Rheological behavior of silica suspensions flocculated by bridging |
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| Institution: | 1. CNR-IPCF, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy;2. Department of Physics, University of Calicut, Kerala, India;3. State Key Lab of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao, Hebei 066004, China;1. Faculty of Chemistry, VNU University of Science, Vietnam National University, 19 Le Thanh Tong, Hanoi 100000, Viet Nam;2. Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan;3. School of Chemical Engineering, Hanoi University of Science and Technology, No.1 Dai Co Viet, Hai Ba Trung, Hanoi 100000, Viet Nam;4. Faculty of Chemical & Natural Resources Engineering, Universiti Malaysia Pahang, Lebuhraya Tun Razak, 26300, Gambang, Kuantan, Pahang, Malaysia;5. Centre of Excellence for Advanced Research in Fluid Flow, Universiti Malaysia Pahang, 26300, Gambang, Kuantan, Pahang, Malaysia;6. Ceramics and Biomaterials Research Group, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City, Viet Nam;7. Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Viet Nam;8. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan |
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| Abstract: | The viscosity and stress relaxation behavior of silica suspensions in polyacrylamide (PAAm) solutions have been studied as a function of particle concentration, particle diameter, and molecular weight of PAAm by the use of a coaxial cylinder type rheometer. The effects of polymer adsorption on the flocculation of particles and the rheological behavior are discussed in terms of bridging. The suspensions of 10-nm silica are remarkably pseudoplastic because the particles are easily flocculated by bridging. The ability of PAAm to flocculate silica particles is very extensive at a molecular weight of 5.5 × 106. For suspensions of 20-nm silica in a solution of PAAm with MW = 5.5 × 106 − 1 × 107, the apparent viscosity irreversibly increases with shearing time at shear rates beyond a certain value. This may be due to the flocculation by the shear-induced bridging. The suspensions of 40-nm silica show similar flow behavior to the medium irrespective of molecular weight of PAAm. The bridging flocculation is not expected for large particles as one polymer molecule cannot bridge through many particles. |
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