Infrared-Catalyzed Synthesis of Tannin-Furanic Foams

Formaldehyde-free tannin-based furanic foams were prepared by applying infrared radiation (IR) as an alternative energy source. Up to now, tannin-based rigid foams have been produced via heat conduction or microwave radiation energy. The present innovative heating system allows for the production of extra-light products with low density (≤ 50 kg/m³). The IR-produced lightweight tannin foams (IR-TF) exhibited similar properties to those made by hot pressing (HP-TF), but IR-TF can be synthesized with much shorter production time. Although microwave-produced foams (MW-TF) can be obtained with even shorter production times, the IR-TFs are much more homogeneous. Therefore, the IR radiation-based process resulted in the most suitable compromise between foam properties and production time. Overall, IR-TF showed very competitive structural characteristics, such as high homogeneity, high porosity, and limited orthotropicity, which was similar to that shown by the hot press-produced foams. The mechanical properties and material costs are rather similar, but the production time for IR-TF is considerably shorter.