Glassy state heat capacity

At room temperature, atactic polystyrene is well below its glass transition temperature of approximately 100 °C. In this state, it is an amorphous glassy material that is brittle, stiff, and transparent. Due to its relatively low glass transition temperature, low heat capacity, and lack of crystallites we can readily raise its temperature until it softens. In its molten state, it is quite thermally stable so we can mold it into useful items by most of the standard conversion processes. It is particularly well suited to thermoforming due to its high melt viscosity. As it has no significant polarity, it is a good electrical insulator. 

The transitions between the bottom five phases of Fig. 2 may occur close to equilibrium and can be described as thermodynamic first order transitions (Ehrenfest definition 17)). The transitions to and from the glassy states are limited to the corresponding pairs of mobile and solid phases. In a given time frame, they approach a second order transition (no heat or entropy of transition, but a jump in heat capacity, see Fig. 1). 

Sugisaki, M., Suga, H., and Seki, S. (1968). Calorimetric study of the glassy state. 4. Heat capacities of glassy water and cubic ic ull. Chem. Soc. Jap., 41 2591-2599. 

The values of ACPo and ACPl are the differences in the heat capacity between the glassy and rubbery state for the uncured resin and the fully cured network, respectively. However, the parameter A can also be used as a fitting parameter. 

Figure 5 (a, b) shows typical heat capacities and thermal expansion coefficient curves for some epoxy-aromatic amine networks. Table 1 gives some numerical values for networks with different component ratios P Cp and P values for the glassy state do not practically depend on the chemical composition of networks and are very... 

Marti E, Kaiserberg E, Moukhina E (2006) Heat capacity functions of polystyrene in glassy and in liquid amorphous state and glass transition DSC and TMDSC study. J Therm Anal Cal 85 505-525... 

The recommended heat capacity data are currently being analyzed in terms of chemical structure, structure of the polymers in the glassy, crystalline and molten states. The data are further being analyzed to study the effect of branching, molecular weight and tacticity on the heat capacity of polymers. Comprehensive tabulation of heat capacities of various structural units are being prepared and will be available in the near future. 

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