Preparation and characterization of semiconducting properties of HDPE and LDPE polymers induced by electron beam irradiation / Mohd Hafiz Yaakob

In this study, high density polyethylene (HDPE) and low density polyethylene (LDPE) sheets were prepared by compression moulding technique. Both sheets were irradiated by electron beam irradiation at 100 to 800 kGy of irradiation dose. Unfortunately, the HDPE sheet showed degradation above 700 kGy of irradiation dose. On the other hand, LDPE can withstand higher irradiation dose up to 800 kGy without showing any degradation. Both sheets became harder after irradiation due to the formation of crosslinking in the polymer structure. This has been confirmed from the thermal gravimetric and differential scanning calorimetry analysis in which the decomposition and the melting temperatures of these irradiated systems were higher than in their un-irradiated systems. The formation of crosslinking in these irradiated HDPE and LDPE system were further confirmed from the formation of interpenetrating structure which were observed from the electron micrograph of these irradiated polymers. From the hot-point probe measurement, both irradiated HDPE and LDPE were p-type semiconductors. The presence of charge carriers in these systems were due to the delocalization of electrons from the conjugated C=C bonds that formed in these irradiated systems.