An international research team has developed certified biodegradable and recyclable multi-purpose foams.

Foams have numerous possible potential applications, for example ranging from the automotive, household and mechanical engineering sectors to leisure and sports applications. Until now, it has been common practice to produce these materials from crude oil, which negatively impacts their ecological footprint. In the EU project BreadCell, an international consortium has developed cellulose-based foams that are produced using a process similar to baking bread. These foams are completely biodegradable and recyclable. Two Institutes at Graz University of Technology (TU Graz), the Institute of Bioproducts and Paper Technology and the Vehicle Safety Institute, played a crucial role in developing the technology.

Many potential areas of application

“It is important to implement sustainability efforts in as many areas as possible,” says Stefan Spirk from the Institute of Bioproducts and Paper Technology at TU Graz. “Cellulose is plant-based and available in large quantities. Replacing oil-based products with those made from cellulose materials is the goal and the foams developed in the BreadCell project have a wide range of potential applications.” The researchers identified the following application areas, among others, as highly suitable for the environmentally friendly foams: the automotive sector for crash impact energy management, the construction sector as an insulating material, and the sports industry for the manufacture of sports equipment and shoe soles. The material also offers potential benefits in terms of moisture management and acoustics.

Fibre design and simulation models

A key aspect of the project was to establish correlations between the foam strength and the fibre design using advanced simulations models. In order to obtain the material input data required for these simulations, the material was comprehensively characterised. This included tests under a wide variety of loads, for which a dedicated test rig at TU Graz was used, that characterises the behaviour of materials under dynamic and rapid loads. Based on the data and developed models, foams with different densities and mechanical properties were produced and applied in various demonstrators.

For example, the researchers have produced and tested a skateboard, a bodyboard, a bicycle helmet and shoe insoles. “The development of the foam also revealed an interesting property: it was a challenge to keep the density perfectly homogeneous over the entire thickness of the foam,” says Florian Feist from the Institute of Vehicle Safety at TU Graz. “But this inhomogeneity proved to be advantageous in one specific application: bicycle helmets. A softer centre layer enables a kind of shearing between the outer and inner helmet layers. This reduces the rotational load on the brain when there is an impact, similar to the principle of modern safety systems such as the MIPS system.”

First project spin-off produces shoe insoles

In addition to Chalmers University (project coordinator) and TU Graz, three other institutions were involved in BreadCell: The University of Vienna worked on sandwich constructions for lightweight components, while Tecnalia in Spain tested the feasibility of industrial implementation and BioNanoNet (BNN) in Graz assessed the biodegradability and life cycle performance. The project has also given rise to a spin-off company, FOAMO, which manufactures lightweight and cushioning insoles based on the developed foams.