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41.
The service life of ABS polymer, stabilized by 2-(3,5-di-tert-butyl-4-hydroxyanilino)-4,6-bis(octylthio)-1,3,5-triazine and containing 50% of a modifying rubber component, was estimated from oxidative induction times measured by DSC in isothermal mode in the temperature interval 140–170°C. The lifetime of ABS powder at the actual temperature of drying was predicted by linear extrapolation according to Arrhenius. However, the extrapolated value was much longer than the real lifetime determined from the long-term oven aging tests at 70 and 90°C, simulating the industrial drying process. The effect of changes in the apparent activation energy of oxidation due to antioxidant consumption during polymer aging is discussed. 相似文献
42.
Bernhard Wunderlich 《Thermochimica Acta》2003,403(1):1-13
Linear, flexible macromolecules are long recognized as phase structures limited to micrometer and nanometer dimensions with covalent bonds crossing the interfaces. This special, usually non-equilibrium structure leads to unique properties and a multitude of changes for different thermal and mechanical histories. Analyses that enable the study of these properties are temperature-modulated calorimetry and related techniques which allow the separation of equilibrium and non-equilibrium responses. Research on these topics is reviewed and combined to a model for the nanophases. The new approach to the complex nanophase systems yields a better understanding of the relationship between structure and thermodynamic properties. Special emphasis is placed on the size and surface effects on the glass and melting transitions, the development of rigid-amorphous phases, and the reversible melting within the globally metastable structure. 相似文献
43.
Liu B. Thomas P. S. Ray A. S. Williams R. P. 《Journal of Thermal Analysis and Calorimetry》2004,76(1):115-122
The effect of sampling conditions on the decomposition of electrolytic manganese dioxide using thermal methods is reported.
Significant differences were observed in the mechanism of the decomposition by simply changing the reaction environment from
a closed pan to an open pan configuration. The purge gas atmosphere was also observed to influence the decomposition mechanism.
As a product of the decomposition is oxygen, the change in the mechanism observed between the experimental conditions may
be explained in terms of the ease of removal of oxygen from the reaction site.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
44.
B. Kowalczyk 《Journal of Thermal Analysis and Calorimetry》2000,60(1):163-166
The comparison of thermal and calorimetric properties of metal derivatives of 6-aminopicolinic acid (APH) is presented. The
salts and complexes of APH with Cr(III), Cd(II), Cu(II), Ni(II), Pb(II), Co(II)and Ag(I) have been studied by TG-DTA and DSC
methods up to 1200°C in a nitrogen atmosphere. Decomposition processes are proposed. The decarboxylation, deamination and
carbonation of the organic fragments of molecules take place. The compounds decompose to metal or to metal oxides. The values
of the transition enthalpy were determinated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
45.
聚苯基单醚喹噁啉薄膜的性能与物理老化 总被引:1,自引:0,他引:1
研究了物理老化对聚苯基单醚喹啉薄膜的结构与力学性能的影响 .用差示扫描量热计 (DSC)及正电子湮没寿命谱 (PALS)方法表征了两种不同物理老化条件试样的凝聚结构以及自由体积的差别 .结果表明 ,物理老化使聚苯基单醚喹啉薄膜玻璃化转变温度移向高温 ,在其末端出现热焓吸收峰 ,分子链堆砌紧密使自由体积减小 ,分子可动性降低 .用动态力学分析 (DMTA)以及静态拉伸性能测试等方法研究了两类试样的力学性能 ,结果表明 ,物理老化后 ,试样的动态储能模量稍有增加 ,力学损耗降低 .而静态拉伸实验的断裂应变降低 ,屈服应力增加 ,断裂能降低 ,试样在宏观上由韧性断裂变为明显的脆性断裂 . 相似文献
46.
Heating rate effect on the DSC kinetics of oil shales 总被引:1,自引:0,他引:1
M. V. Kök 《Journal of Thermal Analysis and Calorimetry》2007,90(3):817-821
This research was aimed to investigate the combustion and kinetics of oil shale samples (Mengen and Himmetoğlu) by differential
scanning calorimetry (DSC). Experiments were performed in air atmosphere up to 600°C at five different heating rates. The
DSC curves clearly demonstrate distinct reaction regions in the oil shale samples studied. Reaction intervals, peak and burn-out
temperatures of the oil shale samples are also determined. Arrhenius kinetic method was used to analyze the DSC data and it
was observed that the activation energies of the samples are varied in the range of 22.4–127.3 kJ mol−1 depending on the oil shale type and heating rate. 相似文献
47.
The dipole dynamics and α-relaxation behaviour of polyvinyl chloride PVC, poly(ethylene-co-vinyl-acetate) EVA70 and blend of them EVA70/PVC have been investigated by differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). The differential scanning calorimetry (DSC) thermograms measured on samples show a single glass transition in the analysed temperature range. These three polymers are wholly amorphous and pure PVC and pure EVA70 are miscible in the ratio 1:1. The glass transition temperature Tg decreases significantly with presence of EVA70. Furthermore, the values of apparent activation energies for molecular motions at the α-relaxation and the values of fragility index have also been determined for each sample using Moynihan expression for DSC results and Vogel-Fulcher-Tammann-Hesse (VFTH) form for DRS results. It is shown a large dependence of all the values of these parameters with the content of EVA70. Comparing these three polymers, we found that the more fragile glass forming liquid is the PVC. Fragility decreases drastically with EVA70 content. EVA70 and EVA70/PVC blend exhibit practically the same behaviour. The effect of inter- and intra-molecular interactions on fragility is discussed to explain these variations. 相似文献
48.
The non-isothermal crystallization kinetics of poly(ethylene terephthalate) (PET) modified by poly (ethlene glycol) (PEG) were determined by DSC. The dual linear regression method was used to evaluate the relationship between the reciprocal of t 1/2 ( the half life of crystallization) and the appropriate temperature variable. The parameters such as the activation energy (Ed) for transport, the equilibrium melting temperature (T_m~0),the nucleation parameter (ψ),themaximum crystallization temperature (T_(e, max)), and the kinetic crystallizability (G) for the copolyesters were obtained. The influence of the PEG content in PET chains on the parameters characterizing crystallization kinetics and crystallization thermodynamics was discussed. 相似文献
49.
Anna Michnik K. Michalik A. Kluczewska Zofia Drzazga 《Journal of Thermal Analysis and Calorimetry》2006,84(1):113-117
The thermal denaturation process of bovine and human
both fatty acid containing and fatty acid free albumins in aqueous solution
was studied by use of differential scanning calorimetry. Human serum albumins
were found to be more stable than their bovine counterparts. Fatty acid free
albumins were characterized as generally less stable, more susceptible to
aggregation, their unfolding endothermic transition was less cooperative and
with the smaller degree of reversibility. Deconvolution analysis with using
a non-two-state model with two component transitions showed essential differences
in the thermodynamic parameters between all studied albumins, particularly
regarding the high-temperature component transition. 相似文献
50.
Torre L. Kenny J. M. Recca A. Siracusa V. Tarzia A. Maffezzoli A. 《Journal of Thermal Analysis and Calorimetry》2000,61(2):565-578
An analysis of the crystallization behaviour of a new poly(aryl-ether-ether-ketone-ketone), PK99, by differential scanning
calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) is presented. Isothermal crystallization TG were obtained in the
whole range between the glass transition temperature (T
g) and the melting temperature (T
m) as a consequence of the slow crystallization kinetics stemming from the closeness of these transitions. The calorimetric
results, compared with WAXD data, were applied to determine the theoretical melting temperature and crystallization enthalpy.
The DSC and WAXD data were combined in order to calculate the total amount of the crystallizable fraction of the polymer,
and a model was proposed to explain the difference between the fractions of crystallinity observed with these techniques.
The thermal and X-ray data were also correlated with different lamellar morphologies arising from the crystallization conditions.
Finally, DSC experiments on the crystallized sample were used to detect the presence of a rigid amorphous phase which does
not relax at T
g.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献