Abstract: A renewable tannin-based resin adhesive with enhanced bonding strength, good water resistance and long storage life has been prepared based on tannin, furfural and furfuryl alcohol coming from forest and agricultural products. Fourier transform infrared spectroscopy (FT-IR), Electrospray ionization mass spectroscopy (ESI-MS) and Differential scanning calorimetry (DSC) indicated that furfuryl alcohol and furfural can react with tannin under acidic conditions, with the involvement of -CH2-O- groups in the cross-linking of tannin-furfuryl alcohol-furfural resin (TFF) adhesive. The gel time of TFF was longer than that of tannin-furfural resin (TF), while the shear strength of TFF-bonded plywood suggested that the cured TFF adhesive acquired a performance superior to that of tannin (T) and TF adhesives. Furthermore, water resistance of TFF adhesive could be further enhanced with respect to T and TF adhesives through cross-linking with 3 % epoxy resin (EPR).

Abstract: In this study, an easily prepared bio-based abrasive grinding wheel based on tannin-glyoxal-urea (TGU)thermosetting matrix is presented.The synthesised resin was prepared via co-polycondensation reaction of glyoxal and ureawith condensed tannin, which is a forest-derived product. Fourier transform infrared spectroscopy and electrospray ionisation mass spectrometry results confirmed that urea and glyoxal react well under acidic conditions and that -(OH)CH-NH-group is primarily involved in TGU cross-linking. Differential scanning calorimetry, thermomechanical analysis and thermogravimetric analysis investigations showed that the preparation of TGU resin is easier compared to commercial phenol-formaldehyde (PF) resin; moreover, TGU resin has a more robust chemical network structure, which contributes efficiently to heat resistance and improved mechanical properties. This observation is supported by Brinell hardness, compression resistance and grinding testing; these showed that the new grinding wheel acquired higher hardness, superior resistance against compression and stronger abrasion resistance compared with a PF-based grinding wheel prepared in the laboratory. Moreover, few holes and no cracks were found in the new grinding wheel.

ABSTRACT Exopolysaccharide (EPS) of two benthic diatoms, Amphora sp. and Stauroneis sp., with different biofilm formation abilities were investigated. The ratio of suspension-cells/biofilm-cells was employed to indicate the diatom biofilm formation abilities. The soluble EPS from the supernatant of whole culture, tightly bound EPS from floating cells, loosely and tightly bound EPS from biofilm cells were fractionated as SL-EPS, F-TB-EPS, BF-LB-EPS and BF-TB-EPS, respectively. The analysis for productions and monosaccharide compositions indicated that EPS from two diatoms were different in terms of the productions, distributions, and monomer compositions. Amphora sp. produced more (1.5-fold) total exopolysaccharides, but less (<0.4-fold) BF-TB-EPS than Stauroneis sp. The monosaccharides of the EPS from Amphora sp. were more diverse than those of Stauroneis sp., with 13 and 10 monomers, respectively. Neutral sugars, Glc, Xyl and Man, were abundant in Stauroneis sp., while Gal, Glc and Xyl were rich in Amphora sp. Uronic acid and hexosamine were present in all fractions of two diatoms, especially Glc-A being the most abundant monomer in SL-EPS of Amphora sp. It was proposed that the high content of uronic acid (especially Glc-A) might be crucial for the strong biofilm formation abilities of Amphora sp.