The glass state

In this chapter we examine the properties of polymeric materials in the glass state, the lowest of the four temperature regions. 

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In contrast, the flexibility of amorphous polymers above the glass state is decreased when stiffening groups (structures 2.10 through 2.13) are present in the polymer backbone ... 

In the next sections I briefly discuss some of the theoretical concepts important to understanding the glass state and nonequilibrium aging dynamics. 

Ice-cream. Crystallization of lactose in ice-cream causes a sandy texture. In freshly hardened ice-cream, the equilibrium mixture of a- and /1-lactose is in the glass state and is stable as long as the temperature remains low and constant. During the freezing of ice-cream, the lactose solution passes through the labile zone so rapidly and at such a low temperature that limited lactose crystallization occurs. 

In general, ordinary substances which can be frozen-in by supercooling will not convert to the glass state when cooled infinitely slowly, whereas for substances... 

In the melt of a two-component system, polymer-plasticizer, the segments of a macromolecule and the molecules of the plasticizer are arranged in such a way that almost no holes exist (Figure 3a). In the glass state such an arrangement is no... 

The condition for valid results in this work is the fact that the system is in the gel-state that is, it is in a state of inner equilibrium, and not in the glass state. Measurements of Hellwege, Knappe, and Lehmann (5) on pure PVC show the expected discontinuity in the compressibility vs. pressure curve at the melting point transition in the glass state. It is inferred from this study that the glass temperature for pure PVC and for the plasticized, gel-type PVC does not rise above 110° C. at pressures of 200 atm. (Figure 7). Our study showed that the system is always in a state of inner equilibrium. 

The linear relationship between compressibility and temperature is valid only when the system is in a state of inner equilibrium. If it should pass over into the glass state or if the gas dissolved in the system is liberated, a sharp deviation from the linear temperature relationship ensues (Figure 11). If the compressibility is plotted as a function of pressure, there is no simple functional relationship, and an expansion of material can not be identified with a deviation in the trends of curvature. Figure 10 illustrates an example. 

The model of Condo permits the determination of the limiting pressure at which the glass state exists, on the basis of a reduced number of parameters (only the glass transition temperature of the pure polymer is needed to calibrate the energy parameter) for this reason, it seems particularly useful for the prediction of the plasticizing effects. 

Lactose in the glass state may be used as a protective coating on certain materials, either to seal in components or to protect the material from the environment. Materials may be coated with lactose solution and dried, or a solution containing the material and lactose can be spray-dried. This latter application has been used to preserve enzymatic activity during spray drying and storage (Nickerson 1974). 

V. A. Moskalenko, M. I. Vladimir, and S. P. Kozhukar, Self-Consistent Field Method in the Theory of the Glass State of Spin and Quadrupole Systems, Shtiintsa, Kishinev, USSR, 1990. 

Liquid relaxation phenomena and the glass state, in Non-crystalline solids . Ed. V. D. Frechette, Part 10, p. 252—268. New York J. Wiley Sons, 1960. 

Liquids with two equilibrium states, one of which (the low-temperature one) is really the glass state, because Xx T) > xg for this state at any temperature. (Clusters have a low configurational entropy.) The vitrification of this type of liquids is possible near T. ... 

In the case of thermotropic liquid crystals, a liquid-crystalline phase is obtained by heating a solid mesomorphic compound. At the melting point (Tm), the thermal motion of the molecules has increased to such an extent that the material passes from the crystalline phase to the liquid-crystalline phase. A mesomorphic compound that exists in the glass state will enter the liquid-crystalline phase at the glass-transition temperature (Tg). On further heating, the orientational order of the molecules is lost as well. The LC transforms into an isotropic, clear liquid at the clearing point (or isotropization point T. Many materials are liquid-crystalline at room temperature. Several types of liquid-crystalline phases can occur between the solid state and the isotropic liquid state. Sometimes decomposition of the material occurs before the... 

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