Living without fossil based plastics? By Sarina Massmann (RUG)

The selective modification of unprotected carbohydrates for cross-linking in waterborne coatings.

As you all know we use a lot of plastic and polymers. There are big problems with plastic since they are oil based and produce a lot of waste. That way they contribute to the problem of global heating because of their carbon footprint.

Also in coatings such polymers are used to protect our metal and wooden surfaces. Even though they do not end up the same way as waste, the oil based polymers do not help the carbon footprint. New inventions are tried and used but often they are expensive and difficult to make.

What if there already was a cheap and green alternative to the “old oil-based plastics and polymers”? Indeed, it is already possible to take plant-based feedstocks for the production of polymers. Moreover, it is even possible to take organic waste feedstocks, e.g. from industry in form of crap shells.

Most of these organic feedstocks have in common, that they are built from large chains of sugar molecules, the so-called polysaccharides. These polysaccharides are perfect starting materials for the production of plastic alternatives because they are already polymerized into large chains and already consist of a large number of functionalities. Functionalities are necessary to perform further chemistry to modify the chains’ properties.

The whole process of modifying the bio-waste feedstock is not only an opportunity but also a challenge. The goal is to do all chemistry in aqueous solutions so that no toxic solvents are needed. The same applies to the reagents used for the modifications. It is for example necessary to use catalysts that do not contain heavy metals.

This is where the ARC CBBC started its flagship project of waterborne coatings. Coatings are in general also just a protective layer made of plastic.

My part of this project is to modify polysaccharides so that they consist of a handle afterwards, which can be used to cross-link chains onto each other. The process of cross-linking will make a water-soluble starting material into a water-resistant coating after drying (comparison between spaghetti and lasagna, figure 1).