes inert to water vapor, liquids and gases. It is possible, for example, to manufacture a hydrophobic paper or a paper with a gas barrier effect. These properties are only obtained thanks to the few nanometers of ceramic grafted onto the surface of each cellulose fiber; it is not a coating or varnish that can move or flake off. These chemical bonds are closely linked to the fiber surface.

In the end, we obtain a material whose barrier properties are similar to those of plastics and composed of more than 99.9% cellulose and some ceramic atoms. This coating is fully transparent and printable; you cannot see the difference between treated and untreated paper. And, good news, this material degrades like paper, under composting or recycling conditions. It is an innovation without equal on the market.

What apps are you targeting?

FOR EXAMPLE: We target all single-use packaging in the broad sense that cannot currently be recycled, whether food or cosmetics. We build a strategy to reach the market step by step. We will start with packaging for dry products and gradually move to those containing liquid products, such as yogurt cups. In this context, we also offer an alternative to today’s complex packaging, such as snack packs that contain several layers, including a metallic one.

What stage of development is your project in?

FM: We just created a start-up on June 1st. From the point of view of technology and industrialization, we will have to make a change of scale, to make our process compatible with the demands of our customers. We are already in contact with food manufacturers who have shown interest in our product.

Our business model, at least initially, will be to provide services in order to transform our customers’ cellulosic material. They will bring us their cellulosic materials and our role will be to fix our ceramic coating. We will also advise you on materials.

Our aim is to commission our first plant in 2024/2025, but in the meantime, we are working with our customers to qualify materials and coatings in concrete applications. With our pilot reactors, located in the SIMAP laboratory with which we collaborate, we are able to meet even the needs of small series production.

We are in the right timing to meet the needs of manufacturers facing the 2025 deadline; a date by which most plastics should have disappeared from single-use packaging. We have already validated our economic model, that is, we will be able to offer a packaging material with barrier functions, fully biodegradable and recyclable, at a cost compatible with the market.

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