Sandwich panels with 100% natural tannin furanic foam core

Tannin foams are innovative materials obtained exploiting the capacity of tannin for undergoing poly-addition reactions and that of furfuryl alcohol to polymerize under acid catalysis. These materials are known for many years, but only recently they have been systematically studied and many of its properties have been evaluated. The first generation of the tannin foams have shown good insulation properties and very significant resistance against fire but unfortunately they were produced with around 5% of formaldehyde needed for keeping the network stable and variable amounts of diethyl ether for allowing the blowing at room temperature. These two drawbacks have hindered the development of the foam for industrialization because formaldehyde is almost completely forbidden for inner application while diethyl ether is an easy-burning VOC. In this study an important upgrading of the original formulation is presented. The synthesis of 100% natural formulation only catalyzed by heat is described. Due to this innovative approach, the toxic chemicals have been replaced with other bio-based resources so that the interest of the insulation industry is arisen again. In particular, these second generation of foams have confirmed many of the properties of the first generation one with the significant advantages of being easily exploited as core material for many a wide range lightweight sandwich panels. The versatility of the new tannin-furanic formulations allows to produce composite materials with a broad set of decking materials according to performance required for the specific final application. © Forest Products Society 2015.