Assessing the structure of recycled polyethylene-modified bitumen using the calorimetry method

The bitumens, having different compositions, and recycled polyethylene, consisting of low- and high-melting point crystallites, were used for the preparation of bitumen/polymer blends. The structure of bitumen/polymer blends is studied using methods of calorimetry, optical microscopy and oscillatory shear test. The different thermal and viscoelastic behaviors are found at low and high contents of the recycled polyethylene in bitumen/polymer blends. A study of the concentration dependences of thermal characteristics shows that an abrupt increase in the melting enthalpy of bitumen/polymer blends with a monotonous increase in the concentration of polyethylene is due to the formation of a co-continuous structure in the blend. It is revealed that the thermal behavior of bitumen/polymer blends can be used for evaluation of the degree of compatibility of polycrystalline recycled polyethylene and bitumens. The assumption is made that the absence of the low-temperature effects on the heat flow curves of bitumen/polymer blends can testify the good compatibility of bitumen and polycrystalline recycled polyethylene.