DEGREE OF CRYSTALLINITY AND LATTICE THERMAL-CONDUCTIVITY OF POLYETHYLENE AT LOW-TEMPERATURES

The lattice thermal conductivity of a semicrystalline polymer was stud ied at low temperatures by calculating the total lattice thermal condu ctivities of four samples of polyethylene with different degrees of cr ystallinity between 0.43 and 0.81 and temperatures between 0.4 and 20 K. The contributions of the crystalline and noncrystalline natures and their percentage contributions were taken into account. The predicted lattice thermal conductivity of polyethylene was in fairly good quant itative agreement with the experimental value, and showed a strong cry stallinity dependence, with a distinctive cross-over point at about 2 K.