Hydrophobic tannin foams

Independently, from the formulation and the production method, tannin foams have always a strong affinity for water. Applying a surface heat treatment with infrared beams, it was possible to significantly decrease the water absorption of these materials. In particular, it was observed that treating the foam surface for 60 s with 12.8 or 16.0 kW m-2 IR beam energies, the drop absorption time increased up to 10 times. Similar effect was observed also when lower energies were applied for longer exposures. The spectroscopy investigation of the surface has highlighted a decreasing of hydroxyl group and an increase of aromatic character because of the partial carbonisation of the material, which explains the improved hydrophobicity.