Building Materials Investment Corporation (Wilmington, DE), a part of GAF Materials Corporation the largest U.S. roofing materials manufacturer, has patented an asphalt nanocomposite materials that can be used in roofing shingles and other building materials The asphalt-based nanocomposites are particle-filled matrices that include an asphalt flux or derivate and a layered clay mineral in an amount ranging from about 1% to 15% of weight. The nanocomposites result in improved mechanical properties such as heat deflection temperature, increased stiffness, higher tensile strength and better fire retardancy.
The asphalt-based nanocomposite is a nano-dispersion that is characterized as having higher melt viscosity as well as new crystallographic order evidenced in wide-angle X-ray diffraction (WAXD) studies. Such nanocomposites have superior tensile strength and significantly higher Young's modulus relative to their respective raw or filled coatings without nanoclays. The asphalt-based nanocomposite can be used as a coating for any material layer of a roofing shingle, according to inventors Vinay Mehta, Brian Kanze, Krishna Srinivasan and Awdhoot Vasant Kerkar, writing in U.S. Patent 7,582,155. It is worth noting, that the term "asphalt-based nanocomposite" denotes a composite material comprising asphalt as the major component. This system is distinct from polymer-based nanocomposites, in which a polymer is the major component.
The asphalt-based nanocomposite is made of particle filled layered clay minerals dispersed into a matrix of asphalt. The asphalt molecules intercalate (or exfoliate) between the clay mineral layers. decrease in ultimate elongation was, however, anticipated since the addition of polymer-based nanocomposites to different systems in the prior art also shows a similar decrease in elongation. The decrease in ultimate elongation is a result of a stiffer product being formed when the nanocomposite is employed.
Layered clay materials such as, for example, montmorillonite, hectorite, saponite and the like, are composed of silicate layers that have a thickness of about 1 to a few nanometers. Dispersions of such layered clay materials in polymers are frequently referred to as polymer-based nanocomposites. These are the type of nanomaterials used in the asphalt nanocomposite.
The asphalt-based nanocomposite can be prepared using a variety of methods, including: (1) a direct blending method; (2) a method in which asphalt is first fractionated into its multiple (usually four) components and then a layered clay mineral is blended therein; (3) a method in which a layered clay mineral is added to an asphalt flux or derivative thereof prior to blowing (i.e., oxidizing); or (4) a method in which asphalt flux or its derivative is first solubilized in an organic solvent, then mixed with a layered clay mineral and thereafter evaporated to remove the organic solvent.