Thermoanalytical characterisation of dromedary hair

Abstract

The aim of this study is to characterise the fine structure of dromedary hair. Using differential scanning calorimetry (DSC) for temperatures up to 180°C, the denaturation transition of the α-helical material of under and guard hair of dromedaries of various ages in excess water was studied. Also, fine fibre samples of a 5-year-old dromedary were investigated using analytical transmission electron microscopy (TEM). Results show that dromedary hair, wool, and some other animal fibres present a classical bilateral structure where the arrangement of ortho- and para-cortex in fibre cross-section is like wool. This is confirmed from the DSC analysis for dromedary fibres, which show a bimodal melting peak. DSC traces show quite a difference between the two types of fibres contained in dromedary fleeces. Indeed, down and guard hair dromedary fibres present different ortho-cortex denaturation temperatures around 120–140°C, respectively, and may have the same para-cortex denaturation temperature in the range of 145°C. The denaturation enthalpy of guard hair (36 J/g) was found to be higher than that of under hair (12 J/g). This probably explains the greater difference in mechanical characteristics between the two types of fibres. The same conclusion is found for fibres from dromedaries of various ages. In fact, the denaturation enthalpy of under hair increases with the dromedary age, the minimum being 11 J/g and the maximum 16 J/g for 1-year-old and 19-year-old dromedaries, respectively.