Thermo-gravimetric analysis (TGA) after different exposures of high density polyethylene (HDPE) and poly vinyl chloride (PVC) geomembranes

This paper presents the results of thermogravimetric analysis (TGA) tests in PVC (1.0; 2.0 mm) and HDPE (0.8; 2.5 mm) geomembranes exposed to weathering and leachate after 30 months. The aim of this paper is the comparison of fresh and exposed samples to assess the degradation process concerning the total loss of mass of geomembranes. The exposure was conducted in accordance with the recommendations of ASTM standards. The TGA tests were carried out according to ASTM D6370 and E2105. Results show, for instance, that for PVC geomembrane the largest reductions of plasticizers occurred for samples exposed to weathering. The loss of plasticizers after the exposure contributed to the decrease of deformation and consequent increase in stiffness. TGA tests shows to be a valuable tool to control the quality of the materials. © 2012 ejge.

Blends of poly(3-hydroxybutyrate) and poly(p-dioxanone): miscibility, thermal stability and biocompatibility

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Enhancement of thermal stability, strength and extensibility of lipid-based polyurethanes with cellulose-based nanofibers

Cellulose was extracted from lignocellulosic fibers and nanocrystalline cellulose (NC) prepared by alkali treatment of the fiber, steam explosion of the mercerized fiber, bleaching of the steam exploded fiber and finally acid treatment by 5% oxalic acid followed again by steam explosion. The average length and diameter of the NC were between 200-250 nm and 4-5 nm, respectively, in a monodisperse distribution. Different concentrations of the NC (0.1, 0.5, 1.0, 1.5, 2.0 and 2.5% by weight) were dispersed non-covalently into a completely bio-based thermoplastic polyurethane (TPU) derived entirely from oleic acid. The physical properties of the TPU nanocomposites were assessed by Fourier Transform Infra-Red spectroscopy (FTIR), Thermo-Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), Dynamic Mechanical Analysis (DMA) and Mechanical Properties Analysis. The nanocomposites demonstrated enhanced stress and elongation at break and improved thermal stability compared to the neat TPU. The best results were obtained with 0.5% of NC in the TPU. The elongation at break of this sample was improved from 178% to 269% and its stress at break from 29.3 to 40.5 MPa. In this and all other samples the glass transition temperature, melting temperature and crystallization behavior were essentially unaffected. This finding suggests a potential method of increasing the strength and the elongation at break of typically brittle and weak lipid-based TPUs without alteration of the other physico-chemical properties of the polymer. (C) 2012 Elsevier Ltd. All rights reserved.

Sugarcane bagasse ash as a potential quartz replacement in red ceramic

Sugarcane bagasse ash (SCBA) is an industrial waste that contains silicon and aluminum oxides as the major components and iron, calcium, magnesium, and potassium oxides as the main minor components. In this paper, SCBA from one Brazilian factory was characterized and tested for its influence on the ceramic properties of clay/ash ceramic probes. Prismatic probes were pressed (18 MPa) using a ceramic mass mixed with 0%, 5%, 8%, and 10% ash. The probes were fired at temperatures between 800 degrees and 1200 degrees C. X-ray diffraction, X-ray fluorescence, thermal analysis (differential thermal analysis, thermo-gravimetric analysis/differential thermogravimetric analysis), and tests for texture (particle-size analysis), flexural strength, and linear shrinkage were carried out to characterize the samples. The results showed that the amount of ash to be incorporated will depend on mainly the composition of clay but also ash, and indicated that the clay used in this work can incorporate up to 10% weight of ash to produce solid bricks. The results also showed an improvement in ceramic/ash properties up to sintering temperatures higher than 1000 degrees C.

Thermo-analyses of polyaniline and its derivatives

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ceramic Primer Heat-Treatment Effect on Resin Cement/Y-TZP Bond Strength

The purpose of this study was to evaluate the effect of different heat-treatment strategies for a ceramic primer on the shear bond strength of a 10-methacryloyloxydecyl-dihydrogen-phosphate (MDP)-based resin cement to a yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic. Specimens measuring 4.5 x 3.5 x 4.5 mm(3) were produced from Y-TZP presintered cubes and embedded in polymethyl methacrylate (PMMA). Following finishing, the specimens were cleaned using an ultrasound device and distilled water and randomly divided into 10 experimental groups (n=14) according to the heat treatment of the ceramic primer and aging condition. The strategies used for the experimental groups were: GC (control), without primer; G20, primer application at ambient temperature (20 degrees C); G45, primer application + heat treatment at 45 degrees C; G79, primer application + heat treatment at 79 degrees C; and G100, primer application + heat treatment at 100 degrees C. The specimens from the aging groups were submitted to thermal cycling (6000 cycles, 5 degrees C/55 degrees C, 30 seconds per bath) after 24 hours. A cylinder of MDP-based resin cement (2.4 mm in diameter) was constructed on the ceramic surface of the specimens of each experimental group and stored for 24 hours at 37 degrees C. The specimens were submitted to a shear bond strength test (n=14). Thermal gravimetric analysis was performed on the ceramic primer. The data obtained were statistically analyzed by two-way analysis of variance and the Tukey test (alpha=0.05). The experimental group G79 without aging (7.23 +/- 2.87 MPa) presented a significantly higher mean than the other experimental groups without aging (GC: 2.81 +/- 1.5 MPa; G20: 3.38 +/- 2.21 MPa; G100: 3.96 +/- 1.57 MPa), showing no difference from G45 only (G45: 6 +/- 3.63 MPa). All specimens of the aging groups debonded during thermocycling and were considered to present zero bond strength for the statistical analyses. In conclusion, heat treatment of the metal/zirconia primer improved bond strength under the initial condition but did not promote stable bonding under the aging condition.

Optimization of neutral hydrolysis reaction of post-consumer PET for chemical recycling

The neutral hydrolysis reaction of post-consumer poly(ethylene terephthalate) in solid state was studied through the reaction of the polymer with water at the molar ratio 1:91 with autogenous pressure. Two sizes of post-consumer PET flakes and temperatures of 135 °C, 170°C and 205°C with pressures of 4.0 atm, 7.5 atm and 13.5 atm, respectively, were considered. With reaction time equal to 6h, the method reached 99% depolymerization at 205°C, 8.2% at 170 °C and 1.7% at 135°C. The reaction extension was measured by separating the terephthalic acid formed in the process and calculating by gravimetry how much material could still be reacted. Through the viscosimetry of diluted, solutions and the counting of carboxylic end groups in the remaining material from the gravimetric assay, it was possible to suggest that the reaction occurs randomly and in the whole volume of the polymeric particle and not solely on the surface. The terephthalic acid obtained and then purified was characterized by elemental analysis, magnetic nuclear resonance, size and panicle size distribution and spectrophotometry in the visible spectrum, and it was similar to the petrochemical equivalent, with purity recorded in carbon base equal to 99.9%.

Contribuiçã ao estudo de caracterizaçã de depó formados no papel

Deposits formed on the surface of. paper were analysed in order to identify the sources of the defects, as well as to solve the problems associated with performance and adjustments at the wet end of the paper forming process. Standard paper samples containing deposits were collected and analysed by comparing the microstructure and composition of the deposit with paper regions adjacent to it. Optical microscopy (OM). energy dispersive X-ray microanalysis (EDX) X-ray powder diffraction (XRD). thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were the techniques used in this study. The results obtained from the EDX, XRD. and TG techniques allowed concluding that the calcium carbonate content in the farm of calcite is 1.6 times higher in the formed deposit them the quantity expected in the standard paper composition. The paper sample microstructure revealed by the SEM images indicates the presence of irregular spherical aggregates up to 20μm in diameter in the deposit region. containing larger amount of calcium carbonate as well as in the regions adjacent to the deposit. These spherical aggregates seem to be absorbed and integrated into the pulp fibres and present characteristics similar to those of partially cooked cationic starch. The analysed deposits are characterised by a dense and thick substance, forming a plate with highly adhesive property. This adhesive substance has a characteristic similar to glue with a large amount of organic matter due to the high weight loss shown by the TG curve. The results are consistent with the interaction ofparticles of negatively charged calcium carbonate and cationic starch, forming sterically stabilized deposits, which firmly adhere to the paper microstructure.

In vivo biological behavior of calcium phosphate cements with different Ca/P ratio

Bioceramics with different Ca/P ratio were prepared from a mechanical mixture of NaPO3, CaCO3, Ca(OH)2 and phosphate buffer solution and implanted in rats subcutaneous tissues. The cements were characterized by Thermo gravimetric analysis (TG-TDA), X-ray diffraction and 31P-NMR. The implant sites were excised after 1, 4 and 16 weeks, fixed, dehydrated, included in paraffin wax for serial cutting and examined under the light transmitted microscope. They were biocompatible and biodegradable when implanted in rat subcutaneous. None of the materials induced ectopic osteogenesis. According to the results, the studied materials seem to be able for manufacturing reabsorbable bone implants.

Estudo das propriedades térmicas e mecânicas de blendas de PVDF/PANI

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência dos defeitos cristalinos nas propriedades dielétricas e não-ôhmicas do 'CA' 'CU IND.3' 'TI IND.4' 'O IND.12'(CCTO)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Degradação de membrana impermeabilizante de polietileno de alta densidade usada em tanques de armazenamento de vinhaça

High-density polyethylene (HDPE) water-proof membranes are used as coatings in vinasse (leachate from sugar cane) storage tanks. The leachate is pumped into the tanks at temperatures of 80-90 °C. Due to these high temperatures and acidity of the waste, these membranes can be degraded, cracked and then loose the function for which they have been designed. This may cause contamination of the soil and groundwater. This study evaluated the effect of vinasse in HDPE membranes after 4 months of exposure in a controlled environment. An aggressive, alkaline pH liquid (sodium hydroxide) was also used. The objective was to evaluate the membrane resistance in contact with acidic and alkaline residues. Physical and mechanical tests, measurement of the carbon black content and thermo gravimetric analysis (TGA) were used to determine degradation of polymer membranes after chemical immersion. While sodium hydroxide resulted caused only minor changes in the physical properties, vinasse induced a thickness change of 7.8%. With immersion in vinasse, an average decrease in strength and deformability (yield) of 34% and 23.5% were measured, respectively. The stiffness increased by 7.8% (average) and the tear strength decreased by 2.7% (average).

Estudo de geopolímeros utilizando cinzas residuais do bagaço de cana-de-açúcar

Pós-graduação em Engenharia Civil - FEIS

Characterization of tetraethylene glycol passivated iron nanoparticles

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

Flexão e análise dinâmico-mecânica de compósitos 5HS e NCF com resina epóxi monocomponente produzidos por RTM

In order to study resin distribution and homogeneity of composite laminates manufactured by RTM, it was used CYCOM 890 monolithic toughened epoxy as a matrix with two different configurations of intermediated modulus (IM) carbon fibers: Satin Weave (5HS) and non crimp fabric (NCF). The injection parameters were defined based on Thermo Gravimetric Analysis (TG), Differential Scanning Calorimetry (DSC) and rheological analysis. After processing the material, the resin/fiber impregnation was studied using ultrasonic test, Thermo Gravimetric Analysis, Differential Scanning Calorimetry, Dynamic Mechanical Analysis (DMA) and flexural tests. Therefore, it was able to observe an internal residual stress during the cooling process in both laminates, higher in the composite using NCF fabric due to the lack of symmetry, although a good proportion of fiber/matrix has been verified by the lower values of flexural modulus deviation. The DMA enabled the visualization of glass transition and its association with the inter and intra molecular interaction and movement, in which the NCF composite presented better permeability due to the lowest temperature of glass transition, when compared to the Satin Weave composite