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한경석 김천대학교 1989 김천대학교 논문집 Vol.10 No.-
A study on induced dielectric and mechanical characterristics changes due to irradiation of polyethylene. The investigations are mainly stressed upon changes of thermal and mechanical properties induced by crosslinking due to irradition of a low density polyethylene in amorphous phase. the test pieces of specimens having defined geometry to fit different experiments are irradiated by Co+^60 gamma source to necessary dose after adequate heat treatment required for experiment. As for thermal characteristics, dose dependent behaviors on softening, melting and liquidizing temperatures are observed. As for mechanical characteristics, dose dependent behaviors observed at room temperature are tensil strengh, elongation at break point, and compressive elasticity as well as temperature dependent torsonal deformation under a constant load. 1) It is Observed in thermal characterist that softening temperature dose not show any noticeable change with increasing doses. however, melting and liquidzing temperatures rapidly increase with increasing doses up to 25 Mrad, thereafter no sign of appreciable change is seen with further increasing doses at b th temperatures, In the speciman, sample 2, for instance, melting point increase to 280℃ by the doses of 25 Mrad and liquidizing temperature is 325℃ at about 15 Mard. 2) It is observed in mechanical characteristics that both of specimens show a peak at about 15 Mard, futher elongaion at break point with sample 2 follows the similar dose dependence to that for tensile strength. Those facts are possibly explainable allowing the use of a proposed model on mechanical relaxation process along with an assumption that cross1inking process starts to predominate at about 15 Mard in amorphous phase of those specimens. It is also abserved with sample 2 that the test of compressive elasticity reveals a typical rubber elastic peak in the range of 20-30 Mard, and from the observa- tion on temperature dependent torsional deformation for different specimen irra- diated by a constant dose, respectively, rigidity increases with increasing doses up to 30 Mrad where a slight peak is obviously observable, all specimens show a rapid decrease in rigidity at about 100℃ near crystal me1ting point. The latter factor suggest that regidity may be a cooperative nature between crystallites and their interlinking molecular chain segments in amorphous phase, and that crosslinks among molecular segments may not be sufficient alone to manifest rigidity.
Metallic Chelate 화합물의 수용액계에서 얻은 방향족 Oligomer들의 열적특성
한경석 김천대학교 1987 김천대학교 논문집 Vol.8 No.-
p-Aminophenol, p-phenylenediamine, and their mixture of 1:1 mdar ratio form homooligomers and cooligomers respectively under the catalytic action of Fe(Ⅲ)-EDTA. type metallic complexes in the aqueous solution. In these oligomerization reactions, it was found that hydroquinone acted as neither inhibitor nor retarder. From DTA and TGA, Oligo(p-aminophenol), Oligo(p-phenylenediamine), and the cooligomer were found to show comparatively high heat-resistant properties, and this tendency was the most significant in the case of cooligomer. Structural change in Oligo(p-aminophenol) when it was heat-treated was considered due to cyclization of the linear type oligomer, and it was clarified from the infrared spectra. These heat-resistant properties were believed to concern ladder type structure, and so it was quite probable that p-aminophenol and p-phenylenediamine in these oligomerization system could form ladder oligomer.
韓敬錫 김천대학교 1992 김천대학교 논문집 Vol.13 No.-
Carbosilane was prepared by pyrolysis of polysilane and the yield was 37~81% when reaction was carried out at 340-380C under nitrogen atomosphare. Liguiol carbosilane was clear below 265ml/min of nitrogen velocity and unclear in more then 300ml/min. They were identified by neans of I. R, DSC. and the moleculat weight was determine al by GC mass, ect.
한경석 김천대학교 1994 김천대학교 논문집 Vol.15 No.-
Hydrosilane (= SiH) group in carbosilane has a high reactivity for hydrogen substitution. The reaction of carbosilane with molecule which have two double bond is carried out by use of chloroplatinic acid (HyPtCl) catalysis and the reactivity is confirmed mole ratio and other conditions which are required to react are to be confirmed. The reaction product was identified by infrared spectroscopic, Gel-Permeation Chromat-ography (GPC) and elementary analysis.