Production of stable polypropylene-modified bitumens

The use of polypropylene polymers and copolymers as modifiers for road bitumens appears promising. The problem of stability during storage for long periods at high temperatures can be solved by adding phosphorus compounds, especially polyphosphoric acid, which changes the bitumen structure from sol to gel. It is demonstrated that the stability of polymer-modified bitumens depends not only on the difference in density and viscosity between bitumen and polymer but also on bitumen structure. Copyright (C) 1996 Elsevier Science Ltd.