Effect of the enzyme concentration on the DIRECT coagulation casting of hydroxyapatite-alumina bodies


Hydroxyapatite-alumina (20 vol%) green bodies were prcduced by a direct coagulation casting process. The direct coagulation of homogeneous high solids loaded particle suspensions was attained by changing the pH of the suspensions with an enzyme (esterase)-catalysed decomposition reaction of a diester of glycerine. The coagulation kinetics and the strength of the wet green bodies have been investigated. The enzyme concentration affects the reaction rate. The dependence of the coagulation time on the enzyme concentration was evaluated by the variation of the pH of the medium. Compressive strength measurements were performed on cylindrical wet coagulated bodies with a constant addition of substrate and different additions of enzyme. Results allow the optimisation of the processing conditions related with the amount of enzyme that will lead to wet coagulated green bodies with a short coagulation time and a relatively high compressive strength.



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Materials Science


Rolo, A; Tavares, A; Senos, AMR; Almeida, M

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