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Abstract  

The thermal properties of discarded bumpers from standard grade automobiles were compared to the corresponding data obtained from binary and ternary blends of virgin polyolefins of composition similar to the recycled product. After grinding and separating by specific gravity, the recycled material was identified by DSC, DMTA, TGA and 13C NMR. We found that it contains three polymers: polypropylyene (PP) as the major component, ethylene, propylene, diene methylene terpolymer (EPDM) and a small amount of high density polyethylene (HDPE).

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Abstract  

Composites of poly(vinyl pyrrolidone)/hydroxyapatite (PVP/HA), at variable proportions (100/0; 80/20; 50/50; 20/80 wt%) were prepared and characterized by Fourier transformer-infrared spectroscopy (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and thermogravimetry/differential thermogravimetry (TG/DTG). PVP carbonyl stretching was slightly shifted to lower frequency in composites indicating the formation of hydrogen bonding with HA hydroxyl groups. At the first cycle of heating, the calorimetric curves revealed a broad peak the intensity of which was reduced insofar as the amount of PVP decreased in the composites. This peak was attributed to the PVP enthalpy relaxation. According to the TG/DTG curves, PVP degraded into two steps sharply perceivable in the composites. The first decay was ascribed to the release of the pyrrolidone pendant groups and the following one concerned the burning of the hydrocarbon chains. The HA molecules seem to exert a catalytic action on the PVP degradation.

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Abstract  

The effects of processing time and concentration of cobalt acetylacetonate III complex in poly(ethylene terephthalate)/polycarbonate reactive blending were investigated. The blend was prepared in an internal mixer at 270C, 60 rpm, at different processing times (5–20 min) and catalyst concentration (0.00625–0.075 mass%). The reaction product was evaluated by differential scanning calorimetry (DSC), thermogravimetry (TG) and wide angle X-rays scattering (WAXS). In general, the DSC curves showed two glass transition temperatures (T g’s) close to each homopolymer, independent of the processing time and complex’s concentration, suggesting the presence of two phases: one rich in PET and other one rich in PC. In all cases, melting temperature (T m), cold crystallization temperature (T cc) and crystallinity degree (X c) were progressively reduced with blending conditions. The TG curves presented two decays. The first one represented the PET rich phase and the other one was related to the PC phase. The WAXS diffractograms showed that the Bragg’s angle and interplanar spacing of PET remaining practically unchanged.

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Abstract

The influence of PC melt flow rate (MFR) on phase behavior, thermal and rheological properties of catalysed and non-catalysed poly(ethylene terephthalate)/polycarbonate (PET/PC) (80/20 wt%) reactive blending were investigated. Two types of PC named PC1 and PC2 with MFR 3.1 and 10.8 g/10 min, respectively, were used. Each PC and the catalyst showed significant influence on calorimetric properties, thermal stability and WAXS patterns of the blends. Regarding to TG/DTG, the blends degraded in two steps which were attributed to PET rich phase and PC one and permit to infer that a partially miscible blends were produced.

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Abstract  

Norfloxacin (NFX) is a synthetic antibacterial drug. The development of extended release tablets improves the patients’ comfort and compliance, resulting in lower discontinuation of the therapy; with consequently decrease in bacterial resistance. In the present work, the thermal behavior of NFX was investigated using TG and DSC techniques. Isothermal and non-isothermal methods were employed to determine kinetic data of decomposition process. Compatibility studies between NFX and pharmaceutical excipients, including three hydrophilic polymers were carried out in order to develop a new formulation of NFX to obtain extended release tablets with an approved quality.

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Abstract  

Sedimentation rates in Guanabara Bay were determined by applying the210Pb CRS method to sediment cores collected at five different stations. The results showed a pronounced increase from 0.1–0.2 cm·year−1 to 1–2 cm·year−1, in sedimentation rate, over the last 40–50 years. Observed heavy metal profiles in sediment could also be explained on the basis210Pb dating and local industrial history.

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Abstract  

The effect of external irradiation on β-thorium phosphate-diphosphate (tetravalent actini des bearing storage matrix) and the influence on its dissolution in aqueous media were studied. Highly energetic heavy ions were used to get the amorphization of the crystalline structure of the ceramic. The ex-situ dissolution expenments showed an increase of the dissolution versus amorphous fraction in several pH and temperature conditions. The in-situ dissolution experiments highlighted the primordial importance of radiolytic produced free radical species. From these results, the ceramic presents a good resistance to aqueous alteration even in amorphous state.

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Journal of Thermal Analysis and Calorimetry
Authors: H. Dantas, R. Mendes, R. Pinho, L. Soledade, C. Paskocimas, B. Lira, M. Schwartz, A. Souza, and Iêda Santos

Abstract  

Gypsum is a dihydrated calcium sulfate, with the composition of CaSO4⋅2H2O, with large application interest in ceramic industry, odontology, sulfuric acid production, cement, paints, etc. During calcination, a phase transformation is observed associated to the loss of water, leading to the formation of gypsum or anhydrite, which may present different phases. The identification of the phases is not so easy since their infrared spectra and their X-ray diffraction patterns are quite similar. Thus, in this work, temperature modulated differential scanning calorimetry (TMDSC) was used to identify the different gypsum phases, which can be recognized by their different profiles.

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