RESUMO
The objective was to establish possible temporal patterns in the microplastics (MPs) abundance in the water and in the intertidal sediment in an urbanized location of the Río de la Plata estuary (Argentina), in relation to environmental factors. The site was sampled monthly for a year (February 2019-January 2020). The presence of MPs was recorded, being more abundant in February in the water (110 MPs m-3) and in April in the sediment (613 MPs m-2). The types of MPs found were fibers, fragments, pellets, film and foam; while the polymers identified were polyethylene (PE) and polypropylene (PP). Regarding the environmental variables, the predominance of wind from the NE direction was related to a greater accumulation of MPs in the sediment, while wind from the NO direction was associated with a lower abundance of MPs in the water. Also, MPs abundance was negatively related to the larger sizes of sediment particles.
Assuntos
Microplásticos , Poluentes Químicos da Água , Argentina , Monitoramento Ambiental , Estuários , Plásticos , Poluentes Químicos da Água/análiseRESUMO
Este trabajo presenta los resultados de un estudio de envejecimiento natural y acelerado en saliva artificial, de un material para uso odontológico de la marca Deflex® a base de poliamida de alto impacto, según lo establece la norma UNE EN IS0 10993-13 (2009) (AU)
is work presents the results of the study of natural and accelerated aging in artificial saliva, of a material for dental use of the brand Deflex® based on high impact polyamide, as established by the standard UNE EN IS0 10993-13 (2009) (AU)
Assuntos
Saliva Artificial , Envelhecimento , Nylons , Polímeros/química , Análise Espectral/métodos , Teste de Materiais , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
Se determinó la solubilidad en agua en ensayos in-vitro de un sellador para uso endodóntico a base de un conglomerado de trióxidos minerales (MTA), marca Endosealer® (Densell SA) de acuerdo a la norma UNE-EN ISO 6876:2012. En el ensayo de solubilidad en agua durante 24 hs se encontró pérdida de masa (3,3 %) y la presencia de sólidos en las aguas de lavado (6,4 %). Esto indica que durante el ensayo ocurre la solubilización de parte del material y la incorporación de agua, lo que no permite establecer un valor real de la solubilidad.(AU)
Solubility of a commercial endodontic sealer (Endosealer® (Densell SA)) was performed according to the UNE-EN ISO 6876:2012. The results show a mass loss of 3.3 % and 6.4 % of solid in the test solution. These indicate that during the solubility test part of the material solubilizes and an actual value of solubility cannot feasible be determined
Assuntos
Materiais Restauradores do Canal Radicular , Cimentos Dentários/análise , Cimentos Dentários/química , Solubilidade , Materiais DentáriosRESUMO
The effectiveness of natamycin supported in corn starch-based films to control environmental molds (mainly Penicillium spp) activity that could colonize the surface of semi-hard cheese during ripening, was evaluated. The starch amount was maximized, and this was achieved by adding polyvinyl alcohol (PVA) and also polyurethane (PU) to the formulation. The PU acted as plasticizer and also provided functional groups that interacted with the natamycin and affected its diffusion. When 5 % PU was added, the natamycin migration of the coating doped with 1% natamycin was reduced by half. The natamycin distribution on both sides of the film was also evaluated, concluding that, in line with the reduced migration, when polyurethane is included, the formulation presents high hydrophobicity and natamycin is left with a preferential distribution towards the air face (exterior). For microbiological tests, microorganisms were isolated from cheese factories. Natamycin solutions showed inhibitory effect against environmental molds including Penicillium spp. Accordingly, films loaded with 0.1 % natamycin showed a significant inhibitory effect against Penicillium spp. The polymer combination in this work was optimized to obtain an active coating with good physicochemical properties and enriched with natamycin that has proven to be available for acting against molds and preferentially on the surface exposed to potential mold attack during ripening.
RESUMO
Nanocrystalline cellulose (CNC), obtained by sulphuric acid hydrolysis, was used to synthesize polyurethane foams (PUFs) based on a functionalized castor oil polyol and a Methylene diphenyl diisocyanate (MDI). Formulations with varying isocyanate index (FI) and NCO number were prepared. At 0.5 wt.%, SEM's of the fractured surface underlined that the CNC acted both as a nucleation agent and as a particulate surfactant with cell geometries and apparent density changing selectively. The chemical structure of the PUF (FTIR) changed after the incorporation of CNC by a relative change of the amount of urea, urethane and isocyanurate groups. A low NCO number and isocyanate index contributed to the migration of the CNC to the Hard Segment (HS), acting as reinforcement and improving substantially the compressive mechanical properties (Ec and σc improvements of 63 and 50%, respectively). For a high NCO number or isocyanate index, the CNC migrated to the Soft Segment (SS), without causing a reinforcement effect. The migration of the CNC was also detected with DSC, TGA and DMA, furtherly supporting the hypothesis that a low NCO number and index contributed both to the formation of a microstructure with a higher content of urethane groups.