Co-injection technology has been in existence for more than three decades, but recently transformed into a mainstream alternative for manufacturers in plastics processing. As consumer demands continue to change, and government sustainability compliance standards for plastics become increasingly difficult to achieve with standard mono-injection molding, the co-injection alternative has manufacturers around the globe paying closer attention.
Milacron pioneered co-injection technology starting in the 1990’s. Before co-injection was utilized in the food and beverage industry, those processors used a monolayer of special and expensive materials incorporating barriers that reduced the permeation of gas, moisture or light in order to extend the shelf life of products. With co-injection, these high-performance barriers are minimized, injected into the core layer, to make up less than 2 percent of total part weight. This not only creates significant savings but allows for the injection molded parts to re-enter the recycling stream.
Currently, the industrial packaging industry answers customer requests using this co-injection alternative in response to the impending US Plastic Pact that incorporates four targets addressing plastic waste slated for 2025. A wide range of packaging materials can now be co-injected to incorporate PCR or regrind materials into the core layer.
When the exterior appearance of a molded part is of critical importance, manufacturers utilize co-injection to fill the core layer of the part with PCR (or regrind) resin while maintaining the outer layer’s appeal utilizing virgin resin.