Preparation of Polyurethane Adhesives from Crude and Purified Liquefied Wood Sawdust

Abstract

Polyurethane (PU) adhesives were prepared with bio-polyols obtained via acid-catalyzed polyhydric alcohol liquefaction of wood sawdust and polymeric diphenylmethane diisocyanate (pMDI). Two polyols, i.e., crude and purified liquefied wood (CLW and PLW), were obtained from the liquefaction process with a high yield of 99.7%. PU adhesives, namely CLWPU and PLWPU, were then prepared by reaction of CLW or PLW with pMDI at various isocyanate to hydroxyl group (NCO:OH) molar ratios of 0.5:1, 1:1, 1.5:1, and 2:1. The chemical structure and thermal behavior of the bio-polyols and the cured PU adhesives were analyzed by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Performance of the adhesives was evaluated by single-lap joint shear tests according to EN 302-1:2003, and by adhesive penetration. The highest shear strength was found at the NCO:OH molar ratio of 1.5:1 as 4.82 ± 1.01 N/mm2 and 4.80 ± 0.49 N/mm2 for CLWPU and PLWPU, respectively. The chemical structure and thermal properties of the cured CLWPLW and PLWPU adhesives were considerably influenced by the NCO:OH molar ratio.

Synergistic Effect of APP and TBC Fire-Retardants on the Physico-Mechanical Properties of Strandboard

“…ATR-FTIR spectra reveals the changes of chemical groups along with the curing process of PMDI resin. Depending on the polymerization reaction mechanism of isocyanate-water, the absorption peaks of PMDI before and after curing are dominated by -NCO (2270 cm −1 ) and ammonia ester group (3750-3000 cm −1 ), respectively [18]. Combined with Figures 2 and 3, the ratio of isocyanate group to amino group(R) in pure PMDI increases first and then decreases during the whole curing process.…”

Characterization of Curing and Bonding of Wood with Adhesive Mixtures of Liquefied Wood and Hexamethylenediamine

“…The LW sample exhibited some chemical components typical of wood composed of cellulose, hemicelluloses, lignin, and extractives, with carbonyl (C=O), OH, ester (RCOORʹ), and ethyl (CH 2 CH 3 ) bonds, as well as carbon-hydrogen (C-H) bonds [30]. The broad peak in the spectra of pure LW, HMDA and LW+HMDA at about 3350 cm -1 corresponded to the OH groups, while the peaks at 2930 cm -1 and 2860 cm -1 were assigned to the CH 2 and CH 3 stretches, respectively.…”

Recent Advances in Development of Waste-Based Polymer Materials: A Review

“…The bio-polyols were characterized by hydroxyl values from 150-156 mg KOH/g. Another kind of renewable resource for bio-polyol synthesis is biomass [128][129][130][131][132].…”