Hybrid coatings of SiO₂ and recycled unsaturated polyester resin (R-UPR) from recycled polyethylene-terephthalate (PET) were prepared by the sol-gel process on glass substrates. First, SiO₂ was synthesized by the sol-gel process using a tetraethyl orthosilicate (TEOS) solution. Next, bis(2-hydroxypropyl-terephthalate) (BHPT) was synthesized from mechanical and chemical recycling (glycolysis) of post-consumer PET bottles in propylene glycol (PG) using ZnA as catalyst, in a Vessel-type reactor (20–200 °C); maleic anhydride (MA) was added and, following the same procedure, the unsaturated polyester (UP) was synthetized, which was cooled to room temperature. Next, styrene (St) and benzoyl-peroxide (PBO)-initiator were added to obtain R–UPR. TEOS (T) and three hybrid solutions were synthesized, with molar ratios of 0:1:0 (T), 1:2:0.25 (H1), 1:1:0.25 (H2), and 1:0:0.25 (H3) for R–UPR:TEOS:3-trimethoxy-(silyl)-propyl-methacrylate (TMSPM), respectively, with which TC, HC1, HC2, and HC3 coatings were elaborated using the immersion technique and polymerized (120 °C for 24 h). The solutions were characterized by FT–IR and TGA, and the coatings by SEM, nanoindentation, AFM, adhesion, and contact angle. The results showed that SiO₂ enhanced mechanical (hardness and Young’s modulus) and thermal properties of the R-UPR. The coatings adhered perfectly to the substrate, with thicknesses of micrometer units and a flat surface; in addition, hydrophilicity decreased as SiO₂ decreased.

A new, sustainable polypropylene terephthalate (PPT) coating was synthesized from recycled polyethylene terephthalate (PET) and applied onto a hydraulic concrete substrate to improve its durability. For the first step, PET bottle wastes were ground and depolymerized by glycolysis using propylene glycol (PG) in a vessel-type reactor (20–180 °C) to synthesize bis(2-hydroxypropyl)-terephthalate (BHPT), which was applied as a coating to one to three layers of hydraulic concrete substrate using the brushing technique and polymerized (150 °C for 15 h) to obtain PPT. PET, BHPT, and PPT were characterized by FT-IR, PET, and PPT using TGA, and the PPT coatings by SEM (thickness), ASTM-D3359-17 (adhesion), and water contact angle (wettability). The durability of hydraulic concrete coated with PPT was studied using resist chloride ion penetration (ASTM-C1202-17), carbonation depth at 28 days (RILEM-CPC-18), and the absorption water ratio (ASTM-C1585-20). The results demonstrated that the BHPT and PPT were synthetized (FT-IR), and PPT had a similar thermal behavior to PET (TGA); the PPT coatings had good adhesion to the substrate, with thicknesses of micrometric units. PPT coatings presented hydrophilic hydrophilic behavior like PET coatings, and the durability of hydraulic concrete coated with PPT (2–3 layers) improved (migration of chloride ions decreased, carbonation depth was negligible, and the absorption water ratio decreased).

Surface protection of hydraulic concrete requires coating systems capable of combining stable interaction with the substrate and effective resistance to water and CO2 ingress. In this work, a coating based on an unsaturated polyester (UP) resin (UPR) derived from recycled poly(ethylene terephthalate) (PET) and another based on a hybrid UPR modified with a silane precursor by sol-gel were prepared and applied by brush to concrete in one, two, and three layers. Pure and hybrid UPRs were analyzed by FT-IR, while their surface behavior and barrier performance were evaluated by tests of water contact angle, adhesion, accelerated carbonation, capillary water absorption, and immersion absorption. The FT-IR results were consistent with the sequential transformation of PET to bis(2-hydroxypropyl terephthalate) and UP, while the hybrid UPR exhibited Si—O- and Si—C-related contributions associated with the sol-gel modification. Both coatings maintained hydrophilic surface behavior and were classified as 5B in the cross-cut tape test. Barrier response varied across the evaluated formulation/layer configurations. Within the pure UPR series, the three-layer system showed the best performance, reducing carbonation depth to 7 mm after 28 days and decreasing capillary and immersion-related water absorption. The two- and three-layer H-UPR systems exhibited the best performance, with the latter showing the lowest carbonation depth (6 mm) and the lowest absorption-related parameters. These results demonstrate that UPR coatings derived from recycled PET can effectively protect concrete and that their silane-based sol-gel modification and the evaluated coating configuration provide a route for modifying the concrete surface barrier response against carbonation and water ingress.

A new sustainable polypropylene terephthalate (PPT) coating was synthesized from recycled polyethylene terephthalate (PET) and applied on hydraulic concrete substrate to improve its durability. First step, PET bottles wastes were grinded and depolymerized by glycolysis using propylene glycol (PG), in a Vessel-type reactor (20–180 °C) to synthesize bis(2-hydroxypropyl)-terephthalate (BHPT), which was applied as coating to one-three layers on hydraulic concrete substrate, by brushing technique and polymerized (150 °C for 15 h) to obtain PPT. PET, BHPT and PPT were characterized by FT-IR, PET and PPT by TGA, and the PPT coatings by SEM (thickness), by ASTM-D3359-17 (adhesion) and by water contact angle (wettability). The durability of hydraulic concrete coated with PPT was studied by resist chloride ion penetration (ASTM-C1202-17), carbonation depth at 28 days (RILEM-CPC-18), and absorption water ratio (ASTM-C1585-20). The results demonstrated that the BHPT and PPT were synthetized (FT-IR), PPT had a similar thermal behaviour to PET (TGA); the PPT coatings had good adhesion to the substrate, with thicknesses of micrometric units; hydrophilic (similar to PET coatings), and the durability of hydraulic concrete coated with PPT (2-3 layers) improved (migration of chloride ions decreased, carbonation depth was negligible, and the absorption water ratio decreased).

La corrosión representa un gran problema en diversas industrias, desde la construcción hasta la generación de energía. Tradicionalmente se han empleado inhibidores sintéticos para reducirla; sin embargo, su toxicidad y efectos ambientales adversos han impulsado la búsqueda de alternativas sostenibles. En este contexto, el presente estudio evaluó el potencial del extracto acuoso de Artemisia ludoviciana (variante mexicana) como inhibidor “verde” de la corrosión del acero en medio ácido (H₂SO₄ 1 M). El extracto se obtuvo mediante el método Soxhlet, utilizando agua destilada como disolvente, y se analizó su desempeño a diferentes concentraciones mediante pruebas de pérdida de peso, espectroscopía de impedancia electroquímica, resistencia a la polarización y polarización potenciodinámica. Los resultados mostraron una eficiencia de inhibición superior al 90% con una concentración del 5% v/v, indicando una notable capacidad del extracto para reducir la velocidad de corrosión. Las mediciones confirmaron que el efecto inhibidor aumenta con la concentración, mientras que los estudios de polarización mostraron un comportamiento de tipo mixto con predominio anódico. La adsorción del extracto sobre la superficie del acero siguió la isoterma de Langmuir, sugiriendo la formación de una monocapa protectora. En conjunto, los hallazgos demuestran que A. ludoviciana es una alternativa eficaz, ecológica y sostenible a los inhibidores convencionales, contribuyendo al aprovechamiento responsable de recursos naturales y al desarrollo de tecnologías más limpias para la protección de materiales metálicos.