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사회적 지지, 외로움, 다문화 적응 및 학업적응 간의 구조적 관계 : 재한 중국인 유학생을 중심으로
SONG QI,안도희 한국국제문화교류학회 2023 문화교류와 다문화교육 Vol.12 No.6
This study explored the structural relationships between social support, cross-cultural adaptation, loneliness, and academic adjustment among Chinese international students studying in South Korea. The final analysis involved 355 Chinese international students enrolled in universities located in Seoul, Korea. The results of this study are as follows: Chinese international students in Korea perceived significant positive correlations between social support, cross-cultural adaptation, and academic adjustment. On the other hand, loneliness showed a significant negative correlation with these variables. Upon analyzing differences based on friendship patterns (i.e., number of friends and frequency of interactions with friends), it was evident that perceptions of social support, loneliness, cross-cultural adaptation, and academic adjustment varied. Loneliness and cross-cultural adaptation were found to fully mediate the relationship between social support and academic adjustment. It is anticipated that these findings can serve as foundational data for the educational field in seeking strategies to enhance the academic adjustment of Chinese international students in South Korea.
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Songqi Ma,Weiqu Liu,Zhengfang Wang,Chaohui Hu,Chunyi Tang 한국고분자학회 2010 Macromolecular Research Vol.18 No.9
A novel highly epoxidized polysiloxane was synthesized to modify the diglycidyl ether of bisphenol-A (DGEBA). The mechanical and thermal properties as well as the morphology of the cured epoxy resins were examined by tensile testing, impact testing, fracture testing, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and environmental scanning electron microscopy (ESEM). The chemical structure of the highly epoxidized polysiloxane (HEPSO) was confirmed by Fourier transform infrared spectroscopy (FTIR), 29Si nuclear magnetic resonance spectroscopy (29Si NMR), and gel permeation chromatography (GPC). The Tg increased by approximately 8 ºC after introducing HEPSO. TGA in air showed that the initial degradation temperature for 5%weight loss (Td 5%), the temperature for 50% weight loss (Td 50%) and the residual weight percent at 800 ºC (R800)were increased after introducing HEPSO. The addition of 4 phr HEPSO2 resulted in the highest increase in tensile strength, impact strength and fracture toughness (KIC). The morphology of the fracture surfaces show that the miscibility of polysiloxane with epoxy resin increased with increasing epoxide group in HEPSO. The high epoxide groups in HEPSO can react during the curing process, and participate chemically in the crosslinking network. HEPSO is expected to improve significantly the toughness and thermal stability of epoxy resin.
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Songqi Ma,Weiqu Liu,Nan Gao,Zhenlong Yan,Yuan Zhao 한국고분자학회 2011 Macromolecular Research Vol.19 No.9
A novel polysiloxane (G_xD_y) containing a large number of epoxide groups and flexible segments was synthesized by hydrolysis and condensation of 3-glycidoxypropyl trimethoxysilane (GPTMS) and dimethyldiethoxylsilane (DMDES) to toughen the 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (ERL-4221). The chemical structures of G_xD_y (molar ratio of GPTMS to DMDES is x/y) were confirmed by Fourier transform infrared spectroscopy (FTIR), ^29Si nuclear magnetic resonance spectroscopy (NMR), and gel permeation chromatography (GPC), and G_4D_6 have the highest degree of branching. The thermal and mechanical properties, morphologies and transmittance of the cured epoxy resins were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile testing, fracture testing, SEM, and UV-vis spectroscopy. The T_g of the G_xD_y modified epoxy depends on the structure and addition content of G_xD_y. The TGA results under a N_2 demonstrate that the thermal stability of the epoxy resin was improved by G_xD_y and the Si-(O-)_3 from the GPTMS part forms silica more easily than the Si-(O-)_2 from the DMDES part. The addition of 10 phr G_4D_6 resulted in greatly improved toughness, but maintained the transmittance of the epoxy resin. In addition the morphology of the fracture surfaces showed that G_xD_y can be dispersed homogeneously in the epoxy resin, and the toughening follows the pinning and crack tip bifurcation mechanism. In conclusion, G_xD_y can increase the toughness and thermal properties of the ERL-4221 system simultaneously, and maintain its transmittance. Therefore, G_xD_y can be used as a toughening agent for light emitting diode (LED)-packaging epoxy resins.
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Songqi Ma,WeiQu Liu,Dan Yu,ZhengFang Wang 한국고분자학회 2010 Macromolecular Research Vol.18 No.1
Polyether-grafted-polysiloxane (FPMS) and epoxy-miscible polysiloxane particles (EMPP) were prepared to improve the toughness of epoxy resin. The chemical structures of the products were characterized by FTIR,1H NMR, 29Si NMR, and gel permeation chromatography (GPC). The morphology of the EMPP was analyzed by transmission electron microscopy (TEM). The thermal and mechanical properties and morphologies of the polysiloxanes modified epoxy networks were examined by differential scanning calorimetry (DSC), tensile and impact testing, and scanning electron microscopy (SEM). Microspheres were observed in the EMPP modified epoxy network,whereas irregular particles were obtained for the FPMS modified epoxy resin. The FPMS and EMPP effectively improved the tensile and impact strength of the cured epoxies, while the glass transition temperatures (Tgs)were depressed slightly. Moreover, with the same content of modifiers, the EMPP-modified epoxy network exhibited higher impact strength and lower Tgs than the FPMS-modified epoxy network.
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Toughening of Epoxy Resin System Using a Novel Dendritic Polysiloxane
Songqi Ma,Weiqu Liu,Chaohui Hu,Zhengfang Wang,Chunyi Tang 한국고분자학회 2010 Macromolecular Research Vol.18 No.4
Dendritic polymers have attracted increasing attention in the field of epoxy resin toughening. This paper is the first report of the use of a novel dendritic polysiloxane (DPSO) bearing high epoxide groups to modify the diglycidyl ether of bisphenol-A (DGEBA). The thermal properties, toughness and morphology of the cured epoxy resins were examined by DSC, TGA, impact testing and SEM. The chemical structure of DPSO was confirmed by FTIR, 29Si NMR and GPC. The Tg increased by approximately 7 oC after introducing the DPSO. The TGA results under N2 and air atmospheres showed that the initial degradation temperature for 5% weight loss (Td 5%), temperature for 50% weight loss (Td 50%) and residual weight percent at 800 oC (R800) all increased after introducing DPSO. Moreover, the addition of 3 phr DPSO100 resulted in a 70.4% increase in impact strength compared to that of the neat epoxy. The morphology of the fracture surfaces shows that the miscibility of polysiloxane with epoxy resin increased with increasing number of epoxy groups in DPSO, and the improved toughness was attributed to the rubber-bridged effect. The high number of epoxy groups in dendritic polysiloxane can react during the curing process,and participate chemically in the crosslinking network. DPSO is expected to improve significantly the toughness and thermal stability of epoxy resin.
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Jingjing Wei,Songqi Ma,Hong Yue,Sheng Wang,Jin Zhu 한국고분자학회 2018 Macromolecular Research Vol.26 No.6
Hydrogenated bisphenol A epoxy resin was cured using different kind of curing agents, resulting in epoxy networks with better shape memory properties than bisphenol A epoxy networks. The non-isothermal curing kinetics investigated by differential scanning calorimetry (DSC) demonstrated that hydrogenated bisphenol A epoxy showed lower curing reactivity than bisphenol A epoxy, while it still could be cured well. The thermal and mechanical properties as well as shape memory properties were studied by dynamic mechanical analysis (DMA), DSC, thermogravimetric analysis (TGA), three-point bending test and U-type shape memory test and cyclic stretch test using DMA. Results manifested that hydrogenated bisphenol A epoxy systems exhibited lower shape transition temperature (lower T g), slightly higher modulus, better toughness, much faster shape recovery rate, and better elongating ability at temperature above T g than bisphenol A epoxy systems, which was due to the rigidity of cyclohexane ring from its steric hindrance and favorable segmental mobility when absorbing external energy such as heating or bending. Moreover, the shape fixity and shape recovery ratio of all the samples were as high as 96.3~98.5% and 100% and their cycling stability during shape memory test was excellent. Although lower than bisphenol A epoxy networks, hydrogenated bisphenol A epoxy networks possessed high thermal stability with initial degradation temperature (T d5%) of >305 ℃.
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Jingjing Wei,Songqi Ma,Hong Yue,Sheng Wang,Jin Zhu 한국고분자학회 2018 Macromolecular Research Vol.25 No.6
Hydrogenated bisphenol A epoxy resin was cured using different kind of curing agents, resulting in epoxy networks with better shape memory properties than bisphenol A epoxy networks. The non-isothermal curing kinetics investigated by differential scanning calorimetry (DSC) demonstrated that hydrogenated bisphenol A epoxy showed lower curing reactivity than bisphenol A epoxy, while it still could be cured well. The thermal and mechanical properties as well as shape memory properties were studied by dynamic mechanical analysis (DMA), DSC, thermogravimetric analysis (TGA), three-point bending test and U-type shape memory test and cyclic stretch test using DMA. Results manifested that hydrogenated bisphenol A epoxy systems exhibited lower shape transition temperature (lower T g), slightly higher modulus, better toughness, much faster shape recovery rate, and better elongating ability at temperature above T g than bisphenol A epoxy systems, which was due to the rigidity of cyclohexane ring from its steric hindrance and favorable segmental mobility when absorbing external energy such as heating or bending. Moreover, the shape fixity and shape recovery ratio of all the samples were as high as 96.3~98.5% and 100% and their cycling stability during shape memory test was excellent. Although lower than bisphenol A epoxy networks, hydrogenated bisphenol A epoxy networks possessed high thermal stability with initial degradation temperature (T d5%) of >305 ℃.
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Qiong Li,Songqi Ma,Jingjing Wei,Sheng Wang,Xiwei Xu,Kaifeng Huang,Binbo Wang,Wangchao Yuan,Jin Zhu 한국고분자학회 2020 Macromolecular Research Vol.28 No.5
Non-planar-ring epoxies together with non-planar-ring hardeners could achieve thermosets combining ultra-high shape recovery speed and excellent thermal properties. High shape recovery speed reflected high efficiency, and could decrease the energy consumption and the harmful effect of external stimuli on the materials, while it often conflicts with the thermal properties of shape memory polymers. In this paper, for the first time, epoxy resins with the super-short shape recovery time within 3 s were developed from non-planar-ring epoxies and hardeners, and their glass transition temperature (T g) were ~127 °C much higher than their benzene ring analogues. The effects of non-planar-ring structures of the epoxies and hardeners on the curing behavior, thermal properties as well as the shape memory properties of the thermosets were systematically investigated; the structure-property relationships were disclosed with the help of computational simulation of structure parameters and ESP maps. The faster shape recovery speed of the non-planar-ring epoxy thermosets is from their higher molecular mobility contributed by the conformational transition of non-planar-rings as well as their higher recovery force compared with benzene ring analogs. Their higher T gs are from the steric hindrance by the larger molecular volume of the non-planar-rings than benzene ring. This work will provide an effective method to produce shape memory polymers with excellent shape memory effects and high performance.
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