RHEOLOGICAL CHARACTERIZATION OF THE GEL POINT - A NEW INTERPRETATION

被引:133
作者
MULLER, R [1 ]
GERARD, E [1 ]
DUGAND, P [1 ]
REMPP, P [1 ]
GNANOU, Y [1 ]
机构
[1] UNIV STRASBOURG 1,INST CHARLES SADRON,CRM,EAHP,CNRS,6 RUE BOUSSINGAULT,F-67083 STRASBOURG,FRANCE
关键词
D O I
10.1021/ma00006a017
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
Winter and Chambon have recently shown that the gel point can be precisely identified in a crosslinking process from rheological measurements on the reaction medium. The cross-linking reaction of poly(ethylene oxide) (PEO), carrying at both chain ends hydroxyl functions, with various pluriisocyanates was chosen to check the validity of this new method. The experimental setup included Fourier transform infrared (FTIR) spectroscopy to follow the conversion of the isocyanate functions with time and a rheometer to investigate the mechanical response of the reaction medium to oscillatory solicitations at various stages of the reaction. In stoichiometric systems at a given conversion, the storage modulus G' and the loss modulus G" become congruent and proportional to omega-1/2 over the entire frequency range. Simultaneously, the extent of reaction reaches the critical value p(c) predicted by branching theory. This excellent agreement substantiates Winter's method and confirms its validity. This investigation has been extended to nonstoichiometric systems. When the end-standing hydroxyl functions of PEO are in excess, the rheological behavior observed at the gel point is quite different, and it was attempted to account for the phenomena observed.
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页码:1321 / 1326
页数:6
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