Synthesis of Copper Nanoparticles Coated with Nitrogen Ligands

The synthesis of copper nanoparticles was studied by wet chemical methods using copper sulfate pentahydrate (CuSO4·5H2O) and nitrogen ligands allylamine (AAm) and polyallylamine (PAAm) as stabilizers. The results suggest that the use of these ligands leads to the exclusive formation of metallic copper nanoparticles (Cu-NPs). The use of partially crosslinked polyallylamine (PAAmc) leads to nanoparticles (NPs) with low yields and high coating content, while linear PAAm leads to NPs with high yields and low coating content. The chemical composition of the particles was determined by XRD and average particle diameters were determined by the Debye-Scherrer equation. TGA analysis provided evidence of the content and thermal stability of the coating on the nanoparticles and PAAm. The morphology, particle size distribution, and presence of PAAm coating were observed through TEM. The use of AAm in the synthesis of NPs could be a good alternative to reduce costs. By using TGA, TEM, and DSC techniques, it was determined that synthesized NPs with AAm presented a coating with similar characteristics to NPs with PAAm, suggesting that AAm underwent polymerization during the synthesis

Certificación de un material de referencia de carne en base a un estudio de colaboración = Certification of a meat reference material based on a collaborative study

Mediante un proyecto de colaboración, se llevaron a cabo estudios de comparación para mejorar la capacidad de mediciónde los laboratorios participantes, apoyándolos en la producción, caracterización y distribución de materiales de referencia delsector agroalimentario. El proyecto fue planteado en cuatro etapas anuales (leche, agua, carne y granos). La tercera etapa enespecífico tuvo el objetivo de cuantificar y certificar el contenido de los parámetros nutrimentales (nitrógeno, grasa, sodio ypotasio) de un lote candidato a Material de Referencia Certificado (MRC) de carne bovina enlatada. Dicho estudio fue realizadoen colaboración entre varios Institutos Nacionales de Metrología (INM) y/o laboratorios colaboradores, los cuales, una vez queidentificaron las posibles causas de variabilidad o de sesgo en las mediciones, así como las oportunidades de mejora, lograronla certificación del material de carne bovina. El MRC fue distribuido entre los participantes para cubrir las necesidades de laindustria alimentaria de productos cárnicos y laboratorios de prueba de sus respectivos países

Ahora / Ara

La cinquena edició del microrelatari per l’eradicació de la violència contra les dones de l’Institut Universitari d’Estudis Feministes i de Gènere «Purificación Escribano» de la Universitat Jaume I vol ser una declaració d’esperança. Aquest és el moment en el qual les dones (i els homes) hem de fer un pas endavant i eliminar la violència sistèmica contra les dones. Ara és el moment de denunciar el masclisme i els micromasclismes començant a construir una societat més igualitària. Cadascun dels relats del llibre és una denúncia i una declaració que ens encamina cap a un món millor

Effect of Plasticizer Content on Mechanical and Water Vapor Permeability of Maize Starch/PVOH/Chitosan Composite Films

Packaging materials based on biodegradable polymers are a viable alternative to replace conventional plastic packaging from fossil origin. The type of plasticizer used in these materials affects their functionality and performance. The effect of different plasticizers such as glycerol (GLY), sorbitol (SOR), and poly(ethylene glycol) (PEG) in concentrations of 5%, 10%, and 15% (w/w) on the structural features and functional properties of starch/PVOH/chitosan films was evaluated. The incorporation of a plasticizer increased the thickness of the biodegradable composite films. Furthermore, the material plasticized with 30% (w/w) sorbitol had the highest elongation at break, lowest water vapor permeability, and better thermal resistance. The results obtained in this study suggest that maize starch/PVOH/chitosan biodegradable composite films are a promising packaging material, and that sorbitol is the most suitable plasticizer for this formulation

Effects of Poloxamer Content and Storage Time of Biodegradable Starch-Chitosan Films on Its Thermal, Structural, Mechanical, and Morphological Properties

Biodegradable packaging prepared from starch is an alternative to fossil-based plastic packaging. However, the properties of starch packaging do not comply with the necessary physicochemical properties to preserve food. Hence, in a previous study, we reported the preparation of a composite polymer material based on starch-chitosan-pluronic F127 that was found to be an adequate alternative packaging material. In this study, we modified the physicochemical properties of this material by storing it for 16 months under ambient conditions. The results indicate that the incorporation of pluronic F127 in the blend polymer can help avoid the retrogradation of starch. Moreover, at higher concentrations of pluronic F127, wettability is reduced. Finally, after storage, the materials exhibited surface modification, which is related to a color change and an increase in solubility, as well as a slight increase in stiffness

Preparation and Physicochemical Properties of Modified Corn Starch–Chitosan Biodegradable Films

Starch is a biopolymer with enormous potential for generating new biodegradable packages due to its easy availability and low cost. However, due to its weak functional properties, limitation of its interaction with some hydroxyl groups and evaluation of blends with other polymers are necessary in order to improve its performance. Glycerol-plasticized acetylated corn starch films were developed using the casting method, and the impact of incorporating chitosan (TPS:CH) in various proportions (75:25, 50:50, and 25:75 v/v) was studied in the present research. The effect of chitosan ratios on the physical, mechanical, water-vapor barrier, and thermal properties of the film was studied. Chitosan-protonated amino groups promoted the formation of intermolecular bonds, improving tensile strength, thermal stability, hydrophobicity, water adsorption capacity, and the gas barrier of starch films. The results show that the film composed of TPS25-CH75 proved to be the best barrier to water vapor; thus, these composite films are excellent choices for developing biodegradable packaging for the food industry

Synthesis and Thermomechanical Characterization of Nylon 6/Cu Nanocomposites Produced by an Ultrasound-Assisted Extrusion Method

A nylon 6 nanocomposite with copper nanoparticles processed by ultrasound-assisted extrusion was prepared at concentrations between 0.01 and 0.50 wt.%, and its thermal and mechanical properties were determined. The presence of the crystalline phase α (α1 and α2) in the polymer matrix was confirmed by X-ray diffraction, and the presence of the α2 phase showed a greater increase than the α1 phase as a function of the copper nanoparticle concentration. This process was attributed to secondary crystallization. Furthermore, it was determined that the chemical composition of the nanoparticles is a blend of metallic copper and cupric oxide. The formation of copper nanowires was observed by scanning electron microscopy, and the concentration of 0.10% exhibited the best dispersion in comparison with the other concentrations. The melting temperature of the nanocomposites underwent a slight decrease in comparison with the nylon 6, while thermal stability, crystallization temperature, and crystallinity were increased in relation to the pure polymer. This behavior is attributed to an efficient dispersion of the nanoparticles and to their functionality as crystal nucleation sites. For the 0.10% concentration nanocomposite, higher mechanical properties were obtained; tensile strength increased by 8.9%, and the tensile modulus increased by 25.4%; as a consequence, elongation at break was 62% less than that of the polymer matrix

Evaluation of the Antimicrobial, Thermal, Mechanical, and Barrier Properties of Corn Starch–Chitosan Biodegradable Films Reinforced with Cellulose Nanocrystals

Packaging materials play an essential role in the preservation and marketing of food and other products. To improve their conservation capacity, antimicrobial agents that inhibit bacterial growth are used. Biopolymers such as starch and chitosan are a sustainable alternative for the generation of films for packaging that can also serve as a support for preservatives and antimicrobial agents. These substances can replace packaging of synthetic origin and maintain good functional properties to ensure the quality of food products. Films based on a mixture of corn starch and chitosan were developed by the casting method and the effect of incorporating cellulose nanocrystals (CNC) at different concentrations (0 to 10% w/w) was studied. The effect of the incorporation of CNC on the rheological, mechanical, thermal and barrier properties, as well as the antimicrobial activity of nanocomposite films, was evaluated. A significant modification of the functional and antimicrobial properties of the starch–chitosan films was observed with an increase in the concentration of nanomaterials. The films with CNC in a range of 0.5 to 5% presented the best performance. In line with the physicochemical characteristics which are desired in antimicrobial materials, this study can serve as a guide for the development this type of packaging for food use