Adhesion of Industrial Lignin-Based Polyurethane Adhesives for Wood Bonding
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초록
내용
Lignin can provide a variety of polymers that may be obtained from petroleum, and thus is attracting much attention as a raw material for polyurethane (PU) adhesives. The aim of this study is to characterize non-isocyanate PU (NIPU) adhesives synthesized with hardwood kraft lignin (HKL) and softwood sodium lignosulfonate (LS), and to optimize the adhesion performance of lignin-based NIPU adhesives for plywood. Crude-HKL (CHKL) extracted from mixed hardwood black liquor was acetone-fractionated to prepare acetone-soluble HKL. Then, NIPU adhesives were synthesized using lignins through the carbonation and polyamination step. A silane crosslinker at different levels was added to improve the performance of NIPU adhesives. ATR-IR spectra showed urethane and silane bonds in the NIPU adhesives. In summary, the adhesion performance of CHKL-NIPU was the best among three NIPU adhesives. The adhesion strength increased, and the formaldehyde emission decreased as the addition of silane increased.