Effect of additives and operating conditions on tablet weight variation: Analysis based on powder flowability

The flowability and compressibility of powders during tableting are crucial for determining the quality of pharmaceutical products. Although silicon compounds are additives that improve compressibility, their type and addition ratio could impair flowability. Therefore, formulation and operating conditions for tablet preparation should be considered. In this study, first, the physical properties of the four types of silicon compounds, that is, particle size distribution, packing fraction, and cohesion, were measured. Next, various powder mixtures were prepared by adding each silicon compound to a diluent at different ratios. Experiments were performed by changing the operating conditions of a rotary tableting machine equipped with a paddle feeder. The tablet weight variation increased with the addition of a highly cohesive silicon compound. However, this variation decreased with an increase in the peripheral velocity of the paddle. A flowability index combining static and dynamic friction properties was proposed to analyze the experimental results, allowing the quantification of the effects of silicon compounds and operating conditions on tablet weight variation.