Answer from The Powder Coat Institute:
“Superdurable” refers to a specific type of polyester resin (it can be carboxyl or hydroxyl functional) that has superior UV durability compared to standard polyester resigns. These superdurable resins contain a high level of isophthalic acid as opposed to terephthalic acid. The high content of IPA provides up to 5 years durability in south Florida. Some clear coats based on this technology have surpassed 8 years in south Florida. A few powder coating manufactures have adopted the description “superdurable” to their powder product lines. A universal definition has not been established, but it is very important to understand that the ultimate durability of the powder coating not only involves the resign but also all the other components in the formula: pigments, fillers, additives, etc. A powder based on superdurable resin will still fail in less than 5 years exposure in Florida if a non-durable pigment or additive is present in the formula. It is most important to specify which durability standards are met by a particular powder coating rather than assume a description like “superdurable” means the product meets a specification.