Photo: Christian Ove Carlsson

A new era of bio-based polymers

Tuesday 05 Mar 19
|
by Morten Andersen

Contact

Anders Egede Daugaard
Associate Professor
DTU Chemical Engineering
+45 45 25 68 15
In a world of scarce resources, bio-based polymers have entered the scene, offering interesting new functionalities.

As crude oil resources are slowly drying out, interest in producing bio-based polymers is rising accordingly. However, we should not only aim for direct substitution, but also take advantage of the new functionalities. This is according to Anders E. Daugaard, Associate Professor with the Danish Polymer Centre (DPC) at DTU Chemical Engineering:

“We do see new developments within fossil-based polymers from time to time, but these are mainly hybrids of well-known systems. We hadn’t seen truly new polymer systems for several decades, until the bio-based polymers began entering the scene. This is really exciting, especially if you keep an open mind to their new functionalities.”

The most prominent example is FDCA (2,5-furan-di-carboxylic-acid). FDCA is not a new substance but only within the last decade has this organic chemical compound become of industrial relevance. FDCA can substitute terephthalic acid (PTA), one of the widely used building blocks for production of polyesters and other polymers. Plastic bottles and wrapping products made from FDCA are already in production.

“The interesting thing for us is that as this business case has become relevant, the FDCA monomer will be produced in much larger quantity, leading to lower prices. This opens the field for other new business cases from this polymer system,” says Anders E. Daugaard.

"Some customers may want to buy a polymer just because it is bio-based, but overall only having ‘the green story’ will not be enough. Once you can show better properties, things will really take off."
Anders E. Daugaard, Associate Professor

Having ‘the green story’ is not enough
In other words, the DPC researchers are not only focusing on how well a bio-based polymer like FDCA can match the properties of a fossil-based polymer like PTA—but also on the properties that are different. For instance, the gas-barrier properties of FDCA are actually better than those of PTA. This means that a FDCA container is more effective in preventing leaks of gasses and thereby also leaks of smell.

“This is where things become interesting. Some customers may want to buy a polymer just because it is bio-based, but overall only having ‘the green story’ will not be enough. Once you can show better properties, things will really take off.”

Another example of different properties is the stability. Bio-based polymers are generally less stable than fossil-based, but this can actually be an advantage:

“For instance, at a football stadium you can serve all food and beverages at plates and cups made from a bio-polymer, and later process the leftovers, plates and cups into compost—saving the resource consumption for rinsing and separation. This would not be possible if the polymer was fossil-based,” explains Anders E. Daugaard, noting that the example is from the US:

“The concept conflicts with current Danish waste treatment, but such regulations could be altered in the future.”

Part of the circular economy
On the same note, bio-based polymers could be introduced for some hardened polymer products.

“If you look solely at properties like stiffness, stability, and mechanical strength, bio-based polymers may not be able to compete with fossil-based polymers. However, as interest in circular economy is growing, the perspective begins to change. It could be a better option overall to have a less stabile product, if the reusability is much better.”

Besides FDCA, several other bio-based polymers are being developed for a range of applications. For instance, the DPC researchers have an ongoing collaboration with Haldor Topsøe on preparation of functional polyesters.

“Currently, polyesters are produced from cleaner raw materials such as sugars, but it will become possible to instead produce it from straw and other types of biomass which are currently seen as agricultural waste materials. Again, this is really exciting from a perspective of using the world’s scarce resources in a sustainable manner,” says Anders E. Daugaard.

Enzymatic polymerization is highly specific
Bio-based monomers are generally more fragile and cannot tolerate the same harsh processing as can fossil-based. However, this does have an upside. Enzymatic polymerization is not only gentle, but also more specific, meaning the products may become of excellent purity and can have a much higher degree of functionality compared with polyesters prepared by classic methods.

“As enzymes cannot tolerate high temperatures, they may not be fit for production of bulk quantities of polymers and can ‘only’ contribute to substances like additives. Still, this will be a valuable contribution to transition to a sustainable use of resources,” says Anders E. Daugaard, summing up:

“The really uplifting thing is that the new bio-based polymer systems are coming. There is no doubt about it. So, as polymer scientists we have a unique chance to investigate all the new functionalities and at the same time contribute to sustainability.”


DPC PROJECTS ON BIO-BASED POLYMERS

Researchers at DPC are engaged in a range of projects focusing on different types of bio-based polymers. Titles of some of the most recent scientific publications indicate the scope of the research:

‘Highly Branched Bio-based Unsaturated Polyesters by Enzymatic Polymerization’
Polymers, 2016. Funded by Innovation Fund Denmark, and enzymes were supplied by Novozymes.

‘Synthesis of a Novel Polyester Building Block from Pentoses by Tin-containing Silicates’
RSC Advances, 2017. Collaboration with Haldor Topsøe, enzymes were supplied by Novozymes.

‘Hybrid Poly(lactid acid)/ Nano-cellulose/ Nano-clay Composites with Synergistically Enhanced Barrier Properties and Improved Thermomechanical Resistance’
Polymer international, 2016. Funded by the Marie Curie International Training Network under the EU FP7.

‘Investigation of Curing Rates of Bio-based Thiol-ene Films from Diallyl 2,5-furandicaboxylate’
European Polymer Journal, 2018. Frontpage of the issue. The project was funded by DTU.