Some temperature-sensitive properties of pure linear alkanes and n-ary mixtures

Abstract

In this paper, the results of thermomechanical analyses (TMA), dynamic mechanical analyses (DMA) on pure linear alkanes and a commercial wax are discussed with the help of structural analyses and differential thermal analyses (DTA) performed at various temperature. Examination of the results show that thermal expansion of pure alkanes is around 10 −4 K −1 at room temperature. It decreases continuously until 0.3×10 −4 K −1 in the structural state corresponding to the rotator phase (α-RII). As concerns DMA, the storage modulus is ranged between 750 MPa (for the commercial wax) at room temperature and 1 MPa near the melting point. It decreases by stages when temperature is increasing. This general evolution is observed with pure linear alkanes as well as with the studied commercial product. Each stage corresponds to the stabilization of a solid phase, whereas a solid–solid transition is highlighted by an increase of the curve's slope. Density measurements performed at various temperature confirm such an evolution. In fact, the density (included between 0.92 and 0.94 g cm −3 at room temperature) decreases by stages versus temperature.