https://hdl.handle.net/10259/4314 2026-09-09T12:42:15Z https://hdl.handle.net/10259/11978 Atmosphere-controlled thermal processing enables tunable optical properties via iron-oxide phase engineering in natural silicate materials Urbaneja Miguel, Álvaro; Torija López, Alba; Carrancho Alonso, Ángel; Iriarte Avilés, Eneko; González Moreno, Sara; González Martín, José Manuel; Trigo López, Miriam; Vallejos Calzada, Saúl Controlled-atmosphere thermal processing was investigated as a method to engineer iron-oxide phase assemblages in iron-bearing silicate materials. Natural sandstone was heated between 200 and 1000 °C under air, N2 and CO2 atmospheres to evaluate how oxygen partial pressure governs redox transformations and the resulting macroscopic optical behaviour. The treatments produced a wide and reproducible range of optical responses from a single starting material. Colour evolution, quantified in the CIELAB space, correlates with bulk mineral transformations. Oxidizing conditions stabilize hematite-dominated assemblages and generate red hues, whereas reduced-oxygen atmospheres promote magnetite formation and progressive darkening. Rock-magnetic measurements identify atmosphere-dependent phase assemblages, including a high-coercivity iron oxide under strongly oxidizing conditions. The magnetic response mirrors the optical evolution, indicating that colour development originates from internal phase transformations. Compressive strength remained within the same order of magnitude as the untreated material across the studied conditions, indicating no catastrophic mechanical degradation. These results show that oxygen availability acts as a key processing variable controlling iron-oxide stability and optical response. The study establishes a process-based approach for tuning optical properties in mineral materials through atmosphere-controlled thermal processing without chemical additives. Unlike previous studies focused on temperature-driven effects or isolated observations, this work demonstrates a reproducible process-based approach to tune optical properties in natural silicate materials through controlled atmosphere engineering. 2026-05-29T00:00:00Z https://hdl.handle.net/10259/11890 Dual-range colorimetric protein quantification in whey and WPC using a smart polymeric film and RGB imaging Vallejo García, Jorge Lucas; Trigo López, Miriam; Ibeas Cortes, Saturnino; Torija López, Alba; Busto Núñez, Mª Dolores; Pilar Izquierdo, María Concepción; López, Gloria; Sánchez, Carlos; Vallejos Calzada, Saúl Whey is an important dairy by-product whose protein content must be accurately determined for quality control and fraud detection. Conventional nitrogen-based methods (e.g., Kjeldahl) require laboratory equipment and overestimate protein in the presence of non-protein nitrogen compounds. Here, we report a rapid analytical approach based on a smart polymeric film (FRGB) prepared by diazotisation–azo coupling chemistry. The film reacts with aromatic residues of whey proteins, producing a colour change quantifiable from a smartphone image. The sensor displays a dual-range response: the blue channel provides high sensitivity at low concentrations, whereas the green channel remains linear at high concentrations, enabling direct analysis of whey protein concentrate without dilution. The method showed excellent linearity (R2 = 0.99) in whey and commercial WPC over 0–120 mg·mL−1, with a detection limit of 0.284 mg·mL−1 and recovery rate of 94 ± 1.46%. Non-protein nitrogen compounds did not interfere, allowing rapid screening and preliminary authenticity assessment of whey-derived products. 2026-06-01T00:00:00Z https://hdl.handle.net/10259/11888 Too many structures for the same function: Market evidence of circularity barriers in food packaging Torija López, Alba; Núñez-Carrero, Karina C.; Sedano Labrador, Carlos; Rodríguez Pérez, Miguel Ángel .; Vallejos Calzada, Saúl; Trigo López, Miriam The transition towards circular food packaging requires not only regulatory compliance but also material and structural harmonization. This study analyzes 163 multilayer films from commercial food packaging available on the European market to quantify structural diversity and assess implications for recyclability. Forty-two distinct multilayer configurations and twenty-seven polymer combinations were identified, with no systematic relationship to food category, film thickness, or functional requirements. Functionally similar packages frequently relied on materially incompatible or over-engineered polymer combinations, revealing a fragmented and non-standardized packaging landscape. Although all analyzed structures comply with current European food-contact regulations (EC 1935/2004 and EU 10/2011), their diversity and incompatibility hinder mechanical and chemical recycling, challenging the objectives of the forthcoming Packaging and Packaging Waste Regulation (PPWR). Overall, the results provide quantitative, market-level evidence of structural redundancy and demonstrate how fragmented design practices undermine design-for-recycling principles and the implementation of circular economy strategies in food packaging. 2026-06-01T00:00:00Z https://hdl.handle.net/10259/11488 Coumarin-inspired light-responsive thermoplastic adhesives for recyclable multilayer packaging Sedano Labrador, Carlos; Herrero, Manuel; Trigo López, Miriam; Rodríguez Pérez, Miguel Ángel .; Merino, Juan Carlos; García Pérez, José Miguel; Vallejos Calzada, Saúl; Núñez-Carrero, Karina C. Multilayer plastic packaging offers essential barrier and mechanical properties for food preservation, but its complex structure prevents effective recycling. Here, we report a light-responsive thermoplastic adhesive designed to enable on-demand separation of polymer layers in multilayer packaging. The adhesive adopts a triblock architecture with terminal blocks compatible with polyethylene (PE) and polyamide (PA), and a central segment functionalised with coumarin-based photoremovable groups. Upon ultraviolet (UV) exposure, the adhesive undergoes complete molecular breakdown, triggering clean delamination without solvents or mechanical force. Fabricated PE – photosensitive adhesive – PA films demonstrated superior adhesion performance compared to a commercial benchmark during service life, and efficient separation upon irradiation, as confirmed by Fourier transform infrared (FTIR) spectroscopy, microscopy, and T-peel testing. Life cycle assessment revealed that, while the laboratory-scale synthesis has higher environmental costs, the impact is offset after a single reuse cycle in projected industrial conditions, reaching up to 80% reduction after six cycles. This approach provides a scalable strategy to reconcile performance and recyclability in multilayer packaging. 2026-01-01T00:00:00Z