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Abstract  

The effect of uni- and biaxial orientation in the morphology of polypropylene films has been investigated by thermal, dynamic-mechanical, X-ray pole figure and diffraction patterns. In uniaxial oriented films the level of damping is roughly three times higher in the MD direction than it is in the TD direction. The stretching always produces crystals of the form independently of the starting type. Fast DSC scans show two melting peaks indicative of two crystalline species. The Fujiyama et al. model for the crystalline structure can be also applied to the uniaxially stretched films. Upon biaxially orienting, the folded lamellae crystals (kebabs) are the ones to support all the force applied, and when their maximum level of stress slippage is reached they deform following the Peterlin's model, forming a new shish structure. These new shishes are aligned to the TD direction and by linking the original shishes in the MD direction produce a planar orthogonal net of linked shish structures. The space among the shishes is filled with small and imperfect folded lamellae with c-axis in the film plane and preferentially oriented in the MD and TD directions, keeping constant crystallinity density throughout.

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Abstract  

The products of the thermal decomposition in air of iron/III/benzoate [Fe3/C6H5COO/6/OH/2]OH.H2O have been studied using conventional thermal analysis, X-ray diffraction measurements and mainly Mössbauer spectroscopy. The decomposition occurs in the temperature range 200–350°C. It was possible to identify benzoic acid and ferric oxide as final products. Above 300°C, the observed ferric oxide showed a particle size distribution, which depends on the heating temperature and the heating time interval, as evidenced by the following detected phases: superparamagnetic -Fe2O3 and magnetically ordered state with crystal structure of the phases -Fe2O3 and -Fe2O3. Also, two iron/III/ benzoate complexes having four and three ligands within the coordination sphere are suggested as intermediate products.

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Abstract  

Instrumental neutron activation analysis was applied to determine La, Ce, Nd, Sm, Eu, Tb, Yb, Lu and Sc in two biological reference materials: NIST 1575 Pine Needles and BCR-CRM 101 Spruce Needles. The purpose was to contribute to the reference data for these two reference materials. The results were obtained with a good precision (relative standard deviations less than 15%). For the Pine Needles reference material there are already some proposed values and our results showed, in general, a good agreement with the data published. The contribution of uranium fission products to La, Ce, Nd and Sm was evaluated and considered in the determination of these elements. Interferences in the determination of rare earth elements in biological materials are also discussed.

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Abstract  

The thermal decomposition kinetics of the solid complexes Cd(S2 CNR2 )2 , where R =C2 H5 , n -C3 H7 , n -C4 H9 or iso -C4 H9 , was studied by using isothermal and non-isothermal thermogravimetry. The superimposed TG/DTG/DSC curves revealed that thermal decomposition reactions occur in the liquid phase. The kinetic model that best fitted the experimental isothermal TG data was the one-dimensional phase-boundary reaction-controlled process R1 . The thermal analysis data suggested the thermal stability sequence Cd(S2 CNBun 2 )2 >Cd(S2 CNPrn 2 )2 >Cd(S2 CNBui 2 )2 >Cd(S2 CNEt2 )2 , which accords with the sequence of stability of the apparent activation energies.

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Abstract  

Hydrogels, in general, can be used as a compliant surface in prosthesis of human synovial joints due to their biocompatible characteristics. In this work, different hydrogels were prepared from two aqueous solutions of PVAL (15 and 20 mass/mass%) by chemical reactions using citric acid as a cross-linking agent and by electron beam (EB) irradiation with doses from 25 to 100 kGy. The hydrogels were evaluated by their mechanical properties through indentation creep test, thermal properties by differential scanning calorimetry (DSC), and also equilibrium water content (EWC).

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Abstract  

The thermodynamic and kinetic parameters of the thermal decomposition of Zn(S2CNR2)2 complexes (R=CH3, C2H5 and n-C3H7) were determined with the dynamic thermogravimetric method. Superimposed TG/DTG/DSC curves show that thermal decomposition reactions for chelates with R=C2H5 and n-C3H7 occur in the liquid phase, at temperatures far away from their melting points, whereas for the complex with R=CH3 the thermal decomposition begins at a temperature closer to its melting point, suggesting a rather complex decomposition mechanism.

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Abstract  

The kinetics of thermal decomposition of solid In(S2CNR2)3 complexes, (R=CH3, C2H5, n-C3H7,i-C3H7, n-C4H9 and i-C4H9), has been studied using isothermal and non-isothermal thermogravimetry. Superimposed TG/DTG/DSC curves show that thermal decomposition reactions occur in the liquid phase, except for the In(S2CNMe2)3 and In(S2CNPri 2)3 compounds.

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Journal of Thermal Analysis and Calorimetry
Authors:
Alaize de Martins
,
A. Craveiro
,
M. Machado
,
Fernanda Raffin
,
T. Moura
,
Cs. Novák
, and
Zsuzsanna Éhen

Abstract  

Inclusion complex between the essential oil of Mentha x villosa Hudson and β-cyclodextrin, with a 1:9 mass/mass oil–β-cyclodextrin ratio was prepared by co-precipitation and kneading methods in a hydroethanolic medium. The GC/MS analysis showed a total volatile content of 99.5% in the Mentha x villosa oil. The characterization of the complex involved the analysis of the original essential oil, the surface and the total extracted oils. Among 28 detected compounds in the original essential oil, 13 are monoterpenes and 10 sesquiterpenes, furthermore, piperitenone-oxide is the major component (35.4%). 12 compounds were totally and 11 partially complexed, 3 have been adsorbed only on the surface of the β-CD and 2 have not been detected neither in the surface oil nor in the complexed oil. A 13.6% encapsulation efficiency was observed, while the total oil and volatiles retention was 15 and 77%, respectively. Non-parametric statistic analysis of the data showed that the profile of the volatiles were not significantly different comparing the original oil and the complexed oil (p>0.04). The results of thermogravimetry-mass spectrometry and XRD analysis have proven the inclusion complex formation between the essential oil and cyclodextrin.

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Journal of Thermal Analysis and Calorimetry
Authors:
M. Evora
,
L. Machado
,
V. Lourenço
,
O. Gonçalez
,
H. Wiebeck
, and
L. de Andrade e Silva

Abstract  

The aim of this work is to study the ionizing radiation effects on thermal properties of there cycled polyamide-6. This polymer was irradiated with an electron beam of 1.5 MeV with different doses. The thermal properties of the samples were determined by TG, DSC and DMA measurements. It was observed that the irradiated samples of recycled polyamide-6undergo a crosslinking process.

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Abstract

Magnetic thermogravimetric analysis (TGM) was used to investigate the influence of the milling time (t mill) in the Curie temperature (T C) of nanocrystalline powders and of a melt-spun amorphous ribbon with composition Fe56Co7Ni7Zr10B20. The TGM analysis was carried in a continuous flow of 99.99% pure argon from room temperature up to 1250 K. A magnetic field of 100 Oe was applied throughout the measurements. Nanopowders of Fe56Co7Ni7Zr10B20 were produced by mechanical alloying the samples in an argon atmosphere for milling times ranging from 1 to 100 h. The samples were characterized by X-ray diffraction and by scanning electron microscopy. The average particle size decreased from 45.4 nm for a powder milled for 1 h to 5 nm after being milled for 100 h. Moreover, T C (=1126.4 ± 4.4 K) was found to be nearly independent of t mill while for the melt-spun amorphous ribbon it was found to be substantially smaller (T C = 482 K). This is a clear indication that T C is quite sensitive to the degree of amorphosity present in the sample. The activation energy associated to the crystallization process was estimated from DSC data by using the Kissinger's method to be 193 kJ/mol.

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