Adhesives can be defined as social substances capable to join permanently to surfaces, by an adhesive process. This process involves two dissimilar bodies being held in intimate contact such that mechanical force or work can be transferred across the interface. The focus is on the new generation of adhesives, based on modern technologies such as nanotechnology, derivatised polymers, and biomimetic adhesives. Besides their role in the adhesion process, they can be used for other purposes, such as sealing agents, in order to eliminate the effect of self-loosening caused by dynamic loads, sealing of areas to prevent oxidation and corrosion, waterproofing, etc.
Bio – based materials are attracting more and more attention in all fields due to their improved environmental footprint and due to the independence from petroleum resources that comes with their use.This is also true in the field of adhesives, where renewable materials from biopolymers to monomers derived from renewable resources are increasingly investigated.
There are several ways in which renewable materials can be introduced into adhesives. The most obvious route is to use natural products, i.e. biopolymers such as proteins, that already have adhesive characteristics. A second possibility is to use building blocks or monomers that can be derived from renewable sources, and combine them to make polymers closely resembling synthetic adhesives. While this route requires initially more efforts to generate the necessary structures, it presents a much easier drop-in solution at the application end as similar equipment can be used for the processing, and formulation components can remain largely unchanged. Lastly, bio-based materials can be introduced as additives into synthetic adhesive formulations.
The primary drive for the introduction of biobased materials has been their positive impact on climate change. While this has to be verified on a product to product basis for example through life cycle analyses, it can be said in general that bio-based materials do not contribute to the depletion of fossil fuels and that, prior to processing. Their environmental benefits, however, go beyond these factors to their comparative toxicity to humans and the environment and to their biodegradability. Both are attractive features for adhesives, not only due to sustainability, but also because lower toxicity and higher biodegradability can increase product appeal and lower costs associated with health, safety and environmental regulations.