Where the functional radicals of the resin are glycidyl, examples of suitable crosslinking agents are polycarboxylic acids and their anhydrides such as phthalic acid, phthalic anhydride, trimellitic anhydride and pyromellitic anhydride; polyphenols such as catecol, resorcinol, hydroquinone, pyrogallol and fluoroglumine; and polyamines such as ethylenediamine, metaphenylenediamine, 4-4'-diaminodiph