scholarly journals Thermal Stability of Wood Fibers Produced from Recycled Medium Density Fiberboards

2019 ◽  
Vol 70 (2) ◽  
pp. 149-155
Author(s):  
Mohammad Ahmadi ◽  
Bita Moezzipour ◽  
Aida Moezzipour
Keyword(s):  
Thermal Stability ◽  
Chemical Structure ◽  
Electrical Heating ◽  
Wood Fibers ◽  
Dsc Analysis ◽  
Scanning Calorimetry ◽  
Different Temperatures ◽  
Thermal Deterioration ◽  
Recycled Fibers ◽  
Thermal Stability Of

In this study, thermal stability of fibers obtained from recycled MDF was investigated and compared with virgin fibers by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Two different methods, including electrical heating and hydrothermal treatment, were used for recycling the MDF wastes. Electrical heating method was performed at two different times (2 and 4 min) and hydrothermal method was done at three different temperatures (105, 125 and 150 °C). Chemical structure of wood fibers was also studied. TGA and DSC analysis showed higher weight loss of recycled fibers as compared to virgin fibers in a similar degradation region, which means that thermal stability of recycled fibers is lower than virgin fibers. In fact, thermal behavior of recycled fibers was medium between wood and UF resin. DSC analysis showed two exotherms at around 340 and 475 °C. The transition at around 340 °C in fibers thermogram was considered to be due to polysaccharides thermal deterioration and the exotherm at 475 °C was related to lignin carbohydrate complex deterioration. The results of chemical structure analysis showed that lignin and hemicellulose content of recycled fibers was significantly lower than that of virgin fibers, which resulted in decreased thermal stability.

scholarly journals Improved thermal stability of SiCf/SiC ceramic matrix composites fabricated by PIP process

2021 ◽  
Vol 15 (2) ◽  
pp. 164-169
Author(s):  
Jian Gu ◽  
Sea-Hoon Lee ◽  
Daejong Kim ◽  
Hee-Soo Lee ◽  
Jun-Seop Kim
Keyword(s):  
Thermal Stability ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Matrix Composites ◽  
Sic Fiber ◽  
Sic Ceramic ◽  
Different Temperatures ◽  
Pre Treatment ◽  
Thermal Deterioration ◽  
Thermal Stability Of

Improvement of the thermal stability of continuous SiC fiber reinforced SiC ceramic matrix composites (SiCf/SiC CMC) by the pre-treatment of SiC fillers and the suppression of oxidation during polymer impregnation and pyrolysis (PIP) process were investigated. Dense SiCf/SiC CMCs were fabricated using the slurry infiltration and PIP process under a purified argon atmosphere. Structure and mechanical properties of the SiCf/SiC CMC heated at different temperatures were evaluated. The flexural strength of the SiCf/SiC CMC decreased only 15.3%after heating at 1400 ?C, which exhibited a clear improvement compared with the literature data (49.5% loss), where severe thermal deterioration of SiCf/SiC composite occurred at high temperatures by the crystallization and decomposition of the precursor-derived ceramic matrix. The thermal stability of the SiCf/SiC CMC fabricated by PIP process was improved by the pre-treatment of SiC fillers for removing oxides and the strict atmosphere control to prevent oxidation.

Systematic Characterization of Different Quaternary Ammonium Salts to be Used in Organoclays

2012 ◽  
Vol 727-728 ◽  
pp. 1552-1556
Author(s):  
Renata Barbosa ◽  
Dayanne Diniz Souza ◽  
Edcleide Maria Araújo ◽  
Tomás Jefférson Alves de Mélo
Keyword(s):  
Thermal Stability ◽  
Quaternary Ammonium ◽  
Chemical Structure ◽  
Quaternary Ammonium Salts ◽  
Ammonium Salts ◽  
Degradation Mechanisms ◽  
Scanning Calorimetry ◽  
Higher Temperature ◽  
Thermal Stability Of

Studies of degradation have verified that the decomposition of some quaternary ammonium salts can begin to be significant at the temperature of about 180 ° C and like most thermoplastics are processed at least around this temperature, the thermal stability of the salt in clay should always be considered. Some salts are more stable than others, being necessary to study the degradation mechanisms of each case. In this work, four quaternary ammonium salts were characterized by differential scanning calorimetry (DSC) and thermogravimetry (TG). The results of DSC and TG showed that the salts based chloride (Cl-) anion begin to degrade at similar temperatures, while the salt based bromide (Br-) anion degrades at higher temperature. Subsequently, a quaternary ammonium salt was chosen to be used in organoclays, depending on its chemical structure and its thermal behavior.

Thermal Stability of N-Heterocycle-Stabilized Iodanes – A Systematic Investigation

2019 ◽  
Author(s):  
Andreas Boelke ◽  
Yulia A. Vlasenko ◽  
Mekhman S. Yusubov ◽  
Boris Nachtsheim ◽  
Pavel Postnikov
Keyword(s):  
Thermal Stability ◽  
Differential Scanning Calorimetry ◽  
Thermogravimetric Analysis ◽  
Systematic Investigation ◽  
Scanning Calorimetry ◽  
Thermal Stability Of

<p>The thermal stability of pseudocyclic and cyclic <i>N</i>-heterocycle-stabilized (hydroxy)aryl- and mesityl(aryl)-l<sup>3</sup>-iodanes (NHIs) through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) is investigated. NHIs bearing <i>N</i>-heterocycles with a high N/C-ratio such as triazoles show among the lowest descomposition temperatures and the highest decomposition energies. A comparison of NHIs with known (pseudo)cyclic benziodoxolones is made and we further correlated their thermal stability with reactivity in a model oxygenation. </p>

Synthesis and properties of phthalonitrile-based resins containing spirocycle acetal

2020 ◽  
pp. 095400832097759
Author(s):  
Ke Li ◽  
Hua Yin ◽  
Kun Yang ◽  
Pei Dai ◽  
Ling Han ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Chemical Structure ◽  
Room Temperature ◽  
Laser Desorption Ionization ◽  
Scanning Calorimetry ◽  
Rheological Analysis ◽  
Ionization Time ◽  
Dynamic Mechanical ◽  
Nmr Spectrometry ◽  
Current Context

Designing novel low-melting, high-rigidity phthalonitrile resin is of great significance in the current context of development. In this study, rigid spirocycle acetal structure was introduced into phthalonitrile to reduce the melting point and maintain their thermal stability. The chemical structure of resins was confirmed by nuclear magnetic resonance (NMR) spectrometry, matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry and Fourier-transform infrared (FTIR) spectroscopy. The curing behaviors were studied by differential scanning calorimetry (DSC). Thermal stability and mechanical properties of the cured resins were investigated by dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The processability was studied by rheological analysis. The results indicated the three monomers had a low melting temperature, wide processing windows and low viscosities. These polymers did not exhibit Tg from room temperature to 400°C, exhibited superb dynamic mechanical property and thermal stability.

scholarly journals Isothermal Vulcanization and Non-Isothermal Degradation Kinetics of XNBR/Epoxy/XNBR-g-Halloysite Nanotubes (HNT) Nanocomposites

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2872
Author(s):  
Seyed Mohamad Reza Paran ◽  
Ghasem Naderi ◽  
Elnaz Movahedifar ◽  
Maryam Jouyandeh ◽  
Krzysztof Formela ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Degradation Kinetics ◽  
Halloysite Nanotubes ◽  
Butadiene Rubber ◽  
Order Model ◽  
Scanning Calorimetry ◽  
Theoretical Methods ◽  
Vulcanization Kinetics ◽  
Kinetics Of ◽  
Thermal Stability Of

The effect of several concentrations of carboxylated nitrile butadiene rubber (XNBR) functionalized halloysite nanotubes (XHNTs) on the vulcanization and degradation kinetics of XNBR/epoxy compounds were evaluated using experimental and theoretical methods. The isothermal vulcanization kinetics were studied at various temperatures by rheometry and differential scanning calorimetry (DSC). The results obtained indicated that the nth order model could not accurately predict the curing performance. However, the autocatalytic approach can be used to estimate the vulcanization reaction mechanism of XNBR/epoxy/XHNTs nanocomposites. The kinetic parameters related to the degradation of XNBR/epoxy/XHNTs nanocomposites were also assessed using thermogravimetric analysis (TGA). TGA measurements suggested that the grafted nanotubes strongly enhanced the thermal stability of the nanocomposite.

Grain Growth in Nanocrystalline Nickel

1999 ◽  
Vol 580 ◽  
Author(s):  
G.D. Hibbard ◽  
U. Erb ◽  
K.T. Aust ◽  
G. Palumbo
Keyword(s):  
Thermal Stability ◽  
Grain Size ◽  
Grain Growth ◽  
Size Distributions ◽  
Nanocrystalline Nickel ◽  
Scanning Calorimetry ◽  
Solute Content ◽  
Grain Size Distributions ◽  
Thermal Stability Of ◽  
Total Solute Content

AbstractIn this study, the effect of grain size distribution on the thermal stability of electrodeposited nanocrystalline nickel was investigated by pre-annealing material such that a limited amount of abnormal grain growth was introduced. This work was done in an effort to understand the previously reported, unexpected effect, of increasing thermal stability with decreasing grain size seen in some nanocrystalline systems. Pre-annealing produced a range of grain size distributions in materials with relatively unchanged crystallographic texture and total solute content. Subsequent thermal analysis of the pre-annealed samples by differential scanning calorimetry showed that the activation energy of further grain growth was unchanged from the as-deposited nanocrystalline nickel.

Synthesis of biomass based plasticizer from linoleic acid and cardanol for preparing durable PVC material

2021 ◽  
Author(s):  
Hongying Chu ◽  
Huabei Li ◽  
Xiaoyan Sun ◽  
Yaowang Zhang
Keyword(s):  
Thermal Stability ◽  
Linoleic Acid ◽  
Chemical Structure ◽  
Dioctyl Phthalate ◽  
H Nmr ◽  
Plasticized Pvc ◽  
Migration Resistance ◽  
Ft Ir ◽  
And Migration ◽  
Thermal Stability Of

Abstract In this paper, we synthesized a kind of bio-based plasticizer epoxidized linoleic acid cardanol ester(ELCE) from cardanol and linoleic acid. Its chemical structure was characterized with FT-IR and 1H NMR. Polyvinyl chloride(PVC) blends plasticized with ELCE were prepared via thermoplastic blending with torque rheometer. The performance including torque, mechanical property, thermal stability, plasticizing property and migration resistance of plasticized PVC blends were investigated and compared with plasticized PVC blends with commercial plasticizer dioctyl phthalate(DOP). The results showed that ELCE improved thermal stability of PVC blends. ELCE played more excellent plasticizing effect on PVC blends than DOP. The better solvent extraction resistance and volatile resistance of ELCE make it impossible to completely replace DOP in PVC products.

STRUCTURE AND THERMAL STABILITY OF THE SULFIDE OVERLAYERS ON CH3CSNH2-PASSIVATED GaAs(100) SURFACES

2001 ◽  
Vol 08 (01n02) ◽  
pp. 19-23 ◽  
Author(s):  
F. Q. XU ◽  
E. D. LU ◽  
H. B. PAN ◽  
C. K. XIE ◽  
P. S. XU ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Electron Spectroscopy ◽  
Photoemission Spectroscopy ◽  
Low Energy Electron Diffraction ◽  
Native Oxides ◽  
Sulfur Passivation ◽  
Different Temperatures ◽  
Low Energy Electron ◽  
Synchrotron Radiation Photoemission ◽  
Thermal Stability Of

Chemically sulfur passivation of GaAs(100) by thioacetamide ( CH 3 CSNH 2) has been studied using synchrotron radiation photoemission spectroscopy (SRPES), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). The measurement of SRPES and AES showed that the top layer of native oxides over GaAs(100) was removed and the sulfides of Ga and As were formed after the passivation process. The thermal stability and surface structure have also been studied by annealing the passivated samples at different temperatures. We found that the surface sulfides could be removed gradually; as a result, a clean, ordered and thus Fermi level unpinning surface was finally achieved. The surface restructures with GaAs(100)–S(2×1) and 4×1 LEED patterns were observed on annealing above 260°C and at 550°C respectively.

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