The effect of wax composition on the injection molding of carbonyl iron powder with LDPE

The effect of waxes on the injection molding of carbonyl iron powder with low-density polyethylene (LDPE) have been examined. Four waxes, paraffin wax (PW), polyethylene wax (PEW), carnauba wax (CW) and acrawax (AW) were selected and compared. Experimental results indicated that the LDPE-rich phase was found to be separated from the wax-rich phase in the binder mixture containing AW, CW or PW. Polar AW or CW showed stronger interactions or adsorptions with iron powder than other nonpolar waxes. AW/LDPE and CW/LDPE mixtures appeared to exhibit higher viscosity, greater pseudoplasticity and lower flow activation energy than PW/LDPE and PEW/LDPE mixtures. Tensile bar specimens of all binder mixtures could be injection molded at an injection temperature of around 170-190 °C, and a pressure of around 5-6 MPa. Except for the PEW/LDPE mixture the parts derived from the other three binder mixtures showed good surface appearance following debinding and sintering. Specimens based on the PW/LDPE mixture exhibited the highest tensile strength in the resulting sintered parts, followed those based on CW/LDPE, AW/LDPE, and PEW LDPE mixtures. The difference in tensile strength of each part results from different flow properties of each wax/LDPE mixture.