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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  

Thermal analysis is a useful tool for investigating the properties of polymer/clay nanocomposites and mechanisms of improvement of thermal properties. This review work presents examples of applications of differential scanning calorimetry (DSC), modulated temperature differential scanning calorimetry (MT-DSC), dynamic mechanical thermal analysis (DMA), thermal mechanical analysis (TMA), thermogravimeric analysis (TG) and thermoanalytical methods i.e. TG coupled with Fourier transformation infrared spectroscopy (TG-FTIR) and mass spectroscopy (TG-MS) in characterization of nanocomposite materials. Complex behavior of different polymeric matrices upon modification with montmorillonite is briefly discussed.

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In the present report, thermal analysis (TMDSC, DMA, TG, stress-strain analysis), nano-indentation and AFM morphological characterization of cross-linkable latexes, prepared with either a pre-coalescence cross-linker (1,3-butylene glycol dimethacrylate) or post-coalescence cross-linker (adipic dihydrazide) at various levels of cross-linking, were done. The study assesses the effect of type and level of cross-linking on the film formation process through the evolution of mechanical properties and latex morphology. In addition, the final fundamental thermal and mechanical properties, specific end-use properties and latex morphology resulting from the film formation process are reported.

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Abstract  

DSC, TGA and DMA thermal analysis techniques are used to characterize a complex adhesive blend. The chemical and thermomechanical property development shown to follow a two-stage process. Beneficial synergy between these analysis tools is demonstrated in this study.

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Abstract  

Thermo-oxidative and thermo-mechanical stabilities of radiation-cured acrylates and epoxides were examined by TG, DMA and DSC.The polymeric trifunctional acrylates PETIA, TMPTA and THEIC displayed the highest temperatures of onset of degradation. The high crosslinking density of the films resulted in an almost temperature-independent complex E-modulus, as measured by DMA. With increasing degree of ethoxylation or propoxylation of the monomers, decreases in thermal stability and strength were found. For difunctional polymeric acrylates and epoxides, the glass transition temperature was measured.The average degree of curing of UV-cured epoxy films can be determined from the temperature of the maximum in the loss modulus (E max.

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Abstract  

The glass transition of lyophilized materials is normally measured by conventional or temperature modulated differential scanning calorimetry (TMDSC). However, because of the weakness of these transitions when protein concentrations are high, these techniques are often unable to detect the glass transition (T g). High ramp rate DSC, where heating rates of 100 K per min and higher are used, has been shown to be able to detect weak transitions in a wide range of materials and has been applied to these materials in previous work. Dynamic mechanical analysis (DMA) is also known to be much more sensitive to the presence of relaxations in materials than other commonly used thermal techniques. The development of a method to handle powders in the DMA makes it now possible to apply this technique to protein and protein-excipient mixtures. HRR DSC, TMA and DMA were used to characterize the glass transition of lyophilized materials and the results correlated. DMA is shown to be a viable alternative to HRR DSC and TMA for lyophilized materials.

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Abstract  

Many of the isomers of polybutadiene and polyisoprene elastomers can be characterized by thermal analysis.T g is sensitive to side chain units (1,2 or 3,4 structure) for both polymers. Crystallinity measurements can characterizecis andtrans isomers. DMA and DEA master curves provide an idea of the heterogeneity of the chain units from the width of the loss factor curves in theT g region. Thermal and thermooxidative degradation, as followed by DSC and DTG, can differentiate specific natural and synthetic isomers of polyisoprenes in raw and vulcanized states.

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A new criterion for evaluating different plasticizers the ability of suppression of the Β transition in plasticized PVC blends. Accordingly, the Β suppression ability is proportional to the PVC-plasticizer compatibility, expressed either by the critical solution temperature, CST, or by the interaction parameter related to the difference between the solubility parameters of the blend components. The criterion is, however, valid for low plasticizer contents (<5%w/w) only, as long as the Β transitions are not overlapped by the α transitions, shifted towards lower temperatures due to the effect of the plasticizer. For higher plasticizer contents the α transition starts to overlap the Β transition and the Β suppression ability of the plasticizer depends increasingly on the efficiency of the plasticizer i.e. on the depression of the glass transition temperature of PVC (related to theT g of the plasticizer). Accordingly, plasticizers with both good efficiency (lowT g) and compatibility are more effective in the Β suppression than plasticizers which have only a higher compatibility but also a highT g (i.e. reduced efficiency).

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Abstract  

This biomaterials overview for selecting polymers for medical devices focuses on polymer materials, properties and performance. An improved understanding of thermoplastics and thermoset properties is accomplished by thermal analysis for device applications. The medical applications and requirements as well as the oxidative and mechanical stability of currently used polymers in devices are discussed. The tools used to aid the ranking of the thermoplastics and thermosets are differential scanning calorimetry (DSC), thermogravimetry (TG), thermal mechanical analysis (TMA) and dynamic mechanical analysis (DMA) as well as a number of key ASTM polymer tests. This paper will spotlight the thermal and mechanical characterization of the bio-compatible polymers e.g., olefins, nylon, polyacetals, polyvinyl chloride and polyesters.

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