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%

Foaming + core back mold movement

Also known as high-pressure foaming or foaming with decompression stroke.
The melt is first injected into the mold and briefly subjected to pressure.
Rapid, defined mold decompression triggers cell formation.
Additional machine equipment required for decompression
Mold must be designed for decompression
Component must be suitable for decompression

Advantages of MuCell + decompression stroke:

Suitable for larger, thicker-walled components.
Very high density reduction of up to 80% and weight reduction achievable.
Cycle time reduction.
Very high warpage reduction, especially for glass fiber-reinforced components.
Maximum flexural strength and stiffness with minimum density.
Very well suited for large and flat components.

Foaming with gas counter Pressure

Gas is applied to the cavity before and during injection of polymer
After the filling phase and a short delay time gas is released in a controlled manner
The pressure drop in all areas result in homogenous nucleation and foaming
Mold setup and process technology is more complex than standard foaming

Advantages:

Reduced silver streaks on surface
Very homogenous cell structure
Very high desnity reduction up to 80% possibel
good for very thick parts up to 30mm and more

Is your part suitable for foam injection molding?

Foam injection molding is much more than a niche process. Whether physical or chemical, the technology offers clear functional and economic advantages. The choice of the right process depends on component requirements, surface quality, and willingness to invest.
Anyone who needs lightweight, low-warpage, and at the same time economical plastic components cannot ignore modern foaming processes.

Find out more about our foam injection molding services.

Or contact us for your free of charge foam feasibility analysis to find out whether your component is suitable for foaming and what potential it offers.