Improvement of thermal and mechanical properties of PE/NG nanocomposite by electron beam irradiation for solar thermal collectors

Polymeric absorbers used in solar thermal collectors must have appropriate thermal and mechanical properties. In this work, polyethylene/graphite (PE/NG) nanocomposite was selected as polymeric absorber and the effect of radiation on the thermal and mechanical behavior of that has been investigated. PE/NG composites containing 0.05, 0.1 and 2.25% nanographite was prepared through melt extrusion process. The SEM images of the samples proved the fair dispersion of NG in polymer matrix. Then the samples were irradiated by electron beam at doses ranging from 100 to 200 kGy. The specimens were characterized by tensile testing, Differential Scanning Calorimetry (DSC) and FT-IR spectroscopy. The results show that nanocomposite containing 2.25% graphite irradiated at 100 kGy has the best tensile strength and thermal stability. The results of DSC show that the addition of 2.25% NG to polyethylene improves the melting point and thermal properties. DSC and carbonyl index results of this composite in accelerated aging condition display no remarkable changes occur in thermal performance and structure of composite during aging. Also, with addition of NG to PE the UV/Vis absorbance of the PE/NG nanocomposite increases. Altogether, the experimental results reveal PE/NG as suitable candidates for solar thermal absorbers.