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여정섭,김기정,류원석,오영세,김준호,Yeo, Jeong-Sup,Kim, Ki-Jeong,Lyoo, Won-Seok,Oh, Young-Se,Kim, Joon-Ho 한국섬유공학회 2007 한국섬유공학회지 Vol.44 No.5
The gelation behaviors of high molecular weight poly(vinyl alcohol)(PVA) solutions were investigated by the measurements of the rate of phase separation and the rate of gelation. PVA solutions were prepared with dimethyl sulfoxide(DMSO)/water mixed solvents in various compositions. Gelation time was gradually shortened with increasing DMSO content in the mixed solvent up to 60%(vol.). Also, the gelation was faster for higher molecular weight PVA due to easier network formation with higher degree of polymerization. Gels of PVA solutions formed at $0^{\circ}C$ showed high transparency with the exception of DMSO/water(v/v)=0/100, 90/10, 100/0 solutions. Particularly, the gel formed in the mixed solvent of DMSO/water(v/v)=80/20 still maintained its transparency after 20,000 min. This means that the most stable PVA gel can be made with the mixed solvent of DMSO/water(v/v)=80/20.
김기정,여정섭,윤지영,김준호,Kim Ki Jeong,Yeo Jeong Sup,Yoon Ji Young,Kim Joon Ho 한국섬유공학회 2005 한국섬유공학회지 Vol.42 No.4
Thermal degradation behavior of the three homologous polyesters, poly(ethylene terephthalate)(PET), poly(trimethylene terephthalate)(PTT) and poly(butylene terephthalate)(PBT) were investigated by using thermogravimetric analysis(TGA) and pyrolysis-gas chromatography-mass spectrometry(PGC-MS). From the results of isothermal thermogravimetry, it was revealed that PTT has higher activation energy of thermal degradation than the other two polyesters. In PGC-MS analysis, the highly volatile products of the polyesters such as acetaldehyde and acetic acid evolved in the early stage of pyrolysis as common degradation products. Benzoic acid, methyl ester of benzoic acid, terephthalic acid and higher oligomers were produced as the main degradation products of poly(alkylene terephthalate)s at longer pyrolysis times. In isothermal pyrolysis, PTT showed the fastest thermal degradation rate among the three polyesters.