Standard Sunbrella is made water resistant by application of fluorine based chemistry that is increasingly being removed from the market place due to 'unforseen possible severe future enviro concerns' ... much as what has happened with "Scotchguard" etc. Such fluorine based compounds are probably the most stable synthesized compounds ever made ... and no one can predict what will happen hundreds/thousands or millions of years from now when such is 'still' there and un-degraded.

The replacement fabrics (Top Gun, Aqua King, etc. etc.) are dual duck (coatings) polyester fabrics with an acrylic 'color coat' on the top surface and a waterproof coating on the bottom surface. Since these fabrics are made from the same exact polyester used in Sunbrella the fabric will last as long as Sunbrella - about 500+ years in a landfill; but, expect the water repellency to be a bit better; most are guaranteed for only 5 years. Top Gun, http://www.marchemcfi.com/top-gun.html, has been the 'popular' choice for dual duck fabrics.

These dual ducks 'seem' to last better in weather in comparison to the vinyl coated polyesters, such as Stamoid, etc.