Polymer modified asphalt, often abbreviated as PMA, is an enhanced form of asphalt used for road surfaces, roofing, and sealing applications that benefits from the addition of polymers to the original asphalt mixture. These polymers, which are large, molecule-based chemicals, are blended with the asphalt to improve its performance characteristics. The introduction of polymers modifies the thermal, mechanical, and durability properties of the asphalt which can lead to a number of improvements including increased resistance to deformation (rutting), better resilience to temperature variations, reduced cracking and aging, and improved fuel resistance.

By tailoring the polymer type and the amount used, PMA can be designed for specific requirements and environmental conditions. For example, Styrene-Butadiene-Styrene (SBS) and Styrene-Butadiene Rubber (SBR) are commonly used polymers that provide enhanced elasticity and flexibility. This results in asphalt pavements that can withstand heavier traffic loads and extreme weather conditions, thus extending the life of the road surface while reducing maintenance costs.

Here are two active web pages where you can find more information about Polymer Modified Asphalt:

1. The Asphalt Institute:
The Asphalt Institute is a U.S. based association of international petroleum asphalt producers, manufacturers, and affiliated businesses. They provide a comprehensive overview of polymer-modified asphalts, technical details, and research publications.
URL: https://www.asphaltinstitute.org/education/publications/shop-detail/?productID=18 rel="nofollow">https://www.asphaltinstitute.org/education/publications/shop-detail/?productID=18

2. Federal Highway Administration (FHWA):
The FHWA is an agency within the U.S. Department of Transportation that supports State and local governments in the design, construction, and maintenance of the nation’s highway system. They offer resources and research findings on high-performance pavements, including polymer-modified asphalt.
URL: https://www.fhwa.dot.gov/pavement/pub_details.cfm?id=944

Please note that the actual content availability and URLs may change over time, and it can also be dependent on your geographic location. These links were active and relevant at the time of writing this description.