Engenharia de Materiais
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/17
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5 resultados
Resultados da Pesquisa
- 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.
- 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.
- Investigation on the effect of a compatibilizer on the fatigue behavior of PP/coir fiber composites(2011) Bettini S.H.P.; Antunes M.C.; Magnabosco R.The mechanical behavior of polypropylene (PP) and 30 wt% coir fiber reinforced PP composites, with and without compatibilizer, were assessed through monotonic (tensile and bending) and cyclic (fatigue) tests. Fatigue load controlled tests were conducted under tension loads at a frequency of 6 Hz. The fracture mechanism was accompanied by surface fracture analyses using both optical microscopy and scanning electron microscopy. The compatibilizer used was the PP grafted with maleic anhydride. The compatibilized composites exhibited longer fatigue life times. It was also concluded that the presence of coir fibers changed the preferential fatigue mechanism, because the fracture mechanism in PP was mainly caused by heat generated by viscous effects during solicitation (thermal fatigue), whereas in the compatibilized and noncompatibilized PP/coir composites the predominant fracture mechanism was mechanical fatigue. However, thermal fatigue was also observed in the composites, especially in the noncompatibilized ones. © POLYM. ENG. SCI., 2011. Copyright © 2011 Society of Plastics Engineers.
- Effect of sawdust surface treatment and compatibilizer addition on mechanical behavior, morphology, and moisture uptake of polypropylene/sawdust composites(2010) Bettini S.H.P.; Bonse B.C.; Melo E.A.; Munoz P.A.R.Polypropylene/sawdust composites were investigated to assess the effect of sawdust surface treatment and compatibilizer addition on polymer/fiber adhesion. Two silane coupling agents were used for sawdust surface treatment: vinyl-tris (2-methoxyethoxy) silane and (3- aminopropyl)triethoxysilane. Maleic anhydride grafted polypropylene was used as compatibilizer. Composites were prepared in a corotating twin-screw extruder coupled to a Haake torque rheometer and submitted to tensile and bending tests as well as scanning electron microscopy (SEM). Moisture uptake tests were also performed. Results showed that incorporation of untreated sawdust to polypropylene (PP) caused reduction in composite tensile strength and increase in stiffness. When the only treatment used was surface modification with silane coupling agents, no significant changes were observed in mechanical properties. However, when compatibilizer was added to the composites, tensile strength was increased, and % elongation at break reduced, indicating improved system compatibility. The composite presenting the highest increase in tensile strength was that containing sawdust treated with amino silane in addition to the compatibilizer. SEM analyses corroborated the mechanical property results. © 2009 Society of Plastics Engineers.
- Fatigue life of coir fiber reinforced PP composites: Effect of compatibilizer and coir fiber contents(2013) Antunes M.C.; Moraes D.V.O.; Magnabosco R.; Bonse B.C.; Bettini S.H.P.The fatigue behavior of polypropylene/coir fiber composites was investigated. Composites were prepared according to an experimental statistical design, in which the independent variables coir fiber and compatibilizer content were varied. The compatibilizer used was maleic anhydride grafted polypropylene (PP-g-MA). Compatibilizer free composites were also prepared. Composites were prepared in a corotating twin-screw extruder and the mechanical behavior of polypropylene/coir fiber composites were assessed through monotonic (tensile) and cyclic (fatigue) tests. Fatigue load controlled tests were conducted under tension-tension loads at a frequency of 6 Hz. The fracture mechanism was accompanied by surface fracture analyses using scanning electron microscopy (SEM). The results indicated the need for using compatibilizer in the composites; however, increase in compatibilizer content did not affect composite fatigue lifetime. Coir content was the variable with the strongest effect on composite properties; increasing this variable caused significant increase in fatigue life. © 2013 Society of Plastics Engineers.