A STUDY ON MATERIAL DISTRIBUTION AND MECHANICAL PROPERTIES IN CO-INJECTION MOLDING

In the co-injection molding process, sometimes referred to as sandwich molding, two different polymer melts are either simultaneously or sequentially injected into a mold to form a part with a skin/core structure. Co-injection molding offers the flexibility of using the best properties of each material to reduce material cost and part weight. Particularly, it allows the use of recycled material in the core without an adverse effect on surface quality. The properties of a co-injection molded product depend on the individual properties of the skin and core layers, and the skin/core volume ratio. This paper presents a study of the effect of molding parameters on material distribution and mechanical properties of co-injection molded plates. Two virgin materials were tried: polypropylene (PP), and thermoplastic polyolefin (TPO) as well as ground TPO from plastic bumpers.