The thermoplastic foam injection moulding process has a high lightweight construction potential without losing rigidity. The process is particularly interesting for lightweight construction applications and is therefore being investigated at the IWK.
Integral foams are foams have a compact outer skin and a porous core, with the core density continuously decreasing towards the centre of the component. The process can be particularly attractive for lightweight construction applications.
Research on injection moulded integral foams
The IWK is investigating the theory of thermoplastic foam injection moulding and its potential for lightweight construction. Tests are used to determine which maximum weight reductions are possible with various chemical and physical blowing agents. The influence on the mechanical properties is examined in each case.
For the production of lightweight components by injection moulding, both the 1K and 2K processes are possible. A highly fibre-reinforced material can be used for the compact outer skin to achieve maximum rigidity and strength. A high degree of foaming should be achieved in the porous core, which should be as shear-resistant as possible. In the tests, a foamed core of polyamide is therefore additionally combined with cover layers of highly fiber-reinforced polyamide.
Findings
The polyamides can be easily foamed both chemically and physically. The figure shows two typical foam structures with compact cover layers and foamed cores. In the upper structure 6% blowing agent was added and a weight reduction of 31% was achieved, in the lower structure 3% blowing agent 8% weight reduction was achieved.
The combination of a foamed core of unreinforced polyamide and outer layers of highly fiber-reinforced polyamide made it possible to achieve the same rigidity despite a weight reduction of 20%. Especially with physical foaming, an increase in bending modulus of approx. 25% could be observed.
The results show that injection moulded integral foams can offer the following advantages:
- Due to their sandwich-like structure, they have a very high lightweight construction potential with very rigid component properties
- Despite a weight reduction of 20%, the same rigidity could be achieved with high-fibre-reinforced polyamides
- Polamyides can be an alternative to back-moulding organo sheets
- Thanks to the porous core, material can be saved
- Cycle times and closing forces can be reduced during the injection moulding process
Presentation at the 13th Rapperswil Plastics Forum
At the 13th Rapperswil Plastics Forum you can experience this application live on an injection moulding machine during the laboratory presentations and learn more details in a short lecture.
