Strength Evolution of Injection-Molded Ceramic Parts During Wick-Debinding

The mechanical properties of partially wick‐debinded, Al2O3‐based ceramic parts, prepared by low‐pressure injection molding have been investigated. These properties depend on the residual paraffin wax binder content and on the chemical nature of the binder, which changes drastically if the wick‐debinding takes place in air at a temperature above 190°C. Under these conditions, the paraffin binder undergoes a transformation, as a result of complex exothermic chemical reactions with oxygen. Part of it forms volatile products, while the remaining part cures into a nonvolatile, brown‐colored, solid substance, which resides in the wick‐debinded part and bonds the powder particles firmly together. The curing can be beneficial, as strong wick‐debinded parts with bending strengths up to 14 MPa, containing less than 2% of the residual binder, can be obtained without flaws. The strength of the partially debinded parts increases with the dwelling time at 200°C, whereas the binder content reaches a minimum value of about 1.6% and then remains constant with the dwell time. Strong debinded parts can be easily manipulated and can be rapidly sintered due to the low amount of the residual organic phase.