Thermal investigations on the crystallization of sorbitol

Abstract

The melting and crystallization of sorbitol were investigated with the DSC method and thermal microscopy. Sorbitol was found to have two crystalline modifications (confirmed by X-ray diffraction) with different melting points, while rapid cooling of molten sorbitol resulted in an amorphous form.The effect of inoculation on the crystallization of the melt was studied too. Powders of both crystalline modifications were used for this purpose.A new technological process for rapid crystallization of molten sorbitol has been worked out on the basis of the thermal analysis results.The present work is a part of a research program on solid-liquid transformations with the aid of thermoanalytical methods. These investigations primarily concern slowly-crystallizing substances, so they have a technological purpose too, i.e. determining the optimum conditions for crystallization.Some 2l. 3. L Thermal Anal 12, 1977

Polymorphism of sorbitol

“…Melting at 120 1C and quenching with liquid nitrogen has been reported by Cammenga and Steppuhn [6], but this can lead to an uncontrolled rate of cooling, with crystallisation taking hours to days [5,7].…”

“…Hales (cited in [3]) described the form as ''glass transition product E'' while Sztatisz et al [5] mentioned ''frozen melt'' or ''molten sorbitol''. These authors have reported DSC runs of sorbitol after melting and storage for some hours after cooling to room temperature.…”

“…Its crystallinity is confirmed by X-ray diffraction. The DSC runs reveal two transitions [4,5,8], denoted SM1 and SM2 by Quinquenet et al [4] and E 0 and E by Yu [8]. The SM terminology is a phenomenological denotation that does not link to crystallinity.…”

“…However, there is no universally accepted nomenclature for the various sorbitol polymorphs described in the literature. We have adopted the following for those identified up to now: (a) the alpha form (sometimes called A), (b) the beta form (sometimes called B), (c) the gamma form (sometimes called B by Sztatisz et al [5]), (d) the delta form, (e) the epsilon form, and (f) the crystallised melt (CM) with subforms E 0 and E (sometimes called E or the solidified melt SM). In addition to these anhydrous crystalline phases, the hydrate exists.…”

Relaxation strength of localized motions in D-sorbitol and mimicry of glass-softening thermodynamics

“…A literature search thereafter revealed that D-sorbitol has two crystalline forms, as indicated by calorimetry and x-ray diffraction. 40 Since some of the unusual findings in an earlier study may have been caused by crystallization, it seemed necessary also to study the ⑀Ј and ⑀Љ spectra of D-sorbitol by avoiding its crystallization and by repeated measurements. Here we report a detailed study of the Johari-Goldstein relaxation in D-sorbitol glass obtained by cooling at different rates, and of the change in its characteristics with time and with temperature.…”