Advanced Powder Technology, Vol.30, No.7, 1378-1385, 2019
Phase-transition induced gelation of ZnO suspensions containing thermosensitive poly(acrylic acid)-graft-poly(N-isopropylacrylamide)
Thermosensitive ZnO suspensions containing poly(acrylic acid)-graft-poly(N-isopropylacrylamide) (PAA-g-PNIPAM) are used to prepare complex-shaped ceramic parts by controlling the phase transition of PNIPAM graft chains. The properties of PAA-g-PNIPAM aqueous solution and the rheological behavior of ZnO suspensions with PAA-g-PNIPAM were investigated. The results show that PAA-g-PNIPAM is a pH-and temperature-sensitive polymer, and its lower critical solution temperature is 32 degrees C. The isoelectric point of ZnO particles shifts from 9.1 to 4.8 after adding PAA-g-PNIPAM, and the adsorption capacity of PAA-g-PNIPAM on ZnO particles decreases with increasing pH value. The 45 vol.% ZnO suspension containing 3.0 mg/g PAA-g-PNIPAM exhibits a good fluidity at room temperature, and a rapid increase in apparent viscosity and shear elastic modulus above 32 degrees C due to the decay of steric hindrance and the increase of effective volume fraction caused by the phase transition of PNIPAM graft chains. The complex-shaped ceramic parts prepared using thermosensitive ZnO suspensions are in good condition with few pores. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.