Phase diagrams and microstructure of mixtures of n-hentriacontane and saturated fatty acids

• Published in: Thermochimica acta Vol. 728; p. 179595
• Main Authors: Hernández-Veloz, M.J., Rousseau, D., Dibildox-Alvarado, E., Pérez-Meza, L.V., Reyes-Hernández, J., Ruiz-Cabrera, M.A., Pérez-Martínez, J.D.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2023
• Subjects: Candelilla wax; Myristic acid; N-hentriacontane; Palmitic acid; Phase diagram; Stearic acid; Candelilla wax; Stearic acid; Myristic acid; Palmitic acid; Phase diagram; N-hentriacontane
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/j.tca.2023.179595

•n-hentriacontane (C31) and saturated fatty acids (SFA) developed eutectic mixtures.•Eutectic mixture composition changed with SFA chain length.•Mixed C31 and SFA crystallized in stable polymorphic forms.•Crystal size of C31 and SFA were modified by mixture composition.•Smaller crystal sizes in mixtures close to the eutectic composition. We determined the phase behavior and microstructure of binary mixtures of n-hentriacontane (C31) and one of three saturated fatty acids (SFA; myristic acid (MA), palmitic acid (PA), or stearic acid (SA)). Phase diagrams were developed through differential scanning calorimetry and X-ray diffraction. The C31/MA, C31/PA, and C31/SA systems all showed eutectic phase behavior. Below the solidus line, these systems consisted of a mechanical mixture of C31 crystals and SFA crystals in the C polymorph, irrespective of the C31/SFA ratio. The C31/SFA eutectic composition increased in C31 content with SFA chain length: XC31 = 0.06, XC31 = 0.37, and XC31 = 0.54 for MA, PA, and SA, respectively. Within specific concentration ranges, small amounts of SFA were incorporated into the C31 crystal lattice. Smaller crystals of C31 and SFA were obtained for mixtures close to the eutectic mixture composition.