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81.
82.
83.
An evaluation of measurements of heat capacities by modulated differential scanning calorimetry, MDSC is presented. Heat capacities were obtained from 130 to 550 K by a non isothermal technique in which a periodic modulation was added to the linear heating rate. Effects of amplitude and period of modulation, sample weight, sample type, pan type, and cell imbalance are described. Results are compared with those obtained using the isothermal technique. Heat capacity could be measured well into the decomposition region and separated from the non reversing signal due to chemical reaction (degradation), thus allowing a precise detection of onsets of the thermal degradation. This additional information will aid in the interpretation of the degradation chemistry, a field vital for the petroleum-industry.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayPart of this paper was presented at the 23rd Conference of the North American Thermal Analysis Society, Toronto, Canada, September 25–28, 1994.The author (MVN) acknowledges the experimental assistance provided by J. Balogh of Exxon Research and Engineering Company, Linden. Helpful discussions with A. Boller of the University of Tennessee at Knoxville, Dr. Y. Jin, General Electrical, and Dr. S. Sauerbrunn formerly of TA Instruments are also acknowledged. 相似文献
84.
A novel dual stage chemiluminescence detection system incorporating individually controlled hot stages has been developed and applied to probe for material interaction effects during polymer degradation. Utilization of this system has resulted in experimental confirmation for the first time that in an oxidizing environment a degrading polymer A (in this case polypropylene, PP) is capable of infecting a different polymer B (in this case polybutadiene, HTPB) over a relatively large distance. In the presence of the infectious degrading polymer A, the thermal degradation of polymer B is observed over a significantly shorter time period. Consistent with infectious volatiles from material A initiating the degradation process in material B it was demonstrated that traces (micrograms) of a thermally sensitive peroxide in the vicinity of PP could induce degradation remotely. This observation documents cross-infectious phenomena between different polymers and has major consequences for polymer interactions, understanding fundamental degradation processes and long-term aging effects under combined material exposures. 相似文献
85.
治理塑料废弃物新技术途径探讨--专论可降解塑料的研究开发 总被引:24,自引:0,他引:24
综述了可降解塑料的研究开发现状及其进展。可降解塑料的降解时控性研究,合成,加工工艺改进以及降低成本的研究,可控光-生物降解的合成降解性研究和一次性使用塑料实用性研究,仍是今后需要深入探讨的重要研究课题。 相似文献
86.
甲烷氧化偶联Na2WO4-Mn/SiO2催化剂热效应的研究 总被引:1,自引:2,他引:1
采用固定床微型反应装置,研究了甲烷氧化偶联反应过程中Na2WO4-Mn/S iO2催化剂床层的热效应和催化性能的关系,考察了反应炉温、CH4/O2比和反应气体空速对催化剂床层热点分布的影响.研究结果表明,甲烷氧化偶联催化剂床层的热效应强烈依赖于反应条件.反应炉温越高,CH4/O2比越低,反应气体空速越大,催化剂床层的热点温度越高.结合催化性能和热效应关系的研究,为优化甲烷氧化偶联的反应操作提供了实验依据. 相似文献
87.
Ewa Rudnik G. Matuschek N. Milanov A. Kettrup 《Journal of Thermal Analysis and Calorimetry》2006,85(2):279-284
Thermal behaviour of different starch derivatives, i.e. starch esters
and ethers having degree of substitution (DS) in the range of 0.02–0.18
were studied. Potato, maize and wheat starches were used. Measurements were
carried out by coupled thermal analysis/ mass spectrometry method (STA-MS)
in air atmosphere.
The major DTG peak during the investigation
for starch derivatives is observed below 300°C. The mass loss up to a
temperature of 300°C is about 50%. The most abundant ions found areH2O+
and CO2
+. For the studied
starch derivatives with a low degree of substitution (DS<0.18) no correlation
was found between thermal stability and the level of substitution regardless
of the nature of substitution. 相似文献
88.
D. J. Burlett 《Journal of Thermal Analysis and Calorimetry》2004,75(2):531-544
The transfer of heat through an elastomeric matrix is important for both the processing of the material and its subsequent
lifetime. Thermal conductivity can be used to evaluate the influence of different polymers and fillers on heat transfer. Additionally,
the dispersion of the filler has an effect on heat transfer and thermal conductivity measurements can be used to provide semi-quantitative
estimations of filler dispersion. The degradation of sulfur-crosslinked elastomer systems has been studied for many years.
The degradation of the crosslinks (changes in sulfur rank) and degradation of the polymer backbone by thermal and/or oxidative
processes have been studied extensively using many techniques including thermal analysis (references). However, the degradation
of the crosslinked-polymer 'network' is less well understood. The relationship of the crosslink network to this degradation
process is a key to both the long term and higher temperature performance of the sulfur-crosslinked elastomer. The changes
in physical properties observed upon exposure of sulfur-crosslinked elastomers can be monitored using dynamic mechanical analysis.
Subsequently, other thermal techniques can be used to monitor the chemistry that is occurring during these degradations. Thermal
desorption/mass spectroscopy and dynamic scanning calorimetry are used to complete the picture of the degradation processes
taking place. Examples of these techniques will be provided to illustrate the utility of the analytical approach, the chemistry
involved in these degradation processes and the effect of changes in the polymer, cure package and other ingredients.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
89.
90.
A. I. Bostan Yu. I. Pyatnitskii L. N. Raevskaya V. G. Pryanikova S. A. Nedil’ko A. G. Dzyaz’ko E. G. Zen’kovich 《Theoretical and Experimental Chemistry》2005,41(1):32-36
The oxidative coupling of methane (OCM) in a periodic regime over the SrMnO3 and its derivatives has been investigated. It has been established that partial replacement of the strontium ion by alkali metal ions leads to an increase in both catalytic activity and in selectivity with respect to higher hydrocarbons. Comparison of the results obtained in the present work with those obtained earlier for catalysts based on SrCoO3 led to the conclusion that the Co-containing catalysts were preferable to the Mn-containing catalysts for carrying out oxidative coupling of methane in a periodic regime.__________Translated from Teoreticheskaya i Éksperimentalnaya Khimiya, Vol. 41, No. 1, pp. 30–34, January–February, 2005. 相似文献