Papers by Keyword: Thermogravimetric Analysis (TGA)

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: Fiber optimization is one of the key factors in fabricating fiber-reinforced composites. A higher amount of fiber loading does not correspond to improved mechanical and thermal properties of composites. Consequences such as poor fiber wetting, formation of voids, and delamination may arise due to the lower amount of matrix at higher fiber loading. In this study, the loading percentage of nito fibers were varied from 5, 10, and 15 wt%. The mechanical and thermal analysis showed that the composite with the lowest fiber loading percentage showed a better performance compared to the two composites with higher fiber loading. The tensile strength of the said composite increased by 3 MPa while the onset of degradation temperature increased by 30.91°C. The SEM micrographs confirmed that the composites with higher fiber loading percentage suffered poor wettability which resulted in poor adhesion of the fiber to the matrix. The micrographs of the composite with 5 wt% showed a superb fiber-matrix bonding which resulted in a more seamless transfer of heat and stress upon heat and load application. These results proved that optimization of fiber loading percentage is an integral step to fabricate an improved composite material.

Abstract: Photopolymerisation of 2-Hydroxyethyl methacrylate (HEMA) through the use of N,N-Diethyldithiocarbamato-(1,2)-propanediol (DCPD) was studied. The photoinitiator DCPD was synthesized from sodium N,N-Diethyldithiocarbamate (NaSR) and 3-chloro-1,2-propanediol. For the photochemical decomposition of the C – S bond, UV light at 254 nm is used. The role of the monomer concentration, reaction time and DCPD to HEMA mol ratio on the conversion of HEMA to PHEMA were studied in this paper. It was found that percentage conversion of HEMA increased both with the rise in concentration of monomer and reaction time. Further, living radical nature of the poly2-Hydroxyethyl methacrylate (PHEMA) was ascertained by the photo block copolymerization of methyl methacrylate (MMA) with PHEMA to form PHEMA-b-PMMA. The PHEMA and PHEMA-b-PMMA were characterized by FTIR, ¹H-NMR, Thermogravimetry.

Abstract: The theoretical aspects of wood material fire protection formation by esterification reactions are considered in the article. The reactivity of polysaccharides and polymers from which wood material is composed has been confirmed by the FTIR method. The IR spectra of the original standard samples of lignin and microcrystalline cellulose were taken and after treatment with solutions with concentrations of 10% of the mass. orthophosphoric (Н₃РО₄) and oxyethylene diphosphonic (CH₃C(OH)(H₂PO₃)₂) acids. Electron scanning microscopy revealed the crystallization of inorganic salts on the wood material surface, which play the role of flame retardants, as well as a film of organopolymer (polyhexamethylene guanidine polyphosphate), which forms a foamed layer of coke when heated. Thermogravimetric analysis (TGA) and gas chromatography (GC) methods show the mechanism of action of fire protection provided to wood material. The formation of foamed coke is visually shown and the results on the effectiveness of fire protection on the example of wood material treatment with a mixture of diammonium phosphate and ammonium sulfate are obtained.

Abstract: The world as we probably are aware of is confronting a major problem known as environmental pollution, therefore, leading to global warming. Researchers from around the world have been focusing on green composites to improve the general effect of polymer pollution leading to environmental pollution. This need has constrained numerous researchers to concentrate on making composites utilizing natural fibers and biodegradable polymers. Moreover, natural fibers are cheaper to purchase, have great mechanical properties, biodegradability and demand lower amount of production energy. This paper focuses on one of the natural fibers known as Luffa Cylindrica (LC). Chemical surface treatments are necessary in order to get the best adhesion possible between the polymer and fiber which leads to better mechanical properties. Therefore, in this paper sodium hydroxide, silane and acetylation chemical surface treatments were performed. Furthermore, with the help of Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and Derivative Thermogravimetry (DTG) it was predicted that all the chemical surface treatments were successful. With the help of the results it was predicted that these specific chemical surface treatments showed removal of hemicellulose and lignin. Furthermore, with the help of thermal analysis it was predicted that silane treated samples showed highest amount of thermal resistance whereas, acetylated samples predicted lowest.

Abstract: The oxidation behavior and mechanism of Ti-Cu alloys (0≤w(Cu)≤20%) in the temperature range of 1000°C～1300°C are studied by thermogravimetric analysis(TGA) combined with SEM, EDS and XRD analysis methods. The results show that the oxidation rates of Ti-Cu alloys increase sharply when the temperature rises above 1000°C. The oxidation products have a three-layer structure, from the outside to the inside, which are dense outer oxide layer of TiO₂, porous inner oxide layer of low valence oxide of Ti and Cu-enriched layer. With the increase of the temperature, the thicknesses of oxide layers of Ti-Cu alloy increase and the Cu-enriched phase increases gradually and melts. The melting Cu-enriched phase flows to the oxidation surface along the grain boundaries of the oxide layer. The high temperature oxidation resistance of Ti-Cu alloys declines with the increase of Cu content. The main reason is that more liquid Cu-enriched phase is formed and flows to the oxidation surface along the oxide grain boundaries in the Ti-Cu alloy, and Ti and O ions can diffuse more easily along the liquid Cu-enriched phase, which increases the oxidation rates.

Abstract: The kinetics of the thermal degradation and thermal stability of thermal conductive silicone rubber filled with Al₂O₃ and ZnO were investigated by thermogravimetric analysis in a flowing nitrogen atmosphere at a heating rate of 10°C/min. The rate parameters were evaluated by the method of Freeman–Carroll. The results show that the thermal degradation of silicone rubber begins at about 350°C and ends at about 600°C. The thermal degradation is multistage, in which zero-order reactions are principal. The kinetics of the thermal degradation of thermal conductive silicone rubber has relevance to its loading of thermal conductive filler. The activation energies are temperature-sensitive and their sensitivity to temperature becomes weak as temperature increases.

Abstract: Phenyl silicone resin reinforced addition type liquid phenyl silicone rubber was prepared by vulcanization of vinyl end-capped polymethylphenylsiloxane (PVPS), phenyl MT resins and hydrogen end-capped polydiphenylsiloxane (PHPS) under Pt catalysis at 150°C for 4h. The effects of the proportion and the vinyl content of phenyl MT resins on the mechanical properties of cured products were investigated. The thermal stability was explored by thermogravimetric analysis. The changes of mechanical properties were also studied before and after irradiation. Phenyl silicone rubber with good performance was obtained when the phenyl MT resin content was 50~60 wt% and the vinyl content was at 5.5~6.6 wt%. The onset temperature of thermal degradation and the center temperature of thermal degradation were 443.7°C and 502°C, respectively. When the radiation dose increased from 0 to 300 KGy, the tensile strength decreased from 4.1MPa to 2.3MPa and the tearing strength decreased from 8.9MPa to 5.1MPa. When the radiation dose continues to increased from 300 to 900 KGy, the tensile strength increased from 2.3MPa to 6.4MPa and the tearing strength increased from 5.1MPa to 6.5MPa. During the process of radiation, the elongation at break had been kept down from 96% to 52%, and the hardness increased from 80A to 90A.

Abstract: The thermotropic liquid crystal copolyester P-BPA2.5 and P-BPAF2.5 with low melting temperature and high glass transition temperature were obtained by introducing 2.5mol% bisphenol A (BPA), bisphenol AF (BPAF) and terephthalic acid (TA) receptively into the molecular chain of poly (oxybenzoate-co-oxynaphthoate). The isothermal and nonisothermal degradation behavior of the two copolyesters P-BPA2.5 and P-BPAF2.5 were studied by thermo-gravimetry analysis (TGA) under nitrogen atmosphere. The degradation kinetics of the copolyesters under dynamic and isothermal heating conditions was evaluated byKissinger-Akahira-Sunose (KAS) and iso-conversional methodrespectively. Results showed that the activation energy (E) values followed the order P-BPAF2.5>P-BPA2.5 under dynamic heating atmosphere. However, the P-BPA2.5 showed a better thermal stability as compared with P-BPAF2.5 under isothermal heating conditions. The differences of degradation mechanism between the two copolyesters may be a reason for this phenomenon, which was discussed in detail in the text.

Abstract: Natural fiber reinforced polylactic acid based biocomposites are broadly considered by the researchers to compete with non-renewable petroleum based products. In this study, the biodegradable composites which are the polylactic acid, PLA and rice straw, RS were prepared by using heated two roll-mill at 180°C. Mechanical properties showed that the tensile strength and elongation at break, E_b decreased with the increasing of RS while the Young’s modulus had increased. The TGA results confirmed that thermal stability of PLA with RS composites decreased when the RS fiber loading increased.