Condensation and crosslinking reactions of furfuryl alcohol(FA)and FA with tris(2-hydro- xyethyl)isocyanurate(THEIC)are studied by means of DSC,TG,TBA,NMR and elemental analysis. Four exothermic peaks are observed on ...Condensation and crosslinking reactions of furfuryl alcohol(FA)and FA with tris(2-hydro- xyethyl)isocyanurate(THEIC)are studied by means of DSC,TG,TBA,NMR and elemental analysis. Four exothermic peaks are observed on the DSC curves of thermal condensation of FA and FA with THEIC in the presence of sulfuric acid.The peaks Ⅰ,Ⅱ(50—80℃),Ⅲ(110—130℃)and Ⅳ(150— 190℃)correspond to linear polycondensation of FA through head-to-tail condensation,head-to-head etherification,crosslinking dehydration reaction between methylene group and terminal hydroxy group of FA polymeric chain and to further crosslinking reaction at higher temperature,respectively.The reactivity of FA and THEIC increases sharply at 130—150℃ and THEIC is reacted completely at 150℃.Addition of THEIC raises the initial decomposition temperature of FA polymer by 60℃.展开更多
The tetrahedral borate ion can crosslink with polymer guar gum in aqueous solutions. If the concentration of guar gum is less than 0.045 g/dL, the intramolecular interaction between guar gum and borate ion increases d...The tetrahedral borate ion can crosslink with polymer guar gum in aqueous solutions. If the concentration of guar gum is less than 0.045 g/dL, the intramolecular interaction between guar gum and borate ion increases due to the formation of crosslinks. As a result, the polymer chains of guar gum in solution shrink in size and the reduced viscosity of polymer solution decreases accordingly. On the other hand, if the concentration of guar gum is greater than 0.045 g/dL, the intermolecular interaction becomes apparent due to the same reason. The polymer chains, therefore, associate together and the reduced viscosity of polymer solution increases considerably. According to this technique, the critical concentration c^＊, presented by de-Gennes, is determined successfully.展开更多
Optimization of reaction variables such as catalyst type and amount, reaction temperature and time, formaldehyde amount, and oxidation extent of starch was studied for the crosslinking reaction of chlorinated cornstar...Optimization of reaction variables such as catalyst type and amount, reaction temperature and time, formaldehyde amount, and oxidation extent of starch was studied for the crosslinking reaction of chlorinated cornstarch with formaldehyde. The reaction was carried out in aqueous suspension dispersed granular chlorinated cornstarch. Catalysts such as hydrochloric acid, sulfuric acid, and nitric acid were individually evaluated. The results show that the type and amount of the inorganic acid, formaldehyde amount, and oxidation extent of the chlorinated starch strongly affect the reaction efficiency. Hydrochloric acid shows the best catalyst effect on the reaction. Increasing the amount of the catalyst favourably raises the reaction efficiency. It is also demonstrated that the reaction efficiency is enhanced with the decrease of the oxidation extent of granular chlorinated starch.展开更多
The cationic polymerizations of 1,3-pentadiene initiated by AlCl3 inn-hexane at 30 degrees C have been carried out in the presence of various arenes, i.e., benzene, toluene, p-xylene, o-xylene, m-xylene and mesitylene...The cationic polymerizations of 1,3-pentadiene initiated by AlCl3 inn-hexane at 30 degrees C have been carried out in the presence of various arenes, i.e., benzene, toluene, p-xylene, o-xylene, m-xylene and mesitylene. The presence of all these arenes have reduced in different degrees the formation of crosslinked products. Namely, the crosslinking reaction, a major side-reaction during the cationic polymerization of 1,3-pentadiene, has been suppressed by adding the aromatic compounds. The results showed that a chain transfer to arene took place and this transfer process hindered the generation of the crosslinked polymer. IR and H-1 NMR spectra have confirmed the existence of the corresponding aryl groups in the resulting polymers.展开更多
基金This project is supported by the National Natural Science Foundation of China.
文摘Condensation and crosslinking reactions of furfuryl alcohol(FA)and FA with tris(2-hydro- xyethyl)isocyanurate(THEIC)are studied by means of DSC,TG,TBA,NMR and elemental analysis. Four exothermic peaks are observed on the DSC curves of thermal condensation of FA and FA with THEIC in the presence of sulfuric acid.The peaks Ⅰ,Ⅱ(50—80℃),Ⅲ(110—130℃)and Ⅳ(150— 190℃)correspond to linear polycondensation of FA through head-to-tail condensation,head-to-head etherification,crosslinking dehydration reaction between methylene group and terminal hydroxy group of FA polymeric chain and to further crosslinking reaction at higher temperature,respectively.The reactivity of FA and THEIC increases sharply at 130—150℃ and THEIC is reacted completely at 150℃.Addition of THEIC raises the initial decomposition temperature of FA polymer by 60℃.
文摘The tetrahedral borate ion can crosslink with polymer guar gum in aqueous solutions. If the concentration of guar gum is less than 0.045 g/dL, the intramolecular interaction between guar gum and borate ion increases due to the formation of crosslinks. As a result, the polymer chains of guar gum in solution shrink in size and the reduced viscosity of polymer solution decreases accordingly. On the other hand, if the concentration of guar gum is greater than 0.045 g/dL, the intermolecular interaction becomes apparent due to the same reason. The polymer chains, therefore, associate together and the reduced viscosity of polymer solution increases considerably. According to this technique, the critical concentration c^＊, presented by de-Gennes, is determined successfully.
文摘Optimization of reaction variables such as catalyst type and amount, reaction temperature and time, formaldehyde amount, and oxidation extent of starch was studied for the crosslinking reaction of chlorinated cornstarch with formaldehyde. The reaction was carried out in aqueous suspension dispersed granular chlorinated cornstarch. Catalysts such as hydrochloric acid, sulfuric acid, and nitric acid were individually evaluated. The results show that the type and amount of the inorganic acid, formaldehyde amount, and oxidation extent of the chlorinated starch strongly affect the reaction efficiency. Hydrochloric acid shows the best catalyst effect on the reaction. Increasing the amount of the catalyst favourably raises the reaction efficiency. It is also demonstrated that the reaction efficiency is enhanced with the decrease of the oxidation extent of granular chlorinated starch.
文摘The cationic polymerizations of 1,3-pentadiene initiated by AlCl3 inn-hexane at 30 degrees C have been carried out in the presence of various arenes, i.e., benzene, toluene, p-xylene, o-xylene, m-xylene and mesitylene. The presence of all these arenes have reduced in different degrees the formation of crosslinked products. Namely, the crosslinking reaction, a major side-reaction during the cationic polymerization of 1,3-pentadiene, has been suppressed by adding the aromatic compounds. The results showed that a chain transfer to arene took place and this transfer process hindered the generation of the crosslinked polymer. IR and H-1 NMR spectra have confirmed the existence of the corresponding aryl groups in the resulting polymers.
