In the present paper, the foaming process of biosourced thermoset foams was considered at the lab scale with the aim of creating a numerical model able to simulate, for the first time, their manufacturing process. A multi-physical model was thus generated, having as driving force of the expansion the inner gas pressure of the foam, calculated from mass, heat and mechanical balances. In addition, and this is another originality of our work, the study was implemented in a 2D axisymmetric mobile mesh. The simulation was not stopped just after the rise of temperature and the related material expansion but, instead, a complete simulation of the whole process was offered, i.e., including cooling. Simulated and experimental data such as temperature changes and foam growth were compared, and a fair agreement was observed, suggesting the relevance of our approach.

This review focuses on the description of the main processes and materials used for the formulation of rigid polymer foams. Polyurethanes and their derivatives, as well as phenolic systems, are described, and their main components, foaming routes, end of life, and recycling are considered. Due to environmental concerns and the need to find bio-based alternatives for these products, special attention is given to a recent class of polymeric foams: tannin-based foams. In addition to their formulation and foaming procedures, their main structural, thermal, mechanical, and fire resistance properties are described in detail, with emphasis on their advanced applications and recycling routes. These systems have been shown to possess very interesting properties that allow them to be considered as potential substitutes for non-renewable rigid polymeric cellular foams.

The physical foaming of thermosetting biosourced formulations, mainly based on tannin extracts and furfuryl alcohol, was investigated in-depth with a specially designed setup. Mass loss, volume expansion, and temperature measured at the bottom, in the middle and at the top of foams were continuously monitored during their preparation, from the first moment after the liquid formulation was poured into a mould until the final foams hardened and dried. Correlations were found between the observed phenomena. Thus, successive foaming mechanisms involving: (i) phase change of the blowing agent at 55°C, (ii) pore opening at a critical inner pressure, which induced 4% mass loss, and (iii) surface evaporation, could be elucidated and were discussed. The effects of the amounts of blowing agent on the one hand, which increases foam expansion, and of polymerisation catalyst on the other hand, which reduces the induction time, were also investigated, leading to some shifts in the aforementioned phenomena. The present results are certainly relevant to other self-foaming formulations based on thermosetting polymers such as traditional polyurethanes expanded by physical foaming with pentane.

This study presents the estimation of the parameters of the polymerization kinetics of a mimosa tannin-based thermosetting resin. A dual approach, experimental and numerical, was used. The numerical approach consisted in solving a time-dependent 0D numerical model of the polymerization kinetics and the heat equation. Thus, the parameters were estimated by minimizing the difference between the measured and the simulation values for four different polymerization kinetics. During the mixing phase, the temperature was recorded in order to observe the impact of the mixer and the introduction of the polymerization catalyst on the temperature. The modeling showed that the reaction starts directly with the introduction of the catalyst and that this data should not be neglected in order to achieve the minimization. A numerical study on the effect of the simulation time showed a very limited impact on the estimation of the parameters. A simulation time of 350 s was chosen in order to better take into account heat losses. The four polymerization kinetics were consistent with the experimental data and the fit improved from kinetics #1 to kinetics #4 as the number of fitting parameters increased, but the results were of the same order of magnitude. In conclusion, this work presents a simple method from an experimental point of view but very effective for estimating the reaction kinetic parameters of a thermosetting resin based on mimosa tannin.The method can probably be adapted to other polymer systems.