A Typical Polyester Molecule.

Advanced Roofing Solutions (TopSeal) resin is a solution of unsaturated polyester resin in Styrene where both the Styrene and the Polyester cross link together as they cure, to form a 3D polymer of Polyester & Styrene whose properties may be tailored to optimise them for any application where weather resistance and a superb finished appearance are required. The Diagram above is what all the fuss is about.