Abstract

A novel natural coloured waterborne polyurethane (PU) based on valonia tannin was successfully synthesised and characterised. A structural study of the polymer by Fourier Transform Infra Red (FTIR) spectroscopy confirmed the incorporation of valonia tannin into the backbone of the PU. The dispersion of valonia tannin and homogeneity of surface of the PU samples were confirmed by scanning electron microscopic (SEM) analysis. Chromaticity and colour difference further verified the colour depth and uniformity of the cured films. Thermogravimetric analysis (TGA) results indicated that the synthesised PU samples exhibited an improved thermal decomposition temperature. Particle size analysis, mechanical testing and water absorption of the synthesised PU samples further showed the effect of the cross-linked structure in the molecular chain segment. Moreover, the colour fastness and folding [flexing] resistance of the leather coating finished with synthesised PU was better than that of valonia tannin blending.