stearates and 1-3-propanediol

The phase behavior of the 1,3 propanediol dicaprylate/1,3 propanediol distearate (CC/SS) and the 1,3 propanediol dicaprylate/1,3 propanediol dipalmitate (CC/PP) binary systems were investigated using different techniques. The two systems presented essentially the same overall features. XRD measurements detected CC-CC, PP-PP and SS-SS bilayers which crystallized in beta forms but no mixed bilayers for all mixtures. The phase diagrams of both systems were comparable and displayed a monotectic behavior. As strongly evidenced by XRD data, both phase diagrams suggested that CC, PP and SS formed largely separate phases but were probably not completely immiscible. Avrami analysis of SFC vs. time indicated heterogeneous nucleation and spherulitic crystal development from sporadic nuclei. However, noticeable differences in the manifestation of the molecular interactions have been detected at all levels of structure and confirmed by the interchange coupling determined by the enthalpy of melt, the final SFC and the hardness data. This was obviously related to the difference in chain size between SS and PP molecules. The effect on texture was highlighted by drastic microstructural differences between the two systems. Furthermore, the differences in nucleation and crystal growth, the more pronounced tendency for phase separation in the CC/SS system compared to the CC/PP system, and the relatively better crystallization of the CC/PP mixtures, particularly visibly for x(CC)< or =0.3 compared to the CC/SS mixtures were associated with the chain length difference.

Topics: Calorimetry, Differential Scanning; Caprylates; Crystallization; Fatty Acids; Palmitates; Phase Transition; Propylene Glycols; Stearates; Thermodynamics; Transition Temperature; X-Ray Diffraction

Polymorphic influences on the phase behavior of two types of binary mixtures of saturated monoacid 1,3-propanediol esters (PADEs), dipalmitate/distearate (PP/SS) and dimyristate/distearate (MM/SS) were examined by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and by solid fat content (SFC), hardness and microscopy measurements. Three stacking modes have been found in the PP/SS binary system. Mixed SS-PP bilayers were detected in all mixtures, SS-SS bilayers in x(PP)=0.0-0.4 mixtures and PP-PP bilayers in x(PP)=0.6-0.1 mixtures. Two different but close beta polymorphs and one beta' polymorph were detected for this system. beta' was only detected in x(PP)=0.5-0.9 mixtures for the mixed bilayers. For the MM/SS binary system, only MM-MM and SS-SS bilayers were detected and both solid phases crystallized in two different beta forms. XRD data evidenced clearly that the MM and SS components were completely immiscible in the solid state. The phase diagrams constructed using DSC data, exhibited a typical eutectic-type phase boundary. The presence of eutectics, the shape of the solidus lines as well as the analysis of the individual enthalpies of melting indicated typical phase separation for both systems. A thermodynamic study based on the Hildebrand equation and using the Bragg-Williams approximation for non-ideality of mixing confirmed the phase separation in the solid phase and suggested that the PP and SS were miscible in the liquid phase and that SS formed an ideal mixing with MM. Avrami analysis of SFC vs. time curves indicated heterogeneous nucleation and spherulitic crystal development from sporadic nuclei, and suggested that the nucleation rate was higher for the mixture at the eutectic composition. The relative hardness was correlated with the enthalpies, the final SFC and the microscopy measurements.

Topics: Crystallization; Esters; Fatty Acids; Myristates; Palmitates; Phase Transition; Propylene Glycols; Stearates; Thermodynamics