Abstract:
An amorphous polyethylene glycol compound (PEG20M) and polymer blends containing PEG20M as a major component were evaluated as binder systems for the dry pressing of spray-dried ceramic powders. Comparisons were made with two types of plasticized polyvinyl alcohol systems commonly used in ceramics.
PEG20M and PEG-based systems resulted in lower viscosity slurries and higher green density compacts than the polyvinyl alcohol based systems. Green strength of specimens prepared with PEG20M was between that of specimens prepared with the two grades of polyvinyl alcohol. Sintered density using PEG20M was equal to that from one grade of polyvinyl alcohol and higher than the other. Thermolysis of PEG20M in a compact was an exothermic process and proceeded more rapidly than that of polyvinyl alcohol.
A binder concentration corresponding to half coverage of surface adsorption sites in the slurry was seen to be significant in pressing and sintering behavior. Phase separations observed when small amounts of polyvinyl alcohol were added to PEG solutions influenced green strength. The rate of thermolysis of PEG20M in a compact was dependent on specimen geometry and the addition of an antioxidant slowed the process.
