BO22 injection and extrusion barrels are specifically designed and manufactured to withstand highly corrosive processing environments, such as molding products containing fluoropolymers. The barrels have a protective layer in the bore and all areas exposed to corrosive gases. This protective layer is a nickel-rich boron base alloy containing 12% molybdenum and a matrix rich in complex borides and carbides. These elements allow the protective layer to maintain its high temperature hardness. It has a hardness from 50-55 Rockwell C at 700°F.

After machining the basic shape of the barrel, the BO22 bore protection is added by using a hot isostatic pressing (HIP) process that creates a non-porous bore lining. The molybdenum and its alloying elements found in the bore protection are said to be superior in corrosion resistance against elements that contain halogen. This reportedly reduces acid attack when compared with conventional nickel-cobalt base alloy. As an extra measure of protection against acidic corrosion of barrel surfaces that cannot be protected as part of the BO22 HIP process?such as the barrel discharge end, transducer holes, or flange surfaces?the company adds acid-resistant material to these areas.

The barrels, when used with corrosion-resistant screws, are said to substantially reduce the absorption of iron particles from the barrel bore to the melted polymer?important when molding medical and other critical plastic products that cannot contain traces of iron.

Fluoropolymer processors that use BO22 barrels see fewer machine teardowns for barrel changes, and cleaner, more consistent product.

Wexco, Lynchburg, VA
(434) 385-6006; www.wexco.com