Foaming of EVA/starch blends: Characterization of the structure, physical properties, and biodegradability

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Anthocyanin incorporated dental copolymer: bacterial growth inhibition, mechanical properties, and compound release rates and stability by (1)h NMR

Objective. To evaluate bacterial growth inhibition, mechanical properties, and compound release rate and stability of copolymers incorporated with anthocyanin (ACY; Vaccinium macrocarpon). Methods. Resin samples were prepared (Bis-GMA/TEGDMA at 70/30 mol%) and incorporated with 2 w/w% of either ACY or chlorhexidine (CHX), except for the control group. Samples were individually immersed in a bacterial culture (Streptococcus mutans) for 24 h. Cell viability (n = 3) was assessed by counting the number of colony forming units on replica agar plates. Flexural strength (FS) and elastic modulus (E) were tested on a universal testing machine (n = 8). Compound release and chemical stability were evaluated by UV spectrophotometry and (1)H NMR (n = 3). Data were analyzed by one-way ANOVA and Tukey's test ( α = 0.05). Results. Both compounds inhibited S. mutans growth, with CHX being most effective (P < 0.05). Control resin had the lowest FS and E values, followed by ACY and CHX, with statistical difference between control and CHX groups for both mechanical properties (P < 0.05). The 24 h compound release rates were ACY: 1.33 μg/mL and CHX: 1.92 μg/mL. (1)H NMR spectra suggests that both compounds remained stable after being released in water. Conclusion. The present findings indicate that anthocyanins might be used as a natural antibacterial agent in resin based materials.

Estudo neuroanatômico do éncefalo bovino por ressonância magnética

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A quantitative analysis of the polarization reversal in the 73 mol % vinylidene fluoride-27 mol % trifluorethylene copolymer

We show that a time-dependent, effective-medium approximation essentially explains the time behavior of the polarization reversals obtained in doped copolymers of vinylidene fluoride and trifluorethylene at 60°C by Ieda, Fukada, and Wada [J. Appl. Phys. 64, 2026 (1988)], who attributed the observed effects to charge accumulation at the boundaries of the permanently polarized crystallites. Moreover, the results seem to indicate that some hindrance (perhaps of mechanical origin) opposes the action of the switching electric field.

Regeneração óssea guiada com o uso de membrana de copolímero PLA/PGA em levantamento da membrana do seio maxilar: estudo experimental com análises histomorfométrica e imunoistoquímica

Pós-graduação em Odontologia - FOA

Avaliação histomor fométrica dos efeitos da movimentação dentária induzida sobre molares murinos submetidos à luxação extrusiva em períodos tardios

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Suppression of vibrations in a nonlinear half-car model using a magneto-rheological damper

The present work investigates the nonlinear response of a half-car model. The disturbances of the road are assumed to be sinusoidal. After constructing the bifurcation diagram, we use the 0-1 test to identify chaotic motions. The main objective of this study is to eliminate chaotic behavior of the chassis and reduce its vibrations. To accomplish this, a semi-active vehicle suspension control system, using magneto-rheological dampers, is proposed. The proposed semi-active control strategy consists of two nonlinear control laws: a feedforward control, and a feedback control. They are obtained by considering the SDRE (State Dependent Riccati Equation) control, where the control parameter is the voltage applied to the coils of the magneto-rheological dampers. Numerical results show that the proposed control method is effective in significantly reducing of the chassis vibration, increasing, therefore, passenger comfort.

On suppression of chaotic motions of a portal frame structure under non-ideal loading using a magneto-rheological damper

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Síntese e caracterização de monômeros azo-carbonatos para a preparação de poli(azo-carbonato)s e poli)azo-uretana)s

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Aplicação de projeto de experimento no processo de manufatura de uma bobina de alumínio

TProducts must follow specifications in order to attend demands requested. In terms of rolled aluminum, one of the most significant items for customers is coil thickness. This is because only a tiny variation in thickness might cause a serious problem on customer's manufacturing line. Thereby, this research aims to analyze through design of experiments which factors and how they affect the thickness of aluminum coils. The response variable of the experiment is the thickness of aluminum coil, tensile strenght and yield strenght are the factors of the experiment and trimmers machines were considered as blocking. Data were obtained through tensile tests. The result of the experiment states that, according to the analysis of variance (ANOVA), while there is significant difference between the two levels of tensile strength, there is not any difference between the two levels of yield strength and trimmers machines. The thickness of the aluminum coils with high values of tensile strength tends to be thicker when compared with low values of tensile strength

Análise de um trocador de calor tipo serpentina de uma planta de hipoclorito de sódio

This study aims to analyze the capacity of a helical coil heat exchanger to reach the requested heat transfer rates by a sodium hypochlorite production process. This heat exchanger was installed in an experimental way in order to reuse a source of low-temperatures water in such a way to become a more economical alternative than the existing cooling tower. Firstly, the concepts related to the theory of heat transfer applicable to the case were introduced. Then, the mapping of the main information about the production process and the technical specification of the current cooling system equipment's was realized. Using the dimensions of the heat exchanger installed today as reference, the calculations for determining the ideal length of the coil to different flows of hot fluid were performed. Finally, it was concluded that the heat exchanger currently employed does not provide heat transfer rates required for the maximum flow rate value supported by the cooling tower

Enhanced Polymer Grafting from Multiwalled Carbon Nanotubes through Living Anionic Surface-Initiated Polymerization

Anionic surface-initiated polymerization of ethylene oxide and styrene has been performed using multiwalled carbon nanotubes (MWNTs) functionalized with anionic initiators. The surface of MWNTs was modified via covalent attachment of precursor anions such as 4-hydroxyethyl benzocyclobutene (BCBEO) and 1-benzocyclobutene-1′-phenylethylene (BCB-PE) through Diels-Alder cycloaddition at 235 °C. Surface-functionalized MWNTs-g-(BCB-EO) n and MWNTs-g-(BCB-PE) n with 23 and 54 wt % precursor initiators, respectively, were used for the polymerizations. Alkoxide anion on the surface of MWNTs-g-(BCB-EO) n was generated through reaction with potassium triphenylmethane for the polymerization of ethylene oxide in tetrahydrofuran and phenyl substituted alkyllithium was generated from the surface of MWNTs-g-(BCB-PE) n using sec-butyllithium for the polymerization of styrene in benzene. In both cases, the initiation was found to be very slow because of the heterogeneous reaction medium. However, the MWNTs gradually dispersed in the reaction medium during the polymerization. A pale green color was noticed in the case of ethylene oxide polymerization and the color of initiator as well as the propagating anions was not discernible visually in styrene polymerization. Polymer grafted nanocomposites, MWNTs-g-(BCB-PEO) n and MWNTs-g-(BCB-PS) n containing a very high percentage of hairy polymer with a small fraction of MWNTs (<1 wt %) were obtained. The conversion of ethylene oxide and the weight percent of PEO on the surface of the MWNTs increased with increasing reaction time indicating a controlled polymerization. The polymer-grafted MWNTs were characterized using FTIR, 1H NMR, Raman spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and transmission electron microscopy (TEM). Size exclusion chromatography of the polymer grafted MWNTs revealed broad molecular weight distributions (1.3 < Mw/Mn < 1.8) indicating the presence of different sizes of polymer nanocomposites. The TEM images showed the presence of thick layers of polymer up to 30 nm around the MWNTs. The living nature of the growing polystyryllithium was used to produce diblock copolymer grafts using sequential polymerization of isoprene on the surface of MWNTs.

High-Pressure Micellar Solutions of Polystyrene-block-polybutadiene and Polystyrene-block-polyisoprene in Propane Exhibit Cloud-Pressure Reduction and Distinct Micellization End Points

Micellar solutions of polystyrene-block-polybutadiene and polystyrene-block-polyisoprene in propane are found to exhibit significantly lower cloud pressures than the corresponding hypothetical nonmicellar solutions. Such a cloud-pressure reduction indicates the extent to which micelle formation enhances the apparent diblock solubility in near-critical and hence compressible propane. Concentration-dependent pressure-temperature points beyond which no micelles can be formed, referred to as the micellization end points, are found to depend on the block type, size, and ratio. The cloud-pressure reduction and the micellization end point measured for styrene-diene diblocks in propane should be characteristic of all amphiphilic diblock copolymer solutions that form micelles in compressible solvents.

Impact of Solvent Quality on the Density Profiles of Looped Triblock Copolymer Brushes by Neutron Reflectivity Measurements

Preferential adsorption of poly(2-vinylpyridine)-deuterated polystyrene-poly(2-vinylpyridine) (PVP-dPS-PVP) triblock copolymers from toluene onto silicon leads to the formation of dPS loops tethered by the PVP end blocks. Using neutron reflectometry, we have determined the segment density profiles of these looped polymer brushes in toluene, a good solvent for the dPS block, and in cyclohexane at 20 °C (poor solvent), 32 °C, (near-Θ solvent), and 50 °C (marginal solvent). While the swelling behavior qualitatively agrees with that observed for singly grafted brushes, there are interesting differences in the local structural details: In a good solvent, the segment density profiles are composed of an inner parabolic region and a long, extended tail. In cyclohexane, the profiles are described by exponential decays. We ascribe these features to a novel polydispersity effect that arises due to tethering the PS loops by both ends. The results also show that the less dense layers undergo more significant changes in swollen height as solvent quality is changed and that the looped brushes of different molecular weight, asymmetry, and tethering density adhere to scaling relationships derived for lightly cross-linked polymer gels.

Aplicação de projeto de experimento no processo de manufatura de uma bobina de alumínio

TProducts must follow specifications in order to attend demands requested. In terms of rolled aluminum, one of the most significant items for customers is coil thickness. This is because only a tiny variation in thickness might cause a serious problem on customer's manufacturing line. Thereby, this research aims to analyze through design of experiments which factors and how they affect the thickness of aluminum coils. The response variable of the experiment is the thickness of aluminum coil, tensile strenght and yield strenght are the factors of the experiment and trimmers machines were considered as blocking. Data were obtained through tensile tests. The result of the experiment states that, according to the analysis of variance (ANOVA), while there is significant difference between the two levels of tensile strength, there is not any difference between the two levels of yield strength and trimmers machines. The thickness of the aluminum coils with high values of tensile strength tends to be thicker when compared with low values of tensile strength