Detecting enthalpy ‘cross-over’ in vitrified solids by differential scanning calorimetry

Structural Relaxation of Acetaminophen Glass

“…In contrast, the T g of amorphous polymers (12Y20, 39Y 43), inorganic network and linear chain structure glasses (27,29,44,45), and metallic glasses (30,31,46) is far above the ambient temperature, and therefore, loss of their beneficial property by structural relaxation or crystallization during storage is not of concern. It is however of concern for cryopreserved biopolymers (47Y51) and small molecule glasses (12,21,29,32Y34,52,53).…”

Memory effect in enthalpy relaxation of two metal–alloy glasses

“…To overcome this difficulty, Hofer et al [48] have used the anneal-and-scan procedure in DSC to study the memory effect in 0.4 Na 2 O, 0.1 CaO, 0.05 Al 2 O 3 , 0.5 SiO 2 , 0.4 P 2 O 5 network structure glass, poly(methyl methacrylate) and in 1,3,5-tri-a-naphthylbenzene rigid molecular glass, now recognized as 1,3-bis (1-naphthyl)-5-(2-naphthyl) benzene [69]. Here, we use their technique [48]. The temperature-time protocols used are illustrated in Fig.…”

“…But this is neither the case here nor is the case in earlier studies [48]. Kovacs [12] had found memory effect at T > T eq and at T = T eq and had modeled it for T < T eq [13,24,80].…”

“…Here we report a study of this effect in two such glasses, Mg 65 Cu 25 Tb 10 and Zr 46.75 Ti 8.25 Cu 7.5 Ni 10 Be 27.5 , by using an anneal-and-scan procedure [39,48,[57][58][59] in DSC. The results show that structural relaxation in these glasses with compositional and topological short range order and delocalized electrons (electron gas) in their structure is remarkably similar to that which has been observed for molecular, linear chain and network structure glasses.…”

“…Its few studies have been limited mostly to polymers by measuring the volume [11,12,19,20,23,24,29,37,38], enthalpy [19,24,26,48], dielectric [28] and dynamic mechanical relaxation [27], creep [29], and combined creep compliance and volume [31,32]. It has been studied by refractive index measurements [11,15,17] and, in a remarkable investigation, by creep-compliance and volume measurements of an epoxy polymer by changing the water content instead of the temperature [49].…”