Efficient lightweight construction technology for modern plastic products
A blowing agent is added to themolten plastic. A pressure drop then causes nucleation and bubbles, which expand in the polymer melt. This creates the foam.
Foam injection molding is an effective method for manufacturing components that are lighter, stiffer and more economical.
- Less material consumption → direct cost reduction
- Greater dimensional stability → fewer warping problems
- Shorter cycle times → lower energy costs
- Lightweight construcions → performance advantages and CO₂-savings
- lower tool load → longer service life
There are two methods for introducing gas into the melt as a blowing agent: physical foaming and chemical foaming. Both methods improve the flowability of the melt and reduce the injection pressure. The expansion pressure of the gas is distributed evenly throughout the cavity, reducing component distortion.
Foaming with physical blowing agent
In physical foaming, inert gases such as CO₂ but mostly nitrogen (N₂) are introduced into the plastic melt under pressure. There are various methods for introducing the gas into the melt.
A very widely used method is the MuCell process developed by Trexel. In this process, the required amount of gas (N2) in a supercritical state is precisely dosed into the melt via the injection molding unit during the dosing phase and converted into a single-phase solution through homogeneous mixing and dispersion.
- Foaming phase is very fast with high energy --> Effective gas pressure is approx. 30 bar
- Inert gas --> no decomposition residues, no corrosion
- Low gas consumption --> lower running costs
- Very homogeneous, fine-pored foam structure in filled plastics
- Coarse-pored foam in unfilled plastics
- Very good improvement in the flowability of the polymer melt --> also well suited for thin-wall applications smaller than 1.5 mm
- Higher weight and clamping force reduction
- Higher investment costs
Foaming with chemical blowing agent
A chemical blowing agent masterbatch is added to the plastic granulate. Here, gas formation, usually CO2, occurs through thermal decomposition of the chemical blowing agent. The gas is released into the melt and forms the cell structure.
- Slower transition to the foaming phase with lower gas pressure of approx. 10 bar.
- Coarser cell structure.
- Less streaking --> More homogeneous surface.
- Faster degassing from the component. Advantage for subsequent processes.
- Better suited for very thick-walled components.
- Easy to integrate into existing processes (granulate → dryer → machine).
- No additional gas technology necessary → Cost-efficient for series products without high investment costs.
- Lower density reduction
- Decomposition residues in the component
Foaming with partial filling of the mold
- Also known as low-pressure foaming.
- Standard variant for foaming plastic components.
- The cavity is only partially filled.
- there is no high-pressure holding phase.
- The cells expand and fill the rest of the cavity.
- This process variant can be used with chemical or physical blowing agents.
Typical advantages:
- Weight savings (typically 5%–15%),
- up to 25% possible with optimal component design for foaming
- Reduction in warping and sink marks
- Clamping force reduction of up to 50% possible
- Cycle time reduction of up to 40%