Putting an iron on a synthetic blend is dangerous, since most people use too much heat and scortch the fabric. The more cotton based collars can be touched up, but only need a slight amount of heat to make them look new.
When you wash, don't fully dry the shirt. Hang it when it's still a bit damp, and smooth the collars out. They will dry just fine then and look smart. I have folded and then traveled with FJ shirts, slacks, and sorts and they always travel well and without wrinkles of any kind.