Modified bitumen systems are popular today for various reasons. They provide excellent weathering and fire-resistant properties as would be expected from a conventional built-up roof, without the need to use a heavy gravel cover. They achieve their superior handling and weathering characteristics through the use of a modifier combined with high-quality asphalt. This unique blend, when used as a coating for the reinforcements of non-woven polyester, fiberglass mat, or a combination of fiberglass and polyester, creates tremendous strength, elasticity and weatherability. The additional advantage of being able to choose from three methods of application — hot asphalt, heat welding (torching or hot air) and cold adhesive — is yet another reason that modified bitumen systems are popular.
APP (Atactic Polypropolyene) “plastic” modifier additive is combined with the asphalt to provide a tougher, better weathering asphalt coating that can be heat welded or applied with cold adhesive. The APP blend is more plastomeric than the elastomeric SBS blend, so it will not have the recovery properties associated with the SBS products. The strength of APP products is their ability to be heat welded (torch applied), although more recently they have been “cold applied” in some specifications.