EFFECT OF THERMOPLASTIC COPOLYMERS ON MICROSTRUCTURE AND VISCOELASTIC BEHAVIOUR OF BITUMEN

This paper presents a part of research to study the effect of the thermoplastic copolymer namely linear low density polyethylene (LLDPE), High density polyethylene (HDPE) and Polypropylene (PP) modified on 80 pen bitumen, using the rheological and morphological parameter. The modification of bitumen by the use of polymers enhances its performance characteristics but significantly affects its rheological properties. The tools used for rheological study of polymer modified bitumen (PMB) were penetration, ring & ball softening point and viscosity test. The morphological analysis was done to study the compatibility of bitumen with polymer, through field emission scanning electron microscopy (FESEM). The results were then related to the changes in the rheological properties of polymer modified bitumen. It was observed that thermoplastic copolymer shows profound effect on penetration rather than softening point. From the viscosity results it is revealed that the viscoelastic behaviour of PMB depend on the concentration of polymer in the mix, mixing temperature, mixing technique, solvating power of base bitumen and molecular structure of polymer used. PP offer better homogeneous blend in comparison to LLDPE and HDPE. The viscosity of base bitumen was enhanced with the addition of polymer and pseudoplastic behavior was also observed for LLDPE and HDPE. Oxidation during blending at 160ºC may be one of the causes of hardness of PMB. The best results were obtained when polymer concentration was kept below 3% for HDPE and LLDPE. PP shows least variation in all the test results.