Polymer modified asphalt is increasingly used in road surfacing. Unmodified asphalt is sensitive to extremes in temperature, it becomes brittle and cracks in cold conditions and softens at higher temperatures, causing rutting and surface deformation. Modification of asphalt by addition of polymer results in a more elastic and durable product with greater temperature stability. One of the most common polymer modifiers is Styrene-butadiene-styrene (SBS).

Polymer, typically in either crumb, pellet or powder form is added to hot asphalt which penetrates the SBS particles and causes them to swell and flow. A number of factors govern the
efficiency of the dispersion process:

* The polymer particle size. Smaller particles present a larger surface area to the asphalt allowing faster penetration.
* The temperature of the process. Asphalt will penetrate the polymer more rapidly at higher temperatures.
* The polymer incorporation system. It must be capable of rapidly wetting out the polymer and uniformly dispersing it throughout the contents of the vessel.
* The dispersion system.Typically a high shear mixer which is required to disperse and dissolve the polymer.

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