Differential scanning calorimetry of hydrolysed mangrove tannin

Abstract

Mangrove-bark-tannin adhesives are potential substitutes for phenol–formaldehyde (PF) wood-bonding adhesives which are derived from petroleum, a finite natural resource. However, mangrove-bark-tannin adhesive exhibits poor adhesive properties, including brittleness, poor wet strength, and poor wood penetration. These shortcomings are due to its high reactivity and structural features. To reduce these shortcomings, the structure of the adhesive was modified by subjecting tannin to (a) caustic hydrolysis and (b) consecutive acetic anhydride and caustic hydrolysis. The effectiveness of these hydrolyses was determined by using differential scanning calorimetry (DSC) to monitor the reaction and cure characteristics of hydrolysed and unhydrolysed tannin with formaldehyde. These hydrolyses resulted in lowering both the activation energy and collision frequency of the cure reaction. Consequently, the initial reactivity of tannin towards paraformaldehyde, which was usually very high, was reduced. The resulting longer reaction time enhanced the extent of reaction, as was evident in the increase in heat of reaction of the hydrolysed tannin. © 2000 Society of Chemical Industry