Surely you have already stumbled upon the term epoxy or epoxy resin in connection with surfboards.
So far, most surfboards have been made of polyester resin.
Epoxy has the advantage of being less prone to impact and therefore firmer on the whole. At the same time, epoxy resin is lighter.
Unfortunately, it is more difficult to process epoxy resin, it takes a very long time for the material to cure and it is more toxic and more expensive.
When you fix your board, you have to be sure of what material it is, because repairing it by the wrong means can destroy your board.
Polyester smells sharp and pungent. You already notice this smell when sanding the board. Epoxy, however, is odorless and often ensures that the surfboard has a slightly yellowish sting.
With these boards, it is more than likely that the blank is made of styrofoam. When it comes into contact with polyester, the solvent contained in the polyester is eaten away by the polystyrene.
A blank can also be made of polyurethane. This material has a finer structure and less air pockets.