1509 is a polymeric thioxanthone initiator with molecular weight over 1,100 so ideal for low migration inks and coatings. 1509 is designed as a companion product to 1508 to improve stability, but it can also be used by itself for even greater compatibility. It can be used alongside polymeric amines, polymeric α-amino ketones, and phosphine oxide initiators such as 1819. 1509 is similar in structure and CAS number to 1508, but differs in the molecular weight distribution.