Preparation of non-isocyanate polyurethane (NIPU) foams by in-situ generation of the blowing agent (CO2)

Abstract

Nowadays, polyurethanes are produced thanks to the reaction between diol and diisocyanate species. Diisocyanate usage beeing subject to restrictions under REACH regulations due to its toxicity, many efforts are devoted to the substitution of diisocyanates for the synthesis of polyurethane. The most elegant pathway for the fabrication of isocyanate-free polyurethane is based on the reaction between CO2 and epoxide, leading to 5-membered cyclic carbonate (5CC) monomer. The 5CC reaction with diamine comonomer allows the formation of poly(beta-hydroxyurethane) polymer (PHU). However, the challenge lies in mimicking the CO2 generating isocyanate-water reaction of conventional PUs for PHU foaming. Herein, we designed a self-blowing technique thanks to in-situ generation of CO2 based on 5-membered CC reactivity. The study of model reactions confirmed the CO2 release thanks to 5CC reactivity in conventional experimental conditions. The study was then extended to linear polymer synthesis as a preliminary step to foam formulation. Basic formulation and foaming process screening were then conducted before more rigourous PHU foam samples characterisation. The effect of conventional PU additives on foam characteristics was also studied. RAMAN spectroscopy, TGA, DSC, SEM and DMA experiments were performed to state on properties of prepared NIPU foams.