Engenharia de Materiais

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Navegando Engenharia de Materiais por Assunto "3D printing"

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    Effect of amine-reactive elastomer on the properties of poly(lactic acid) films obtained by solvent-cast 3D printing
    (2022-01-05) OLIVEIRA, L. R. D.; NONATO, R. C.; Baltus Cornelius Bonse; MORALES, A. R.
    © 2022 Society of Plastics Engineers.Blends of poly(lactic acid) (PLA) and amine-terminated butadiene-acrylonitrile (ATBN) elastomer were prepared by solution with ATBN contents of 8–20 wt%. Films were molded by liquid deposition modeling 3D printing. Fourier transform infrared (FTIR) spectroscopy showed that the terminal carboxylic groups of the PLA chains reacted with the terminal amino groups of ATBN. Water was the byproduct of this reaction, causing PLA hydrolysis and accelerating the reaction. Thermogravimetric analysis (TGA) showed that components interaction caused a loss of PLA thermal stability. Scanning electron microscopy (SEM) of the blends revealed a porous morphology and no phase separation. There was change in the elongation when compared with neat PLA. Although the addition of a telechelic elastomer could improve PLA toughness, any benefits arising from such addition seem to be neutralized by PLA chain scission due to hydrolysis and porosity, resulting from the condensation reaction.
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    Nanocomposites of PLA containing ZnO nanofibers made by solvent cast 3D printing: Production and characterization
    (2019) Nonato R.C.; Mei L.H.I.; Bonse B.C.; Chinaglia E.F.; Morales A.R.
    © 2019 Elsevier LtdPLA nanocomposites containing 1 wt% ZnO nanofibers have been prepared by solvent-cast 3D printing. The ZnO nanofibers were produced by electrospinning and dispersed in PLA by ultrasound. Scanning electron microscopy revealed that the fibers were dispersed throughout the nanocomposite. Surface specimen assessment by atomic force microscopy indicated the presence of nanofibers near the surface of the nanocomposite. TGA tests showed the nanocomposite had a lower thermal stability than the neat PLA, probably induced by PLA hydrolysis catalyzed by ZnO. DSC results revealed higher crystallinity in the nanocomposite, induced both by the presence of ZnO nanofibers and by the 3D printing process, though the 3D printing process showed to be more important in increasing the crystallinity. XRD results also showed a higher crystallinity for the nanocomposite. The study opens an interesting field for the development of PLA/ZnO nanocomposites using ZnO nanofibers made by electrospinning, e.g. in medical and packaging applications.
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    Artigo
    Nanocomposites of PLA/ZnO nanofibers for medical applications: Antimicrobial effect, thermal, and mechanical behavior under cyclic stress
    (2022-01-18) NONATO, R.C.; MEI, L.H.I.; Baltus Cornelius Bonse; LEAL, C.V.; LEVY, C.E.; OLIVEIRA, F.A.; DELARMELINA, C.; DUARTE, M.C.T.; MORALES, A.R.
    The application of biodegradable and biocompatible polymer poly(lactic acid) (PLA) in the medical field has been widely studied. In this study, films of neat PLA and PLA containing 1 wt% ZnO nanofibers obtained by electrospinning (PLA/ZnO) were successfully molded by solvent-cast three-dimensional (3D) printing. Mechanical behavior was assessed by conventional dynamic mechanical analysis (DMA) and by adapting the equipment conditions to simulate a mechanical fatigue test at human body temperature—cyclic stress in isotherm at 36.5°C. DMA results showed that for temperatures above 30°C, the storage module of PLA/ZnO was higher when compared to neat PLA, and in the fatigue test, PLA/ZnO withstood more than 3600 cycles while neat PLA failed after an average of 1768 cycles. Differential scanning calorimetry (DSC) tests revealed that cyclic stress did not cause changes in the degree of crystallinity of the PLA. The microdilution and plating methods were applied to bacteria (Staphylococcus aureus, Salmonella, and Escherichia coli) and to yeast (Candida albicans) and revealed the antimicrobial effect of ZnO nanofibers and the PLA/ZnO composite. The antimicrobial activity and fatigue resistance of PLA/ZnO nanocomposites indicate that the material has potential for application in bone implants.