Polymers have been widely used to improve the performance of bitumen. Polypropylene (PP), one most common plastomer for bitumen modification, is utilized specially in roofing application adding up 30 wt% This article presents an investigation four different polypropylene (PP) polymers having differences tacticity (atactic and isotactic), molecular weight (Mw ~ 12 000 g/mol ~250 g/mol) functiona...