Papers by Keyword: Glass Transition Temperature

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Authors: Valérie Nassiet, Bouchra Hassoune-Rhabbour, Yves Baziard
Abstract: A method is described for measuring the glass transition temperature (Tg) of epoxy joints bonding ceramic (SiC) substrates. This method is based on the strain measure of a single-lap joint subjected to a temperature variation. The resulting displacement (d) is observed as a function of the temperature (T) by means of a contact strain gauge extensometer. Thus Tg value can be determined using (d-T) curves recorded. The influence of joint parameters (joint thickness and overlap length) and of other parameters such as the applied load and the surface state of substrates were studied for a structural epoxy adhesive showing different thermomechanical behaviours. The results show that it is possible, with appropriate experimental conditions, to measure Tg with this method and to find Tg values similar to those found by classical techniques such as the static thermomechanical analysis (TMA) and the differential scanning calorimetry (DSC). This method shows similarities with TMA, but it has the advantage to allow the thermomechanical analysis of adhesives without destructive sampling of joints.
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Authors: Asghari Jila, Khoje Golshad
Abstract: Composite of Cadmium sulphide (CdS) nanoparticle on the surface of polystyrene- co- maleic anidride (St-co-MMA) were prepared via surfactant free emulsion polymerization. Methylmetacrylate (MMA) was used as auxiliary monomer which co-polymerized with styren (St) and provided the side for coordinating with Cd2+. By the coordination of Cd2+ ions to methyl metacrylate, decoration of the Cd2+ ions on the surface of copolymer were prepared successfully. With the release of S2- ions from the thioacetamide (TAA), CdS was formed on the surface of nanorods copolymer in facile method. Fourier transform infrared spectroscopy (FT-IR) of nanocomposite was confirmed the polymerization of monomers. Structure and morphology of CdS nanoparticles have been characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD measurements suggest the cubic structure for CdS and the particles size was estimated to about 3.35 nm by applying Scherrer’s equation. The SEM analysis confirmed the nanorode structure of CdS/ (St-co-MMA) composite. The photoluminescence (PL) and UV–Vis spectroscopy revealed the quantum confinement effect in the CdS/ (St-co-MMA) nanocomposite. Using effective mass approximation (EMA) method particle sizes were calculated from the shift in optical band gap. The thermal properties of the CdS/ (MMA-co-St) were explored by thermal gravimetric analysis (TGA). The improved thermal stability of nanocomposite was attributed to the interaction of CdS nanoparticles with polymer. The CdS/ (MMA-co-St) nanocomposite exhibited a glass transition temperature around 250C.
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Authors: Harry Ku, Peter Wong, Andrew Maxwell, J. Huang, H. Fung, Mohan Trada
Abstract: The mechanical and thermal properties of hollow glass powder reinforced epoxy resin composites have been measured and evaluated in earlier studies. This basic but critical and important data have caused interests in the relevant industry in Australia. This study is therefore carried out to measure and evaluate the dielectric properties of the composites with a view to benefit the relevant industry. The relationship between the dielectric and thermal properties will also be studied and correlated. The original contributions of this paper are that samples post-cured in conventional ovens have higher electrical as well as mechanical loss tangent values than their counterparts cured in microwaves only. The storage modulus of all samples post-cured conventionally is higher than its counterpart. This is in line with the fact that they are softer material with lower glass transition temperatures. For all percentages by weight of glass powder, the glass transition temperature for the microwave cured sample was higher and the composite was stiffer; the opposite was true for the conventionally cured samples.
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Authors: Kameshwar Kumar, Nagesh Thakur, S.C. Katyal, Pankaj Sharma
Abstract: In the present communication, a study was made of the compositional variation of physical properties: average coordination number (), average number of constraints (Ncon), number of lone-pair electrons (L), mean bond energy (), cohesive energy (CE), average heat of atomization (Hs), glass transition temperature (Tg), density (ρ) and theoretical energy gap (Eg) for Te15(Se100-xBix)85 (x = 0, 1, 2, 3, 4, 5at%) glassy alloys. The mean bond energy and the cohesive energy have been calculated using the chemical bond approach (CBA). The glass transition temperature was calculated using the Tichy-Ticha approach, and has been found to increase with Bi content. The mean bond energy is found to be proportional to the glass transition temperature and the average coordination number. It has been found that the average coordination number, average number of constraints, mean bond energy and density increase, whereas the cohesive energy, average heat of atomization and theoretical energy gap decrease with increasing Bi content in Se-Te alloys.
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Authors: Andrey Askadskii, Tatyana Matseevich, Marina Popova, Valerii Kondrashchenko, Shi Cheng Qi
Abstract: A calculation method for predicting compatibility of two polymers on blending is proposed. The method is based on the criterion of polymer solubility in organic solvents; the criterion takes into account the chemical structure of both polymer and solvent, surface forces, and the polymer-solvent intermolecular interaction energy. When two polymers are mixed together, one of them is regarded as a "solvent". The applicability of the method to fully compatible, partially compatible, and absolutely incompatible polymers is analyzed. It is shown that the composition of microphases at microphase separation can be approximately calculated using the dynamic mechanical analysis (DMA).
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Authors: L.K. Sudha, Roy Sukumar, K. Uma Rao
Abstract: This paper describes how glass transition temperature (Tg) and capacitance (Cp) of a nanomodified composite polymer changes as compared to that of its base polymer. Because of its versatile applications, polycarbonate materials (grade PC1100 and PC1220 respectively), which are commercially available, were chosen as the base polymer in this study and nanostructured alumina material was used as filler for fabricating the desired composites by varying the filler weight in the composite materials. The Tg of the composites has been evaluated by differential scanning calorimetry (DSC) technique and Cp of the composites are derived from AC conductivity measurements of the composites. Results show that the Tg decreases as a function of filler load in the composite material whereas capacitance of the composites increase with the filler load in the composites. A filler concentration equal to or greater than 5 wt% in the said composites, the Tg of the composites reduces upto 15°C, whereas Cp shoots up in the pico-farad range with the same level of filler load, as compare to base polymers.
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Authors: Yasuaki Shinoda, Ichiro Shiota, Yuichi Ishida, Toshio Ogasawara, Rikio Yokota
Abstract: TriA-PI is a newly developed phenylethnyl terminated polyimide. It exhibits excellent mechanical properties and processability with high glass transition temperature (Tg>300°C). Nano-size particles of fullerene were dispersed throughout a thermosetting polyimide Triple API (TriA-PI) to elevate the glass transition temperature. The increase of the glass transition temperature of the composites with the fullerene was confirmed by dynamic mechanical analysis (DMA).
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Authors: Rahul K. Desai, Laxmi Tomar, B.S. Chakrabarty
Abstract: The purpose of this work is to provide a comparative study of polyacrylic acid alumina (PAA/Al2O3) bulk composites with PAA/Al2O3 nano composites. This work also provides a study in the variation of glass transition temperature due to the doping of metal. Alumina nano particles were prepared using hydrothermal method. This sample was doped with Cu. Polyacrylic acid alumina nano composites were prepared using two different methods. The alumina samples were added to acrylic acid. In the first method the mixtures of acrylic acid and alumina samples were heated in oven. In the second method the same mixtures were irradiated with microwaves. The samples prepared were allowed to cool down and dried. Also the alumina bulk particles were also dispersed in acrylic acid and the similar procedure was carried out. The effect of preparation methods on the glass transition temperature of PAA/Al2O3 and PAA/Al2O3 nano composites have been studied. The glass transition temperatures Tg were determined using DSC analysis.
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Authors: Cirlene Fourquet Bandeira, Sérgio Roberto Montoro, Elton Luiz Espindola, Edson Cocchieri Botelho, Michelle Leali Costa, Maria Odila Hilário Cioffi
Abstract: In recent years a number of studies were conducted in order to obtain polymer composites with superior performance when compared to the metallic alloys. However, these new materials must meet a series of rigid project requirements. One way to evaluate the polymer composites is through their transition temperatures, especially the glass transition temperature (Tg). It is possible to evaluate the Tg of a polymeric material through the study of changes in dimensions of a sample as a function of temperature. These measurements can be made on an equipment of thermomechanical analysis (TMA), however, despite great sensitivity, this technique is basically unknown by most users when compared to others such as DSC or DMA. Even with different technical principles of operation, the results show similarity. Thus, this study aims to compare the results of Tg polymer composites obtained via TMA with those obtained from DSC curves in epoxy resin/carbon fiber laminates.
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Authors: S.K.M. Jamaria, K. Rameshb, B. Vengadaesvaranc, S. Rameshd, S.R. Raue, A.K. Aroff
Abstract: Coating systems consist of acrylic polyol resin and silicone intermediate resins were tested for their corrosion resistance properties. The corrosion protection property of the coating was evaluated by using Electrochemical Impedance Spectroscopy (EIS) which showed that system with 70 % of acrylic has the highest corrosion resistance. The maximum value of corrosion resistance obtained was found to be 1.40 x 109 Ω on the 30th day for the 70 % of acrylic sample. The glass transition temperature (Tg) obtained using the Differential Scanning Calorimetry (DSC) were in the range of 23 °C to 65 °C. It showed that all samples are suitable for decorative paints, general industrial coatings and floor care coatings. The functional groups and also the cross-linking between the organic resins were analyzed using Fourier Transform Infra-Red Spectroscopy.
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