Characterization, Solar Reflectance, and Crystal Properties of Polyethylene and Ethylene Copolymer after Thermal Treatment

Various kinds of polyethylene and ethylene copolymers were prepared by non-isothermal crystallization and isothermal crystallization methods. Solar reflectance of all samples was determined by a series of characterization (UV-vis-NIR measurement, wide-angle X-ray diffraction, differential scanning calorimetry analysis, polarized optical microscopy). It was found that lamellar thickness, degree of crystallinity, and microstructure played an important role in affecting the solar reflectance of these polymers. Long-branched chains in ethylene copolymers lowered the solar reflectance by decreasing lamellar thickness and the degree of crystallinity of these polymers. The isothermal crystallization method is a way to promote lamellar thickness and the degree of crystallinity, and make the microstructure more compact.