EVALUATION OF ADHESION STRENGTH MEASUREMENT FOR PREDICTING AGGREGATION PROPENSITY DURING FLUIDIZED-BED COATING

The relationship between the percentage of aggregates forced during fi lm coating of spheroids with sodium carboxymethyl cellulose, using the bottom-spray fluidization technique and some polymer related properti es, was investigated. Adhesion strength measurement was developed to d etermine the aggregation propensity, measured by the percentage of agg regates after test coating. The aggregation propensity was positively correlated with the adhesion strength of the sodium carboxymethyl cell ulose cast films. The apparent tack force and viscosity of the sodium carboxymethyl cellulose coating formulations also showed good correlat ion with the aggregation propensity. However, there is no correlation between aggregation propensity and the mechanical strength of the cast film Aggregation propensity was found to correlate best with tack for ce. Viscosity of the coating solution was often regarded as a causativ e factor of aggregation during film coating only associated non-linear ly with the percentage of aggregates. The simple method of adhesion st rength measurement was able to provide reproducible results. The incor poration of plasticizers and film formers into the sodium carboxymethy l cellulose solution decreased aggregation propensity, adhesion streng th, apparent tack force and viscosity, whereas the reverse was lille w ith the presence of thickener.