Finaliste SRA 2020: Tessy – Lignin-based cyanate ester resins

Using nature’s design to develop innovative, renewable and safe high-performance thermosets.

Tessy Hendrickx

Today, plastics are an indispensable part of our everyday life. It seems (almost) impossible to think of a world without plastic bags, bottles etc. However, 99% of modern-day plastics is produced from crude oil, evoking concerns about sustainability and environmental impact. Therefor, looking into biomass as a resource to create sustainable alternatives is mostly desirable. By breaking down wood to its building blocks, components can be obtained that are useful for the production of bio-based plastics. Among these components are bisguaiacols, which serve as a good replacement for fossil-based plastics that are made from the high-volume chemical bisphenol A (BPA) and its analogues. Besides the fact that BPA is not renewable, it is controversial since it is an endocrine disruptor that can cause harm to people and the environment. Thus, by developing bisguaiacol-based alternatives, not only renewability, but also safety is improved drastically.

Bio-based plastics that have found their way to the market are almost completely composed of thermoplastics, which soften by heating and stiffen by cooling repeatedly. This is in contrast with thermosets, which are irreversible hardened once they are formed, in a process called ‘curing’. It is thus a priority to study the production of biobased
thermosets.

This master thesis focusses to create a specific type of thermoset, composed of the lignin-derived bisguaiacols. Cyanate ester resins (CERs) are a type of high-performance plastic. They are known for their great electrical and mechanical properties and are used in more advanced applications like space structures, aerospace and electronics.

During this research, a variety of bisguaiacols were employed to create bio-based CERs. This was possible since nature offers a gamma of structurally different substrates for bisguaiacol synthesis. By comparing with traditional, fossil-based CERs, it was found that these bisguaiacol-based CERs offer an advantage because they have the possibility to be cured without addition of an external catalyst whereas by curing the fossil-based CERs, extensive degradation was observed. Since structurally different substrates were used, it was also possible to determine a structure-property relationship. This is of value because it allows us to estimate what structures are necessary to create certain polymers with specific targeted properties. In addition, these innovative bio-based CERs offer desirable thermoset properties and open the way for the transition of a linear to a circular economy, incorporating high-performance renewable bio-based materials.

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