Papers by Keyword: Thermal Stability

Abstract: By compounding all of its components through extrusion and injection moulding, chemically functionalized high-density polyethylene (CF-HDPE) hybrid composites reinforced with oil palm empty fruit bunch (OPEBF) and nettle (NETLF) fibers have been developed by the Palsule process. H1, H2 and H3 hybrid composites of (OPEBF/NETLF)/CF-HDPE have been developed with increasing OPEBF but fix total amounts of 30% of both OPEBF and NETLF. The thermal stability of all these H1, H2 and H3 hybrid composites increases with increasing OPEBF and decreasing NETLF in them. The overall thermal stability of H1, H2 and H3 hybrid composites is between their CF-HDPE matrix and the reinforcing OPEBF and NTELF reinforcing fibers. These composites show thermal stability till 245^°C, after releasing their volatile matters and moisture.

Abstract: This study presents the results of thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy to investigate the effects of air plasma treatment on polyamide 12 (PA12) powder for 1 and 2 h. Plasma treatment raised the degradation starting temperature from 376 °C for untreated PA12 powder to 389 °C for 2 h of treated powder. The crystallization temperature revealed by DSC increased from 133.31 to 141.7°C, whereas the melting point remained essentially unaltered at approximately 185°C. The fusion enthalpy decreased from 90.64 to 73.5 J/g, and the crystallinity also decreased from 41.9% to 34%. SEM results show a steady improvement toward homogeneity, accompanied by a diminishing amount and size of surface defects as the treatment proceeds. Such findings promote plasma treatment as an alternative route without any additives in raising the PA12 crystallization level and changing surface morphology together with improving its thermal stability, thus finding broad future application prospects in modified polymer engineering processing.

Abstract: This study investigates the potential of typha domingensis fibers to be used as reinforcement in composite materials. Morphological, mechanical, and thermal analyses were conducted on fibers extracted from leaves and stems using various methods. The leaf fibers (LNF-00, LRD-41, LRS-41), with transverse dimensions ranging between 185 to 244 µm, were on average 48% thinner than stem fibers (SNF-00, SRD-20, SRS-20), whose transverse dimensions ranged from 305 to 334 µm. Transverse dimensions variations were most pronounced for fibers retted in distilled water (65%), followed by those retted in seawater (47%) and mechanically processed fibers (37%). Stem fibers subjected to seawater retting (SRS-20) exhibited less dispersion in mechanical properties, with a Young’s modulus of 2.2 GPa and a tensile strength of 55.9 MPa. Overall, leaf fibers outperformed stem fibers, with average increases of 38, 60, and 31% for Young’s modulus, tensile strength, and elongation at failure, respectively. Finally, thermal analysis revealed that fibers retted in distilled water provided the highest thermal stability, attributed to a reduction in lignin and hemicelluloses.

Abstract: In this work, jute and bamboo fiber is used as reinforcement to prepare hybrid composites. The alkali treatment of both the fibers are carried out and the strength of composites prepared with the alkali treated fiber is compared with the composites made from untreated fibers. The bamboo fibers are chopped and pulverized and added to matrix while the jute fiber is used in continuous form. Tensile, flexural, impact, hardness, thermal absorptivity test is carried along with the flammability test. The tensile strength of jute –bamboo-epoxy composite (JBEC) with untreated fibers is observed to be 12.21 MPa while the tensile strength of jute-epoxy composite (JEC) with untreated fiber composite is observed to be 11.72 MPa. Further, the alkali treatment of fiber increases the tensile strength of both the JEC and JBEC by 8%. About 11.12% rise in tensile strength in JEC and 14.35% rise in JBEC is observed due to alkali treatment of fibers. JBEC with alkali treated fibers [JBEC(AT)] shows 42.5HV hardness, while JBEC shows the hardness of 40.2HV. The hardness of JEC increased from 31.3HV to 35.5HV due to alkali treatment. JBEC and JEC with alkali treated fibers [JBEC(AT), JEC (AT)] shows higher thermal absorptivity than JBEC and JEC owing to the fact that higher thermal conductivity of bamboo fibers. The JBEC(AT) shows an ignition temperature of 301°C, while JBEC starts burning at a temperature of 285.6°C. JEC starts burning at 256.56°C and JEC burns by 248.52°C.

Abstract: Tissue engineering provides a promising approach to addressing the global shortage of organ and tissue donors by developing biological substitutes that can restore or enhance tissue function. This study presents the development and characterization of PEG-PVA biodegradable hydrogels, synthesized through chemical crosslinking with varying concentrations of glutaraldehyde, for tissue engineering applications. Mechanical, thermal, and structural properties were systematically analyzed to determine the optimal formulation for different applications. Hydrogels synthesized with 0.10g and 0.15g of glutaraldehyde were selected for detailed evaluation. The hydrogel with 0.10g glutaraldehyde exhibited a tensile strength of 1200 MPa, a glass transition temperature (Tg) of ～50°C, and a swelling ratio of 7.65, demonstrating superior mechanical robustness and thermal stability for load-bearing applications such as bone and cartilage regeneration. In contrast, the hydrogel with 0.15g glutaraldehyde, with a tensile strength of 1000 MPa, a Tg of 45°C, and a swelling ratio of 4.49, showed greater flexibility and a denser microstructure, making it more suitable for soft tissue applications requiring controlled degradation. These results underscore the importance of tailoring crosslinking density to optimize hydrogel performance for specific biomedical applications. Future studies should explore the behavior of these hydrogels in biologically relevant environments, including enzymatic degradation and in vivo testing. With further development, PEG-PVA hydrogels could play a key role in regenerative medicine, offering customizable mechanical and degradation properties for diverse clinical applications.

Abstract: In this work, Fe₃₅Cr₃₅Ti₁₀Ni₁₀Zr₁₀ (at%) is a new light-weight medium entropy alloy subjected to different annealing conditions (at 700 - 1000°C for different durations) to examine its thermal stability, microstructural evolution, and microhardness change. The developed alloy was characterized by Optical light microscopy, X-ray diffraction (XRD), and Vickers microhardness. It was observed that the alloy demonstrated high microhardness value of ~707and high thermal stability with minor changes in its microstructures after different annealing treatments. These excellent properties displayed by the alloy highlight its promise for high-temperature applications.

Abstract: The thermal instability of the perovskite layer hinders the commercialization of perovskite solar cells (PSCs). In this work, the effect of cold isostatic pressing (CIP) on the thermal stability of poly (methyl methacrylate) (PMMA) interlayer-encapsulated methylammonium lead iodide (MAPbI₃) perovskite (PMMA-MAPbI₃) film was investigated. The MAPbI₃ perovskite film was prepared via a vacuum-assisted solution process (VASP) on the SnO₂-coated FTO glass substrate. Following this, a PMMA interlayer was spin-coated on the MAPbI₃ film. The PMMA-MAPbI₃ film was then vacuum-sealed in a thermoplastic bag and pressed in a CIP chamber filled with silicone oil at a pressure of 5 MPa for 10 min. The CIP-treated film was then subjected to thermal stressing at 150 °C for 1–5 h to compare its thermal stability against a pristine film untreated with CIP. The CIP treatment densified the MAPbI₃ perovskite grains and enhanced the interfacial bonding between the PMMA interlayer and the perovskite film. These enhancements contributed to the superior thermal stability of the CIP-treated film, as its morphology retained most of the MAPbI₃ perovskite grains with minimal conversion to PbI₂ nanorods, evidenced by the minimal evolution of the PbI₂ XRD peak. The photoluminescence (PL) spectra of the CIP-treated film showed higher retention of the emission peak at 770 nm after 5 h of thermal stressing, signifying less thermal degradation than the untreated pristine film. Thus, CIP is demonstrated as a simple method that can enhance the thermal stability of the PMMA-MAPbI₃ film.

Abstract: Oil reservoir formation damage is a significant issue in secondary and tertiary oil recovery operations. Enhanced oil recovery (EOR) approaches can address these issues while increasing production rates and resource recovery. However, challenges include chemical degradation, high chemical volumes, and high costs. Nanotechnologies can improve oil recovery by improving subsurface porous media and pore fluids, separating fluid phases, and introducing influencing coatings. Cobalt oxide-based materials have been extensively evaluated for their amphiphilic properties, thermal stability, and high reactivity, which can modify physicochemical properties and improve crude oil recovery. CoO nanoparticles were characterized using various techniques, including Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectronic spectrometry, and Field Emission Scanning Electron Microscope (FSEM). Results showed that CoO nanofluid positively affects reservoir minerals with electromagnetic fields and improves oil recovery. It also improves thermal stability, promotes stable emulsion formation, decreases the interfacial tension (IFT) up to 15% for the light-crude-oil/water system at concentrations of 0.5 wt% nanofluid, and can improve thermal stability with respect to CoO in a wide range of temperatures, favouring the formation of stable emulsions.

Abstract: The thermal degradation process of layered molybdenum disulfide nanosheets/flake graphite nanosheets/expanded flame retardants/epoxy resins (MDNs/FGNs/IFR/EP) was analyzed using thermogravimetric analysis. The effect of binary nanolayered molybdenum disulfide/flake graphite nanosheets as enhancing flame retardants on thermal stability was studied. The thermal degradation kinetics activation energy of MDNs/FGNs/IFR/EP was calculated using the Coats Redfern method. The mechanism function of MDNs/FGNs/IFR/EP was determined using the Phadnis method, and the thermal degradation mechanism of MDNs/FGNs/IFR/EP was obtained. Binary nanoMD/FG helps to improve the thermal stability of EP.

Abstract: The production of the jute fibers and yarns in enormous amounts and their use in different fields requires an overall comprehension of the evolution of their performance during their use and before their end life. Exposing the jute yarns to the extreme environmental conditions, such as high humidity, severe weathering, severe environments, freezing environments and others can degrade the mechanical properties jute yarns. Besides, the use of these jute yarns on the appropriate applications immersed in normal water may be accelerated them to reach their end-of-life. In this work, the thermal and mechanical properties of the jute yarns immersed in normal water for different duration were evaluated. This environmental condition was selected owing to the high probability to the exposing of yarns to the immersing in normal water on outdoors which affect their performance. The thermal stability of the jute yarns was effectuated in order to explain the chemical and physical changers occurred and linked to the mechanical properties. Results show that the mechanical properties of the jute yarns degraded by along immersion in water compared to the raw one. The tensile stress and the tensile modulus are dropped by 47 % (from 52 to 28 MPa) and 46 % (from 2.28 to 1.24 GPa), respectively for the samples immersed in water along duration (9 months) compared to the raw samples. Besides, the thermal stability of the immersed samples shows that there are no significant changes except a slight high residue for the immersed ones.