Perkadox® BTW-50 is a paste containing 50% dibenzoyl peroxide without phthalate for the curing of unsaturated polyester resins at ambient and elevated temperatures. At temperatures up to 80°C, Perkadox® BTW-50 should be used in combination with an aromatic tertiary amine accelerator, above 80°C the use of an accelerator is not required. Perkadox® BTW-50 has primarily been developed for the putty market. For non filled systems, Perkadox® 40E is better applicable with respect to miscibility with the UP resin. Perkadox® BTW-50 shows a very good chemical and physical stability and is therefore very suitable for tube filling. The curing system Perkadox® BTW-50/amine accelerator shows a very fast cure that is hardly influenced by humidity and fillers. Even at low temperatures a relatively good cure will be obtained. A disadvantage may be the yellow color and poor light resistance of the moulded product.