Papers by Keyword: DSC

Abstract: Poly (ethylene 2,5-furandicarboxylate) (PEF) is a bio-based polyester that is the subject of growing interest as a potential alternative to Poly (ethylene terephthalate) (PET) for sustainable packaging. Its excellent gas-barrier properties and reduced carbon footprint make it a promising candidate, but its use at industrial scale requires a solid understanding of how temperature and thermal history affect its mechanical and viscoelastic behavior. In this study, Differential Scanning Calorimetry (DSC), Dynamic Mechanical Thermal Analysis (DMA), and optical microscopy were used to characterize the thermal transitions and crystallization behavior of PEF, compared with PET and recycled PET (rPET). DSC results show that thermal crystallization of PEF proceeds very slowly, a result confirmed by in-situ microscopy. DMA measurements provide complementary information on the evolution of both storage and loss moduli with temperature, highlighting its dependence on crystallinity and thermal history. Together, these thermal and mechanical analyses clarify how PEF’s crystallization behavior affects its thermo-mechanical response. From a processing perspective, the very slow thermal crystallization of PEF is advantageous for stretch blow molding (SBM) process of bottles, as the polymer remains essentially amorphous during heating and crystallizes predominantly under deformation during the fast forming stage.

Abstract: This study aims to determine the key thermal parameters of plastic waste degradation, specifically polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS), using differential scanning calorimetry (DSC), differential thermogravimetry (DTG), and thermogravimetric (TG) analysis. The thermal stability of these materials was evaluated by analyzing residual solid and wax quantities, conversion percentages, liquid and gas product yields, and process duration. Experiments were conducted at 550–600°C with a heating rate of 50°C/min. Key thermal parameters investigated include onset decomposition temperature, temperature at 50% conversion, completion temperature, maximum DTG temperature, peak DTG value, melting point, and pyrolysis temperature. The activation energy for mass loss was calculated, ranging from 35 to 68 kcal/mol, with PS exhibiting the highest thermal stability (68 kcal/mol). The degradation conversion efficiency ranged from 85% to 99%. Notably, PET pyrolysis produced significantly more solid residues (0.136–0.150 g/g₀) than PP and PS (0.006–0.088 g/g₀). These findings provide valuable insights into the thermal behavior of plastic waste, supporting advancements in waste management and energy recovery applications.

Abstract: We present a novel attempt to combine in-situ and ex-situ measurements -- here exemplary for aluminum alloys. For this research we have chosen an Al-1.7Cu-1.3Mg (at.\%) alloy, which has been cast from high purity elements (5N5 Al, 4N Cu and 4N Mg). DSC (differential scanning calorimetry) serves as a basic method, which is employed to determine different precipitation states towards the final S-phase formation: before the formation starts, at the maximum of the exothermal peak, and after the end of the exothermal reaction. By an abrupt truncation of the heating ramp (5 K/min), i.e. cooling quickly to room temperature, the current sample state is frozen-in for a defined temperature. After truncation all samples have been measured without further preparation by X-ray diffraction (XRD), positron annihilation lifetime spectroscopy (PALS). By this treatment we could correlate exactly different sample states, which is impossible by conventional experiments, i.e. heating to a defined temperature and holding for a certain time. This attempt opens new possibilities to investigate defined and comparable sample states by methods, which require extensive sample preparation, like TEM or 3DAP, and in-situ methods like DSC or XRD / EXAFS / SAXS at synchrotron beam lines.

Abstract: The sepiolite and Al₂O₃-doped sepiolite contents in the as-received sepiolite/epoxy systems were maintained at 2 and 4wt %, respectively. The flame-retardant capabilities and combustion behavior of Al₂O₃-doped sepiolite in epoxy resin were meticulously evaluated through a series of tests including cone calorimetry (CC), limiting oxygen index (LOI), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). Several features, including degradation kinetics, combustion characteristics, thermomechanical properties, flame retardancy, and thermal degradation were evaluated with the intention of drawing comparisons to standard sepiolite. The findings from the studies were positive. In contrast, Al₂O₃-doped sepiolite not only further improved the LOI values and char formation post-cone testing but also decreased the previously mentioned combustion-related parameters in the composites. A potential synergistic interaction between sepiolite and Al₂O₃ in augmenting the flame retardancy of the composite was suggested. The thermal degradation of composites was only little affected by addition of sepiolite, although Al₂O₃-doped sepiolite addition seemed to speed up the deterioration process. The epoxy composite’s glass transition temperature (Tg) was shown to increase when sepiolite or Al₂O₃-doped sepiolite was added, as determined by DMA. The findings presented in this research provided a practical approach to improving the fireproofing of polymers. Keywords: Al2O3-doped sepiolite; TGA, flame retardancy; DSC, epoxy; thermal properties.

Abstract: This paper discusses the fire and heat resistance of a polylactic acid/Hemp/Polypropylene hybrid laminated composite. Hybrid composites had their impacts analysed, specifically with regards to the fibre composition and stacking order. Using a hot press, the hybrid composites were created. In this work, Hemp/Polypropylene-reinforced polylactic hybrid composites with thermogravimetric, differential calorimetric, dynamic mechanical, and flamability properties were reported. Thermomechanical studies show that hybridization affects the laminate’s viscoelastic characteristics and thermal stability. Hybrid composites' burning rates were also evaluated for this flammability test. Most of the Hemp layers in sample C7 had the most char residue (10%), while sample C8 had the highest decomposition temperature (450°C). When it comes to hybrid composites, however, the C5 sample offers the best results, with a large char production and a low burning rate of just 36 mm/min. Also, viscoelastic properties like storage and loss modulus are best in class for the C5 sample, which is a hybrid composite. Keywords: Hemp; flammability Polypropylene; PLA; TGA; DSC.

Abstract: Non-isothermal DSC has been used to investigate the curing kinetics of epoxy adhesives (DGEBA-cycloaliphatic amine). The epoxy samples were scanned on DSC with five heating rates (5°C/min, 7.5°C/min, 10°C/min, 12.5°C/min, and 15°C/min). The curing kinetics were obtained through ASTM standards E2890 and E698 (the Ozawa and Kissinger methods). The kinetic parameters obtained include Ea (activation energy), A (pre-exponential factor), and n (reaction order). The activation energy calculated from the Kissinger and Ozawa method was slightly different but insignificant. The reaction rate (dα/dt) and degree of curing/conversion (α) relationship towards temperature (T), and time (t) was also investigated. The curing process's reaction rate (dα/dt) has maximum value; it can no longer increase after a specific conversion rate (α).

Abstract: A straightforward technology for the thermal cyclic processing of the Fe-C melt has been developed to induce significant super-cooling before crystallization. Eutectic crystallization of pro-eutectic alloys under substantial super-cooling is demonstrated to be a complex process, comprising several partial crystallization processes and the synchronous dissolution of crystalline phases: austenite and two metastable carbides, Fe₃C and Fe₇C₃. The kinetics of the eutectic transformation L→L+Fe₇C₃ in its microscopic and thermal (DSC) imaging has been studied. In general, crystallization proceeds according to the scheme L→L+Fe₇C₃+γ→L+Fe₇C₃+γ+Fe₃C→ Fe₇C₃+γ+Fe₃C. Consequently, plate-like eutectic (Fe₇C₃+γ) with an austenite matrix and ledeburite (Fe₃C+γ) with a cementite matrix are formed. A schematic diagram of the metastable phase equilibria in the Fe-C system is provided. In the conducted experiments, phase transformations occur in two subsystems: Fe-Fe₃C (at low supercooling) and Fe-Fe₇C₃ (a subsystem of metastable equilibria of the second, higher degree of metastability at large supercooling). This is confirmed by the replacement of the carbide phase and different equilibrate concentrations of austenite in metastable equilibrium with each of the carbides.

Abstract: This study attempted to focus the light on the characterization possibility of the vulcanized, chlorinated, natural rubber products (as the commercial rubber band used in this study) as a shape memory smart material in the case of impregnating it with fused stearic acid by swelling mechanism. Where in this study, the ability of the commercial rubber band on fixing the stretching strain chosen in this study which is of 70% after removing the applied load off the rubber band, was measured after impregnating it with stearic acid (SA) material of weight ratio (30.4%) and swelling time=2hr. At the same time, measuring the ability of that rubber band on rid of this mechanical deformation once it is thermally stimulated and returning to its original shape (before the deformation) by subjugating it to the hot classical shape memory cycle (based on normal cooling at room temperature) with its two stages represented by the shape memory effect (SME) property activation and deactivation stages. Also, the techniques of differential scanning calorimetry (DSC) and x-ray diffraction (XRD) were used to know the agreement between these tests and the SME property test results (thermomechanical cycle test). Through the practical results of all the tests depending on the diagnosis, it was shown that the direct responsibility for the characterization of the commercial rubber band as a shape memory smart material is the stearic acid (SA) material, which acted as a lock in the rubber band structure that can be opened and closed with a temperature change within the melting range of (SA).

Abstract: Sheet Molding Compound (SMC) materials offer attractive specific strength and stiffness properties. With an addition of short cycle times, the possibility for complex geometries and a high recycling potential, this material is a promising solution for the manufacture of lightweight components of numerous industrial sectors. Accurate and reliable simulation can contribute to a fast and competitive development process and effectively reduce the time-to-market. Especially, the accuracy of the simulative filling process is crucial to be able to predict the mechanical properties and hence, pave the way to structural parts. An appropriate characterization of the rheological behavior is therefore, crucial for accurate simulation results. To this purpose bar flow tests are performed and the experimental results are compared to the numerical results. A sensitivity analysis is performed to investigate the influence of each parameter on the simulation outcome. Furthermore, guidelines to improve the simulation accuracy and the testing equipment are derived. In the testing method some improvement potential was identified and the necessity for a testing method closer to the compression process could be established.

Abstract: Prosthetic socket is the device that link artificial limb with the amputee part. This work has been done on seven laminated composite were prepared by vacuum technique from Polyester resin reinforced with (Jute, Carbon, Glass, Perlon) fibers. The interaction between fibers and matrix material was studied using Fourier transform infrared (FTIR) spectroscopy. DSC test also had been studied for different laminated composite materials to make prosthetic socket. The infrared spectra result of the Polyester composite specimens with natural and synthetic fibers indicate that no additional new peak was observed. While DSC results showed the increase in the glass transition temperature (Tg) as the number of Jute layers increased and this may be related to the nature of Jute fibers. As well as Carbon lead to increase Tg but Glass fiber decreased Tg when added to natural fiber (Jute fiber). The composite specimen reinforced with three layers of Jute fibers plus four layers of Carbon fibers (3 Jute + 4 Carbon) had the highest Tg (107°C).