Powder Blending From Art to Science

By Angelo De Palma, Ph.D., Contributing Editor
PharmaManufacturing.com
Predictive models, PAT, and continuous processing promise to reduce variability and improve product quality.
Dry powder blending may be the most widely recognized unit operation in pharmaceutical manufacturing, but it’s also one of the least understood. The uniqueness of each individual drug formulation assures that no two blending processes can ever be identical. Powder blending’s unpredictability has challenged engineers to explain in quantitative terms a phenomenon typically described empirically. One team at Rutgers University (New Brunswick, N.J.), led by engineering professors Benjamin Glasser and Troy Shinbrot, is moving closer to this elusive goal. Their research, so far, has yielded surprising results. For one thing, it suggests that agitating a mixture longer and faster will not always result in a homogeneous blend. Blending that appears uniform may degrade into turbulence, causing ingredients to separate into layers. In one experiment, researchers found that fine glass beads of different sizes blended uniformly at low mixing speeds, but formed distinct layers as mixing speed increased. The researchers were able to identify patterns of granular motion that promoted layer formation and interfered with uniform mixing.

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