MQ silicone resins were prepared through hydrolytic condensation of ethyl polysilicate or tetraethoxysilane and hexamethyl disiloxane. The unit ratio of the MQ resins was determined by Si-29-NMR. The relationship of t...MQ silicone resins were prepared through hydrolytic condensation of ethyl polysilicate or tetraethoxysilane and hexamethyl disiloxane. The unit ratio of the MQ resins was determined by Si-29-NMR. The relationship of the unit ratio of the product resins with that in the feed was studied. When the reaction was catalyzed by aqueous hydrochloric acid, and the unit ratio of M to Q in the feed was more than 1, the unit ratio of the product was usually lower than that of the feed. The MQ silicon with an unit ratio of M/Q > 2 could not be obtained. However, if the reaction was catalyzed by concentrated sulfuric acid and the reverse hydrolysis process was employed, MQ silicone resin with very high M/Q ratio was successfully prepared.展开更多
Vapor-liquid equilibrium data of hexamethyl disiloxane+vinyl acetate system at 101.3kPa were measured by using double circulating vapor-liquid equilibrium still.The thermodynamic consistency of the VLE data was examin...Vapor-liquid equilibrium data of hexamethyl disiloxane+vinyl acetate system at 101.3kPa were measured by using double circulating vapor-liquid equilibrium still.The thermodynamic consistency of the VLE data was examined by Herrington method.Experimental data was correlated by non-random two-liquid(NRTL),Wilson and universal quasichemical(UNIQUAC)parameter models.All the models satisfactorily correlated with the VLE data.The result showed that the NRTL model was the most suitable one to represent experimental data satisfactorily.The system had a minimum temperature azeotrope at 345.71 K and the mole azeotropic composition was 0.0541.展开更多
文摘MQ silicone resins were prepared through hydrolytic condensation of ethyl polysilicate or tetraethoxysilane and hexamethyl disiloxane. The unit ratio of the MQ resins was determined by Si-29-NMR. The relationship of the unit ratio of the product resins with that in the feed was studied. When the reaction was catalyzed by aqueous hydrochloric acid, and the unit ratio of M to Q in the feed was more than 1, the unit ratio of the product was usually lower than that of the feed. The MQ silicon with an unit ratio of M/Q > 2 could not be obtained. However, if the reaction was catalyzed by concentrated sulfuric acid and the reverse hydrolysis process was employed, MQ silicone resin with very high M/Q ratio was successfully prepared.
文摘Vapor-liquid equilibrium data of hexamethyl disiloxane+vinyl acetate system at 101.3kPa were measured by using double circulating vapor-liquid equilibrium still.The thermodynamic consistency of the VLE data was examined by Herrington method.Experimental data was correlated by non-random two-liquid(NRTL),Wilson and universal quasichemical(UNIQUAC)parameter models.All the models satisfactorily correlated with the VLE data.The result showed that the NRTL model was the most suitable one to represent experimental data satisfactorily.The system had a minimum temperature azeotrope at 345.71 K and the mole azeotropic composition was 0.0541.
