Emergence of polymer-bitumen materials was an important innovation in the development of roofing technologies. Unlike products of similar purpose, bitumens modified with polymers are corrosion-proof and retain their chemical stability. Due to the above, roofing service live can be significantly extended. In this case glass-fabric, fiberglass mats or polyester are used as a base.
Polyester is the most expensive but tends to be preferred in most cases. Durability of this material is higher than durability of glass-fabric, and this property is very important for soft roofing materials. Around the joints, there is usually a lot of heat expansion and contraction, that’s why the base must not tear in such conditions. The higher its stretchability, the longer the service life of roofing.
Thickness of polymer-bitumen materials usually equals 3 to 5 mm; hence, one or two layers are enough. If the traditional technologies are applied, the required number of layers is four or five.
Key advantages of applying modified bitumens for roofing are the following:
- reduced labor costs;
- reduction of pores in covering;
- lower emissions of carbon oxide and soot;
- instead of pouring hot bitumen, the lower layer is heated with a propane burner.
For bitumen modification, atactic polypropylene (APP) and Styrene Butadiene Styrene (SBS) can be used. In the first case, the material shows high resistance to ultraviolet exposure and doesn’t require roofing sand. If SBS modifier is applied, plasticity is better, but lower ultraviolet resistance requires a top cover. This material possesses particular flexibility properties at low temperatures and shows high cold durability and good adhesion, as well as durability under cyclic stress.