The polycrystals of 2,4 diaminotoluene were produced by slow evaporation of solvent. The polycrystalline samples were exposed to 60 Co gamma rays with dose rate of 0.950 kGy/h, at room temperature, for 12, 24, 48, and 72 hours. The electron paramagnetic resonance measurements were carried out on these samples in the temperature range between 298 K and 400 K. No electron paramagnetic resonance signal was observed in the samples irradiated for 12, 24, 48 hours. Two types of radicals were detected using ESR spectrometer in the sample irradiated for 72 h. These radiation damage centers were called RI and RII. The average values of g and the hyperfine coupling constant were calculated. This study also investigates the potential usage of machine learning methods and aims to test the success of these methods and to select the best method.
Poly(2-hydroxyethyl methacrylate)-co-poly(4-vinyl pyridine) and poly(HEMA)-co-poly-(4-VP) copolymers were synthesized by free radical polymerization. K2S2O8 was used as an initiator. Chain lengths of the copolymer was changed by varying the monomer/initiator ratio. These polymers have molarites of 2.6 and 2.1 respectively and are called COP2 and COP4. The samples were exposed to gamma rays at room temperature. After irradiation, the EPR spectra of COP2 and COP4 were recorded between 120 K and 450 K. From the temperature dependence of the line intensity, it was concluded that unpaired spin concentration in the irradiated samples has been changing with temperature. A theoretical study, presented in this report, was aimed to test success of the machine learning methods and to select the best learning method.
For the assessment of irradiation influence on 2-(piperidin-1-ylmethyl)phenol single crystals (C12H17NO), electron paramagnetic resonance measurements were carried out on the samples exposed to 60 Co radiation at dose values of 22.8, 45.6 and 68.4 kGy at room temperature. Electron paramagnetic resonance signals were not observed in non-irradiated sample and in samples irradiated at dose values of 22.8 and 45.6 kGy. The electron paramagnetic resonance measurements were performed on the single crystals. This irradiated single crystal was rotated in steps of 10• . One type of radical center was found. The average values of g and hyperfine constant of the detected radiation damage center were calculated from experimental spectra as follows: g = 2.0052, AH = 0.74 mT.
ABSTRACT:The kinetics of nonisothermal decomposition of (2-phenyl-1,3-dioxolane-4-yl) methyl methacrylate (PDMMA), 2-hydroxyethyl methacrylate (HEMA), and vinyl-pyrrolidone (VPy) copolymers were investigated by thermogravimetry (TG) and differential thermal analysis (DTA). The data indicated that the major weight loss occurs in the range of 270 to 450°C. The decomposition characteristics showed essentially two regimes and varied depending on the temperature and the copolymer composition. The apparent kinetic parameters of the decompositions were estimated from both TG and DTA data by using the alternative calculation methods. The results suggest that the weight loss rates may be represented, depending on the type of sample, by a reaction model of overall order 1.0 to 1.6, with an activation energy of approximately 65-95 kJ mol
Ϫ1. The DTA data estimated considerably higher values for the overall activation energies, around 198 -240 kJ mol Ϫ1 .
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