Binder burnout

If the mass contains organic additives, combustion heat is generated during their burnout. Inside the green parts, where the oxygen concentration is very low during binder burnout, pyrolysis reactions can take place at the same time, which consume heat. The resulting temperature differences cause thermal stresses, which in turn can lead to cracks or destruction of the green parts. If the binder burns out too quickly, the resulting gases cannot be transported quickly enough from the pore channels to the component surface. The resulting overpressure in the pore channels also leads to component damage. Similar to drying, it is important to find the fastest and safest temperature profile with which the binder burnout can still be carried out without defects. The flow rate and composition of the kiln gases can be varied in many cases.

Analogous to drying, experiments on binder burnout are carried out in a controlled atmosphere and temperature. The degree of reaction is determined by continuous measurement of the sample mass, cracking is detected by acoustic emission analysis. The optimisation of the process parameters is carried out analogously to the drying by means of FE simulation, the verification of the optimised conditions by additional experiments on large components. A gas-heated measuring furnace, TOM_gas, is available at the HTL for testing binder burnout on large components. Green parts with a mass of up to 15 kg can be weighed at this oven during binder burnout.