App Modified Bitumen Roofing
APP stands for
atactic (or amorphous) polypropylene. First produced in 1960s using a modifier that was a sideproduct of isotactic propylene production, later manufactured directly as an atactic polypropylene for asphalt membranes.
How does APP influence the bitumen features?
APP improves durability of the bitumen roofing membrane at standard temperatures but practically doesnīt influence its properties at temperatures below 0 degrees C, therefore also polyolefins are added to the compound (polyalpha-olefins, ethylene-propylene-butene) which improve the under-zero durability.
How much APP is in the APP modified bitumen roofing?
In a standard APP modified roof there is 17-34% of atactic propylene.
APP modified bitumen advantages
- due to great thermal endurance of the material, APP modified roofing membranes can be used on sunny roofs with high temperatures (both flat and sloped);
- APP modified roofing provides superb UV (ultraviolet radiation) protection. With high-APP-volume membranes no gravelling is necessary;
- APP modified membranes (compared with other modified bitumens) are harder. Even though they are not 100% puncture-proof, they provide better protection against hail, stones or tree limbs damage.
APP modified bitumen disadvantages
APP modified membranes cannot be combined with SBS modified membranes as the joints will loosen over the time.
Cheap APP roofing membranes can act the same way even without combining with SBS membranes. The APP is an emulsion and during the manufacturing proces it must be fine-mixed with asphalt particles. If it is not mixed-in enough, the propylene emulsion tends to permeate through the membrane which is most visible in the joints. Also in this case joints can loosen with aging.
