Physical foaming of injection molded reinforced thermoplastics parts with IQ-Foam

Collaboration between: UW-Madison and Volkswagen Group Research  

Due to federal fuel-efficiency rules, automakers must meet a fleet average of 54.5 miles per gallon by 2025. As more efficient engines and electric powertrains will not carry the whole load, the automotive industry is pressured into finding additional solutions. One of those solutions has been light weighting car components by using microcellular injection molding (IM). Upgrading traditional IM machines to offer microcellular IM capabilities requires a high economic investment.

Due to the high initial investment as well as the complexity to control the production, Volkswagen has developed a new foaming IM technology – “IQ-Foam”. Their patented technology introduces gas under moderate low pressure with the pellets into the system by employing a special two-chambered unit. Increased mechanical properties and increased weight reduction can be achieved, while no change in screw geometry is required. Various car manufacturers showed interest into using IQ-Foam, however fundamental research is required to understand how and when gas is getting introduced into the polymer/melt to control and simulate the process.

This project involves characterizing and predicting foaming behavior of fiber-reinforced parts. In particular, the foaming cell structure within the molded part will be analyzed and the relationship between foaming and fiber orientation and breakage will be investigated. Experiments will include using an in-line, non-invasive measuring technique (borescope) to capture data and images from inside the extruder to understand when gas is getting introduced into the polymer/melt. Additionally, a pressurized system will be designed to investigate the diffusion of gas into pellets/melt. This stationary experiment will then be expanded to introduce a screw/mixing element to study the gas diffusion behavior more realistically. Additional work will include validating commercial available simulation software packages to investigate their ability to accurately predict properties of end-use parts. If necessary existing models will be altered to produce a comprehensive model able to accurately predict foaming and performance in a finished part.