Resumen en Inglés:

Abstract Poly(methyl methacrylate) (PMMA) is a polymer that can be used in applications requiring its exposition to gamma radiation, nevertheless, the radiation induces main chain scission backbone, leading to modification in some properties. Therefore, using materials such as layered double hydroxide (LDH), was evaluated as a new radiation shielding agent. This work synthesized LDH and added to PMMA by an in-situ polymerization method. Viscosimetric analysis showed that LDH at 0.25 wt% concentration promotes polymer radiolytic protection of 90% against damage caused by gamma radiation. The topographic images obtained by AFM revealed increasing PMMA/LDH film roughness, which impacted the lower film transmittance. The combined effect of LDH and gamma radiation interferes with the degradation process of PMMA, promoting reduced rigidity, greater mobility of polymer chains, and lower optical gap energy. Thus, these results open a promising path for using LDH as additives in polymers exposed to gamma radiation.

Resumen en Inglés:

Abstract This work aimed to develop biodegradable films from yellow passion fruit (Passiflora edulis f. flavicarpa) peel flour. The Central Composite Rotational Design was used in a total of 11 tests, in which the independent variables were the concentrations of starch and glycerol, characterized with regard to physical, mechanical and barrier properties. The films were classified as soluble and showed low permeability to water vapor. The tensile strength, elastic modulus and deformation rate were directly related to the concentration of starch and glycerol. The film of test 7 had the best characterization results; therefore, it was analyzed for biodegradability. As for biodegradability, the film obtained an average mass loss of 92.77 ± 4.28%, being a great alternative to the use of non-biodegradable polymers. The films showed acceptable degree of plasticization, which was favored by intermolecular interactions between the components of the flour, starch and glycerol.

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Abstract Composite based on PP/CaCO3 contained micro and nanoparticles were investigated in relation its activation volume, mechanical, thermal and transport properties. The additives were initially dispersed in homopolymer polypropylene (hPP) blended with compatibilizer maleic anhydride grafted polypropylene (PP-g-MA) in twin-screw extruder, producing CaCO3 masterbatches, that were subsequently diluted in hPP. To optimize fillers dispersion in the polymer matrix, a Design of Experiment (DOE) was used, that combined Extruder screw rotation (N: 250 and 500 rpm); Extruder feed flow (Q:10 and 15 kg/h) and Average particle size (ϕ: 40 nm and 1.7 μm) at four different filler concentrations. Based on mechanical characterization results, the best process found was 500 rpm@10 kg/h, which provided suitable Specific Mechanical Energy (SME), increasing the nanocomposites strength. Finally, improvements of Impact Resistance up to 7.8% and Young's Modulus up to 9.3% related to microcomposite and Tensile Strength (Fmax), up to 7.9%, related to hPP, with higher strain.

Resumen en Inglés:

Abstract This study aimed to evaluate the coating based on Amaranthus flour (AF), montmorillonite, and three essential oils (clove, muña, and matico) to extend the shelf life of minimally processed mango. The mango cubes were divided into four different treatments. T1- control (uncoated mango), T2 (0.3% w/v of clove), T3 (0.3% w/v of muña), and T4 (0.3% w/v of matico). All treatments had 0.6% w/v Amaranth flour and 0.02% w/v montmorillonite (MMT) and were subjected to 5°C for 12 days. Water activity (Aw), pH, Total soluble solids, acidity, weight loss, color, texture, and antimicrobial activity were evaluated for each treatment. Matico treatment maintained pH and had the lowest count of yeast and mold forming units on mango (3.47 log UFC g-1). On the last day of storage, all coating treatments showed less weight loss and favorable results than the control. The matico treatment showed higher efficiency for mango preservation.

Resumen en Inglés:

Abstract Oil spills have had catastrophic effects on marine ecosystems. The removal of oil spills from the water surface has then attracted worldwide attention. Natural rubber (NR) is a well-known example of a hydrophobic material, due to its hydrocarbon structure. For this purpose, the potential of NR as an oil absorbent is demonstrated. NR was formed into a cellular structure where oil absorbency can be controlled by their densities. It can be done by varying the foaming volume from 2-8 fold (2×, 4×, 6×, and 8×) the original volume of the beater. Increasing the foaming volume has reduced the densities. Over the variations of densities, the oil absorbencies were 10.58 to 16.76 g/g for crude oil, and 6.56 to 13.18 g/g for diesel oil. This indicated that the absorbent based on NR latex foam provided excellent performance and could be practically used as an oil-absorbent material.

Resumen en Inglés:

Abstract This study investigated the impact of alkaline treatment on mallow fibers used as reinforcement in bi-axially oriented polypropylene (BOPP) waste composites. Fibers were treated with a 5% NaOH solution and characterized by XRD, FTIR, TGA, and tensile testing. Composites were fabricated with both untreated and treated fibers, and their physical, thermal, morphological, and mechanical properties were evaluated. XRD analysis revealed an increase in crystallinity index after treatment, correlating with enhanced breaking stress in treated fibers. Composites with treated fibers exhibited significantly reduced thickness swelling and water absorption, indicating improved fiber-matrix compatibility. SEM micrographs confirmed enhanced fiber-matrix adhesion in composites using treated fibers. Overall, the results demonstrate that alkali treatment significantly improves the properties of mallow fiber/BOPP composites, promoting their use as sustainable and eco-friendly materials. This research highlights the potential of valorizing agricultural waste and recycled plastics for the development of high-performance composites.

Resumen en Inglés:

Abstract Packaging generates approximately 40 tons/month of waste from Solid Bleached Sulfate (SBS) paperboard coated with Poly (Ethylene Terephthalate) PET. Concerns about environmental sustainability are pushing innovative materials with diverse applications to replace conventional synthetic materials. Biocomposites, which use fungal mycelium as a binder for the particles, are an emerging option in biodegradable and naturally sourced materials. This study aimed to make Pleurotus sajor-caju biocomposites, employing SBS paperboard packages coated with PET as the substrate. The study investigated two inoculum fractions (30% and 50%) and two drying methods (conventional and vacuum) at 60 °C. The biocomposites produced with a 50% inoculum and conventional drying displayed favorable characteristics, including a shorter processing time (16 days), a higher drying rate (5.58 g/day), low porosity (21,7%), compressive strength of 0.16 MPa, apparent density of 315 kg/m3 and satisfactory thermal stability.

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Abstract A promising yet underexplored alternative for biomedical applications involves incorporating polymer, metal, and ceramic materials into hybrid structures. In this study, a biocomposite consisting of polylactic acid (PLA) with 20 wt% of nearly spherical sub-micron hydroxyapatite (HA) particles was successfully synthesized. The HA particles were uniformly dispersed and distributed within the PLA matrix, leading to a biocomposite with a well-balanced combination of thermal and mechanical properties. This PLA−HA biocomposite was then directly joined through injection overmolding onto a laser-surface-structured titanium alloy Ti6Al4V substrate. The PLA−HA/Ti6Al4V hybrid joints demonstrated robust mechanical anchorage, achieved through the thorough filling of the polymer biocomposite into the micro-scale structures engineered onto the metal surface. This mechanism ensured good lap-shear strength, making these hybrid joints promising candidates for orthopedic applications.

Resumen en Inglés:

Abstract The SARS-CoV-2 Coronavirus pandemic and the rise in climate disasters have fueled a surge in disposable mask production, exacerbating waste challenges. The study proposes a sustainable pathway for recycling Non-Woven Fabric (NWF) originating from masks made of Polypropylene (PP) used as Personal Protective Equipment (PPE). Eco-friendly blends of virgin polypropylene (vPP) and recycled non-woven fabric (NWF) were produced through extrusion, and the physicochemical and mechanical properties of the blends were evaluated. The addition of NWF resulted in lower tensile and flexural strengths than vPP. However, from 50%wt of recycled NWF, the blends proved to be as stiff as, or even stiffer than, the virgin polymer. While slightly lower, the 50%wt NWF blend achieved properties close to those of vPP, making it the ideal composition for replacing PP in conventional applications. This approach offers a sustainable solution for mask recycling, reducing disposal impacts and supporting a circular economy.

Resumen en Inglés:

Abstract The hollow glass microspheres (HGM), exhibit low density, reduced dielectric constant, and good thermal conductivity. This study assessed the mechanical performance of polypropylene (PP) reinforced with HGM under artificial thermal aging conditions. The compositions underwent two rounds of reprocessing in a single-screw extruder, and samples were prepared for both tensile and impact testing. Tensile specimens were subjected to thermal aging at 100 ºC for seven and 21 days. Mechanical tests were carried out on samples before and after aging, while exposed samples underwent visual inspection, optical microscopy, and Fourier transform infrared spectroscopy analysis. Visual inspection and microscopy revealed improved PP-HGM interaction due to the additives, with no deformation or damage from reprocessing. Infrared spectroscopy showed minor degradation in the PP structure post-exposure. In summary, the presence and content of HGM, reprocessing, and aging time significantly affect the mechanical properties (elastic modulus, breaking stress, elongation at break, and impact resistance).

Resumen en Inglés:

Abstract This study reports the ex-situ anchoring of two metal organic frameworks (MOF-199 and MOF UiO-66-NH2) onto TEMPO-oxidized cotton fibers. While in-situ anchoring methodologies are reported, ex-situ protocols are underreported despite their advantages in industrial scaling-up and control. The functionalized composites were characterized after 48 h of Soxhlet treatment. X-ray diffraction and infrared spectra confirmed MOFs anchorage through super positioning signals corresponding to cotton and MOFs. Likewise, X-ray photoelectron spectra (XPS) show the presence of Cu2+ (4.73% molar ratio) and Zr4+ (12.06%) coordinated to the -COO groups of the organic linkers, indicating a stable chemical interaction. Finally, SEM confirmed the expected MOF morphology. The potential antibacterial activity of these materials was evaluated. The assays revealed a bacteriostatic effect for MOF UiO-66-NH2@cotton, even after 48 h of contact. Meanwhile, the MOF-199@cotton showed a bactericide effect under the same conditions.

Resumen en Inglés:

Abstract This study compares the thermal degradation and aging resistance of NBR compounds activated with ZnO or MgO-green synthesized with the assistance of Camellia sinensis extract. Thermal degradation was studied using the Flynn-Wall-Ozawa method. Aging resistance was investigated by the changes in crosslink density and mechanical properties before and after the samples are exposed in a forced-air oven at 100 °C/72 h. The activation energies for NBR compounds with MgO-green and ZnO are, respectively, 220 kJ mol-1 and 700–200 kJ mol-1. After oxidative-thermal aging, the crosslink density of NBR compounds goes up by 24% with MgO-green and 120% with ZnO. Consequently, the changes in hardness and tensile properties of the NBR with MgO-green are more subtle than those observed with ZnO. Based on Fisher's minimum significant difference procedure, the data analysis shows that MgO-green can be used instead of ZnO as an activator in the vulcanization of NBR.