Specific heat of melting

H is the heat given off by that part of the polymer sample which was already in the crystalline state before the polymer was heated above T. With this number H it is possible to figure out the percent crystallinity it is divided by the specific heat of melting, H, which is the amount of heat given off by a certain amount of the polymer. So the mass of crystalline material, m, follows as ... 

In principle the heat required to bring the material up to its processing temperature may be calculated in the case of amorphous polymers by multiplying the mass of the material (IP) by the specific heat s) and the difference between the required melt temperature and ambient temperature (AT). In the case of crystalline polymers it is also necessary to add the product of mass times latent heat of melting of crystalline structures (L). Thus if the density of the material is D then the enthalpy or heat required ( ) to raise volume V to its processing temperature will be given by ... 

Specific Heats of Solid Mixtures.—The specific heat of a homogeneous solid mixture of solid components is not usually additively composed of the specific heats of the latter. W. Spring (1886) found that the total heat capacity of alloys of lead and tin was always greater than the sum of those of the components, but above the melting-point the two were equal. A. Bogojawlensky and N. Winogradoff (1908) find, however, that the heat capacities of the isomorphous mixtures ... 

Ewan took account of the variability of Q with temperature, which introduces the specific heat of the solution this is usually quite negligible within the range of validity of (14). Q is the heat absorbed when a mol of ice melts and the liquid mingles with the solution. 

Example 1.—If the specific heats of the solid and liquid forms are linear functions of temperature, show that the melting-point is determined by dividing the latent heat of fusion by the difference between the specific heats of the solid and liquid forms at the melting-point (cf. Taramann, Kryst. and Schmelz., p. 42). 

C mean specific heat including heat of melting over the range 80-Te, BTU/lb F r = throughput, lb/hr... 

Figure 4.8 shows the comparison of three lots of loperamide hydrochloride, each obtained from a different supplier. The displayed thermograms represent normal behavior for this material, and while the figure shows the uniqueness of each source, the variations were within acceptable limits. Owing to the decomposition that followed on the end of the melting endotherm, specific heats of fusion were not calculated in this case. 

If the heat capacity of a chemically complex melt can be obtained by a linear summation of the specific heat of the dissolved oxide constituents at all T (i.e., Stebbins-Carmichael model), the melt is by definition ideal. The addition of excess Gibbs free energy terms thus implies that the Stebbins-Carmichael model calculates only the ideal contribution to the Gibbs free energy of mixing. 

Figure 1. Schematic presentation of volume and enthalpy as functions of temperature in the liquid, crystalline, and glassy state. Tg, melting temperature, TQf glass temperature, IIs, heat of melting, V8, specific volume difference between crystal and melt.

Tellurium melts at 452° C.1 and boils near 1390° C. under ordinary pressure,2 but volatilises at as low a temperature as 430° C. in a cathode-ray vacuum the vapour is yellow in colour.3 Like the density, the specific heat of the solid is inconstant, ranging from 0-0475 for the distilled element to 0-0524 for the precipitated amorphous substance.4 It has been observed 5 that exposure to X-rays increases the specific heat of tellurium by about 8 per cent., possibly owing to a change in the structure of the element. 

A beam of 1 particle-p,A of 48Ca10+ ions is incident on an A1 foil that is 5 mg/ cm2 thick, (a) Estimate the energy deposit/s in the foil, (b) If the foil has an area of 4 cm2 and it is mounted in a vacuum with no cooling, how long will it take until the foil reaches the melting point of A1 (660°C) Assume the specific heat of A1 is independent of temperature and is 0.25 cal/deg/g. 

Fig. 11. Specific heat of annealed80/20 copolyester of polyethylene terephthalate-sebacate in the neighborhood of the melting point. Dotted line, calculated values from adaptation of theory of Feory...

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