An experimental analysis of the effect of gamma and X-ray irradiation with dose rate 0.25-6mSv/h on low-density polyethylene (LDPE) and PMMA samples is presented. The focus of attention is on their DC conductivity as a dielectric of a capacitor. This system is based on the discharge of a capacitor by radioactive radiation through ionization of the dielectric consists of an inner electrode of the capacitor. The experimental setup contains a special electronic circuit in which polymer samples are placed as dielectric of parallel-plate capacitor which is connected to electrodes and a high voltage power supply is in series with other components of the circuit. It is understood that the resistance of polymers varies with the applied voltage and absorbed gamma ray dose from 137Cs with 0.661 MeV energy. The influences of this parameter on LDPE and PMMA electrical properties as a result of polarization of dielectric are also presented. The experimental results show elevation of LDPE and PMMA electric conduction properties as irradiation dose rate increases. Indications of predominance of charge accumulation are also observed.

In this article, waste plastics (low-density polyethylene, LDPE) and crumb rubber have been utilized to solve one of the most important environmental issues and to improve bitumen performance properties by these low cost materials. At first, modified bitumen samples were made using high shear mixer, then classic and performance tests were performed on them. It has been observed that adding low-density polyethylene and crumb rubber to the bitumen leads to improvement of classical characteristics. Then, after conducting dynamic shear rheometer test on modified bitumen samples, it was found that the sample containing 3% LDPE and 3% crumb rubber has the best performance. Conducting short-term and long-term aging experiments on samples containing 3% LDPE showed improved performance at high temperature services. After BBR test, more appropriate performance grade is observed for the sample containing 3% LDPE 3% crumb rubber.