【Frontiers in HaiChuan Chemical Technology】German researchers have developed thin sheets that, when heated, transform into polyurethane foam with shape-memory properties

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Researchers have developed a sheet with shape-memory properties that turns into polyurethane foam when heated 2025-02-26 12:39:18 Researchers at Germany’s Fraunhofer Institute for Applied Polymer Research (IAP) have created a sheet that transforms into polyurethane foam when heated, with no health risks at all. This type of sheet enables isocyanate-free foaming, thereby improving safety in the workplace. In addition, it offers logistical advantages for storage and transportation. This material can be customized for various applications such as the automotive, construction, and packaging industries. Dr. Thorsten Pretsch, head of the Research Department for Synthesis and Polymer Technology at Germany’s Fraunhofer Institute for Applied Polymer Research (IAP), explained: “One aspect that is often discussed in the production of polyurethane foams is the health risks associated with isocyanates, which are one of the key components in the chemical reactions that form polyurethanes.” ” Dr. Thorsten Pretsch emphasized: “Our sheets enable isocyanate-free foaming.” It minimizes health risks in the workplace and enhances occupational safety, especially for on-site applications such as the construction industry. ” When handling isocyanates, strict regulations must be followed and protective measures taken. They are toxic and can cause allergies in the respiratory tract and skin ； Some isocyanates are suspected to pose a carcinogenic risk. The newly developed sheets can be converted into polyurethane foam simply by heating, without any chemical reactions taking place. The research team’s innovative approach also represents a new technology for foam production itself: thermal foaming. The product is named FOIM – a combination of the words “Foil” and “Foam”. Flexibility: Shape-memory polyurethane foam. This new material is a shape-memory polymer. It can return to its original shape after deformation. External stimuli such as heat can trigger the shape memory effect. For such sheets, the researchers synthesized polyurethane foam and then compressed it. At a temperature of 60°C, the sheet expanded from 2.5 mm thick to a foam that was 40 mm thick—a 16-fold increase in thickness. The result is a soft elastic polyurethane foam with a density of 80 kg/cm3. According to the DIN EN ISO 33861 standard, this is a low-density foam suitable for use as packaging material, among other things. Space saving: Semi-finished products made of shape memory foam. Industrial production typically uses polyurethane foam as standardized prefabricated intermediate products in cut form. These so-called semi-finished products are further processed during the manufacturing process or directly integrated into the final product. They can enable mass production while maintaining consistent quality. Their drawback is that polyurethane foam occupies a large amount of volume. Dr. Thorsten Pretsch said, “Our sheets save space during transportation and storage, and they only become foamy when heated to 60°C.” This is beneficial for industries that wish to reduce logistics costs, as well as those that need to decrease their volume of shipments, such as the aerospace industry. ” Multifunctionality: These sheets can be used in a variety of applications. Low-density polyurethane foam is suitable for many fields and industries: furniture manufacturers use it for interior decoration; in the packaging industry, it protects fragile items during transportation; in the construction industry, polyurethane foam is used to fill gaps between surfaces… Tests on using these new sheets to fill hollow structures have been successful. Even in complex geometric shapes, the material almost completely foams when heated. Shards are also suitable for bonding and joining techniques. Researchers have demonstrated that it is possible to fix two objects in place by creating a cavity between them. The properties of this innovative material are adjustable: research scientists can independently adjust the flexibility and transparency of the sheets before foaming. The same applies to the density, thermal conductivity, elasticity, and compressibility of foam. Dr. Thorsten Pretsch concluded, “We adjust the properties of the materials according to the technical requirements of different applications.” From car interiors to the protection of medical and fragile items. ”