Corrosive, abrasive, and high-temperature resins can degrade screws and barrels before you know it. Certain engineering materials, thermoplastic elastomers, plus the wave of newly developed biopolymers, often create a corrosive condition that can quickly degrade equipment. Reinforcements such as glass fibers, spheres, and other fillers and additives are abrasive and also take a toll on equipment, especially screws and barrels.

Acid & Glass attack on surface

Corrosive wear such as pitting on the surfaces of barrels and screws occurs when metal is attacked during processing by acids and acidic gases, which can dissolve oxide coatings. Highly corrosive polymers include PVC, which produces hydrochloric acid; acetals, which produce formic acid; and fluoropolymers, which produce hydrofluoric acid. Standard bimetallic, nitrided, or tool-steel barrels can be severely damaged by fluoropolymers in a very short time. Other corrosive melts are those containing flame retardants and foaming agents.

HIP barrels and screws are the best of the best terms of corrosion resistance for injection molding and extrusion. Even fluoropolymers are no threat to these barrels. When used with corrosion-resistant screws, HIP barrels reduce substantially the absorption of iron particles from the barrel bore into the melted polymer.

Typical treated parts include:

• Injection / extrusion molding screws
• Injection / extrusion molding barrels
• Extrusion screw segment
• Backflow check valves
• Check rings
• Rear seats