scholarly journals Thermo-oxidative stability of waterborne polyurethanes with catalysts of different selectivity evaluated by non-isothermal thermogravimetry

2007 ◽  
Vol 72 (7) ◽  
pp. 723-735 ◽  
Author(s):  
Suzana Cakic ◽  
Goran Nikolic ◽  
Jakov Stamenkovic
Keyword(s):  
Thermal Stability ◽  
Oxidative Stability ◽  
Temperature Interval ◽  
Activation Energies ◽  
Kinetics Parameters ◽  
Arrhenius Plots ◽  
Isothermal Thermogravimetry ◽  
Degradation Processes ◽  
Waterborne Polyurethanes ◽  
Degree Of Degradation

Thermogravimetry was used for the evaluation of the thermo-oxidative stability of waterborne polyurethanes (wbPUR) containing catalysts of different selectivity. From Arrhenius plots, activation energies of between 50 and 120 kJ mol-1 for wbPUR were determined, depending on the temperature interval, selectivity of the catalyst and degree of degradation. Waterborne polyurethanes without catalyst showed lower thermal stability than waterborne polyurethanes with catalysts of different selectivity. Non-isothermal thermogravimetry indicated the presence of different degradation processes and enabled the kinetics parameters at higher degrees of degradation to be evaluated. .

Thermooxidative Aging Studies on Silicone Rubber and Lifetime Prediction

2013 ◽  
Vol 777 ◽  
pp. 11-14
Author(s):  
You Shan Wang ◽  
Sha Sha Jiang ◽  
Yu Peng Liu
Keyword(s):  
Silicone Rubber ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Activation Energies ◽  
Lifetime Prediction ◽  
Arrhenius Behavior ◽  
Compression Set ◽  
Degradation Processes ◽  
Aging Studies ◽  
Significant Compression

Silicone rubber have been aged in air while under 25% compression at temperature up to 250°C. These studies examined the compression set of silicone rubber at accelerated (elevated) temperatures and were then used to make predictions about compression set at room temperature. The data obtained could be amenable to timetemperature superposition and Arrhenius treatment. The results suggest the presence of two degradation processes with activation energies of 71.6 kJ mol-1 (for temperatures above 165 °C) and 26.08 kJ mol-1 (for temperatures below 165 °C). Based on the extrapolation of the non-Arrhenius behavior, it was estimated that significant compression set loss would occur after around 67 years at 25 °C.

Thermal and Thermo-Oxidative Degradations of Deproteinized Natural Rubber and Natural Rubber

2011 ◽  
Vol 306-307 ◽  
pp. 50-57 ◽  
Author(s):  
Can Zhong He ◽  
Zheng Peng ◽  
Jie Ping Zhong ◽  
Shuang Quan Liao ◽  
Xiao Dong She ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Natural Rubber ◽  
Oxidative Stability ◽  
Natural Rubber Latex ◽  
Oxidative Degradation ◽  
Decomposition Reaction ◽  
Nitrogen Atmosphere ◽  
Degradation Temperature ◽  
Air Atmosphere ◽  
Deproteinized Natural Rubber

Deproteinization of natural rubber was achieved in the latex stage. The structure of deproteinized natural rubber (DPNR) was characterized by fourier transform infrared spectroscopy (FTIR). The thermo degradation of DPNR was studied by thermogravimetry analysis (TG) under air atmosphere and nitrogen atmosphere. The kinetic parameters apparent activation energies (Ea) of the thermal decomposition reaction been calculated from the TG curves using the method described by Broido. And the results were compared with the thermo degradation of natural rubber (NR) under the same conditions. The effect of proteins in natural rubber latex on thermal/ thermo-oxidative stability of NR was discussed. The results show that: the absorptions of the proteins in DPNR at 1546 ㎝-1, compared to NR, become significantly weaker, nearly disappear, which indicates most of proteins has been removed from NR. The thermo degradation of DPNR in nitrogen atmosphere is a one-step reaction. The initial degradation temperature (T0) 、the maximum degradation temperature（Tp） and the final degradation temperature（Tf）as well as the Ea of DPNR are higher than those of NR, which indicates that DPNR represents a better thermal stability than NR under nitrogen atmosphere. Thermo-oxidative degradation of DPNR and NR are two-step reaction. The characteristic temperatures (T0, Tp and Tf) of DPNR are lower than those of NR. The Ea during the First Step of Thermooxidative Degradation of DPNR are also lower than those of NR. These results prove that the thermo-oxidative stability of DPNR is worse than that of NR. Protein is the key role to the thermal stability of natural rubber.

scholarly journals Improvement of Thermal Stability of Nd-Tb-Fe-Co-B Sintered Magnets by Additions of Pr, Ho, Al, and Cu

2012 ◽  
Vol 2012 ◽  
pp. 1-4 ◽  
Author(s):  
A. A. Lukin ◽  
E. I. Il'yashenko ◽  
A. T. Skjeltorp ◽  
G. Helgesen
Keyword(s):  
Heat Treatment ◽  
Thermal Stability ◽  
Magnetic Properties ◽  
Thermal Treatment ◽  
Temperature Interval ◽  
Magnetic Parameters ◽  
Sintered Magnets ◽  
Additional Doping ◽  
As Solubility ◽  
Thermal Stability Of

The present work investigates the influence of Pr, Al, Cu, B and Ho which were introduced into the Co-containing sintered magnets of Nd-Dy-Tb-Fe-Co-B type on the magnetic parameters (α, Hci, Br, BHmax⁡). The effect of heat treatment parameters on magnetic properties was also studied. It was revealed that the essential alloying of NdFeB magnets by such elements as Dy, Tb, Ho, Co as well as by boron-forming elements, for example, by titanium, may lead to reducing of F-phase quantity, and, as a consequence, to decreasing of magnetic parameters. It was also shown that additional doping of such alloys by Pr, B, Al and Cu leads to a significant increase of the quantity of F-phase in magnets as well as solubility of the Dy, Tb, Ho and Co in it. This promotes the increase of magnetic parameters. It was possible to attain the following properties for the magnets (Nd0,15Pr0,35Tb0,25Ho0,25)15(Fe0,71Co0,29)bal ⋅ Al0,9Cu0,1B8,5 (at. %) after optimal thermal treatment {1175 K (3,6–7,2 ks) with slow (12–16 ks) cooling to 675 K and subsequently remaining at T=775 K for 3,6 ks—hardening}: Br=0,88 T, Hci=1760 kA/m, BHmax⁡=144 kJ/m3, α<|0,01|%/K in the temperature interval 223–323 K.

Raman spectra of single walled carbon nanotubes at high temperatures: pretreating samples in a nitrogen atmosphere improves their thermal stability in air

2017 ◽  
Vol 19 (10) ◽  
pp. 7215-7227 ◽  
Author(s):  
J. Molina-Duarte ◽  
L. I. Espinosa-Vega ◽  
A. G. Rodríguez ◽  
R. A. Guirado-López
Keyword(s):  
Carbon Nanotubes ◽  
Thermal Stability ◽  
Raman Spectra ◽  
Temperature Interval ◽  
Theoretical Study ◽  
Chemical Reactivity ◽  
Single Walled Carbon Nanotubes ◽  
Nitrogen Atmosphere ◽  
Single Walled Carbon ◽  
Walled Carbon Nanotubes

We present a combined experimental and theoretical study dedicated to analyzing the structural stability and chemical reactivity of single walled carbon nanotubes (SWCNTs) in the presence of air and nitrogen atmospheres in the temperature interval of 300–1000 K.

Thermal properties and thermal degradation kinetics of phenolic and wood flour-reinforced phenolic foams

2016 ◽  
Vol 51 (1) ◽  
pp. 125-138 ◽  
Author(s):  
JC Domínguez ◽  
B del Saz-Orozco ◽  
M Oliet ◽  
MV Alonso ◽  
F Rodriguez
Keyword(s):  
Thermal Stability ◽  
Thermal Degradation ◽  
Degradation Kinetics ◽  
Wood Flour ◽  
Activation Energies ◽  
Thermal Degradation Kinetics ◽  
Kinetic Methods ◽  
Model Free ◽  
Phenolic Foam ◽  
Kinetics Of

In the present work, the thermal stability, changes in chemical structure during thermal degradation, and the kinetics of thermal degradation of a phenolic foam were studied. An 8.5 wt% of Pinus radiata wood flour reinforcement was added to the phenolic foam. A commercial phenolic resol was used as the matrix for the foam. The wood flour-reinforced foam showed a structure similar to the phenolic foam according to the Fourier transform infrared spectroscopy results. The wood flour increased the thermal stability of the phenolic foam in the first stage of thermal degradation ( T 5%), decreased it in the second step ( T 25%), and negligibly influenced the final stage. The activation energies of the degradation processes of the studied materials were obtained by the Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa model-free kinetic methods and a 2-Gaussian distributed activation energy model. The values of the activation energies obtained by the model-free kinetic methods for the first degradation stage of the phenolic foams were in a range between 110 and 170 kJ mol−1, whereas for the wood flour it was 162 kJ mol−1 for almost all of the conversion range of its main degradation stage. The applied models showed good fits for all the materials, and the activation energies calculated were in agreement with the values found in the literature.

Thermal Degradation of Aged Chloroprene Rubber Studied by Thermogravimetric Analysis

2001 ◽  
Vol 74 (4) ◽  
pp. 622-629 ◽  
Author(s):  
Elton L. G. Denardin ◽  
Dimitrios Samios ◽  
Paulo R. Janissek ◽  
Gabriel P. de Souza
Keyword(s):  
Thermogravimetric Analysis ◽  
Thermal Degradation ◽  
Mass Loss ◽  
Activation Energies ◽  
Half Width ◽  
Temperature Elevation ◽  
Kinetic Methods ◽  
Degradation Processes ◽  
Chloroprene Rubber ◽  
Differential Thermogravimetric Analysis

Abstract The thermal degradation of original and aged chloroprene rubber was studied using thermogravimetric analysis. Thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTG) techniques were used to detect the mass loss during the temperature elevation. By the analysis of the mass loss curves through usual kinetic methods, it was possible to evaluate the different degradation processes present in the overall degradation. The activation energies of the degradation processes were obtained using the dynamic, non-isothermal Kissinger and Osawa methods and the half-width at half-high technique (HWHH). The results obtained demonstrate clearly the differences between original and aged chloroprene rubber as well as the influence of the air and N2 in TGA.

Thermal Analysis of Kenaf Sandwich Core Panel

2012 ◽  
Vol 576 ◽  
pp. 488-491
Author(s):  
S.K. Abdul Rahman ◽  
Z. Halim
Keyword(s):  
Thermal Stability ◽  
Thermal Analysis ◽  
Sandwich Panel ◽  
Degradation Processes ◽  
Sandwich Core ◽  
Thermal Stability Of

The thermal stability of kenaf sandwich panel core structures are presented in this paper. Sandwich core structures tested are of varying kenaf percentage being 10, 20 and 30 wt%. The result indicated that all composite have two step degradation processes due to the presence of kenaf in epoxy. From the discussion, increasing the kenaf percent ratio will decrease the percent residue.

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