Polymers thermophysical properties

Before proceeding, we mention sources for a few areas not covered in this chapter. Basic chemical thermodynamics is the subject of Chapter 4. For polymers and their solutions, the Polymer Handbook [1] is an indispensable source, and more on polymer thermophysical properties may be found in two books from AIChE s DIPPR project [2, 3]. The estimation of properties of mixtures described by distillation curves (typically petroleum fractions), or of the pseudocomponents derived from such curves, is covered in the AP7 Technical Data Book [4]. Many molecular data, such as dipole moments and spectroscopic constants, are tabulated in the NIST Chemistry Webbook [5]. 

W. Brostow (Ed.). Polymer Liquid Crystals Mechanical and Thermophysical Properties. Chapman Hall, London (1996). 

Y.K. Godovsky. Thermophysical Properties of Polymers. Springer-Verlag, Berlin, 1992. 

Example 5.3 The Semi-infinite Solid with Variable Thermophysical Properties and a Step Change in Surface Temperature Approximate Analytical Solution We have stated before that the thermophysical properties (k, p, Cp) of polymers are generally temperature dependent. Hence, the governing differential equation (Eq. 5.3-1) is nonlinear. Unfortunately, few analytical solutions for nonlinear heat conduction exist (5) therefore, numerical solutions (finite difference and finite element) are frequently applied. There are, however, a number of useful approximate analytical methods available, including the integral method reported by Goodman (6). We present the results of Goodman s approximate treatment for the problem posed in Example 5.2, for comparison purposes. 

Example 5.5 Continuous Heating of a Thin Sheet Consider a thin polymer sheet infinite in the x direction, moving at constant velocity Vq in the negative x direction (Fig. E5.5). The sheet exchanges heat with the surroundings, which is at T = T0, by convection. At x = 0, there is a plane source of heat of intensity q per unit cross-sectional area. Thus the heat source is moving relative to the sheet. It is more convenient, however, to have the coordinate system located at the source. Our objective is to calculate the axial temperature profile T(x) and the intensity of the heat source to achieve a given maximum temperature. We assume that the sheet is thin, that temperature at any x is uniform, and that the thermophysical properties are constant. 

The thermophysical properties, such as glass transition, specific heat, melting point, and the crystallization temperature of virgin polymers are by-and-large available in the literature. However, the thermal conductivity or diffusivity, especially in the molten state, is not readily available, and values reported may differ due to experimental difficulties. The density of the polymer, or more generally, the pressure-volume-temperature (PVT) diagram, is also not readily available and the data are not easily convertible to simple analytical form. Thus, simplification or approximations have to be made to obtain a solution to the problem at hand. 

TABLE A.2 Thermophysical Properties of Semi-crystalline Thermoplastic Polymers... 

Godovsky YK, "Thermophysical Properties of Polymers", Springer, Berlin, 1992. 

Oner, M. Dincer, S., "Thermophysical Properties of Polymer-Probe Pairs by Gas Chromatography," Polymer, 28, 279 (1987). 

Lazaridou, A., and Biliaderis, C.G. (2002). Thermophysical properties of chitosan, chitosan-starch and chitosan-pullulan films near the glass transition. Carbohydrate Polymers. 48,... 

The effectiveness of coke as a heat barrier retarding heat transfer to the undecomposed polymer depends primarily on the thermophysical properties of coke. Semiempirical models of intumescent coatings > -i ) allow the coke effectiveness to... 

In Table 6, we can see the average thermophysical properties of kerogenes as compared to the values of the same characteristics of thermoplasts. Thermophysical properties of processed compositions in the area of phase transitions are of prime importance. In Table 6, we can see the avera values of the corresponding thermal co-efficients at 100-150 °C. The data for polymers are cited from [69,70]. Assuming that there are no local thermal tensions in the melt, we can calculate the composition s thermal linear expansion coefficient by the additive equation [69,70] ... 

Novichenok, L. N., Shulman, Z. P. Thermophysical Properties of Polymers. Minsk Nauka i Tekhnika Press 1971, pp. 117 (Russ.)... 

The main type of properties of concern from a chemical point of view are the intrinsic properties. Among these are the mass (molecular weight), the volume, as well as various thermophysical, mechanical, optical, electrical, transport properties, etc. Analytical pyrolysis is able not only to probe some thermophysical properties of polymers, but also to give some structural information that can be used indirectly for other characterizations of polymers. 

V. P. Privalko and V. V. Novikov, The Science of Heterogeneous Polymers Structure and Thermophysical Properties, Wiley, New York, 1995, p. 235. 

The relationship between other flammability characteristics and the polymer tendency for carbonization has also been studied 112-114). Flame retardant effectiveness of coke is, primarily, related to the reduced release of fuels into the gas-phase, and to the ability of the coke to undergo heterogeneous oxidation. Therefore, not only the composition is important but also the morphological structure, porosity, specific surface area and thermophysical properties of the carbonaceous residue115, U6). 

Instabilities in UTR polymer films are manifested in two main ways, namely, (i) defects resulting from the coating process, substrate nonuniformities, and conjoining pressure, and (ii) discontinuihes in the thermophysical properties of the hlms due to interfacial effects and polymer cooperative and surface dynamics. 

---