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1.
Molecules ; 26(5)2021 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-33668952

RESUMO

In this study, we investigated the influence of epoxy resin treatment on the mechanical and tribological properties of hemp fiber (HF)-reinforced plant-derived polyamide 1010 (PA1010) biomass composites. HFs were surface-treated using four types of surface treatment methods: (a) alkaline treatment using sodium chlorite (NaClO2) solution, (b) surface treatment using epoxy resin (EP) solution after NaClO2 alkaline treatment, (c) surface treatment using an ureidosilane coupling agent after NaClO2 alkaline treatment (NaClO2 + A-1160), and (d) surface treatment using epoxy resin solution after the (c) surface treatment (NaClO2 + A-1160 + EP). The HF/PA1010 biomass composites were extruded using a twin-screw extruder and injection-molded. Their mechanical properties, such as tensile, bending, and dynamic mechanical properties, and tribological properties were evaluated by the ring-on-plate-type sliding wear test. The strength, modulus, specific wear rate, and limiting pv value of HF/PA1010 biomass composites improved with surface treatment using epoxy resin (NaClO2 + A-1160 + EP). In particular, the bending modulus of NaClO2 + A-1160 + EP improved by 48% more than that of NaClO2, and the specific wear rate of NaClO2 + A-1160 + EP was one-third that of NaClO2. This may be attributed to the change in the internal microstructure of the composites, such as the interfacial interaction between HF and PA1010 and fiber dispersion. As a result, the mode of friction and wear mechanism of these biomass composites also changed.


Assuntos
Resinas Compostas/química , Resinas Epóxi/química , Nylons/química , Biomassa , Teste de Materiais , Tamanho da Partícula , Estresse Mecânico , Propriedades de Superfície
2.
Molecules ; 26(4)2021 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-33546097

RESUMO

Polymer blends is a well-established and suitable method to produced new polymeric materials as compared to synthesis of a new polymer. The combination of two different types of polymers will produce a new and unique material, which has the attribute of both polymers. The aim of this work is to analyze mechanical and morphological properties of bio-phenolic/epoxy polymer blends to find the best formulation for future study. Bio-phenolic/epoxy polymer blends were fabricated using the hand lay-up method at different loading of bio-phenolic (5 wt%, 10 wt%, 15 wt%, 20 wt%, and 25 wt%) in the epoxy matrix whereas neat bio-phenolic and epoxy samples were also fabricated for comparison. Results indicated that mechanical properties were improved for bio-phenolic/epoxy polymer blends compared to neat epoxy and phenolic. In addition, there is no sign of phase separation in polymer blends. The highest tensile, flexural, and impact strength was shown by P-20(biophenolic-20 wt% and Epoxy-80 wt%) whereas P-25 (biophenolic-25 wt% and Epoxy-75 wt%) has the highest tensile and flexural modulus. Based on the finding, it is concluded that P-20 shows better overall mechanical properties among the polymer blends. Based on this finding, the bio-phenolic/epoxy blend with 20 wt% will be used for further study on flax-reinforced bio-phenolic/epoxy polymer blends.


Assuntos
Resinas Epóxi/química , Teste de Materiais , Estresse Mecânico , Resistência à Tração
3.
Carbohydr Polym ; 256: 117520, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33483041

RESUMO

Xylan and gelatin-based hydrogels are prepared in different molar ratios using ethylene glycol diglycidyl ether cross-linker. The hydrogels are characterized by Fourier transform infrared spectroscopy, morphology, thermal analysis, and swelling ratio. The rheological experiment shows the gels are cross-linked successfully by revealing the viscoelastic nature. The xylan-gelatin gel synthesized in a 5:1 molar ratio (hence XG5) has higher storage modulus, gelation temperature, and time among the synthesized gels. The adsorption behaviour of the synthesized gels is studied for the removal of methylene blue, by varying adsorbate concentration, pH, and temperature. Among the synthesized hydrogels, XG5 shows the highest adsorption capacity of 26.04 mg g-1 at pH = 5.84 and 25 °C. The kinetics of the adsorption process follows the pseudo-second-order model, and monolayer adsorption is adequately represented by the Langmuir isotherm model. The adsorption process is established as spontaneous, exothermic, and physisorption from the thermodynamic parameters.


Assuntos
Gelatina/química , Hidrogéis/química , Azul de Metileno/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Xilanos/química , Adsorção , Reagentes para Ligações Cruzadas/química , Elasticidade , Resinas Epóxi/química , Concentração de Íons de Hidrogênio , Cinética , Azul de Metileno/química , Reologia , Temperatura , Termodinâmica , Viscosidade , Poluentes Químicos da Água/química , Molhabilidade
4.
J Chromatogr A ; 1638: 461886, 2021 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-33465586

RESUMO

Major type of internal can coating used for food and beverages is made from epoxy resins, which contain among their components bisphenol A (BPA) or bisphenol A diglycidyl ether (BADGE). These components can be released and contaminate the food or beverage. There is no specific European legislation for coatings, but there is legislation on specific substances setting migration limits. Many investigations have paid attention to BPA due to its classification as endocrine disruptor, however, few studies are available concerning to other bisphenol analogues that have been used in the manufacture of these resins. To evaluate the presence of this family of compounds, ten cans of beverages were taken as study samples. Firstly, the type of coating was verified using an attenuated total reflectance-FTIR spectrometer to check the type of coating presents in most of the samples examined. A screening method was also performed to investigate potential volatiles from polymeric can coatings of beverages using Purge and Trap (P&T) technique coupled to gas chromatography with mass spectrometry detection (GC-MS). Moreover, a selective analytical method based on high performance liquid chromatography with fluorescence detection (HPLC-FLD) for the simultaneous identification and quantification of thirteen compounds including bisphenol analogues (BPA, BPB, BPC, BPE, BPF, BPG) and BADGEs (BADGE, BADGE.H2O, BADGE.2H2O, BADGE.HCl, BADGE.2HCl, BADGE.H2O.HCl, cyclo-di-BADGE) in the polymeric can coatings and in the beverage samples was applied. In addition, a liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) method was optimized for confirmation purposes. The method showed an adequate linearity (R2 >0.9994) and low detection levels down to 5 µg/L. Cyclo-di-BADGE was detected in all extracts of polymeric coatings. The concentrations ranged from 0.004 to 0.60 mg/dm2. No detectable amounts of bisphenol related compounds were found in any of the beverage samples at levels that may pose a risk to human health, suggesting a low intake of bisphenols from beverages.


Assuntos
Bebidas/análise , Cromatografia/métodos , Polímeros/química , Compostos Benzidrílicos/análise , Compostos Benzidrílicos/química , Dieta , Compostos de Epóxi/química , Resinas Epóxi/química , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Fenóis/análise , Padrões de Referência , Reprodutibilidade dos Testes , Espectrofotometria Infravermelho , Espectroscopia de Infravermelho com Transformada de Fourier , Volatilização
5.
Carbohydr Polym ; 253: 117213, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33278978

RESUMO

Effective methods to treat bacterial infections are highly desired as the abuse of antibiotics has caused multidrug-resistant. Polysaccharide hydrogel-based drug delivery systems possessing inherent large surface area and biocompatibility attributes provide a promising strategy for effective use of antibiotics. Here, we presented an effective method for fabricating macroporous polysaccharide hydrogels composed of dextran (DP) and polydopamine (PDA) for controlled release of antibiotics. The physicochemical properties of resulting DP hydrogels were systematically evaluated by measuring their swelling, viscoelasticity, morphology, sorption and thermal stability, and we could control these properties through simply changing the PDA concentration in a pre-gel solution. The low cytotoxicity of DP hydrogels was demonstrated through a co-culture with mouse fibroblast cells. Moreover, in vitro/vivo antibacterial properties of the drug-loading DP hydrogels were evaluated, and they exhibited good antibacterial and healing performances. We believe that the proposed strategy for facilitation and optimization of polysaccharide hydrogels could offer more hydrogel dressings when choosing suitable carriers for sustained release of antibiotics.


Assuntos
Antibacterianos/administração & dosagem , Clorexidina/administração & dosagem , Dextranos/química , Portadores de Fármacos/química , Hidrogéis/química , Indóis/química , Polímeros/química , Cicatrização/efeitos dos fármacos , Animais , Materiais Biocompatíveis/química , Sobrevivência Celular/efeitos dos fármacos , Reagentes para Ligações Cruzadas/química , Liberação Controlada de Fármacos , Resinas Epóxi/química , Escherichia coli/efeitos dos fármacos , Masculino , Camundongos , Células NIH 3T3 , Ratos , Ratos Sprague-Dawley , Staphylococcus aureus/efeitos dos fármacos
6.
Sci Rep ; 10(1): 21871, 2020 12 14.
Artigo em Inglês | MEDLINE | ID: mdl-33318540

RESUMO

In-resin CLEM of Epon embedded samples can greatly simplify the correlation of fluorescent images with electron micrographs. The usefulness of this technique is limited at present by the low number of fluorescent proteins that resist CLEM processing. Additionally, no study has reported the possibility of two-color in-resin CLEM of Epon embedded cells. In this study, we screened for monomeric green and red fluorescent proteins that resist CLEM processing. We identified mWasabi, CoGFP variant 0, and mCherry2; two green and one red fluorescent proteins as alternatives for in-resin CLEM. We expressed mitochondria-localized mCherry2 and histone H2B tagged with CoGFP variant 0 in cells. Green and red fluorescence was detected in 100 nm-thin sections of the Epon-embedded cells. In the same thin sections, we correlated the fluorescent signals to mitochondria and the nucleus using a scanning electron microscope. Similar results were obtained when endoplasmic reticulum-localized mCherry2 and histone H2B tagged with CoGFP variant 0 were expressed in the cells. Two-color in-resin CLEM of two cytoplasmic organelles, mitochondria and endoplasmic reticulum, was also achieved using mitochondria-localized mCherry2 and endoplasmic reticulum-localized mWasabi. In summary, we report three new fluorescent protein-alternatives suitable for in-resin CLEM of Epon-embedded samples, and achieved Epon-based two-color in-resin CLEM.


Assuntos
Células Imobilizadas/metabolismo , Resinas Epóxi/química , Fluorescência , Proteínas de Fluorescência Verde/metabolismo , Osmio/farmacologia , Células HEK293 , Humanos
7.
Niger J Clin Pract ; 23(6): 811-816, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32525116

RESUMO

Background: An optimum bonding between the sealer and dentin is important for impermeable root canal filling and many procedures were applied to improve root canal dentin and in turn the bond strength between the sealer and dentine. There is lack of sufficient data on the effect of nonthermal plasma application on the bond strength of sealers to the root canal dentin. Aim: The purpose of this study was to evaluate the effect of NAP on the push-out bond strength (PBS) of a bioceramic and resin-based root canal sealer (RCS) to root canal dentin. Materials and Methods: Forty single-rooted mandibular premolars were decoronated. After preparation and final irrigation, the specimens were divided into four groups (n = 10). Group AH: Root canals were filled with gutta-percha (GP) and AH Plus RCS, Group P-AH: Root canals were filled with GP and AH Plus RCS following the NAP application, Group BC: Root canals were filled with GP and Endosequence BC RCS, and Group P-BC: Root canals were filled with GP and Endosequence BC RCS following the NAP application. Then roots were sectioned horizontally to obtain ~1 mm thick dentin disks. PBS test was performed to the second (coronal) and fourth (middle) slices. Data were analyzed with the Kruskal-Wallis and t-test. Results: There was a statistically significant difference among the groups for both coronal and middle regions (P < 0.05). P-BC group showed higher PBS than AH and P-AH groups in the coronal region. P-BC group showed higher PBS than the other groups in the middle region. Conclusions: The use of NAP did not influence the push-out bond strength of AH-Plus sealer to the root canal dentin. The Endosequence-BC sealer showed a better bond strength than the AH-Plus sealer after NAP application.


Assuntos
Cavidade Pulpar , Materiais Restauradores do Canal Radicular/química , Obturação do Canal Radicular/métodos , Cimento de Óxido de Zinco e Eugenol , Dente Pré-Molar , Colagem Dentária , Dentina , Resinas Epóxi/química , Guta-Percha/química , Humanos , Teste de Materiais , Pressão , Preparo de Canal Radicular/métodos , Temperatura
8.
Carbohydr Polym ; 237: 116189, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32241412

RESUMO

(1→3)-α-d-glucan synthesized by glucosyltransferase J (GtfJ) cloned from Streptococcus salivarius was regioselectively aminated as 6-amino-6-deoxy-(1→3)-α-d-glucan (aminoglucan) through three steps: bromination, azidation, and reduction. The degree of substitution of the amino group was determined by elemental analysis to be 0.97 and the molecular weight was 3.74×104 as measured by size exclusion chromatography. The regioselective amination at the C6 position of every pyranose ring was confirmed by 1H/13C NMR and solid state 15N cross polarization/magic angle spinning NMR spectroscopy. Aminoglucan was characterized by FT-IR, X-ray diffraction and thermogravimetric analysis. Solubility of aminoglucan in various solvents was investigated and confirmed in aqueous solution at pH ≤ 11. Therefore, aminoglucan was crosslinked with ethylene glycol diglycidyl ether (EGDE) by an epoxy-ring opening reaction under alkaline conditions. The obtained EGDE-crosslinked aminoglucan hydrogels were highly swellable in water owing to a strong water-holding ability and no water was released on compression and breaking of the gels.


Assuntos
Reagentes para Ligações Cruzadas/química , Resinas Epóxi/química , Glucanos/química , Hidrogéis/química , Aminação , Solubilidade , Água/química
9.
Int J Mol Sci ; 21(3)2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-32012889

RESUMO

Composite lightweight materials for X-ray shielding applications were studied anddeveloped with the goal of replacing traditional screens made of lead and steel, with innovativematerials with similar shielding properties, but lighter, more easily formed and workable, with lowerimpact on the environment and reduced toxicity for human health. New epoxy-based compositesadditivated with barium sulfate and bismuth oxide were designed through simulations performedwith software based on Geant4. Then, they were prepared and characterized using differenttechniques starting from digital radiography in order to test the radiopacity of the composites,in comparison with traditional materials. The lower environmental impact and toxicity of theseinnovative screens were quantified by Life Cycle Assessment (LCA) calculation based on the ecoinventdatabase, within the openLCA framework. Optimized mixtures are (i) 20% epoxy/60% bismuthoxide/20% barite, which guarantees the best performance in X-ray shielding, largely overcomingsteel, but higher in costs and a weight reduction of circa 60%; (ii) 20% epoxy/40% bismuth oxide/40%barite which has slightly lower performances in shielding, but it is lighter and cheaper than thefirst one and (iii) the 20% epoxy/20% bismuth oxide/60% barite which is the cheapest material, stillmaintaining the X-ray shielding of steel. Depending on the cost/efficiency request of the specificapplication (industrial ra.


Assuntos
Sulfato de Bário/química , Bismuto/química , Resinas Epóxi/síntese química , Resinas Epóxi/química , Dureza , Peso Molecular , Intensificação de Imagem Radiográfica , Software
10.
Talanta ; 208: 120348, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31816782

RESUMO

This manuscript presents a voltammetric biosensing study with use of molecularly imprinted polymers to detect histamine in wine. Polymer beads were synthesized by standard precipitation polymerization method and implemented on the electrode surface via sol-gel immobilization. Scanning and confocal microscopy examinations permitted characterizing the material. Adsorptive stripping voltammetry in differential mode was the technique chosen for final application, selecting an enrichment time of 5 min. These conditions permitted a limit of detection of 0.19 µg mL-1 (1.0 µM), with a linear response range from 0.5 to 6.0 µg mL-1 (2.71-32.4 µM). The repeatability of the measurements was 4.6% relative standard deviation (n = 12). Principal component analysis showed the ability of the prepared receptor for discriminating other biogenic amines and potential interfering species. A final application, illustrating the determination of histamine, was completed to show agreement of results between the fluorimetric reference method and the proposed electrochemical approach.


Assuntos
Técnicas Biossensoriais/métodos , Eletrodos , Resinas Epóxi/química , Grafite/química , Histamina/análise , Polímeros/química , Vinho/análise , Técnicas Eletroquímicas , Limite de Detecção , Impressão Molecular
11.
J Appl Oral Sci ; 28: e20190005, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31800870

RESUMO

other: Chitosan is a natural, biocompatible chelating substance with potential for dental use. This study compared the effects of final canal irrigation with chitosan and EDTA on dentin microhardness, sealer dentin tubules penetration capacity, and push-out strength. METHODOLOGY: Fifty canine roots were distributed according to the final irrigation protocol (n=10): G1- 15% EDTA with conventional irrigation; G2- 15% EDTA with Endovac; G3- 0.2% chitosan with conventional irrigation; G4- 0.2% chitosan with Endovac; and G5- without irrigation. Specimens were obturated (AH Plus) and sectioned in 3 slices per root third. The first slice was used for microhardness and sealer penetration assessments under a laser confocal microscope. The second was utilized in a push-out strength test. The third slice was discarded. Data were analyzed using 2-way ANOVA and Tukey's post hoc test (α<0.05). Failure mode was determined at x40 magnification. RESULTS: Microhardness reduction was more significant in groups G2 and G4 (p<0.05). Sealer penetration through dentin was significantly greater in group G2 (p<0.05). There was no significant difference between groups G1, G3, and G4 (p>0.05). In general, all experimental groups presented similar bond resistance (p>0.05) that significantly differed from the control (p<0.001). Mixed type failures were predominant. CONCLUSIONS: In general, 0.2% chitosan and 15% EDTA solutions act in a similar manner with regard to the variables studied. The use of Endovac potentiates the effect of these solutions.


Assuntos
Quelantes/química , Quitosana/química , Colagem Dentária/métodos , Dentina/efeitos dos fármacos , Ácido Edético/química , Irrigantes do Canal Radicular/química , Análise de Variância , Resinas Epóxi/química , Testes de Dureza , Humanos , Teste de Materiais , Microscopia Confocal , Pessoa de Meia-Idade , Valores de Referência , Reprodutibilidade dos Testes , Materiais Restauradores do Canal Radicular/química , Resistência ao Cisalhamento , Propriedades de Superfície/efeitos dos fármacos
12.
Nat Methods ; 17(1): 55-58, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31611693

RESUMO

Super-resolution correlative light and electron microscopy (SR-CLEM) is a powerful approach for imaging specific molecules at the nanoscale in the context of the cellular ultrastructure. Epon epoxy resin embedding offers advantages for SR-CLEM, including ultrastructural preservation and high quality sectioning. However, Epon embedding eliminates fluorescence from most fluorescent proteins. We describe a photocontrollable fluorescent protein, mEosEM, that can survive Epon embedding after osmium tetroxide (OsO4) treatment for improved SR-CLEM.


Assuntos
Resinas Epóxi/química , Proteínas Luminescentes/química , Proteínas Luminescentes/metabolismo , Microscopia Eletrônica/métodos , Organelas/ultraestrutura , Tetróxido de Ósmio/química , Manejo de Espécimes/métodos , Animais , Células CHO , Cricetulus , Fluorescência , Imunofluorescência/métodos , Humanos , Microscopia de Fluorescência , Imagem Molecular , Organelas/metabolismo
13.
J Chromatogr A ; 1609: 460448, 2020 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-31421793

RESUMO

In this work, we reported a simple two-step method for the synthesis of magnetic mesoporous epoxy resin (MMER), including one-pot template-free hydrothermal synthesis of nanoscale amine-functionalized magnetic nanoparticles (MN-NH2) and initiator-free ring-opening polymerization of epoxy resin. The resultant MMER was characterized in detail by transmission electron microscope (TEM), Fourier transform-infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS), thermogravimetic analysis (TGA) and magnetization curves. These results demonstrated successful synthesis of MMER with sufficient magnetic property and excellent thermal stability. The epoxy resin was covalent bonding MN-NH2 on and synthesized by hydrophobic monomers, so the MMER exhibited excellent adsorption quantity for hydrophobic bile acids. The MMER was used as magnetic solid-phase extraction (MSPE) sorbent, and combined with liquid chromatography-tandem mass spectrometry to extract and monitor 11 kinds of bile acids from serum sample. The proposed MSPE combined with LC-MS/MS method exhibited low limit of detection between 0.1 and 5 ng mL-1. In blank serum sample, 9 kinds of bile acids were detected, and ranged from -2.29 ng mL-1 to 6.86 ng mL-1. In standard addition recovery test, the recovery values of detectable bile acids ranged 102.4% to 108.5%, 96.0% to 104.0% and 82.3% to 103.3% when spiked with 0.2, 2.0 and 20 ng mL-1, respectively. The intra- and inter-day precision (n = 6) ranged 3.7% to 5.9% and 7.0% to 9.5%, respectively. The above results demonstrated that the MSPE combined with LC-MS/MS method was accurate and effective for quantitative determination of bile acids from complex biological samples.


Assuntos
Ácidos e Sais Biliares/sangue , Ácidos e Sais Biliares/isolamento & purificação , Resinas Epóxi/química , Fenômenos Magnéticos , Polimerização , Adsorção , Cromatografia Líquida , Humanos , Limite de Detecção , Nanopartículas/química , Nanopartículas/ultraestrutura , Porosidade , Extração em Fase Sólida , Soluções , Espectroscopia de Infravermelho com Transformada de Fourier , Espectrometria de Massas em Tandem
14.
Luminescence ; 35(4): 478-485, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31854500

RESUMO

A facile approach for possible industrial production of long-persistent phosphorescence, continuing to emitting light for a long time period, smart cobbles were developed toward photoluminescent hard surfaces. The inorganic strontium aluminium oxide pigment doped with rare earth elements was added to a synthetic organic epoxy in the presence of polyamine as a hardener to make a phosphor-loaded viscous fluid that can then be hardened in a few minutes. The transparency of the solid cobbles can be accomplished easily using homogeneous dispersion of the phosphor in the epoxy resin fluid before the addition of a hardener to avoid pigment aggregation. This pigment-epoxy formula can be easily applied industrially onto flagstones surfaces under ambient conditions. The photoluminescent cobblestones demonstrated an optimum excitation wavelength at 366 nm and an emission band at 521 nm with a long-persistent phosphorescence cobble surface. The development of a translucent white colour under normal daylight, bright green under ultraviolet (UV) irradiation, bright white colour after 30 sec in the dark, and phosphorescent green colour after 75 min in the dark was indicated using Commission Internationale de l'Eclairage (CIE) Laboratory coloration measurements. The luminescent hard composite cobble exhibited a highly durable and reversible long-persistent phosphorescence light. Photoluminescence, morphological, and hardness properties as well as the elemental composition of the prepared cobbles were explored.


Assuntos
Óxido de Alumínio/química , Resinas Epóxi/química , Európio/química , Luminescência , Estrôncio/química , Medições Luminescentes , Tamanho da Partícula , Processos Fotoquímicos , Propriedades de Superfície
15.
Histochem Cell Biol ; 153(2): 121-127, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31848702

RESUMO

Epoxy-embedded semithin sections are useful for the analysis of cell and tissue organization, as well as for the processing of samples for transmission electron microscopy. Because only a very limited number of staining protocols have been developed for epoxy-embedded sections; semithin sections are used infrequently compared to conventional paraffin sections. Here, we describe a simple and reproducible polychromatic protocol for the routine staining of epoxy-embedded semithin sections by adapting Twort's staining method (mixture of neutral red and fast green FCF). The method can be used for the visualization of cellular organization as well as for the detection of elastic and collagen fibers. The proposed protocol demonstrated the best results for samples fixed for transmission electron microscopy, which suggests, as we demonstrated here, that this staining protocol can also be used for correlative light and electron microscopy.


Assuntos
Resinas Epóxi/química , Técnicas Histológicas , Tetróxido de Ósmio/química , Coloração e Rotulagem , Animais , Glutaral/química , Camundongos , Camundongos Endogâmicos BALB C , Microscopia Eletrônica , Coelhos
17.
Molecules ; 24(23)2019 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-31810163

RESUMO

The aim of the present study was to establish a standard methodology for the extraction of epoxy resin precursors from several types of food packages (cans, multi-layered composite material, and cups) with selected simulation media (distilled water, 5% ethanol, 3% dimethyl sulfoxide, 5% acetic acid, artificial saliva) at different extraction times and temperatures (factors). Biological analyses were conducted to determine the acute toxicity levels of the extracts (with Vibrio fischeri bacteria) and their endocrine potential (with Saccharomyces cerevisiae yeasts). In parallel, liquid chromatography-tandem mass spectrometry was performed to determine levels of bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (mixture of isomers, BFDGE), ring novolac glycidyl ether (3-ring NOGE), and their derivatives. The variation induced by the different experimental factors was statistically evaluated with analysis of variance simultaneous component analysis (ASCA). Our findings demonstrate the value of using a holistic approach to best partition the effects contributing to the end points of these assessments, and offer further guidance for adopting such a methodology, thus being a broadly useful reference for understanding the phenomena related to the impacts of food packaging materials on quality for long- and short-term storage, while offering a general method for analysis.


Assuntos
Resinas Epóxi/análise , Resinas Epóxi/química , Temperatura , Resinas Epóxi/toxicidade , Embalagem de Alimentos , Modelos Teóricos
18.
Biomed Res Int ; 2019: 3512606, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31815132

RESUMO

Objective: The aim of the present study was to characterize a novel resin-based monoblock endodontic obturation system consisting of a polymeric cone and a resin-based endodontic sealer. Methods: The preliminary tests performed for the experimental cone were as follows: cohesive strength, dimensional stability, standardization of the diameter and taper, calcium ion release, and radiopacity, for the characterization of the experimental sealer, film thickness and flow tests were performed. Tests were performed according to the American National Standards Institute/American Dental Association (ANSI/ADA) Standards Nos. 57 and 78. The experimental cone was compared to gutta-percha, whereas the experimental sealer was compared to AH Plus. Data were analyzed by Student's t-test (α = 0.05). Results: The experimental cone had superior values for cohesive strength and dimensional stability compared to gutta-percha. Regarding calcium ion release, the experimental system continued to release calcium ions after 30 days. Film thickness was similar for both endodontic sealers; conversely, the experimental resin-based sealer achieved higher values for flow compared to AH Plus. Conclusion: The experimental resin-based monoblock obturation system fully met the requirements of the ANSI/ADA Standard No. 78 and the ANSI/ADA Standard No. 57, except for radiopacity. Considering this, further studies are still needed to evaluate other radiopacifiers and the effect of their incorporation on the physicochemical properties of this novel resin-based monoblock endodontic obturation system.


Assuntos
Resinas Epóxi/química , Teste de Materiais , Materiais Restauradores do Canal Radicular/química , Obturação do Canal Radicular , Cálcio/química , Compostos de Cálcio/química , Guta-Percha/química , Humanos , Reologia , Propriedades de Superfície , Resistência à Tração
19.
Molecules ; 24(21)2019 Nov 03.
Artigo em Inglês | MEDLINE | ID: mdl-31684155

RESUMO

The bending properties of three-dimensional (3Dim) and five-directional (5Dir) braided/epoxy resin composites at room temperature, 90 °C, 110 °C, and 150 °C and heating for 0.25 h, 10 h, and 30 h, respectively, were studied. The effect of different temperatures and heating times on the bending property of these composites was discussed. The results showed that the bending strength of these composites at 90 °C, 110 °C, and 150 °C and heating time of 0.25 h is 33.86%, 46.27%, and 83.94% lower, respectively, than that at room temperature. In addition, 3Dim-5Dir braided composites exhibit different damage modes at different temperatures, revealing different failure mechanisms. Heating temperature has greater influence on the bending properties of these composites than heating time. The results provided a basis for the application of resin-based 3Dim-5Dir braided/epoxy resin composites at different temperatures.


Assuntos
Resinas Compostas/química , Resinas Epóxi/química , Teste de Materiais , Temperatura Alta , Polimerização
20.
Molecules ; 24(23)2019 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-31779081

RESUMO

The aim of this work was an investigation of the ability of gallic (GA) and ellagic (EA) acids, which are phenolic compounds encountered in various plants, to act as flame retardants (FRs) for epoxy resins. In order to improve their fireproofing properties, GA and EA were treated with boric acid (to obtain gallic acid derivatives (GAD) and ellagic acid derivatives (EAD)) to introduce borate ester moieties. Thermogravimetric analysis (TGA) highlighted the good charring ability of GA and EA, which was enhanced by boration. The grafting of borate groups was also shown to increase the thermal stability of GA and EA that goes up respectively from 269 to 528 °C and from 496 to 628 °C. The phenolic-based components were then incorporated into an epoxy resin formulated from diglycidyl ether of bisphenol A (DGEBA) and isophorone diamine (IPDA) (72, 18, and 10 wt.% of DGEBA, IPDA, and GA or EA, respectively). According to differential scanning calorimetry (DSC), the glass transition temperature (Tg) of the thermosets was decreased. Its values ranged from 137 up to 108 °C after adding the phenolic-based components. A cone calorimeter was used to evaluate the burning behavior of the formulated thermosets. A significant reduction of the peak of heat release rate (pHRR) for combustion was detected. Indeed, with 10 wt.% of GA and EA, pHRR was reduced by 12 and 44%, respectively, compared to that for neat epoxy resin. GAD and EAD also induced the decrease of pHRR values by 65 and 33%, respectively. In addition, a barrier effect was observed for the resin containing GAD. These results show the important influence of the biobased phenolic compounds and their boron derivatives on the fire behavior of a partially biobased epoxy resin.


Assuntos
Ácido Elágico/química , Resinas Epóxi/química , Retardadores de Chama/síntese química , Ácido Gálico/química , Compostos Benzidrílicos/química , Calorimetria/métodos , Cicloexilaminas/química , Fenóis/química , Temperatura de Transição
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