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


  • Supported by the Ministry of higher education, science and technology of the Republic of Slovenia, under Grant No. P-MR-07/50.

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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.