Evaluation of the physical properties of leathers tanned with Plectranthus barbatus Andrews extracts

This study was designed to assess the potential use of Plectranthus barbatus Andrews, a plant growing locally in Kenya as a vegetable tanning agent. The aim was a deliberate attempt to adopt green chemistry and provide cheap locally available eco-friendly tanning materials. Anova statistical test (αu003c0.05) was used to compare the physical properties of leather tanned with three kinds of liquors made from the plant and the following mean values were recorded: Shrinkage temperature of 61.5 to 67.5°C; Grain crack range of 7.5 to 8.7 mm; Grain burst range of 7.9 to 9.1 mm; tear strength of 41.8 to 78.2 N with percentage (%) elongation of 68.4 to 75.9%; tensile strength of 17.6 to 40.8 N/mm2 with % elongation of 15.9 to 42.2% and thickness of 0.7 to 1.2 mm. The study concluded that P. barbatus Andrews leaves have adequate tannin content of hydrolysable type required for tanning. Furthermore, the brown colour of the leather produced is unlikely to undergo saddening as usually observed in Mimosa because of relative stability of hydrolysable tannins to light.   Key words: Shrinkage temperature, distension, pelts, tannins, vegetable tanning, pyrogallol.