The high-yield synthesis of zinc oxide (ZnO) primary nanoparticles with high purity and with diameters between 6 and 22 nm using bicontinuous microemulsions is reported in this work. The ZnO nanoparticles were made by hydrolysis of Zn(NO3)2with NaOH aqueous solution and precipitation, followed by calcination of the precipitate. Higher yields and productivities of ZnO nanoparticles were obtained compared to values produced with w/o micremulsions reported in the literature. Particles were characterized by transmission electronic microscopy (TEM), X-ray diffraction, and atomic absorption spectroscopy.
RESUMENEn la búsqueda de plásticos reforzados con fibras que sean más amigables con el medio ambiente, aquí se presenta el primer estudio que evalúa la posibilidad de utilizar la brea natural de pino (en forma pura o maleinizada) como agente de acoplamiento (biodegradable). Polipropileno (matriz) y fibra de agave (Agave tequilana) de desecho a diferentes concentraciones (agente de refuerzo), fueron acoplados con cada uno de los agentes utilizados; su efecto en las propiedades mecánicas se comparó con el de un agente comercial de polipropileno modificado (Epolene E-43). Igualmente se prepararon, materiales compuestos sin agente de acoplamiento como referencia genérica. El desempeño mecanodinámico y mecanoestático de los materiales muestra claramente el incremento de propiedades mecánicas con los 3 agentes utilizados. La brea maleinizada mostró similitud o ligera superioridad sobre el agente comercial en el efecto logrado. La afectación en cristalinidad por la presencia de la fibra y el agente de acoplamiento correspondiente, fue evaluada mediante calorimetría diferencial de barrido. La absorción de agua como función del tiempo, permitió medir de forma indirecta el cambio logrado en la superficie de los materiales, y un análisis de FTIR, la valoración de la interacción fibra-polímero obtenida con el agente de acoplamiento. Tal interacción lograda con los agentes de acoplamiento, pudo ser además apreciada utilizando microscopía electrónica de barrido. Los resultados alcanzados marcan el camino para poder usar resinas naturales biodegradables como agentes de acoplamiento en el área de plásticos reforzados con fibras celulósicas.Palabras clave: Agente de acoplamiento, materiales compuestos, brea, colofonia, brea maleinizada, propiedades mecánicas. ABSTRACTIn the search of useful environmentally friendly fiber reinforced plastics, this is the first study that evaluates the capability to use natural pine rosin (in pure or maleated glycerol ester form) as a biodegradable coupling agent. Polypropylene as polymer matrix and discarded agave fiber (Agave tequilana) as reinforcing agent at different concentrations, were coupled with each one of the two rosins above mentioned; a commercial maleated polypropylene (Epolene, E-43) agent was used to compare their effect. As generic reference, composites without coupling agent were also tested. Mechanodynamic and mechanostatic tests clearly show an increment in mechanical properties of the composites, using any of the 3 coupling agents. The results obtained with maleated rosin were similar or slightly better than the ones obtained with the commercial agent for composites with high fiber content. Fiber content and coupling agent effect on composites crystallinity,
The synthesis of core/shell polymers with tunable mechanical properties made of poly(hexyl methacrylate) (PHeMA) and poly(methyl methacrylate) (PMMA) by a two‐stage semicontinuous heterophase polymerization, is presented here. This polymerization technique is characterized by employing low surfactant concentrations to produce large polymer‐to‐surfactant ratios. In this process, monomer is added in a continuous low rate to achieve monomer starved conditions, allowing to control particle size (usually smaller than 50 nm). To modulate the mechanical properties, the weight ratio of core/shell polymers are varied from 10/90 to 90/10 for direct and reverse compositions, respectively. Conversion was followed gravimetrically; nanoparticles were characterized with quasi‐elastic light scattering, IR spectroscopy, differential scanning calorimetry, transmission electron microscopy, and mechanical tests (tensile and hardness). Highly stable latex formed of nanoparticles, with high conversions are obtained. Tensile tests show that the mechanical properties can be tuned according to core/shell composition, mainly in the system formed by PMMA/PHeMA. These results are explained in terms of core‐and‐shell polymers location, composition and hardness. As expected, an increment in concentration of PMMA produces a more rigid material independently of its position. POLYM. ENG. SCI., 59:365–371, 2019. © 2018 Society of Plastics Engineers
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