Preparation And Characterization Of Formaldehyde Free Wood Adhesives Lignin Extracted From Oil Palm Empty Fruit Bunch

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Date
2015-07
Authors
FARIS, ABBAS HASAN
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Abstract
In this work, environment-friendly lignin/tannin and liquefied OPEFB-based wood adhesives have been studied to prepare formaldehyde-free wood adhesives and to increase the proportion of renewable environmentally friendly materials in these wood adhesive formulations. The oil palm empty fruit bunch (OPEFB) was used as raw material. The delignification processes from OPEFB were conducted using Kraft pulping and auto-catalyzed ethanol–water (organosolv) pulping. Lignin polyols were prepared from the liquefaction of Kraft lignin and from the direct liquefaction of OPEFB lignocellulosic waste. The Mannich reactivity analysis illustrated that the Kraft lignin has comparatively higher amounts (2.99%) of activated free aromatic ring positions compared with organosolv lignin (2.06%), suggesting favourable reaction with the glyoxal than organosolv lignin. The average molecular weight of liquefied product exhibited significant increase with lignin liquefaction process (16427 g mol-1) and with the direct liquefaction process of OPEFB (12203 g mol-1) compared with Kraft lignin (1564 gmol-1), which confirms the successful preparation of targeted lignin polyol products. Modification of tannin using hyperbranched poly (amine-ester) has been studied. FTIR, 1H NMR and 13C NMR spectra confirmed the successful preparation of hyperbranched poly (amine-ester) and modified tannin/glyoxalated lignin adhesive (MTGKL). The plywood specimens with MTGKL resin exhibited water resistant properties when soaked in tap water for 24 hours, where no delamination occurred in any of the specimens while delamination of TGKL plywood resin specimen was evident. The lignin based-wood adhesives was also evaluated in boiling water after the modification of lignin polyols/tannin adhesive (TGLP) with polyethyleneimine (PEI). At 10% of PEI with TGLP resin, the delamination of plywood specimens did not occur after exposure in the tap water and boiling water. In the same context, this work demonstrates the possibility of synthesizing water resistant wood adhesives from the liquefaction of OPEFB in the presence of glyoxal as a curing agent that meets the requirements of relevant international standards for the manufacture of plywood. The FTIR spectra confirmed the reaction between liquefied OPEFB and glyoxal through the presence of C-C, C-O-C, and C=O groups in the resol structure. Tensile strength tests clearly demonstrated that the tensile strengths for both dry and wet TGLW plywood specimens (21.4 and 19.71 MPa) respectively, surpassed the requirements of relevant international standards. The effect of inorganic and organic clay on the glyoxalated lignin polyol/tannin wood adhesive was also studied. The FTIR, XRD, and SEM characterizations indicated that the modification of bentonite via octadecylamine (ODA) salt occurred. The tensile strengths of TGLP plywood resin specimen increased significantly through the incorporation of low contents of ODA-BT (1, 2, and 3 wt%). Comparison between pure TGLP resin and the composites shows that the thermal stability was decreased.
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Preparation And Characterization Of Formaldehyde Free Wood Adhesives Lignin , Extracted From Oil Palm Empty Fruit Bunch
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