Binder burnout thermal

A complete picture of polymer thermal degradation is clouded because multiple reaction mechanisms can be operable for a single polymer at a single temperature, leading to a host of volatile products and residues. Therefore, one has to consider the relative rates of these competing reactions to establish an optimized and controlled binder burnout. 

The effects of oxides on the binder burnout of poly(vinyl butyral) (PVB) was studied by Masia et al. [26]. The binder decomposition kinetics in air was shown to be a strong function of the ceramic oxide present. In all cases, the oxide decreased the temperature necessary for thermal decomposition compared to PVB alone. The order was the following ... 

To discuss binder burnout in detail, let us consider a spherical green body of radius R with a polymer completely filling its pores undergoing an oxidative thermal decomposition. Figure 15.9 is a schematic of this process. We will use the case where the number of moles of oxygen, n, is 1 that is,... 

The thermal stress in binder burnout is the same as those discussed in Section 14.5.1. For a detailed treatment, please refer to that section. Here we give a brief description of the stress for an infinite plate, to specify the nomenclature. Table 15.8 gives the details of thermal stresses for plate, cylinder, and sphere geometries. 

Binder removal can be accomplished by thermal decomposition or by dissolutiion. In ceramics, the thermal decomposition method is commonly used and will be considered here. The process is referred to as thermal debinding or, more simply, as binder burnout. In thermal debinding of ceramic green bodies, both chemical and physical factors are important. Chemically, composition of the binder determines the decomposition temperature and the decomposition products. Physically, the removal of the binder is controlled by heat transfer into the body and mass transport of the decomposition products out of the body. 

Pre-sinter thermal processes typically involve weight changes and thermochemical reactions. Two important pre-sinter thermal processes include drying and binder burnout. 

Laminated stacks are fired in belt or box furnaces to bum out organic binders and den-sify the ceramic and metallic constituents. Burnout and firing can be accomplished in one continuous operation so that the part does not experience thermal gradients from end to end as temperature is changed. Finished parts may be metallized with either a screen-printed thick film or sputtered and etched thin-film conductor. 

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