Preparation and Characterization of Condensed Tannin Non-Isocyanate Polyurethane (NIPU) Rigid Foams by Ambient Temperature Blowing

Abstract

Ambient temperature self-blowing mimosa tannin-based non-isocyanate polyurethane (NIPU) rigid foam was produced, based on a formulation of tannin-based non-isocyanate polyurethane (NIPU) resin. A citric acid and glutaraldehyde mixture served as a blowing agent used to provide foaming energy and cross-link the tannin-derived products to synthesize the NIPU foams. Series of tannin-based NIPU foams containing a different amount of citric acid and glutaraldehyde were prepared. The reaction mechanism of tannin-based NIPU foams were investigated by Fourier Trasform InfraRed (FT-IR), Matrix Assisted Laser Desorption Ionization (MALDI-TOF) mass spectrometry, and 13C Nuclear Magnetic Resonance (13C NMR). The results indicated that urethane linkages were formed. The Tannin-based NIPU foams morphology including physical and mechanical properties were characterized by mechanical compression, by scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). All the foams prepared showed a similar open-cell morphology. Nevertheless, the number of cell-wall pores decreased with increasing additions of glutaraldehyde, while bigger foam cells were obtained with increasing additions of citric acid. The compressive mechanical properties improved with the higher level of crosslinking at the higher amount of glutaraldehyde. Moreover, the TGA results showed that the tannin-based NIPU foams prepared had similar thermal stability, although one of them (T-Fs-7) presented the highest char production and residual matter, approaching 18.7% at 790 °C.

Ambient Temperature Self-Blowing Tannin-Humins Biofoams

“…A few types of ambient temperature, or even moderate temperature, self-blowing foams derived by mostly biosourced raw materials have been described in the literature. These have been based either on the self-blowing reaction of tannins with furfuryl alcohol, these being the older types [ 1 , 2 , 3 , 4 , 5 , 6 ], or on mono-and disaccharides non-isocyanate polyurethanes (NIPU) [ 7 , 8 , 9 ], or on tannin-based NIPUs [ 10 ], or even on tannin–monosaccharide NIPUs [ 11 ], or on mixtures of these strategies of approach. The emphasis here is on ambient temperature self-blowing, the use of temperature to obtain foams being less attractive for a certain number and types of applications.…”

Preparation and properties of a novel type of tannin-based wood adhesive

“…Finally, the third degradation stage showing a large weight loss can occur in the 400-600℃ range, is due to the degradation of the cured adhesive skeleton. Some more stable chemical bonds, such as C-C and C-O, are cleaved within this temperature range [34][35][36] . Remarkably, the degradation temperature peak shifts to a higher value, while the weight loss rate shifts to smaller value with the increase in GDE.…”

“…MALDI-TOF mass spectrometry is now used to determine the tannin oligomers formed and their distribution [36,44,45] . As we all known, there are four typical oligomers, which are shown in Figure 6, i.e.…”

Bio-Based Polyurethane Resins Derived from Tannin: Source, Synthesis, Characterisation, and Application

“…Due to all these application areas, tannins are significant "green" biochemicals that have attracted the interest of many researchers [30,[32][33][34]. Pine and Norway spruce (Picea abies) bark tannins have been used to produce bio-based foams and glucose-based nonisocyanate polyurethane (NIPU) foams [19,[35][36][37][38]. In another study, condensed tannins were extracted from radiata pine (Pinus radiata) barks to produce polyurethane foams.…”