Bringing non-isocyanate polyurethanes closer to industrial implementation using carbonated soybean oil-based amino hardeners

The polyaddition between cyclic carbonates and diamines to form non-isocyanate polyurethanes (NIPUs) is a safer alternative than traditional PU synthesis. However, the lower reactivity of cyclic carbonates requires of long reaction times and/or high temperatures for their curing, hampering their industrial implementation in the coating industry. Starting from carbonated soybean oil (CSBO) and amine excess, and through a stepwise addition process, cyclic carbonate full conversion has been achieved, yielding amino-terminal NIPUs with up to 62 % of biobased content. These amino-terminal NIPUs act as regular amino hardeners, and have been used to cure epoxy resins under the time and temperature required by the coating industry. The performance of these partially bio-based, NIPU-epoxy hybrid coatings was evaluated by pot-life, drying, hardness and solvent resistance, achieving comparable results to the industrial formulations. The simple synthesis process, the suitable curing conditions and the properties of the coatings, bring NIPU chemistry closer to industrial implementation.