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- 저자 : Zhiwang Yang (검색결과 4 건)
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Li Li,Fenglin Hua,Hui Xi,Jing Yang,Ting Xiao,Rui Zuo,Xueqing Xu,Zhiwang Yang,Ziqiang Lei 한국고분자학회 2022 Macromolecular Research Vol.30 No.12
A new type of phosphorus-containing intrinsic flame retardant was prepared with L-tryptophan (L-Trp) and 9,10-dihydro-9-oxa-10-phosphorbenzophenanthrene- 10-oxide (DOPO) as the main components. The Schiff base from the reaction of 1,4-terephthalaldehyde and L-tryptophan provides active sites, and then the phosphorous compound, DOPO, is successfully introduced into the Schiff base to synthesize L-Trp-DOPO flame retardant. The intrinsic flame retardant property of LTrp- DOPO comes from the reaction of carbonyl groups and the epoxy groups in epoxy resin (EP) matrix. The prepared L-Trp-DOPO flame retardant can efficiently improve the flame retardancy and smoke suppression of the base material of EP. Cone calorimetric test (CCT) of EP/L-Trp-DOPO composite material was carried out. The data showed that the peak heat release rate (pk-HRR) value was reduced by 50.8% (from 1459 kW/m2 to 717 kW/m2), the THR value reduced by 78.3%, and the limiting oxygen index (LOI) value was increased by 24%. The addition of new flame retardant greatly reduced the release of toxic CO gas. The flame retardant mechanism was explored, and it can be found that after thermal decomposition of L-Trp- DOPO a dense carbon layer can be produced to isolate the fire source. In addition, during the combustion process, L-Trp-DOPO will produce phosphorus-containing free radicals which will quench the active free radicals in the gas phase and dilute the combustible gas. The prepared L-Trp-DOPO flame retardant has a flame retardant effect in both the condensed phase and the gas phase during the combustion process.
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Huan Wang,Li Li,Yan Kang,Xue Yin,Xuedi Lei,Jing Yang,Hui Xi,Xueqing Xu,Zhiwang Yang,Ziqiang Lei 한국고분자학회 2022 Macromolecular Research Vol.30 No.8
To reduce the fire hazard of epoxy resin (EP), PA-CS-M (where PA = phytic acid, CS =c hitosan, M=Cu2+, Co2+, Al3+, Zn2+, Mn2+) environmental friendly flame retardant is prepared by a simple and green method. By comparing the data after cone calorimetry test (CCT) of various composites, it is found that when 5 wt% PA-CS-Mn is added to EP, it has good flame retardant and smoke suppression performance. The peak heat release rate (pk-HRR) decreased by 38% and the smoke production rate (SPR) decreased by 33%. In addition, some toxic smoke such as CO has been significantly inhibited. The structures and morphologies of the materials were investigated by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). When combined with expandable graphite (EG), it is found that when the ratio of PA-CS-Mn to EG is 1:5, the pk-HRR value and SPR value decreased by 69.8% and 66.6%, respectively. More importantly, the mechanical properties of the EP composites have also been greatly improved. The flexural modulus reaches 5.04 GPa, which is 52.3% higher than pure EP, and the flexural strength increases to 79.4 MPa, which also shows an increase of 41.4% as to the matrix.
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Li Li,Huan Wang,Fenglin Hua,Mingming Wang,Yuanshuo Zhang,Hui Xi,Jing Yang,Zhiwang Yang,Ziqiang Lei 한국고분자학회 2021 Macromolecular Research Vol.29 No.9
An effective ternary organic-inorganic composite flame retardant of reduced graphene oxide-poly-dopamine@graphitic carbon nitride@10-(2,5-dihydroxyphenyl)- 10-H-9-oxa-10-phosphaphenanthrene-10-oxide (RGO-PDA@g-C3N4@ODOPB) was successfully fabricated by co-precipitation method. Its property concerning the intrinsic flame retardancy and the mechanical performance was well studied when it was used as co-additives in combination with ammonium polyphosphate (APP) in epoxy resin (EP) samples. The surface morphology and the structure of RGO-PDA@g-C3N4 @ODOPB were characterized by SEM, and the molecular structure and compositions were investigated by FT-IR, powder XRD and 1H NMR. TGA, limit oxygen index (LOI), vertical burning test (UL-94), cone calorimeter test, and SEM were also used to investigate the thermal properties and flame retardancy of materials. As expected, the flame retardancy of EP was significantly heightened after adding of RGOPDA@ g-C3N4@ODOPB composites. It showed that with the 20% adding of RGO-PDA@g-C3N4@ODOPB/APP into EP led to the decreasing of the peak heat release rate and the total heat release at 78% and 62.5%, respectively. Meanwhile, the LOI value of the EP composites was as high as 29% and reached UL-94 V-0 rate. It was deemed that the excellent flame retardancy was attributed to the forming of compact and stable carbon layer, which was being catalytic carbonization by APP existed in the RGO-PDA@g-C3N4@ODOPB/APP composites. At the same time, the non-combustible gas released from thermal cracking of g-C3N4 during the combustion also benefited the flame retardant performance of EP.
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How Feasible is China’s Path of “Land for Social Security”?*
Zhi Wang,Yifan Yang 연세대학교 빈곤문제국제개발연구원 2013 Journal of Poverty Alleviation and International D Vol.4 No.1
The purpose of this paper is to offer political advice and decision making for the reform and development of a social security system for land-lost peasants. At present, some research results and policy designs lack clear plans, which still simply regard the social security system as a supporting policy for land expropriation and separate the relationship between land system, land expropriation, and social security. Based on that, firstly, this paper analyzes the possibility of the system by introducing the successful practice of “Land for Social Security” in China. Secondly, it rethinks hazards and secret worries behind the system from the core views of “compensation or security” and “for social security or transfer the land”. Third, from the perspective of land rent, the article explores how to make “Land for Social Security” more feasible. Finally, based on the dual nature of land, the article puts forward relevant policy suggestions. The conclusion is that to improve the social security measures for land-lost peasants, it is important to establish a compound social security system adapting to its own features based on the condition of confirming the special land property rights of both collective and individual.
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