THE EFFECT OF BINDERS ON THE STRENGTH AND YOUNGS MODULUS OF DRY PRESSED ALUMINA

The strength of green samples prepared from spray-dried powders of alu mina is investigated versus forming pressure. The binders wed are poly ethylene glycol and polyvinyl alcohol (3 wt% with respect to alumina). The variation of strength is discussed in tel ms of, ii) the binder d istribution in granules and in the pressed compacts, (ii) the glass tr ansition temperature of the polymer and (iii) the adhesive properties of the external part of spray-dried granules. A transition from intra- to intergranule fracture mode is observed wizen the glass transition temperature of the binder increases. Finally, the results of a prelimi nary investigation concerning the variation of the Young's modulus ver sus forming pressure are also presented and discussed. (C) 1998 Elsevi er Science Limited.