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

The effects of different kneading sequences on the homogeneity, strength and Weibull modulus of green density and sintered parts were studied. Polypropylene (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 kneading sequences were implemented and analyzed using several techniques, including capillary and torque rheometries, Fourier transformed infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and pycnometry to reveal the properties of the feedstocks. Subsequently, the properties of injection molded samples subjected to the same solvent and thermal debinding conditions were observed. After sintering, the results of the fracture strength and Weibull modulus of Al2O3 strongly suggest that the kneading process closely control the homogeneity of feedstocks. The p3 process (kneading sequence, Al2O3->PP->SA->PW) could produce the largest torque and homogeneous feedstock. The produced specimens showed the greatest average strength (371 MPa) and Weibull modulus (8.1).