5. Bitumen-APP waterproofing coatings

Composition

APP is atactic polypropylene. It is a by-product of the manufacture of conventional polypropylene (which is a crystalline form of PP). Its use was developed in Italy.

As with SBS, the addition of APP to bitumen increases (but to a lesser extent) the bitumen's flexibility at high and low temperatures. It also improves waterproofing and UV resistance. Above all, the addition of 15-30% APP to bitumen raises the softening point to 145-150°C, thus preventing hot creep and slippage on slightly sloping roofs (figure 9 and table 13 ).