Torque evolution and effects on alumina feedstocks prepared by various kneading sequences

The effects of different kneading sequences on the homogeneity, strength an d Weibull modulus of green density and sintered parts were studied. Polypro pylene (PP), paraffin wax (PW) and stearic acid (SA) in a mass ratio of 25: 70:5 mass% were mixed with Al2O3 to produce feedstocks. Five different knea ding sequences were implemented and analyzed using several techniques, incl uding capillary and torque rheometries, Fourier transformed infrared spectr oscopy (FTIR), differential scanning calorimetry (DSC) and pycnometry to re veal the properties of the feedstocks. Subsequently, the properties of inje ction molded samples subjected to the same solvent and thermal debinding co nditions were observed. After sintering, the results of the fracture streng th and Weibull modulus of Al2O3 strongly suggest that the kneading process closely control the homogeneity of feedstocks. The p3 process (kneading seq uence, Al2O3- > PP- > SA- > PW) could produce the largest torque and homoge neous feedstock. The produced specimens showed the greatest average strengt h (371 MPa) and Weibull modulus (8.1). (C) 1999 Published by Elsevier Scien ce Ltd. All rights reserved.