After irradiation, fusible cleavage products remain on the paper surface and seal under heat and pressure without any additional material. “By irradiating the paper with a CO laser, we create refusible, sugar-like reaction products that we use instead of the synthetic materials or adhesives that would otherwise be required to seal the paper by the heat sealing process. In this way, we are essentially producing our own adhesive in the form of the cleavage products,” says Volker Franke, Group Manager Laser Micro Processing at Fraunhofer IWS in Dresden. “After laser treatment, we have succeeded in using heat sealing, an established thermal contact process, to bond two layers of paper with heat and pressure.”

Bond strength defines seam quality

The project partners at Fraunhofer IVV are developing the necessary sealing system for processing laser-treated papers with fusible cleavage products. To achieve this, the researchers are accounting for the effects of material properties, laser parameters and the properties of the fusible reaction products on bond strength based on data already recorded by the teams at Fraunhofer IAP and Fraunhofer IWS. They are also testing the extent to which bond strength and leak-tightness can be improved by using suitable sealing parameters and tool geometries and are transferring the results to a packaging solution with the goal of achieving seam properties suitable for the market. “Bond strength determines how difficult it is to tear open or to open packaging,” explains Fabian Kayatz, research scientist and project coordinator at Fraunhofer IVV in Dresden. “By measuring mechanical stability under different types of loads (shear test, T-peel test), we can demonstrate the effects of laser parameters and sealing parameters on the bond strength of the seams. Crucial sealing parameters are sealing time, sealing temperature, sealing pressure, and tool geometry. Fiber direction also plays a role, i.e., the orientation of the material relative to the sealing tool.” Marek Hauptmann, head of the joint project, adds: “We are essentially striving for a bond strength that is higher than the interply adhesion of the paper layers. We are already achieving good bonds in the shear tests. We can easily lift 20 kilograms with a seal that is only two centimeters long and three millimeters wide.”

Adhesive-free sealing integrates into existing production

At Fraunhofer IWU in Dresden, a laboratory-scale modular paper processing manufacturing unit is currently being developed that replicates the process for manufacturing a flat four-sided bag—commonly used for packaging—in a roll-to-roll process. The primary focus of the work is developing and integrating a laser and a sealing module into the approximately six-meter-long, one-meter-deep and two-meter-high industrial-type demonstrator. The adhesive-free sealing process is being adapted based on sensors proven in industry (including image and moisture sensors) and a digital twin with a trained data model. The surface of the paper web running continuously through the plant is first irradiated with the CO laser, producing the cleavage products mentioned above. A second paper web is then fed in, joined with four seams using a combined sealing and punching tool in a heat-sealing process, and is then punched out to form a bag. The heat generated during the sealing process activates the cleavage products, causing the two paper webs to bond together. In the future, a seal seam measurement system installed in the pilot plant as a quality control measure will record real-time changes in seal seam quality, enabling rapid adjustment of laser and sealing parameters. Fraunhofer IWU research scientist Christer-Clifford Schenke: “Our goal is to produce ten packages per minute on the pilot system by the end of the project in September 2026.”

Presentation at Interpack 2026

The practical, modular demonstrator shows that the process can be integrated into existing production processes in the future. Both the laser module and the sealing tool can be implemented separately in production. This makes the process especially attractive for packaging machine manufacturers, packaging material producers and packagers. The integration of PAPURE technology enables companies in this industry to position themselves as pioneers in the field of “green packaging.” Together with interested companies from the packaging and food industries, as well as paper manufacturers and mechanical engineering firms, the project partners intend to further develop the plant for large-scale production. Fraunhofer researchers will be presenting the potential applications of this technology and showing how the system works at the Interpack 2026 trade show from May 7 to 13 in the Technology Lounge of the German Machinery and Equipment Manufacturers Association (VDMA) in Düsseldorf (Hall 4, Booth C54).