Comparative studies of the curing and hardening process of soaps produced from locally processed saturated and unsaturated fatty acids

Abstract

This paper presents a comparative study of the curing and hardening processes of five soaps produced from Nigerian local oils (Palm oil, Palm-kernel Oil, Groundnut oil, Shea-butter oil and Tallow oil). The curing process was investigated by drying the soap samples under natural conditions and obtaining their daily moisture loss for duration of 21 days. Hardness tests based on the Brinell Hardness Methodology was conducted using a locally improvised manual indenter with a test load of 6.585kgf or 64.553N. Graphical plots of the moisture loss versus a one day time interval showed that all the soaps exhibited similar behaviour in the curing process, characterized by exponential decay in the rate of moisture loss. Superimposition of the curves into one graph showed very close fitting between the curves, indicating that the rates of moisture loss are very close. Graphs of the hardening process of the soaps showed that there are similarities in the hardening behaviour of the soaps with the curves exhibiting two hardening regions, a region of non-linear hardening and a region of constant hardening. Results showed that the hardness of the soaps varies in this order: tallow (1.88 HN) >shea butter (0.3 HN) >palm kernel (0.25 HN >palm Oil (0.15 HN) > groundnut oil (0.13 HN).