Papers by Keyword: Differential Scanning Calorimetry

Abstract: For a simulation of pultrusion processes with polyester resin C-L ISO 112 G, the curing kinetic model for the matrix material should be developed. This resin is characterized by excellent glass fibre wet out properties and for this reason is suitable for the utilization in pultrusion processes. The first order, n-th order, Prout-Tompkins and Kamal-Sourour models were used to build the curing kinetic models for the examined resin. The models’ accuracy was determined by calculating the relative errors between theoretical and experimental results. The curing kinetic models with the best accuracy are recommended for the development of future pultrusion processes.

Abstract: Hydrogen peroxide is a strong oxidizing agent containing a peroxide functional group that easily decomposes. In this research, a commercial grade of 35 % w/w hydrogen peroxide was evaluated for thermal hazard and reactivity by differential scanning calorimetry (DSC). It was found that the calculated activation energy was 70.03 kJ/mol. The risk assessment of thermal hazard evaluated in terms of the adiabatic decomposition temperature rise at heating rate 2, 4 and 8 °C/min, were 236.5, 159.2 and 217.5 K, respectively. While the time-to-maximum rate were 79.1, 52.6 and 28.3 second, respectively. Therefore, the storage, transportation and usage, proper care must be highly careful by trained and qualified person or the chemist knowledgeable personnel.

Abstract: Both differential scanning calorimetry (DSC) and differential thermal analysis (DTA) were employed to analyze the thermal performance of the prepreg made by different companies. The results were shown that glass transition temperature (Tg), conversion rate and residual amount of carbon had a large difference. Tg ranged from 130.10 °C to 198.99 °C. After heat-treating from 20°C to 230°C for 23minutes, conversion rate ranged from 19.47% to 100%. After heating from 20°C to 500°C, residual amount of carbon had a range from 13.149% to 39.834%. Tg was not directly proportional to residual amount of carbon. When the residual amount of carbon was more than 30%, Tg would be more than 150°C. It was indicated Tg was relevant to carbon content of resin and inorganic fillers.

Abstract: Chemical admixtures are frequently used to regulate the setting and strength development of concrete materials. In this study, tricalcium silicate (C₃S) was used as a model of the cement system, and the influence of calcium chloride, an extremely useful accelerator, on C₃S hydration and the pore structure of hardened C₃S paste were investigated by the combination of the techniques of differential scanning calorimetry (DSC) and the N₂ adsorption (BET). The results indicated that the addition of calcium chloride would significantly shorten the pre-induction and induction periods and enhance the specific surface area and porosity of hardened C₃S paste. However, the presence of CaCl₂ has little effect on the pores, with a width ranging from 2.5 nm to 5 nm. DSC technique has an advantage of measuring continuously the process of C₃S hydration by changes of free water in hydrated C₃S.

Abstract: A new generation of high energy materials depends on the use of Nano-particle oxides. Nano-scale copper oxide (nano-CuO) has large surface area and surface energy which is suitable for its application in the field of energetic materials. This manuscript reports a method for the synthesis of nano-CuO by a liquid-state reaction method. The prepared nano-CuO was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) to check the particles size, purity and morphology of the crystals. The effect of Nano-CuO on the thermal behavior of AP was tested by differential scanning calorimeter (DSC). The results proved that the average particle sizes of the nano-cuo particles are in the range of 10-20 nm. The thermal degradation rate of AP was increased by 23% in the presence of 1% nano-CuO and the heat release was increased by 51%. It was concluded that nano-CuO could have obvious effect on the burning behavior, performance and combustion characteristics of the solid rocket propellants.

Abstract: The method of synthesis of new polyurethane urea thermoplastic elastomers with controlled physical network density by varying the crystallization rate of the soft block and the structure of the interphase has been developed. Fine-tuning of morphology and mechanical properties allows to desighn adaptive materials with shape memory. By combination of calorimetric and X-ray diffraction methods, the influence of chemical nature of diaisocyanates and the ratio of two types of crystallizable blocks, polybutylene glycol adipate diol (PBA) and poly-ε-caprolactone diol (PCL), on the structure and termal behavior of the thermoplastic elastomers has been studied.

Abstract: Recycling of polymers is an important environmental task. However, during the recycling of polymers many technological problems arise because usually not only one polymer, but also mixtures of polymers are recycled. To improve technological properties, such as increasing fluidity, improving processability and quality, reducing the melt pressure in the spinneret head, addressing surface defects caused by viscosity anomaly and excessive shear stresses, preventing the formation of deposits and residue on the forming tool, increasing productivity, reducing the amount gelic, etc., use processing and technological additives. In the research, the effect of technological additives manufactured by Weihai CY Dendrimer Technology Co., Ltd (China) on the technological and thermal properties of recycled polyolefins was studied. It was shown that the technological additives improved the technological properties of recycled polymers: the mixing energy decreased when receiving compositions, the melt flow index values increased, the thermal properties did not deteriorate. The results show the possibility of using of the technological additives in production to increase the productivity of processing equipment and reducing its energy consumption.

Abstract: Polyethylene is widely used in the production of products for the automotive industry, due to the unique properties and the possibility of manufacturing hollow products of complex geometry. In this work the thermal research of polyethylene in finished productsand the quality assessment of autocomponents materials, depending on the type of polyethylene were conducted. An assessment methodologyof the material of products is suggested, which indicates the difference between the batches of autocomponents products for the acceptance or rejection thisbatch by conducting DSC-analysis. It was found that the products of autocomponents, in particular, "splash-absorbing shield", based on LDPE with a melting point above 110 °C have unsatisfactory performance characteristics. It is shown that modifying additives to improve the elasticity of the LDPE lead to partial the amorphization of PE, that is, a decrease in the degree of crystallinity by 4% relative to the LDPE without additives.

Abstract: This work is focused on a development and research of a new lead-free Sn-Mg solder, alloy compatible with the human body. Tin and magnesium are biocompatible elements which do not cause an inflammation or allergic reactions with living tissues. We have prepared the Sn₉₇Mg₃ solder (wt. %) by a rapid solidification of its melt on a copper wheel (melt-spinning technique). This solder may find applications in electronic devices for intracorporeal utilisation. The microstructure of the prepared solder exhibits a heterogeneous distribution of the SnMg₂ intermetallic particles within the β-Sn matrix. Structure of the solder was studied by an in-situ high energy X-ray diffraction experiment (energy of an X-ray photon: 60 keV) where 2D XRD patterns were collected from the sample in the temperature range from 298 K to 566 K. The experiment was performed at a high brilliance 3^rd generation synchrotron source of radiation (PETRA III storage ring, DESY, Hamburg, Germany) at the P02 undulator beamline. From the measured X-ray diffraction data by applying the Rietveld refinement technique we have obtained thermal volume expansion data, mean positions of atoms as well as isotropic atomic displacement parameters of the constituent SnMg₂ and the β-Sn crystalline phases. Thermal behaviour was studied by differential scanning calorimetry at heating rates of 5, 15, 30 and 60 K.min^-1 and compared with the measured X-ray data. Our main goal lies in a preparation of a lead-free solder with fine grain structure made exclusively of biocompatible elements. We demonstrated that the rapid melt solidification technique leads to in an improvement and better thermal stability of this alloy.

Abstract: Differential scanning calorimetry was used to study the temperatures and character of phase transitions of fibers based on polyether ether ketones. It is shown that in the production of fine fibers from polyether ether ketones, a predominantly amorphous structure is formed. Increasing the temperature to the crystallization temperature leads to an almost twofold increase in the degree of crystallinity. Lower molecular weight polyether ether ketone is characterized by a higher rate of crystallization and the formation of a more homogeneous crystalline structure.