Titre de la dissertation: « Designing more sustainable thermosetting non-isocyanate polyurethane foams: from greener blowing agents to functional applications ».

Promoteurs de thèse: Monsieur Jean-Marie Raquez, Monsieur Sylvain Caillol (Université de Montpellier)

Résumé de la dissertation: Polyurethane (PU) foams are among the most widely used polymeric materials, but their conventional production presents significant drawbacks: the synthesis relies on toxic isocyanates, while the foaming process employs environmentally harmful physical blowing agents (PBAs) such as chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs), with high ozone depletion potential (ODP) and global warming potential (GWP). Polyhydroxyurethanes (PHUs), also known as non-isocyanate polyurethanes (NIPU), synthesized via aminolysis of five-membered cyclic carbonates, have emerged as a safer alternative. However, research on NIPU foams toward industrial applications remains limited. This thesis aims to bridge this gap by developing thermosetting NIPU foams through two sustainable foaming strategies: (i) Rigid foams using supercritical carbon dioxide (scCO₂) as a greener PBA, non-toxic, non-flammable, with zero ODP and negligible GWP, and (ii) Flexible foams using water as a chemical blowing agent (CBA).The first part establishes an innovative approach for scCO₂-blown rigid NIPU foams through a batch process involving pressure-induced CO₂ absorption followed by temperature-induced desorption and simultaneous curing. This strategy, scarcely explored for thermosetting NIPU systems, yielded foams with tunable densities (270–451 kg/m³), compression moduli (16–350 kPa), and cell sizes (0.33–0.99 mm). Notably, these foams exhibited humidity-triggered shape memory behavior with recovery ratios over 99%, expanding their potential for stimuli-responsive applications.Building upon this platform, flame-retardant NIPU foams were developed by incorporating a phosphorus-containing diamine (DOPO-diamine) as a reactive flame retardant (RFR). Covalently bonded phosphorus (0.5–2 wt%) foams achieved a 66% reduction in total heat release compared to phosphorus-free foams and V-0 classification in UL-94 testing, addressing a critical limitation for building applications where fire safety is paramount.To further expand the NIPU foam portfolio, water-blown flexible foams containing renewable bio-based nanofillers were developed and investigated. The incorporation of chitin nanocrystals (ChNC), chitin nanofibers (ChNF), and cellulose nanofibers (CNF) revealed an unexpected plasticizing effect on the PHU matrix, with glass transition temperatures decreasing from 23°C to 7–18°C. Despite this, mechanical characterization demonstrated concentration-dependent enhancement, with ChNF achieving a 165% increase in compressive modulus at 2 wt% loading, following a performance hierarchy of ChNF > CNF > ChNC.By addressing the ongoing challenges toward industrially relevant NIPU foams, this thesis establishes versatile strategies for sustainable thermosetting foams with tailored properties, bridging the gap between emerging PHU foam technology and industrial applications while contributing to greener alternatives aligned with sustainability goals, circular economy principles, and European regulatory frameworks.