A family of biobased polyimine elastomeric vitrimers was synthesized by reactions between di-and trifunctional polyetheramines and a furan-based dialdehyde. By varying the triamine to diamine ratio and the molar mass of the diamine, a set of cross-linked networks with similar chemical structures but different cross-link densities was obtained. All these materials exhibit a vitrimeric behavior because of the dynamic nature of the imine bonds. This fundamental study clearly reveals that the crosslink density has a drastic effect on the relaxation properties of the vitrimers. For instance, the relaxation times and the activation energies reduced when the cross-link density of the vitrimer networks decreased. This shows that the relaxation properties of vitrimers can be controlled by the sole modification of the network physical properties without the introduction of a catalyst, a change in chemical structure, or the introduction of additional chemical groups. In addition, a fast dual relaxation process has been clearly evidenced during stress relaxation experiments, which could potentially lead to double relaxation modes based on supramolecular interactions. The selective solubility of these polyimine networks was also demonstrated, opening interesting possibilities for chemical recycling while still offering robustness against aggressive conditions such as highly basic solutions. Finally, the dynamic properties and the high thermal stability of the designed polyimine networks provide an interesting reprocessability and tunable mechanical properties, showing the versatility of this sustainable family of vitrimer materials.

Flax fabrics were modified through two grafting methods in order to improve their flame retardancy. Vinyl phosphonic acid was used to treat flax fabrics via a condensation reaction between phosphonic acid function and flax hydroxyl groups. It was also grafted under radiation conditions taking advantage of its carbon-carbon double bond. Grafting efficiency of each method was assessed by X-ray fluorescence and scanning electron microscopy. The effect of the phosphorus grafting on fire behavior was studied using thermogravimetric analysis, pyrolysis combustion flow calorimetry and a preliminary fire test. In all cases, the diffusion of the phosphorus molecules into the elementary fibers bulk was observed. Phosphorus content reached 1.4 wt% using radiation grafting, leading to self-extinguishing fabrics.