Self-Blowing Non-Isocyanate Polyurethane Foams Based on Hydrolysable Tannins

Abstract

Non-isocyanate polyurethane (NIPU) foams using a hydrolysable tannin, also vulgarly called tannic acid, namely here commercial chestnut wood tannin extract was prepared. Compression strength did not appear to depend on the foam apparent density while the formulation composition of the NIPU foams has been shown to be more determinant. These NIPU foams appeared to be self-extinguishing once the high temperature flame is removed. The ignition time gave encouraging results but for improved fire resistance the foams may need some fire-retardant addition. FTIR spectrometry showed the formation of non-isocyanate urethane linkages. Thermogravimetric analysis indicated a good thermal resistance of these foams, with thermal degradation following four phases. First in the interval 25°C-120°C range, mainly evaporation of water occurs with a maximal loss of 10% weight. In the 150°C-450°C temperature range foams mass loss is of almost 70%. In particular in the 125°C-275°C range occurs the degradation of some small molecular weight substances. In the 500°C-790°C temperature range the foams do not present any further large degradation.

Comparing Condensed and Hydrolysable Tannins for Mechanical Foaming of Furanic Foams: Synthesis and Characterization

“…The mimosa foams of this work even have comparable compression strength of pine, mimosa or quebracho tannin furanic foams using Formaldehyde (CH 2 O) as additional crosslinker, which is known to improve compressive strength [ 10 , 46 , 47 ]. Isocyanate-free polyurethane foams (NIPU) made from mimosa and chestnut have a much lower compressive strength at comparable density than the various tannin foams of the presented work [ 7 , 33 ]. Aside of the difference in usage of tannin, comparing these foams to others in the literature suggests that the foaming method in combination with the formulation results in improved mechanical stability without using an additional aldehyde.…”

“…Conversely, hydrolysable tannins are much less reactive and little research was conducted on their use for polymerization processes. Though a partially usage in a phenolic system, using tannic acid and furfuryl alcohol as the main building blocks and a urethane-based approach already revealed that hydrolysable tannins also have some potential for foam production [ 30 , 33 , 34 , 35 ]. Since several parameters differ in the various tannin foam formulations found in research, it is difficult to compare the influence of different types of tannins on foam properties.…”

Adhesion of Technical Lignin-Based Non-Isocyanate Polyurethane Adhesives for Wood Bonding

“…Oligomers terminated with carbonate-modified 5-membered cyclic carbonate successfully formed hydroxy urethane bonds in reaction with diamine [6]. Many studies have been conducted to improve the function of NIPU, and significant improvements have been found in the mechanical strength [7][8][9][10], fire retardancy [8,11,12], and thermal stability [11,[13][14][15] of NIPU itself, as well as adhesion performance of wood composites [13,14,[16][17][18]. Advanced NIPUs must be prepared with superior materials with economic and environmental benefits.…”

“…Meanwhile, lignin [9,10,18,[30][31][32][33], tannin [8,[11][12][13][14][22][23][24]29,34], saccharides [11,16], plant oil [35], and soy protein [28] are examples of bio-polyols that can form the framework of the NIPU. Ingredients except lignin and tannin were excluded because of the disadvantage of having to compete with the food industry.…”

Effect of Amine Type on Lignin Modification to Evaluate Its Reactivity in Polyol Construction for Non-Isocyanate Polyurethanes (NIPU)

“…All of these routes are different from the classical approach using isocyanates, even if using natural polyols [28]. The dimethyl carbonate route has led to applicable NIPUs as adhesives and coatings and has been pursued with some success, and moreover by using a number of biomaterials [29][30][31][32][33]. The route presented in this paper is another, different, alternative approach to preparing NIPUs from biosourced materials such as lignin.…”