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[en] Full text: Thermal degradation behavior during polymer pyrolysis can typically be described using three apparent kinetic parameters (i.e., pre-exponential factor, activation energy, and reaction order). Several efficient techniques have been developed to estimate these apparent kinetic parameters for simple thermal degradation behavior (i.e., single apparent pyrolysis reaction). Unfortunately, these techniques cannot be directly extended to the case of polymer pyrolysis with complex thermal degradation behavior (i.e., multiple concurrent reactions forming single or multiple DTG peaks). In this work, we proposed a deconvolution method to determine the number of apparent reactions and estimate three apparent kinetic parameters and contribution of each reaction for polymer pyrolysis with complex thermal degradation behavior. The proposed technique was validated with the model and experimental pyrolysis data of several polymer blends with known compositions. The results showed that (1) the number of reaction and (2) three apparent kinetic parameters and contribution of each reaction can be estimated reasonably. The simulated DTG curves with estimated parameters also agree well with experimental DTG curves. (author)
[en] It is a necessary that using mechanical structure such plant brings degradation. Especially corrosion environment under high temperature and high pressure, mechanical equipment makes error suddenly, so it stops operation or breaking. It has been responsible for major costs and unit outage time.
[en] Autoradiographical analysis was used to investigate the radionuclides distribution in the process of thermal decontamination of asphalt. Cs-137 and Sr-90 were introduced in asphalt to simulate real contamination. It was found that penetration of these radionuclides is very small (about 1 mm). No significant emission of radionuclides was observed in the process of thermal decontamination
[en] It was determined that grain growth takes place during isothermal annealing of uranium metal fuel elements at 5500 C. The average grain size changes with annealing time according to a relationship of the type D= -0.003 t 2 + 0.995 t + D0. (author)
[en] Degradation in piezoelectric materials properties due to extensive electrical and thermal cycling is a common phenomenon, which some time alter their internal characteristics. The degradation in properties can affect the function and efficiency of instruments in which these materials are being used. Therefore, it becomes important to identify the extent of changes in performance when exposed to different types of solutions. A piezoelectric ceramic disc was exposed to 3 different solutions, ordinary water, de-ionized water and a solution of NaCl. The PZT (Lead Zirconate Titanate) was immersed in these solutions at 80 deg. C and performance characteristics recorded for different frequencies. After effects of the immersed disc due to three different solutions have been analyzed and it is observed that the PZT ceramic is sensitive to the type of water, but regains its original performance characteristics within short period of time. Thin PZT Disc after immersion in NaCl solution in regaining its maximum output voltage in longer period as compared to ordinary and de-ionized water. (author)
[en] Complete text of publication follows. Fluorinated polymers are known to be prone to degradation under radiation. Crosslinking under melt conditions were developed in the last few years, it occurs in absence of oxygen at just above melting temperature of PTFE. The crosslinks are formed through Y-type structure. Crosslinked PTFE has been attained by irradiation in its molten state above the melting temperature under oxygen-free atmosphere. It shows improvements in radiation resistance, mechanical properties, friction, light transparency, compared to non-crosslinked PTFE. Another recent process to promote PTFE crosslinking was based on PTFE irradiation in acetylene. Ethylene-tetrafluoroethylene copolymer (ETFE) is a thermoplastic partially fluorinated polymer with many important technological application in wire and cable industry. It has been crosslinked by high energy in presence of multifunctional agents. Recently a potential application of styrene grafted membranes has fuelled the interest in ETFE crosslinking and many studies were conducted by Scherrer's group at PSI. Perfluorinated polymers are insoluble. Ethylene-tetrafluoroethylene copolymer is also difficult to dissolve; therefore its crosslinking behaviour is hard to study. Fortunately, crosslinking changes the mechanical behaviour of polymers, but this evaluation is also hard as the mechanical properties of partially crystalline polymers are dominated by morphology. One way to evaluate crosslinking is examining the properties under melting.