One effective strategy to improve the barrier performance of polymeric coating layers is the incorporation of layered silicate particles. This study investigates how the drying technology of silicates—specifically freeze-drying versus oven-drying—affects the permeation properties of the coatings. Modified layered silicates, prepared using both drying methods, are incorporated in varying amounts into polyimide coatings. The arrangement, orientation, and exfoliation of the particles are analysed using SEM. Results indicate that a higher proportion of layered silicates enhances the tortuosity of the diffusion pathway, thereby reducing permeability. Furthermore, permeation measurements of oxygen and water vapor, along with the calculated activation energies, reveal distinct differences in the permeation mechanisms of these gases through the coating films, highlighting the significant impact of the drying method on the barrier properties of the coatings.

The development of bio-based adhesives that complement crop-derived materials is essential for advancing circular bioeconomy value chains. This work presents a temperature-optimized process for extracting keratin from duck feathers-an abundant, underutilized biowaste-and its application as a renewable adhesive for wood. Keratin was obtained via ultrasound-assisted alkaline hydrolysis (25-85 degrees C) followed by acidic precipitation. Structural, thermal, and mechanical analyses revealed that processing temperature is the main factor influencing disulfide bridge regeneration, a key feature in adhesive performance. Unlike synthetic systems that rely on artificial aromatic disulfide bonds, this study demonstrates intrinsic control of disulfide re-networking in natural keratin, offering a green and dynamic alternative for high-performance adhesives. The optimal results were achieved at a hydrolysis temperature of 75 degrees C (KA75), yielding the highest tensile shear strength (10.16 MPa), surpassing the minimum requirement for indoor wood bonding and approaching the performance of polyvinyl acetate (PVAc) adhesives under lap shear test conditions. Raman spectroscopy confirmed the correlation between disulfide bond regeneration and adhesive strength. At the same time, thermal analysis revealed stability up to similar to 200 degrees C, and enhanced flame-retardant properties, enabling hot-press processing, debonding on demand, and recycling-features aligned with the principles of the circular bioeconomy. Overall, this study demonstrates that controlled hydrolysis can induce intrinsic disulfide re-networking in natural keratin, creating a dynamic covalent adhesive system without toxic additives. The combination of high performance, renewable sourcing, and recyclability positions temperature-optimized feather keratin adhesives as a viable alternative to synthetic wood adhesives. This approach demonstrates how agricultural residues from animal processing can be integrated into industrial-crop value chains, expanding the portfolio of sustainable bio-based adhesives for wood applications.

Marine organisms colonize all water-contacting surfaces. The accumulation of these organisms, known as biofouling, on ship hulls can increase fuel consumption by up to 45%, causing higher emissions. Remedy is offered by nonbiocidal fouling-release (FR) coatings, which weaken the adhesion between organisms and surfaces, enabling removal by hydrodynamic forces or gravity. This study investigates the FR performance of biocide-free polyurethane, polyurea, and silicone-based systems in relation to their Young's modulus. The rationale is to better understand the influence of Young's modulus across different polymer classes. Within these classes, Young's modulus varies in a narrow range (0.2-2.2 MPa) to study its effect on FR behavior. In polyurethane and polyurea systems, modulus adjustments are made by altering resin-to-hardener ratios, affecting crosslink density. Coatings underwent static immersion in the North Sea, and FR performance is monitored monthly. After 15 weeks, samples are cleaned with a high-pressure water jet. Compared to a hard reference system, all soft coatings exhibit FR performance identical to Intersleek 1100 SR after full immersion period and cleaning, highlighting the importance of mechanical softness for effective fouling release.

This study reveals temperature-dependent pathways in the regeneration of keratin from duck feathers via ultrasound-assisted alkaline hydrolysis, establishing direct links between molecular transformations and resulting material morphologies. By systematically varying the hydrolysis temperature from 25 degrees C to 85 degrees C, we identify a critical threshold around 55 degrees C that governs keratin's unfolding and refolding behavior. At lower temperatures (<= 55 degrees C), keratin retains its native disulfide linkages and regenerates into fibrous structures resembling feather morphology. Above this threshold, extensive cleavage and reformation of disulfide bonds induce supramolecular reorganization, yielding uniform keratin microspheres with enhanced thermal stability and distinct Raman signatures. Comprehensive characterization (ATR-IR, Raman, solid-state NMR, XRD, SEM, TGA, DSC) provides unprecedented insights into how temperature and sonochemical activation modulate protein structure at both molecular and mesoscopic scales. These findings establish a chemistry-based design principle for tailoring keratin into functional biomaterials with tunable properties, enabling scalable and sustainable approaches to bioplastics, composites, and biointerfaces.

Soft polyurethane fouling-release coatings are modified with synthesized mPEG-305, a hydrophilic PEG-based additive, and a commercially hydrophobic PDMS-based additive by click chemistry to generate hydrophilic and hydrophobic surface domains. Sessile drop contact angle measurements reveal polarity gradients ranging from triangle theta = -32 degrees to triangle theta = 120 degrees. AFM and SEM demonstrate successful additive incorporation (hydrophilic and hydrophobic additive addition of 2.5-20 mol% and 5-15 mol%) and the formation of two-phase systems with microstructures, including spherical hydrophobic and characteristic "wrinkled" morphologies. Captive bubble contact angle measurements of systems with "wrinkled" microstructures indicate dynamically hydrophilic behavior, with contact angle changes of up to 15 degrees over 33 days of immersion in demineralized water. Static immersion tests in the North Sea (Helgoland) for 18 weeks demonstrate enhanced bio-repulsivity, with LoF values decreasing from 4 to 2-3 for systems with the strongest polarity gradient (triangle theta = 112 degrees-120 degrees), additive contents of 5-10 mol%, dominant wrinkled microstructures with pronounced stiffness (5 mPa) and topographical (100 nm) gradients, and dynamically hydrophilic contact angles changes of 15 degrees. This highlights the critical influence of polarity gradients, microstructural heterogeneity and dynamic hydrophile behavior on the bio-repulsivity of polyurethane coatings.

As an alternative to current commercially available fossil-based raw materials used in hot-melt adhesives, starch is attractive due to its broad availability. In addition, it is a bio-based and renewable raw material. However, starch could not be used in hot-melt adhesives without the ability to melt at a dedicated temperature without thermal decomposition. To overcome the physical interactions between the starches OH-groups, starch esters were synthesized with fatty acids having chain lengths from C5 to C18, together with propionic anhydride. They were synthesized to achieve thermoplastic behavior with suitable cohesion, thermal stability and crystallinity to be applied in hot-melt adhesives. FTIR and NMR confirmed formation of co-esters with propionic and fatty acid hydrocarbon chains. The degree of substitution ranged from 2.26 to 2.99 from a theoretical maximum of 3. By fatty acid chain length variation glass transition temperature, melting behavior, viscosity and modulus could be varied. For the preparation of hot-melt adhesives tackifier resins and wax, which are also bio-based, were added, similar to formulation of synthetic hot-melt adhesives. Lap-shear testing of the obtained hot-melt adhesive formulations on beech wood confirms that with these bio-based formulations an adhesion performance close to certain synthetic reference adhesives can be obtained. The resulting performance depends on the specific fatty acid combination used. It was obtained that short-chain esters contribute to higher tensile and lap-shear strength, while starch esters with long alkyl chains (e.g., myristate or oleate) lead to ductile materials with higher elongation at break.

Biobased benzoxazine monomers derived from sesamol and monofunctional amines with aromatic side groups were synthesized to study the influence of aromatic side groups on the thermomechanical properties. Furfurylamine is a typical component for biobased benzoxazines and is known to influence the thermomechanical properties of the benzoxazine polymers by increasing the cross-linking density. In this study, the effect of amines similar to furfurylamine on the thermomechanical properties has been investigated. Differential scanning calorimetry analysis was used to analyze the impact of the aromatic side groups on the melting temperature of the monomers, with the pyridine side group having the lowest melting point and onset temperature. All monomers showed cross-linking capabilities to various degrees. Thermogravimetric analysis revealed the thermal stability of the polymers up to 260 °C with less than 5% weight loss and a good char yield of at least 44%. Microcombustion calorimetry data revealed that the peak and total heat release rates decreased with different aromatic side groups, with sesamol furfurylamine-based benzoxazine exhibiting the lowest values. Dynamic mechanical analysis results showed that the furfurylamine and aniline-based polymers exhibited high glass transition temperatures of 220 and 180 °C, respectively. In contrast, the benzylamine-based polymer was mechanically weak and the pyridine-based polymer was extremely brittle, preventing mechanical measurements for these systems. All in all, this study presents various alternatives for furfurylamine, offering promising cross-linking capabilities and subsequent thermomechanical properties.

Non-isocyanate polyurethanes (NIPUs) are a promising and environmentally sustainable alternative to conventional polyurethanes (PUs). In the present study, a multifunctional cyclic carbonate was obtained from bio-based epoxy precursor via cycloaddition reaction with CO2. These cyclic carbonates were subsequently utilized in the synthesis of poly(hydroxy urethane)s (PHUs) through polyaddition reactions with a series of diamines. A systematic investigation was conducted to evaluate the influence of diamine structure, especially chain length and presence of aromatic or aliphatic units, on the physicochemical properties of the resulting PHUs, such as water uptake, glass transition temperature (Tg), elastic modulus (E- modulus), hardness, dimensional stability in water, and adhesion properties on different substrates. Furthermore, by adjusting the stoichiometric ratio between cyclic carbonate and amine functionalities, an adhesive formulation was optimized and the resulting adhesive exhibited excellent adhesion performance across various substrates, with notably high bonding strength on stainless steel, thereby highlighting the potential of NIPU-based adhesives for industrial applications.

Adhesives that enable debonding on demand through an external trigger are of great interest for the recycling and repair of bonded components. Among the various external stimuli that enable debonding, heat-induced debonding is particularly popular as it can be easily implemented in many applications. However, thermally activated debonding poses a particular challenge for polysiloxanes (silicones), as they lose their characteristic temperature resistance if the decomposition temperature is too low, whereas the debonding process requires too much energy if extensive heating to high temperature is required. In this work, moisture-curing crosslinkers based on an azodicarbonamide structural motif are used to enable the thermal decomposition of polydimethylsiloxane (PDMS) based adhesives. The crosslinkers decompose readily above 200 °C, thus cleaving the polymer network while simultaneously causing vigorous gas release, which in combination leads to foaming of the PDMS. In this way, the advantages of debonding by gas release and by decomposition of the polymer network are combined. Crosslinker content and debonding temperature are optimized, and the influence of the crosslinkers functionality on mechanical and debonding properties are investigated. An increase in the number of crosslinkable groups improves the mechanical properties and adhesive strength, while the debonding ability deteriorates as a higher crosslink density counteracts the foaming of the silicone. A decline in the silicone's tensile strength of up to 95% and in its tensile lap shear strength on glass by up to 94% can be achieved upon heating to 300 °C for 5 min or 10 min, respectively, enabling quick and simple debonding.

Freeze-drying of layered silicates modified with dodecylamine (DDA) is a highly effective technique for the preparation of barrier pigments that significantly mitigate the permeation of oxygen, water vapor, and hydrogen through polymer films containing these particles. In contrast to oven-dried modified silicates, the delamination of the particles is markedly enhanced. Additionally, the solvent used in the coating preparation is critical to the delamination and exfoliation processes. By applying Hansen solubility parameters, it is feasible to predict suitable solvents that facilitate these processes. The concentration of DDA employed for silicate modification influences the morphological characteristics of the particles. A maximum interlayer spacing of 2.15 nm is attained at a silicate-to-DDA weight ratio of 2.25:1. The permeation rates of oxygen, water vapor, and hydrogen through coatings devoid of particles, as well as those containing varying amounts of oven-dried and freeze-dried clay particles, are systematically investigated. The permeation is found to be minimal in systems incorporating freeze-dried particles, with a notable reduction by four orders of magnitude observed when compared to the coating without any filler. Notably, for hydrogen, even low concentrations (0.1-2%) of modified layered silicates also lead to a reduction of permeation by up to four orders of magnitude.

This work aimed to investigate the adhesive properties of polysiloxanes (silicones) on polymer surfaces in relation to their acid-base properties. To adjust the acid-base properties of polydimethylsiloxane (PDMS) based formulations, (3-aminopropyl)-trimethoxysilane (AMMO) and [(3-triethoxysilyl)-propyl]succinic anhydride (SAS) were added as silane coupling agents. The acid-base properties of the resulting formulations were investigated by measuring the isoelectric point (IEP) via zeta potential measurements as well as by measuring the contact angle on cured samples with probe liquids of different pH. The IEP could be increased gradually from 5.7 to 9.3 by addition of AMMO and decreased gradually from 5.7 to 2.7 by addition of SAS. The adhesion to various polymers was determined by tensile lap shear strength measurements on HDPE, PET, PMMA, PVC and PA as well as on glass. Silicones containing AMMO showed a higher shear strength on all polymers compared to the acidic SAS containing silicones. The IEP leading to maximum shear strength depends on the respective polymer surface, which makes the adjustment of the acid-base properties a useful tool for optimizing adhesion. Furthermore, measuring the zeta potential as well as the surface energy of the substrate surfaces revealed significant differences in their polarity. In addition, an approximately linear increase of the maximum shear strength measured on each substrate could be observed with increasing zeta potential of the substrate at pH 9.7. These findings show that zeta potential measurements of both adhesive and substrate have the potential to be a powerful tool for predicting adhesive interactions.

Benzoxazine/polyetheramine-based vitrimers are synthesized through the polymerization of bisbenzoxazine in the presence of polyetherdiamine, resulting in aminoalkylated phenols that are capable of engaging in nucleophilic substitution-like covalent amine exchange reactions. To examine the effect of benzoxazine's molecular structure on these reactions, seven model monobenzoxazines with varying electronic properties and substituent configurations were synthesized and reacted with a polyether monoamine. This study found that the molecular architecture of benzoxazine significantly impacts the rate and outcome of the ring-opening reaction and the benzoxazine/amine reaction. Notably, N-phenyl benzoxazines facilitate the formation of vitrimer-analogous polyether-aminoalkylated phenols, essential for the amine exchange reaction, whereas N-cyclohexyl benzoxazines do not undergo this reaction and are unsuitable for vitrimer formation. Additionally, electron-deficient benzoxazines demonstrate higher reaction rates in both the benzoxazine/amine and amine exchange reactions. This research highlights the crucial role of the benzoxazine structure in determining the efficiency and feasibility of the formation of dynamic vitrimer systems.

The potential of aminoterminated hyperbranched polyglycerol (hPG-NH2) crosslinked by polyethylene glycol dialdehyde (DA) hydrogel as a bone adhesive is presented in this proof-of-concept study. The hydrogel system, crosslinked by Schiff base bonds, is designed to degrade hydrolytically when applied internally. To elaborate the relationship between the crosslinker length and the material properties, three different DAs with different molecular masses were used, as well as glutaraldehyde, and also blends of those components. It was shown that the hydrogel's properties could be adjusted by application of these aldehydes and their mixtures. In general, the gelation time decreases with lower molecular mass of the dialdehyde crosslinker, whereas the gel strength increases. The hydrogel model adhesives lead to a bond strength of up to 800 kPA on bone substrates.

This study investigates the potential of keratin, a waste from duck feathers, as a sustainable alternative for wood adhesive applications. Keratin was extracted by sonochemical hydrolysis, a green and innovative method. Keratin was compared in its properties with casein, soybean, and pea proteins, three of the most studied proteins, as alternative eco-friendly materials to petroleum-derived products. However, these proteins remain used in the food industry. Protein-based adhesives were activated with sodium and calcium hydroxide. A comprehensive analysis was also conducted to study the influence of solid content, alkali, pH, viscosity, polarity, and structural composition of adhesives on their mechanical properties. The thermal properties of proteins and adhesives and the effects of post-alkaline treatment on protein secondary structure, crosslinking, and water resistance were studied. The key finding is that keratin shows potential as an eco-friendly adhesive, with tensile shear strength tests on beech wood meeting European standards. In addition, it showed superior water resistance due to its effective crosslinking ability compared to other food-derived proteins. The results position keratin as a feasible replacement for food-derived and formaldehyde-based adhesives, offering a sustainable option for interior wood applications and presenting an environmentally friendly solution with appropriate performance.

Pressure-sensitive adhesive tapes are used in automotives, railway vehicles and construction, where flame retardancy is of major importance. This is why industrial applicants often buy, and industrial tape manufacturers often produce, flame-retardant adhesive tapes, advertised for their good flammability characteristics. Yet, how flame-retardant tapes influence the fire behavior of bonded materials is a rather open question. To investigate this issue, three different substrates were bonded, using eight double-sided adhesive tapes containing two different carriers and two different flame retardants. The bonded substrates were compared to their monolithic counterparts in terms of flammability, fire behavior and fire stability. The fire behavior of adhesive tape bonded materials differed significantly from the monolithic substrates. The usage of different adhesive tapes let to different burning behavior of the bonded materials mainly due to different carrier systems. In contrast, the implementation of flame retardant into the adhesive had rather minor or no effect on the burning behavior of the bonded substrates despite their positive effect on the flammability of the free-standing tape. The carrier changed the HRR curve in the cone calorimeter and was able to both, reduce and increase fire hazards. Using the carrier with the better fire performance can lower the fire growth rate by 20

Fixation of carbon dioxide is a key issue for the sustainable synthesis of chemical compounds. A catalyst system for the preparation of cyclic carbonates by the fixation of carbon dioxide (CO2) onto epoxides is presented. This system is designed for easy application due to the availability of the compounds on an industrial scale as well as moderate reaction conditions. Notably, it avoids the use of metal-halogen catalysts and instead employs a tertiary amine as the catalytic center, in conjunction with an alcohol acting as a hydrogen bond donor (HBD). The kinetics of the cycloaddition reaction between epoxides and CO2 were thoroughly investigated using IR spectroscopy. Remarkably, optimization of the amino-to-alcohol group ratio and the amine structure was carried out to enhance the overall performance of the catalyst system showing a synergistic effect between the tertiary amine and the hydroxyl. Most notably, this entire process is conducted without the use of solvents and operates at ambient pressure, underscoring its significant ecological advantages.

Pressure-sensitive adhesive tapes are used in several industrial applications such as construction, railway vehicles and the automotive sector, where the burning behavior is of crucial importance. Flame retarded adhesive tapes are developed and provided, however, often without considering the interaction of adhesive tapes and the bonded materials during burning nor the contribution of the tapes to fire protection goal of the bonded components in distinct fire tests. This publication delivers an empirical comprehensive knowledge how adhesive tapes and their flame retardancy effect the burning behavior of bonded materials. With a special focus on the interaction between the single components, one flame retarded tape and one tape without flame retardant are examined in scenarios of emerging and developing fires, along with their bonds with the common materials wood, zinc-plated steel, mineral wool, polycarbonate, and polymethylmethacrylate. The flame retardant significantly improved the flame retardancy of the tape as a free-standing object and yielded a V-2 rating in UL 94 vertical test and raised the Oxygen Index by 5 vol.%. In bonds, or rather laminates, the investigations prove that the choice of carrier and substrates are the factors with the greatest impact on the fire properties and can change the peak of heat release rate and the maximum average rate of heat emission up to 25%. This research yielded a good empirical overall understanding of the fire behavior of adhesive tapes and bonded materials. Thus, it serves as a guide for tape manufacturers and applicants to develop tapes and bonds more substrate specific.

Pressure-sensitive adhesive tapes are used in a variety of applications such as construction, aircrafts, railway vehicles, and ships, where flame retardancy is essential. Especially in these applications, phosphorus-based flame retardants are often chosen over halogenated ones due to their advantages in terms of toxicity. Although there are pressure-sensitive adhesives with phosphorus flame retardants available on the market, their flame-retardant modes of action and mechanisms are not entirely understood. This research article provides fundamental pyrolysis research of three phosphorus-based flame retardants that exhibit different mechanisms in a pressure-sensitive adhesive matrix. The flame-retardants modes of action and mechanisms of a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivate, an aryl phosphate, and a self-synthesized, covalently bonded DOPO derivate (copolymerized) are investigated. The blended DOPO derivate is volatilized at rather low temperatures while the covalently bonded DOPO derivate decomposes together with the polymer matrix at the same temperature. Both DOPO derivates release PO radicals which are known for their flame inhibition. The aryl phosphate decomposes at higher temperatures, releases small amounts of aryl phosphates into the gas phase, and acts predominantly the condensed phase. The aryl phosphate acts as precursor for phosphoric acid and improves the charring of the pressure sensitive adhesive matrix. All flame retardants enhance the flammability of the adhesives depending on their individual mode of action while the covalently bonded flame retardant additionally improves the mechanical properties at elevated temperatures making it a promising future technology for pressure-sensitive adhesives.

Abstract Organically modified layered silicates can be used as barrier pigments in organic coating systems to reduce the permeation of water vapor and gases, e.g., oxygen as well as harmful gases that promote corrosion. Unmodified layered silicates are not sufficient to reduce the permeation significantly. However, the arrangement and orientation of the particles have an enormous impact on the later performance in the barrier film. In organic solvents or non‐aqueous polymer matrices the non‐modified layered silicates cannot exfoliate adequately. The organic modification influences the layer spacing and the compatibility to organic solvents. Layered silicates are modified with dodecylamine to enhance the spacing layer. The spacing layer is enhanced by 55% caused by the organic modification as it is commonly known. In contrast to previous work freeze drying of the organically modified layered silicates improved the particle distribution and by this barrier properties significantly. The modified particles reduce the diffusion of water and oxygen by ≈99.6% and 97.2%, respectively. The corrosive gas test of electronic circuit boards shows no growth of dendrites and no failure of the electronics in contrast to protective coating without the layered silicates.

Formation of a Schiff base crosslinked hydrogel based on hyperbranched aminoterminated polyglycerol and polyethylene glycol dialdehyde and a first insight on its mechanical properties.