Methylcellulose, hydroxypropyl methylcellulose and hydroxyethyl methylcellulose are largely used as plasticizers and lubricants in the paste extrusion of tungsten carbide, steel and other powder metallurgical pastes. The process is performed in aqueous or solvent based media.
While the extrusion process normally runs quite well at very low temperatures, above a certain temperature the extrusion paste gets brittle, the extrusion pressure increases significantly and defects like crack formation occurs. this "temperature window of best processing" is larger or smaller depending on the conditions. We found that the upper temperature limit depends on the cellulose ether gelation temperature. The lecture will explain the different influencing parameters steering the gelation temperature in the formulation up- or downwards. Numerous examples of extrusion pastes will demonstrate the problem and its solution.