Sustainable bio-based functional additives for adhesives and coatings - a review

The climate crisis, the depletion of fossil fuels and health concerns about petrochemical components in adhesives and coatings have led to a social and political paradigm shift. As a result, there has been an intense search for sustainable bio-based materials that are also comparable to petroleum-based products in terms of cost and performance. A promising approach is the development of materials with (multi)functional properties that can be achieved by adding functional additives. This review article first explains the requirements for adhesives and coating materials and then presents the current state of research on sustainable bio-based functional additives, with a focus on flame retardant, UV protective, antimicrobial and antioxidant, mechanical stability, superhydrophilic and superhydrophobic, as well as anti-icing properties. Great attention is paid to the use of readily available raw materials such as lignin, cellulose(derivatives) and tannic acid. However, many other substances such as dyes, essential oils or their components, proteins and biopolymers of plants and animals are also promising additives. Hence, there are still some challenges to overcome, such as higher susceptibility to microbial attack or lower durability, in order to obtain market-relevant products. The approaches taken so far are presented in this article, critically analysed and the remaining challenges discussed in detail.