Viscoelastic Properties of Glucose Glass near Its Transition Temperature

Abstract

Storage (G′) and loss (G″) shear moduli of supercooled glucose have been measured at thirteen temperatures from 27.4 to 41.1°C in the frequency range from 0.3 to 1.8 cps. Shear creep has been measured at four temperatures from 41.1 to 47.6°C. The temperature dependence of the storage moduli and the creep compliance was described by reducing the time and frequency scales with shift factors calculated from the WLF equation, the constants corresponding to a fractional free volume of 0.026 at 41.1°C and a free volume expansion coefficient of 3.6×10−4 deg−1. The loss moduli plotted against reduced frequency did not give a single composite curve, however. Conversion of the dynamic measurements to creep compliance by approximation methods provided the latter function over ten decades of logarithmic time except for a gap of three decades in the middle of the range. At long times, the creep was indistinguishable from viscous flow; the viscosity at 41.1°C was 1.82×1010 poise. At short times, the limiting creep compliance appeared to be 0.32×10−16 cm2/dyne, and there was an additional time-dependent compliance of at least this magnitude with a broad distribution of retardation times. The relaxation and retardation spectra were calculated for this region.

Calorimetric study of the glass transition occurring in aqueous glucose: Fructose solutions

“…The interpretation of both in view of their significant nutritive role in the thermograms obtained by differential scanning calorhuman organism and as a consequence of their use in imetry (DSC) has aroused the interest of many research specific food products. Early investigations of these workers and a variety of approaches has been suggested materials were confined either to measurements of (Levine and Slade 1988a,b,c;Simatos et a1 1989;Izzard viscosity (Parks and Gilkey 1929;Parks et a1 1934;et a1 1990;Roos and Karel 1990;Ablett et a1 1992, Davies andJones 1953;Meyer and Ferry 1965;Barlow 1993). The work of Levine and Slade in this field has been et a1 1966; Soesanto and Williams 198 I ; Ollett and particularly valuable.…”

“Cooling by Heating”—Demonstrating the Significance of the Longitudinal Specific Heat

“…It is, however, not unusual for liquid expansivities to be near 10 −3 K −1 for which we would expect an enhancement of the thermomechanical coupling a = (c p − c V )/c p by a factor of 30. The shear modulus of glucose in the glassy state is G ∞ = 3.1 · 10 9 Pa as deduced from the shear compliance data of Meyer and Ferry [5].…”

“…It follows from Eqs. (4) and (5) and the fact that ǫ rr = ∂u ∂r and ǫ θθ = ǫ φφ = u r that σ rr = (K T + 4 3 G) ∂u ∂r + 2(K T − 2 3 G) u r − β V δT , which by Eqs. (24) and (25) becomes…”

“…Here the high-frequency shear modulus can be taken to be G ∞ = 3.1 • 10 9 Pa [5]. The values of the thermodynamic parameters used to parametrize the model are given in Table I.…”

Dynamic Mechanical Relaxation Behavior of Low Molecular Weight Side-Chain Cyclic Liquid Crystalline Compounds near the Glass Transition Temperature

“…As these materials approach the glass transition temperature ( T g ), their viscoelastic behavior becomes complex as molecular interactions become pronounced. Investigations of these interactions near T g have been made by probing dynamic mechanical relaxation behavior and correlating the results to chemical structure for over a dozen low molecular weight organic compounds. − Interestingly, most of these compounds appear to display similar relaxation features just above T g despite significant differences in chemical structure. One such feature includes storage ( G ‘) and loss shear moduli ( G ‘‘) that closely resemble those prescribed by a single Maxwell element.…”