purified aromatic dicyanates are cured with a catalyst which is an mn , ag , fe , bi , in or hf salt at 150 °- 200 ° c . and then at 200 °- 300 ° c . for a time sufficient to cure the dicyanate without causing color formations to the extent of a yellowness index over 30 . in some forms the dicyanate is combined with the catalyst and a thermoplastic .