Intelligent Material with Potential: Shape Memory Polyurethane Enables New Applications

A film that remembers its original shape and turns into foam "at the touch of a button"? This is exactly what a research team at the Fraunhofer IAP is working on. The combination of polyurethane and the shape memory effect results in a completely new material that can be stored as a space-saving film and transforms back into a high-performance foam structure when required.

In an interview with K-Mag, Dr Thorsten Pretsch explains how this material works, what advantages it offers compared to classic PU foams – and where the greatest potential for industry, sustainability and safety lies.

Dr Pretsch, PU foam is a widely used material. What motivated you to rethink this material?

Dr Thorsten Pretsch: The motivation to rethink PU foam stems from the potential to develop innovative properties and applications.

As far as we know, there has never before been a process for producing a film from a shape memory polymer foam and then transforming it back into the foam by heating it. The programming results in a thermally switchable semi-finished product in which the information about the foam structure is stored. The product bears the name FOIM, a neologism made up of the English terms "foil" and "foam".

What specific advantages does the foil foam offer – especially in comparison to conventional PU foams?

Pretsch: Strict regulations and protective measures apply to the handling of isocyanates in the construction industry, for example, as they are toxic and have sensitizing effects on the respiratory tract and skin. In addition, some isocyanates are suspected of causing cancer.

The newly developed film transforms into polyurethane foam simply by applying heat, without reacting chemically. This is why we refer to this type of foam production as "thermal foaming". Our solution therefore offers a healthy alternative that focuses on both personal safety and environmental protection.

Which specific parameters can be adjusted – and how do they affect functionality in different applications?

Pretsch: First of all, the chemical formulation can be used to influence the thermal and mechanical properties of the foam. Another important factor is the density, which influences the strength and load-bearing capacity of the foam. A higher density ensures greater stability, while a lower density enables lighter and more flexible applications. High-density foam is therefore well suited for structural applications, while low-density foam is predestined for use in packaging or upholstery.

In addition, additives can be incorporated into the film foam to improve its properties, for example in terms of fire resistance, UV resistance or elastic properties. Such modified foams are particularly beneficial in more demanding environments where there are additional safety or performance requirements.

The degree of mold recovery when the shape memory effect is triggered also plays a crucial role as it influences the final structure and mechanical properties. This can be important in applications that require a high degree of adaptability, such as the fixing of fragile objects, or in the case of thermally sequentially adjustable damping or insulation.

In short, the targeted adjustment of these parameters enables the film foam to be optimized for a wide range of applications.

Are there application scenarios in which foil foam represents a real game changer?

Pretsch: It could actually be a game changer in several application scenarios. For example, the space-saving storage and simplified transportation enable more efficient logistics and cost savings. In addition, the gradually adjustable property profiles allow flexible adaptation to different applications when resetting the mold, which makes handling easier.

In sectors such as the automotive, construction and packaging industries, the lower system costs and compact shape of the film foam could offer significant advantages. Innovative applications in medical technology and pharmaceuticals, such as drug delivery systems, could also benefit from the unique properties of the film foam.