Influence of Initiator Systems on Gelation Process of Alumina Slurry

The effect of initiator systems on the gelation process of alumina slurry was studied.The gel former system based on the free-radical polymerization of acrylimade(AM)and N,N'-menthylene- bis-acrylamide(MBAM)was used in gelcasting of alumina.Three initiator systems,ammonium per- sulfate(APS),ammonium persulfate and N,N,N',N',-tetramethylethylenediamine redox system(APS- TEMED),and 2,2'-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochlorid(AZIP.2HCl),were used to ini- tiate the polymerization of AM and MBAM.The effect of initiator systems on the polymerization process was investigated by the elastic modulus change during polymerization.Among these initiator systems, idle time of polymerization initiated by AZIP.2HCl shows remarkable dependence on temperature while the elastic modulus of polymer gelled is slightly increased with increasing temperature from 40℃to 50℃.Elastic modulus in gelation process of 50vol% alumina slurry initiated by AZIP.2HCl shows that both temperature and initiator concentration have strong effect on the gelation process,by which the gelation process can be controlled.Compared with gelation initiated by other initiators,gelation of 50vol% alumina slurry initiated by AZIP.2HCl gains modulus of 2.3×10~6pa at 50℃,which is higher than these by APS(1.58×10~6pa)at 55℃and APS-TEMED(1.58×10~6pa)at 25℃.