Kategorie: ‘Publication’
New Publication: From Shell Waste to Strong Wood Glue: The Future of Bio-Based Adhesives
Sustainable adhesives are becoming increasingly important, especially in applications where petrochemical resins containing problematic substances such as formaldehyde still dominate. Our latest study now shows that chitosan-based wood adhesives are a promising bio-based alternative. Chitosan is derived from chitin, a natural polymer found, among other sources, in the shells of crustaceans and generated in large quantities as a by-product of the food industry.
Two fully bio-based adhesive systems were investigated: chitosan itaconate and chitosan maleate. Both are based on renewable raw materials and were specifically developed for wood bonding. What is particularly interesting is that the acids used not only solubilize the chitosan, but also enable curing into a stable network. Both acids can be obtained via biofermentation, making the adhesive system entirely bio-based.
The results are remarkable: in the dry state, both adhesives met the requirements of DIN EN 12765 class C1 and exhibited so-called cohesive wood failure. This means that under mechanical stress, it was not the adhesive bond that failed, but the wood itself. Chitosan itaconate, in particular, also performed well under wet conditions: after treatment in boiling water, its bond strength remained at 2.7 N/mm², close to the demanding C4 class.
Chitosan itaconate is therefore a promising candidate for wood bonding applications requiring moderate moisture resistance, such as interior construction or semi-exposed uses. Chitosan maleate also showed good dry adhesion, but lost significant stability upon contact with water.
In conclusion, bio-based wood adhesives made from chitosan are far more than a niche concept. Chitosan itaconate in particular combines renewable raw materials with convincing adhesive performance and could represent an important step toward more environmentally friendly materials in the wood industry.
N. Münstermann, O. Weichold
Chitosan-itaconate and chitosan-maleate as fully bio-based sustainable wood adhesives
International Journal of Adhesion and Adhesives, 2026, 149, 104327 https://doi.org/10.1016/j.ijadhadh.2026.104327
New publication: Moisture absorption in cationic hydrogels
We are delighted to present another study by our working group in the specialist journal Polymers. In their latest publication, Tim Mrohs and Oliver Weichold show how the water absorption behaviour of diallylammonium-based hydrogels can be specifically controlled by cross-linking density and ionic interactions. The results provide design rules for moisture control, demonstrate endothermic sorption processes and shed light on how reversible ionic crosslinks can improve water absorption.
Mrohs, T.; Weichold, O.
Dynamic water vapour sorption behaviour of crosslinked polycationic diallylammonium-based hydrogels
Polymers 2025, 10.1016/j.polymer.2025.129219
New publication: Self-foaming polyester resin systems
We are pleased to once again present a study by our working group in the journal Polymers. In their current publication, Fabian Weitenhagen and Oliver Weichold present an innovative modular system for the production of bio-based polyester foams in which the reaction water itself serves as a blowing agent – without any external additives. The work shows how a versatile foam system can be developed through the targeted selection of bio-based dicarboxylic acids and various polyols. By systematically varying these building blocks, mechanical properties such as hardness, density, thermal conductivity and thermal stability can be flexibly adapted. Particularly noteworthy are the significantly improved fire properties compared to many organic materials.
A particular highlight of the work is the scanning electron microscope (SEM) images, which provide a detailed insight into the internal structure of the foams. Compact cell walls without microporosity become visible, whereby the pore structure is specifically influenced by the varying densities.
SEM images of polyester resin foams with low (A) and higher (B) density.
Weitenhagen, F.; Weichold, O.
Preparation, Reaction Kinetics, and Properties of Polyester Foams Using Water Produced by the Reaction as a Foaming Agent.
Polymers 2025, 17, 1266. https://doi.org/10.3390/polym17091266
New publication: Self-crosslinking chitosan hydrogels with carboxylic acids
We are pleased to announce a new publication from our research group in the journal Gels. In this study, Nils Münstermann and Oliver Weichold investigated the conditions under which chitosan forms stable hydrogels without additional crosslinkers.
The formation of self-crosslinking chitosan hydrogels using simple carboxylic acids alone is severely limited. Although viscous solutions can be produced with dicarboxylic acids such as oxalic, malonic or succinic acid, stable gels cannot. Stable ionic hydrogels can only be produced by specific chemical modifications such as N-carboxyalkylation or N-succinylation. The length and flexibility of the alkyl spacer and the presence of a covalent bond are crucial for gel formation and mechanical strength. N-carboxypropylchitosan in particular forms very strong gels with low swelling, while shorter side chains produce weaker gels.
Münstermann, N.; Weichold, O.
On the Conditions Determining the Formation of Self-Crosslinking Chitosan Hydrogels with Carboxylic Acids,
Gels 2025, 11(5), 333. https://doi.org/10.3390/gels11050333
Contributions to our publication: Fire-retardant wood coating
The publication “Fire-retardant Coating For Wood Made From Chitosan Itaconate” is internationally recognised by an article in the Italian trade journal Pitture e Vernici – European Coatings (Issue 1/2025, page 36) and by a web post by European Coatings entitled “A fire-retardant coating for wood made from chitosan itaconate” – News and insights for the European coatings industry. The chitosan itaconate glaze is transparent, emphasises the natural wood grain and renders the surface water-repellent. It reliably protects the wood from moisture, prevents UV-induced greying and efficiently reduces the burning rate. With just two applications on spruce and three on beech wood, the glaze is self-extinguishing. Find out more.
This bio-based approach combines resource conservation with effectiveness and demonstrates how environmental preservation and safety requirements can be successfully combined. It fills us with joy and appreciation to see that our work is attracting greater attention.
Pitture E Vernici: Fire-retardant Coating For Wood Made From Chitosan Itaconate, Fascicolo 1/Gennaio – Febbraio 2025 – Pitture e Vernici, https://www.pittureevernici.it/archivio/archivio-2025/fascicolo-1-gennaio-febbraio2025/.
European Coatings: A fire-retardant coating for wood made from chitosan itaconate – News and insights for the European coatings industry, https://www.european-coatings.com/news/application-areas/a-fire-retardant-coating-for-wood-made-from-chitosan-itaconate/.
Joint publication:Plant protection from insect larvae
The black soldier fly (Hermetia illucens) not only offers a sustainable source of protein, but also the potential to extract chitosan – a versatile biopolymer – from the larval skins. A joint study with the research group led by Dr. Sabine Gruber from the University of Innsbruck and the FH Campus Vienna shows how biological waste from BSF production can be processed into bioactive chitosan using environmentally friendly enzymatic processes. This chitosan has strong antifungal properties and improves the germination and disease resistance of plants such as sugar beet. It therefore offers an environmentally friendly alternative to chemical fungicides and chitosan, which is obtained from crescent shells. This innovation underlines the potential of the insect industry to make good use of waste and create sustainable solutions for agriculture and industry.
C. Escobar Rodríguez, V. Zaremska, T. Klammsteiner, I. Kampatsikas, N. Münstermann, O. Weichold, S. Gruber
Chitosan obtained from black soldier fly larval cuticles expands the value chain and is effective as a biocontrol agent to combat plant pathogens
Carbohydrate Polym. 2025, 349, Part B, 123023 https://doi.org/10.1016/j.carbpol.2024.123023
New publication: Fire-retardant wood coating
Wood is currently experiencing a renaissance in the construction and furniture industry. With its natural charm, versatility and environmental friendliness, wood is a popular building material. However, this natural material is susceptible to external influences such as moisture, UV radiation, stains and, above all, fire. Fire in particular poses a major risk in the construction industry due to the easy flammability of wood. Once ignited, untreated wood often burns down completely without any external heat supply. N. Münstermann and O. Weichold have now developed an innovative, sustainable wood coating based on polymerized chitosanitaconate. The basis of the coating, chitosan, is a residual product from the food industry and itaconic acid can be obtained biotechnologically. The coating is therefore made entirely from bio-based materials and not only offers protection against moisture, UV radiation and stains, but is also non-flammable. When applied to wood, it delays ignition and significantly inhibits the spread of flames. Just one coat reduces the burning rate by a third. Two coats on spruce wood are enough to make the material self-extinguishing. Three layers are required for hardwoods such as beech. This bio-based approach combines resource conservation with high effectiveness and shows that environmental protection and safety requirements can go hand in hand.
N. Münstermann, O. Weichold
A fire-retardant coating for wood made from chitosan itaconate
Progress in Organic Coatings 2024, 197, 108793 https://doi.org/10.1016/j.porgcoat.2024.108793
New publication:Approaches to upscaling alkaline gels as particles
Highly alkaline hydrogels are becoming increasingly important in building materials research. We have been able to show repeatedly that cationic alkaline hydrogels based on diallyldimethylammonium hydroxide (DADMAOH) in particular can be used effectively to seal water-bearing cracks or as coupling media for electrochemical chloride extraction. Upscaling is a challenge, as commercial cation-selective membranes have proven to be less effective here. On the other hand, neutral gels and gel particles can be easily prepared from diallyldimethylammonium chloride (DADMAC) in large quantities and with a wide range of compositions. Here it is shown that these neutral gel particles can be converted into DADMAOH particles with residual halide contents of <0.3 % by means of inverse static anion exchange in NaOH solution. The physical and chemical properties of the alkaline particles correspond to those of the alkaline gels and fulfill all necessary requirements for building material applications, but are much easier to produce.
T. B. Mrohs, O.Weichold
A Simple Preparation of Crosslinked, Highly Alkaline Diallyldimethylammonium Hydroxide Hydrogel Particles via Inverse Static Anion Exchange
Gels 2024, 10, 743. https://doi.org/10.3390/gels10110743 (open access)
17th ICPIC conference papers reprinted
The articles on the presentations “Ionic Conductive Polyesters-Assessing the Risk of Corrosion in Steel-Reinforced Concrete” by Prof. Weichold and “Alkaline Hydrogels-Multifunctional Materials for Concrete Rehabilitation” by Tim Mrohs (see also entry from 19.9.2023) at the 17th International Congress on Polymer in Concrete (ICPIC 2023) in Warsaw, Poland, have now been published in print.
Weichold, O. (2025). Ionic Conductive Polyesters—Assessing the Risk of Corrosion in Steel-Reinforced Concrete. In: Czarnecki, L., Garbacz, A., Wang, R., Frigione, M., Aguiar, J.B. (eds) Concrete-Polymer Composites in Circular Economy. ICPIC 2023. Springer Proceedings in Materials, vol 61. Springer, Cham. https://doi.org/10.1007/978-3-031-72955-3_34
Mrohs, T., Jung, A., Weichold, O. (2025). Alkaline Hydrogels—Multifunctional Materials for Concrete Rehabilitation. In: Czarnecki, L., Garbacz, A., Wang, R., Frigione, M., Aguiar, J.B. (eds) Concrete-Polymer Composites in Circular Economy. ICPIC 2023. Springer Proceedings in Materials, vol 61. Springer, Cham. https://doi.org/10.1007/978-3-031-72955-3_37
New publication: Wood coating made from biogenic residues
Wood has been a central building material for mankind for thousands of years and is characterised by its bioavailability, sustainability and versatility. Nevertheless, the chemical structure of wood poses a number of challenges. It is susceptible to biological degradation processes, for example by fungi, bacteria or insects, and shows signs of graying due to lignin degradation when exposed to UV radiation. To prevent this, N. Münstermann and O. Weichold have developed an environmentally friendly coating based on chitosan, a biopolymer obtained from food waste.
The newly developed chitosanitaconate coating is transparent, emphasizes the wood grain and gives the wood hydrophobic properties with contact angles of over 90°. It effectively protects the wood from moisture, prevents graying caused by UV radiation and reduces staining caused by coffee or red wine, for example. Thanks to its strong adhesion and adaptability, the coating is highly versatile. By adding pigments, the coating can be adapted to the aesthetic requirements of modern interior design. Chitosanitaconate combines wood protection, modern aesthetics and sustainability – a versatile solution for environmentally friendly construction.
N. Münstermann, O. Weichold
Chitosan itaconate based water- and stain-repellent coatings for wood
Progress in Organic Coatings 2024, 194, 108630 https://doi.org/10.1016/j.porgcoat.2024.108630
