Side streams from wheat processing, such as the bran and gluten fractions, show great potential as a feedstock for the production of novel food ingredients and materials. In this study, we prepared hybrid polysaccharide-protein hydrogels via enzymatic crosslinking of wheat bran arabinoxylan and gluten fractions. Arabinoxylan was first isolated from wheat bran via subcritical water extraction, which preserved the covalently bound ferulic acid moieties to the arabinoxylan core amenable for laccase crosslinking. Gluten was fractionated into its main protein components (glutenin and gliadin) via treatment with aqueous ethanol. Hydrogels with different contents of arabinoxylan and gluten were prepared, demonstrating the integration of the protein fractions within the polysaccharide gel network. Increased addition of gluten led to gradually softer hydrogels, suggesting that the gluten fractions were not involved in the covalent crosslinking with the ferulic acid moieties to any noticeable level. Freeze-drying and regeneration of the hydrogels led to a 3-fold–10-fold increase in the storage and loss moduli, depending on the sample. Analysis of the structure of the hydrogels revealed that the addition of gluten upon enzymatic crosslinking impacted the physical interactions and crystallinity of the arabinoxylan populations, resulting in phase separation of the protein and polysaccharide components. This study demonstrates that tunable hydrogels can be prepared from cereal side streams, with potential as functional plant-based food hydrocolloids with improved nutritional properties, combining dietary fibre and protein components.

The packaging industry's shift towards recyclable mono-materials necessitates high-performance barrier coatings to replace traditional multi-layer structures that do not hinder recycling streams. This study explored the feasibility of mixed oxide (silica-alumina) hybrid coatings, synthesized through an aqueous sol-gel route, as barrier layers on biaxially oriented polypropylene (BOPP) substrates. Alkoxide precursors were reacted in a water-based solution using HCl as the catalyst, and the resulting sols were deposited by rod coating to form optically transparent layers. The incorporation of polyvinyl alcohol (PVA) was critical, producing a homogeneous, crack-free coating that improved the oxygen barrier by a factor of 12. A subsequent two-layer construct with a PVA topcoat was also evaluated. Despite the excellent oxygen barrier, due to the inherent humidity sensitivity of the hydrophilic moieties of PVA, no significant enhancement in water vapor barrier properties was observed. This research demonstrates a method to achieve effective oxygen barriers using an aqueous sol-gel process, thereby reducing reliance on organic solvents and presenting a novel approach for developing hybrid barrier coatings, advancing the design of more recyclable packaging solutions.

Developing biodegradable menstrual products using co-stream proteins as a material alternative to fossil counterparts presents a significant environmental advantage across their entire value chain. The intrinsic properties of wheat gluten foams derived from wheat starch production have been validated with respect to their potential as absorbent core layers in disposable sanitary pads, which is relevant to the rising demand for eco-friendly disposable sanitary pad alternatives. Here, we report the fabrication of a gluten-porous absorbent layer and evaluate its liquid absorption properties and mechanical stability under relevant operating conditions compared to a commercial absorbent foam layer used in sanitary pads. The porosity was achieved using sodium and ammonium bicarbonate, which are non-toxic and food-grade blowing agents, and the materials were shaped/foamed using a conventional oven. The use of sodium bicarbonate resulted in a more homogeneous and lower-density foam with smaller pores than with ammonium bicarbonate. The developed prototypes show comparable mechanical properties under compression to foams used in commercial pads, retaining up to 95% of their initial shape after 3 h of compression. Moreover, the foamed structure permitted a liquid uptake of saline and blood of 4.5 g g−1 and 1 g g−1, respectively, with the possibility to absorb up to 1.5 g g−1 of saline under load. The results indicate that the choice of blowing agent has a large impact on the performance of gluten pads under constant pressure. It is thereby demonstrated here that protein-based foams have adequate mechanical and absorption properties that make them interesting for their future use as the absorbent layer in sanitary products following a circular economy model.

Protein-based foams are potential sustainable alternatives to petroleum-based polymer foams in e.g. single-use products. In this work, the biodegradation, bioassimilation, and recycling properties of glycerol-plasticized wheat gluten foams (using a foaming agent and gallic acid, citric acid, or genipin) were determined. The degradation was investigated at different pH levels in soil and high humidity. The fastest degradation occurred in an aqueous alkaline condition with complete degradation within 5 weeks. The foams exhibited excellent bioassimilation, comparable to or better than industrial fertilizers, particularly in promoting coriander plant growth. The additives provided specific effects: gallic acid offered antifungal properties, citric acid provided the fastest degradation at high pH, and genipin contributed with cross-linking. All three additives also contributed to antioxidant properties. Dense beta-sheet protein structures degraded more slowly than disordered/alpha-helix structures. WG foams showed only a small global warming potential and lower fossil carbon emissions than synthetic foams on a mass basis, as illustrated with a nitrile-butadiene rubber (NBR) foam. Unlike NBR, the protein foams could be recycled into films, offering an alternative to immediate composting.

Fossil-based polymers dominate the packaging industry thanks to their performance and low cost. However, their negative impact on the biosphere demands a paradigm shift in the industry. Nature may provide an alternative in the form of suberin. Suberin is an amorphous polyester present in plants, where it contributes to controlling the water and gas exchange with the environment. The bark is rich in suberin, and it represents a large byproduct of the forestry industry; hence, it is a potential source of renewable monomers for the synthesis of packaging materials. In this study, we demonstrated that unrefined suberin monomers, extracted from birch bark, could be exploited to synthesize a cross-linked polyester film through a standard melt polycondensation and compression molding process. The polyester film resulted in being translucent while blocking UV radiation and having an elastomer-like behavior. The average measured water vapor transmission rate of 2660 g mu m day-1 m-2 was comparable to other polyesters, such as polylactide (1500-2000 g mu m day-1 m-2) and polycaprolactone (2653 g mu m day-1 m-2) at 23 +/- 2 degrees C, with an imposed gradient of 0-50% relative humidity. Finally, the thermal gravimetric analysis showed the absence of any unreacted suberin monomers, and although specific migration tests are required, these suberin-reconstructed polyester films are potential candidates for packaging applications.

Water-soluble polymers are materials rapidly growing in volume and in number of materials and applications. Examples include synthetic plastics such as polyacrylamide, polyacrylic acid, polyethylene glycol, polyethylene oxide and polyvinyl alcohol, with applications ranging from cosmetics and paints to water purification, pharmaceutics and food packaging. Despite their abundance, their environmental concerns (e.g., bioaccumulation, toxicity, and persistence) are still not sufficiently assessed, especially since water soluble plastics are often not biodegradable, due to their chemical structure. This review aims to overview the most important water-soluble and biodegradable polymers, their applications, and their environmental impact. Degradation products from water-insoluble polymers designed for biodegradation can also be water soluble. Most water-soluble plastics are not immediately harmful for humans and the environment, but the degradation products are sometimes more hazardous, e.g. for polyacrylamide. An increased use of water-soluble plastics could also introduce unanticipated environmental hazards. Therefore, excessive use of water-soluble plastics in applications where they can enter the environment should be discouraged. Often the plastics can be omitted or replaced by natural polymers with lower risks. It is recommended to include non-biodegradable water-soluble plastics in regulations for microplastics, to make risk assessments for different water-soluble plastics and to develop labels for flushable materials.

Simple renewable furans can be used to derive various monomer structures for use in polymeric materials. The dimethyl esters of 2,5-furandicarboxylic acid (FDCA), 5,5′-thiodi(2-furoic acid), and 5,5′-sulfonyldi(2-furoic acid) were reacted with diethylene glycol, yielding renewable polyesters with excellent O2 barrier properties and facile chemical recyclability. Glass transition temperatures for the polyesters were 33-70 °C, while thermal decomposition took place at 321 °C or above. Oxygen permeabilities were measured from free-standing films and compared to poly(ethylene terephthalate). The polyesters showed excellent barrier improvement factors (BIFs) of 3.1-6.0 and 5.2-11.0 at 50 and 0% relative humidities, respectively, with the polyester from the sulfide having the highest BIFs, followed by the polyesters of FDCA and the sulfone in an order that depended on humidity. The three polyesters were remarkably easy to chemically recycle under mild conditions. The original dimethyl esters were recovered by filtration after a room temperature reaction with anhydrous methanol and catalytic K2CO3. Monomer yields from film recycling reached as high as 96% for the sulfide-based polyester with high purity.

Fossil-based packaging materials pose significant environmental challenges due to their persistence and carbon footprint, resulting in pollution and long-term climate change. Here we develop bioplastic packaging alternatives (films and trays) from protein-rich microbial biomass with glycerol as the plasticizer. The microbial biomass demonstrated excellent film-forming properties through compression molding, and the final materials exhibited good mechanical properties and excellent gas barrier properties - an average oxygen permeability coefficient of 0.33 cm3 mm m-2 day-1 atm-1 at 50% relative humidity and 23 degrees C. The oxygen barrier properties highlight these microbial biomass materials as a promising, sustainable alternative to fossil-based synthetic films like EVOH, which are widely used in multilayer food packaging. Beyond offering a microplastic-free solution, the protein-rich materials present an opportunity to mitigate microplastic pollution at the end of their lifecycle. The current results position bioplastics based on microbial biomass as a critical step forward in addressing environmental sustainability challenges with current commercial packaging materials.

This study examined the high-temperature stability of polyether ether ketone (PEEK) and polyphenylene sulfide (PPS) in an oxygenated environment. Both polymers were extrusion-coated onto copper wires for electrical insulation in traction motors. Accelerated testing using thermogravimetry and calorimetry showed that copper catalyzed thermal oxidation of PEEK (at very high temperature), which was accelerated by a lower molar mass of the PEEK and an increased copper-polymer contact area. Both techniques indicated a complex thermal oxidation pattern for both polymers. Notably, the presence of copper seemed to reduce/retard the degradation of PPS. Overall, both polymers demonstrated high oxidation resistance at elevated temperature in an air environment, indicating long service life in electric motor, excluding factors like moisture, oil spray cooling and Joule heating.

We here report the properties of polyether ether ketone (PEEK) loaded with hexagonal boron nitride (BN) with and without aluminum nitride (AlN), produced through extrusion compounding and compression molding. The primary purpose of this work was to improve the thermal conductivity of PEEK for electric insulation applications in electric motors. The thermal conductivity, thermal diffusivity, and effusivity increased with filler content reaching maximum values at 30 wt % filler that were a factor of approximately 2, 2, and 1.5 of those of the pure polymer. On a volume content, the ternary system PEEK/BN/AlN was more effective than the binary system (PEEK/BN) in raising the thermal conductivity. By the use of a developed model, it was possible to conclude that a small synergy in terms of thermal conductivity did exist. Density revealed compact systems with a porosity of 0–3%. Scanning electron microscopy revealed a uniform dispersion of BN and a combination of dispersed AlN nanoparticles and agglomerates in the ternary system. Dielectric and breakdown voltage results indicated that the composite properties were acceptable for electric motors, even though the DC breakdown strength decreased in the presence of the fillers.