Chemistry for sustainable building materials

The teaching and research area focuses on three central research themes, along with complementary analytical methods, which together form the foundation for innovative developments in the field of polymer materials.

🌱 Biobased Materials:

Nature provides an impressive abundance of materials in large quantities, many of which remain underutilized or entirely unused. Each of these substances exhibits a unique combination of properties, offering significant potential for the development of new materials. Nevertheless, many of these resources are either thermally recovered or disposed of at considerable expense, rather than being sustainably integrated into value chains.

Our research focuses on the development of innovative methods for the feedstock and material utilization of biogenic residues. We concentrate on materials that are produced by nature in large quantities but have so far seen little use as raw materials and do not compete with food production. Our primary sources include poultry feathers, shrimp shells, insect exoskeletons, and grasses. Through targeted chemical processes, these raw materials are fractionated, modified, and further processed to make them economically viable. This not only opens up new application possibilities but also improves the CO₂ balance and supports the transition toward a society based on renewable resources.

One example of the efficient utilization of biogenic residues is the use of chitosan, which is derived from waste streams of the food industry. We have successfully demonstrated the use of chitosan for the coating and bonding of wood. Wood is experiencing a renaissance due to growing environmental awareness, yet it requires protection against moisture, UV radiation, and contamination. In addition to providing protection against moisture and UV radiation, our chitosan itaconate coating also enhances fire resistance. Untreated wood typically burns completely once ignited, even without a continuous external heat source. In contrast, our new coating makes the wood more resistant to flames. A single layer of the coating reduces the burning rate by one third, while multiple layers enable the wood to self-extinguish once the external flame is removed. As an adhesive, our chitosan formulation easily achieves the strength of commercial wood glues, and the bonded joints remain stable even under elevated moisture exposure.

Another example is our work with protein hydrolysates derived from poultry feather waste for the production of flame-retardant fiberboards. Wood fibers impregnated with these proteins exhibit a significantly reduced decomposition rate in the temperature range of 300 to 450 °C, as determined by thermogravimetric analysis. The final combustion phase of the impregnated fibers is shifted by approximately 50 °C to the range of 450 to 500 °C and proceeds gradually, rather than occurring abruptly as in untreated wood.

Even at a protein content of around 10 wt%, fiberboards produced via the wet process are self-extinguishing and show only minimal afterglow. In three-point bending tests, these boards withstood stresses of up to 15 N/mm², meeting the requirements of the DIN EN 622 standard for commercial, formaldehyde-bonded fiberboards. This demonstrates that the recycled protein hydrolysates not only exhibit remarkable flame-retardant properties but can also serve as a fully sustainable binder for a new generation of eco-friendly fiberboards. As these boards consist exclusively of natural materials, they can be shredded and composted after use.

Contact: Nils Münstermann, Paul Marten, Fabian Weitenhagen, Lena Schmitz

Category: Chitosan, Keratin, Polykondensationsharze

💧 Gels:

The preservation and rehabilitation of existing structures represent a key challenge in modern construction. Conventional methods often require invasive intervention in the building fabric and involve substantial material use as well as high costs. Hydrogels—three-dimensional, water-swellable polymer networks—offer a resource-efficient alternative. They are highly adaptable and are already being successfully applied in industry.

In addition to moisture regulation, hydrogels are also suitable for the rehabilitation of reinforced concrete, which can be damaged by carbonation and chloride ingress. Highly alkaline hydrogels provide an innovative approach, as they remove carbonate ions from the pore structure via ion-exchange mechanisms and replace them with hydroxide ions, thereby restoring the original alkaline protection of the concrete. Their electrical conductivity also makes them suitable as a coupling medium for electrochemical processes such as electrochemical chloride extraction (ECE). By precisely tuning their rheological properties, they can be applied to vertical surfaces, within cavities, or in fine cracks without uncontrolled runoff. Another advantage lies in their reversibility: once the rehabilitation process is complete, the gels can be removed from the surface without leaving any residue.

Current research projects focus on precisely controlling ionic exchange processes in order to further enhance the efficiency of hydrogels in structural preservation. In addition, efforts are being made to optimize their water vapor and moisture sorption properties for different climatic conditions. Another key objective is the development of scalable manufacturing and application processes to enable the economically viable use of hydrogels in large-scale industrial applications.

The integration of hydrogel technologies into the construction sector opens up new possibilities for sustainable structural preservation and rehabilitation. The targeted modification of their chemical and physical properties allows for flexible adaptation to specific applications, thereby creating new perspectives for the resource-efficient management of existing structures.

Contact: Prof. Oliver Weichold

Category: Gels

⚡ Ion-Conductive Polymers:

Electrically and ionically conductive polymer materials based on polyethylene glycol and lithium salts play a central role not only in the energy sector but also hold significant potential in the construction industry. Their electrical properties form the foundation of our application-oriented material development, with a current focus on electrochromic detectors and polymer-based sensors for the detection of reinforcement corrosion in concrete.

Within the research focus “Ionically Conductive Polymers,” our primary work as chemists lies in the field of preparative and applied polymer chemistry. We employ methods of “classical” chemical structure elucidation, such as NMR, IR, and DSC. In addition, we utilize typical electrochemical and electronic measurement techniques, including impedance spectroscopy (EIS) and cyclic voltammetry. In the spirit of interdisciplinary technology transfer, we translate chemical principles into solutions for engineering challenges, thereby making a significant contribution to the advancement of a solution-oriented strategy portfolio.

Contact: Prof. Oliver Weichold

Category: Ion-Conductive Polymers

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