Polyurethane adhesives have long demonstrated their outstanding performance and are a well-established bonding technology in a lot of industrial applications. A common method for the production of PUs involves the reaction of isocyanates with diols/polyols catalyzed by a tin catalyst. In this process, the use of hazardous isocyanates and phosgene has raised severe toxicity and environmental issues.
However, with the recent scientific eagerness towards achieving biofriendly PUs, current attention is being focused on the development of non-isocyanate polyurethanes (NIPUs). Sustainable routes to NIPUs essentially revolve around the valorization of various renewable natural oil polyols (referred to as NOPs) derived from plants. Extensive studies aim at chemically modifying vegetable oils (triglycerides, i.e. soybean, sunflower, palm, linseed oils, etc.) so as to establish a chemical platform as non-petrochemical feedstock for the synthesis of NIPUs.This approach certainly shows numerous advantages among which the major one is the accessibility to renewable triglycerides which remain the cheapest and most abundant biological sources available. However, the one significant limitation of these NIPU precursors remains their molar mass which cannot be fine-tuned − as it is essentially dictated by the natural oil itself − which restrains their range of properties and therefore of applications.
In our ongoing studies on NIPUs derived from synthetic polymers, we are developing such polymer materials with a tunable/controlled soft segment molar mass. Our general strategy involves the synthesis of α,ω-dicyclocarbonate endfunctionalized pre-polymers. These pre-polymers can subsequently be used as part A of a 2-component adhesive. By reaction with a di or triamine in a polyaddition reaction, they provide PHUs in an isocyanate-free process with properties comparable or superior to standard Polyurethane 2-components adhesives.