Artigos
URI permanente para esta coleçãohttps://repositorio.fei.edu.br/handle/FEI/795
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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.
- Tribology and Crystallinity in pivot bearings of Ventricular Assist Devices(2020-03-05) MARQUIORI, D. S.; FLORENTINO, P. C.; ARAKI, S. Y.; FUJITA, I. K.; BASSO, R.; BABETTO, A.; MORO, J.; Baltus Cornelius Bonse; LEÃO, T. F.; ANDRADE, A. J. P.; BOCK, E. G. P.Ventricular Assist Devices are blood pumps used in patients with Congestive Heart Failure who are waiting for a heart transplant. They aim to assist the ventricle to pump out blood in physiological circulation by increasing aortic pressure and decreasing intraventricular pressure. The IFSP Laboratory of Bioengineering and Biomaterials (BIOENG) has been developing an Implantable Centrifugal Blood Pump called CARoL for mechanical circulatory support. The objective of this dissertation is to evaluate the changes in the crystallinity of the polymeric Pivot Bearings supporting the impeller of this pump when subjected to friction generated by rotation of zirconia oxide ceramic shafts. The adopted methodology consisted of submitting new and used samples of: a) bearings set made of polyamide 6; and b) the set made of poly-ether-ether-ketone. Those new and used samples were characterized by X-ray diffraction tests and Infrared Spectroscopy. The diffractograms and spectra obtained were compared to evaluate the bearing crystallinity, for both polymers before and after friction. The tests carried out showed diffractograms and similar spectra for the new and used samples, thus, there are indications that the friction generated by the rotation of the shafts did not change the crystallinity of the polymeric bearings supporting the pump rotor.
- A Recycling-Focused Assessment of the Oxidative Thermomechanical Degradation of HDPE Melt Containing Pro-oxidant(2019-12-21) BABETTO, A. S.; ANTUNES, M. C.; BETTINI, S. H. P.; Baltus Cornelius BonseThis study shows the effect of a pro-oxidant (oxo-biodegradable) additive on the oxidative thermomechanical degradation of high-density polyethylene (HDPE). It also allows us to predict the behavior of the material when subjected to mechanical recycling or to biodegradation. When HDPE, one of the most consumed thermoplastics worldwide, is transformed into a product or when subjected to primary and/or secondary recycling it will undergo thermomechanical degradation. According to current standards HDPE is not biodegradable, therefore pro-oxidants are added to many HDPE products, which can compromise the product's life. Knowledge on the influence of pro-oxidants on HDPE in the melt is limited and the objective of this study is to assess the behavior of HDPE containing pro-oxidant manganese stearate (MnSt) in the oxidative thermomechanical degradation process. Thermomechanical degradation tests were conducted in a closed-chamber torque rheometer. FTIR and SEC results agreed with those of torque rheometry and showed that oxidative thermomechanical degradation of HDPE increases with increasing manganese stearate concentration. Degradation resulted in an increase in the number of oxygenated functional groups, mainly ketones, aldehydes and carboxylic acids, and reduction in the weight-average molar mass of HDPE. MnSt may have acted both as a lubricant and pro-oxidant during processing with predominance of one or the other effect at different stages along the oxidative thermomechanical degradation of HDPE.