The effect of pressure on the phase diagram of n-triacontane (C30)/n-docosane (C22) binary mixture and n-triacontane (C30)/n-hexaeosane (C26) binary mixture was studied up to 500MPa by high-pressure differential thermal analysis. The C30/C22 mixture at 0.1 MPa has a eutectic-type phase diagram, with the hexagonal phase appearing just below the melting temperature on the C3o side. The eutectic temperature, Te, is 45.1°C and the eutectic composition lies between 15 and 20 wt% C3o. The hexagonal phase and the low-temperature transition disappear above 100 MPa. The change of the phase diagram with pressure was interpreted by the different pressure dependence of the melting temperature, Tin, of C3o and C22 and that of T~. Pressure dependence of Te was 0.247 K MPa- 1, which is smaller than that of C22 (0.279 K MPa 1) and C3o (0.276 K MPa-1). The C30/C26 mixture has a solid-solution-type phase diagram, showing an almost linear melting curve from the Tm of C3o to the Tm of C22, and the lower critical transition temperature on the hexagonal transition curve at 0.1 MPa. At elevated pressure, the melting curve changes to become downwardly convex and the transition curve moves close to the melting curve.
Посилання на статтю:
Effect of pressure on the phase diagram of binary mixtures of n-alkanes / Chitoshi Nakafuku* and Takeshi Sugiuchi // Polymer. – 1993. – Vol 34. – P. 4945-4952.