Physicochemical and thermal properties of phenol-formaldehyde-modified polyphenol impregnate

Tannin, a natural polymer belonging to the polyphenolic group of compounds, is widely used in the leather industry, specifically as a tanning agent fo r the conversion of putrescible collagen fibers into leather matrix during the leather-manufacturing process. Unspent tannin poses a serious environme ntal threat to the public because it has a very high half-life, leading to groundwater pollution when discharged into soil. Attempts have been made to separate tannins through chemical means and recovered tannin needs to be e ncapsulated for its safe disposal. In the present study the recovered tanni n was impregnated in phenol-formaldehyde (PF) resin. Spectroscopic and ther mogravimetric (IR, NMR, TGA and DSC) studies revealed that the modified pol yphenol was held physically in the impregnate. The impregnated matrix showe d resistance to mineral acids, strong alkalis and organic solvents and was tested for its adhesive property on leather sheets. The leather that bonded with PF-modified polyphenol impregnate (PFT) had a 27% increase in peel st rength and a 40% increase in lap shear strength as compared to the sample b onded with PF resin. The corrosive resistance result of the PFT resin shows it has potential application as an anticorrosive paint in the paint indust ry. (C) 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1567-1571, 2001.