Effect of Crystallization on Thermal Conductivity

Thermal conductivity is an important parameter used for material thermal calculations in the injection molding simulation. A variation in the thermal conductivity will alter the cooling rate and hence cause a variation in the temperature this in turn will cause the viscosity, pressure, and frozen layer to vary. Classical Fourier theory, which assumes thermal conductivity to be a constant scalar value depending only on temperature alone, is inadequate to describe the heat conduction in deformed molten polymer. Van den Brule (1989, 1990) and van den Brule and O Brien (1990) suggested that heat transport mechanisms along the backbone of a polymer chain are more efficient than those between neighboring chains. Hence, the orientation of polymer chain segments induced by flow leads to an anisotropic thermal conductivity. To describe anisotropic thermal conduction, one 

Van den Brule proposed a connection between the thermal conductivity tensor and the total stress tensor as follows  

Measuring the flow-dependent thermal conductivity is difficult. Nevertheless, some experimental results were reported by Venerus et al. (1999, 2000, 2001 and 2004) and Schieber et al. (2004) for amorphous polymers. The results indeed support the theory of van den Brule. In addition, they found that the product of stress-thermal coefficient Q and the melt plateau modulus Gjv is a nearly universal value, i.e., C,Gn 0.03. 

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