Browsing by Author "Moreno-Serna, Viviana"
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Publication Mechanical and antimicrobial properties of low-density-polyethylene/MgO nanocomposites(2022) Cament, Alejandro; Moreno-Serna, Viviana; Loyo, Carlos; Quintana, Pabla; Seura, Pablo; Vallejos Baier, Raúl; Benavente, Rosario; Ulloa, María Teresa; Rivas, Lina; Pino, Eduardo; Gómez, Tatiana; Zapata, Paula A.Low-density polyethylene (LDPE) nanocomposites containing magnesium oxide (MgO) nanoparticles are obtained by melt mixing. MgO nanoparticles ca. 29 ± 2 nm are synthesized by sol–gel and organically modified on the surface with oleic acid (Mod-MgO), whose final concentration in the polymers is 3, 5, and 10 wt%. The presence of these nanoparticles did not affect the crystallization process of LDPE. However, Young's modulus increases with 10 wt% of Mod-MgO nanoparticles, rendering higher reinforcement effects with an increase as high as 48%. This affects the elongation at break, which decreases ca. 57% compared to neat LDPE. The storage and loss modulus of the LDPE/MgO and LDPE/Mod-MgO nanocomposites increases at room temperature and low temperatures ( 150 to 50C) compared to neat LDPE. SEM analysis showed that the organic modification of MgO nanoparticles improved their dispersion within the polymer matrix. Nanocomposites present antimicrobial properties against Escherichia coli, reaching an efficiency ca. 53%.Publication PLA/CaO nanocomposites with antimicrobial and photodegradation properties(2022) Loyo, Carlos; Moreno-Serna, Viviana; Fuentes, Jairo; Amigo, Nicolás; Sepúlveda, Francesca Antonella; Ortiz, Andrés; Rivas, Lina; Ulloa, María Teresa; Benavente, Rosario; Zapata , Paula A.CaO nanoparticles sized ca. 26 nm were organically modified with oleic acid (Ol-CaO), and both were incorporated into PLA at concentrations of 5 and 8 wt.% by a melting process. Modification of nanoparticles improved the distribution into PLA, as seen by transmission electron microscopy (TEM). Thermal analysis revealed that the presence of Ol-CaO in the PLA matrix promoted a decrease ca. 13% in the glass transition temperature (Tg). The thermal stability of the PLA/Ol-CaO decreased ca. 23% compared to the neat PLA due to the catalytic activity from nanoparticles, while Vickers Microhardness (HV) for nanocomposites PLA/Ol-CaO increased ca. 9%, compared with the neat PLA, due to the good dispersion of modified-surface Ol-CaO nanoparticles in PLA. PLA/Ol-CaO nanocomposites reached 99.9% of antimicrobial effectiveness against E. coli for nanoparticles content above 8 wt.%. From photodegradation tests under irradiation during five days, it was verified that the presence of CaO nanoparticles accelerated the photodegradation of the polymer matrix nanoparticles into PLA promoted a decreasing ca. 13% of Tg and an increase in the degree of crystallinity (Xc) (ca. 7%), compared to PLA/CaO without irradiation. Besides, the viscosity molecular weight (M¯ v) of PLA/CaO showed a higher decrease than neat PLA after irradiation, and SEM analysis showed that the nanocomposites presented cavities around the nanoparticles after irradiation. Our results showed that incorporating CaO nanoparticles into the PLA polymer matrix allows future development of more sustainable materials as nanocomposites for food packaging or medical devices.