Green, formaldehyde-free, foams for thermal insulation

Abstract

New, green and cheap rigid foams presenting outstanding performances for thermal insulation are described. Such ultralightweight cellular materials are mainly based on renewable chemicals: tannin and furfuryl alcohol, are very easy to produce and have thermal conductivity as low as 38 mW/m/K. Compared to previously reported tannin-based foams, these new materials are much "greener" and present improved resistance to compression and to water. Especially the formaldehyde, formerly used as cross-linking agent of tannins but known as a volatile and harmful chemical, could be successfully removed from the formulation. The as-obtained, 2 nd generation, tannin-based foams are totally stable and have an expected interest for thermal insulation of buildings.

MALDI-TOF and 13C NMR Analysis of Tannin–Furanic–Polyurethane Foams Adapted for Industrial Continuous Lines Application

“…Thus, Basso et al [11] have observed the same effect when formaldehyde is eliminated from purely tannin-furanic foam formulations. Increasing the relative proportion of surfactant extends reaction times and causes a decrease of the temperature during foaming [14], giving more controlled, but slower foaming and rising foam density (R80S).…”

“…Thus, all of the foams obtained presented a homogeneous aspect and were less friable than the simples tannin-furanic foams prepared in the past [7][8][9]11]. This effect is due to the appropriate balance between the different components of the resins and the selection of a suitable surfactant.…”

“…Recently, increasing interest has been shown for these tannin-derived materials by foam manufacturing polyurethane companies because of their fire resistance and environmental-friendliness [6][7][8]11,12]. However, the tannin-furanic foams described cannot be manufactured in their usual continuous lines, simply because the plants available are exclusively designed for polyurethane rather than phenolic foam production.…”

“…Renewable resources can constitute an attractive alternative to conventional petrochemical resources [1][2][3]. Thus, recent work on resins derived from natural products has led to the development of rigid foams based on polyflavonoid tannins-furfuryl alcohol copolymerization, giving foams of excellent performance and characteristics [4][5][6][7][8][9][10][11][12][13][14][15][16].…”

Wood products and green chemistry

“…Afterwards, major advances were achieved first with tannin-furanic foams without formaldehyde (Basso et al 2011) or modification with small amounts of polyisocyanate (Li et al 2012a), second with foams using a safer blowing agent, namely pentane, and even with no blowing agent at all (Basso et al 2013a;Li et al 2013b), third with foams using alternative non-toxic, nonvolatile aldehydes , and finally using the much more reactive and difficult to handle procyanidin-type tannins such as for example pine and spruce bark tannins (Cop et al 2014;Lacoste et al 2013Lacoste et al , 2014. Even simplified foams in which the tannin was substituted with fine wood powder were tried (Srivastava and Pizzi 2014).…”