Bioresourced pine tannin/furanic foams with glyoxal and glutaraldehyde

Rigid foams based on tannin extracted form Pinus radiata bark have been recently developed and present many advantages for use as an insulation material instead of synthetic foams. Formaldehyde-free, in reality any-ldehyde-free pine tannin foams have been developed but present lower mechanical resistance undergoing compression. In this work, formaldehyde-free pine tannin/furanic rigid foams are prepared by a new approach, namely using alternative non-toxic, non-volatile aldehydes as hardeners: glyoxal or glutaraldehyde. Physical properties - thermal conductivity, cell size - and mechanical - compressive strength - are tested. It was found that glyoxal can completely substitute formaldehyde to prepare foams with good properties for insulation whereas glutaraldehyde is not suitable for the purpose because of its lower reactivity with pine tannins. (C) 2013 Elsevier B.V. All rights reserved.