Hydrogels are classified as a three-dimensional network system, capable of retaining large amounts of water while preserving their shape and dimensional stability. Due to their natural origin and biocompatibility with human tissue, cellulose nanofibrils are often considered to be promising candidates for bioactive hydrogels preparation. For such applications, their responsiveness under different types of mechanical load, including multiple cyclic compressions, is of crucial importance. In the present study, cellulose nanofibril-based hydrogels were initiated though a simple alkali neutralization treatment. Structural, rheological and compressive features were investigated as a function of elevated NaOH concentration and physical gelling conditions. It was found that a sufficiently concentrated alkaline solution allows the formation of mechanically robust cellulose nanofibril hydrogels, which can be dried to the state of ultralight material, aerogel, of low density (0.057 g cm ⁻³), superior porosity (96.2%), super water absorbant capacity (1200%), and exceptional shear and compressive load resilience with elasticity modulus of 9.3 kPa. These outstanding characteristics can be predominantly attributed to the polymorphic conversion of cellulose I to cellulose II, which results from the mercerization of cellulose nanofibrils and creates a stable and firm hydrogels texture.

The utilization and advancement of a wide variety of polymer materials have led to the development of corresponding plastic injection mould steels. This study aimed to enhance the properties of the commercially available steel EN X33CrS16 (1.2085), specifically designed for corrosion-resistant mould bases. To achieve this, the impact of the addition of boron and nitrogen into the commercially available steel grade was examined, focusing on their effects on polishability, workability, and wear resistance. The analysis revealed a martensitic microstructure with moderate segregation in all investigated samples. The steel modification had no discernible impact on hardness, which remained relatively constant. However, the addition of boron and nitrogen significantly reduced polishing time, with boron exhibiting a more pronounced effect compared to nitrogen. Moreover, the inclusion of boron in the alloy resulted in an impressive 40% decrease in the wear rate, while the wear rate of the other investigated alloys remained relatively unchanged.

This study evaluates the industrial-scale feasibility of injection moulding of a recycled polypropylene composite reinforced with recycled fibers derived from an industrial waste stream. Although previous laboratory-scale research has demonstrated the potential of natural fiber-reinforced thermoplastics, their large-scale industrial implementation remains limited due to uncertainties related to processability, reproducibility, and manufacturing robustness. In this work, the composite material is validated through injection moulding trials carried out in four independent industrial companies located in Andalusia (Spain) and three industrial case studies across different industrial sectors in Slovenia, operating under real production conditions. The extrusion process was characterized in terms of process stability, confirming continuous operation with automated dosing and stable material flow without interruptions under industrial conditions. Injection processing parameters, cycle stability, part quality, and defect formations are also considered important when assessing the manufacturing feasibility. The multi-site validation approach enables the evaluation of reproducibility across different injection moulding systems and mould geometries, providing critical insights into the scalability and technological readiness level of recycled natural fiber-reinforced polypropylene composites. Although direct energy consumption measurements were not systematically recorded, the observed processing stability and cycle repeatability indicate a consistent and energy-efficient operation under industrial processing conditions. The results contribute to bridging the gap between laboratory-scale material development and real industrial implementation.

This study addresses the development, thermal characterisation, and dimensional stability of circular composites based on a post-industrial recycled polypropylene (rPP) matrix from household appliances. The matrix was reinforced with natural (B600 and BC300) and recycled (SIS250, PWC500, and ZZC500) cellulosic fibres at 10%, 20%, and 30% dosages, using 3% MAPP as a compatibilizer. Processing was conducted via twin-screw extrusion and injection moulding. Systematic evaluations (TGA-DTG, DSC, and DIL) showed a minor reduction (2.6–5.1%) in thermal degradation onset, maintaining a safe processing window. Cellulosic fibres generally promoted matrix crystallization through heterogeneous nucleation, increasing matrix crystallinity up to 39.3% in composite B600-30 compared to 20.4% for the reference rPP matrix. Furthermore, the reinforcements acted as dimensional stabilizers, reducing the linear thermal expansion coefficient (α₄₀₋₁₂₀) by up to 28.9% (ZZC500-30) while increasing thermal conductivity by up to 32.7% (B600 series). This approach demonstrates a viable upcycling strategy, yielding high-secondary-content circular composites by combining post-industrial recycled polypropylene matrices with reinforcements (virgin wood cellulose benchmarks (B600 and BC300), pre-consumer recycled cellulose (PWC500), post-consumer recycled cellulose (ZZC500), and recycled technical sisal (SIS250), complemented by 3 wt.% commercial MAPP compatibilizer.

In this work new biocomposite materials from wasted citrus peels has been validated for a value-added packaging and novel cosmetic products. Specifically, extracted natural fibres and dehydrated pulp from citrus fruit were combined with polylactic acid and other additives as materials for the production of bio-based packaging jars and cosmetic products. For the composition of the packaging an orange powder (dehydrated wastes) was found to be the best performing, while orange comminute, which results from milling the orange peel, was most suitable for composition of the cosmetic formulations. Polylactic acid was compounded with citrus fibres by up to 25 wt.% by twin screw extrusion and processed via injection moulding, one of the most widespread processing technologies for producing rigid packaging containers. Composites were characterized, defining their mechanical, morphological and thermal properties. Validation of packaging thermostability performance was performed by Heat deflection temperature in compliance to ISO75 and VICAT softening temperature in accordance with ISO306. Compatibility tests of packaging demonstrators with newly formulated cosmetic products has been investigated as well. An accelerated compatibility test of the cosmetic jars with water and oil-based simulants was performed at ambient temperature, -5 °C, and at 45 °C. The results indicated that new cosmetic packaging are not consistent with water-based cosmetic formulations but are compatible with products based on natural oils. While the price of these products is generally higher than those using conventional plastics, they are competitive for premium cosmetic brands.