Q1. What are the flow properties of powders, and why are they important in the pharmaceutical industry?
A:
Flow properties refer to the ability of a powder to move or flow under specified conditions. They are critical in pharmaceutical processes such as tablet compression, capsule filling, and granulation to ensure uniformity and product quality.

Q2. What are the factors that affect the flow properties of powders?
A:
Key factors include:

• Particle size: Smaller particles may reduce flow due to cohesion.
• Shape: Irregular shapes lead to poor flow, while spherical shapes improve it.
• Density: Higher density powders generally flow better.
• Moisture content: Excessive moisture can cause clumping.
• Surface texture: Rough surfaces hinder flow.

Q3. What are some common methods to measure the flow properties of powders?
A:

• Angle of repose: Measures the maximum angle at which a powder pile remains stable.
• Bulk and tapped density: Determines compressibility index and Hausner ratio.
• Flow rate through an orifice: Measures how quickly a powder passes through a funnel.
• Shear cell testing: Measures powder flow under stress.

Q4. Can you explain how to determine the angle of repose?
A:

1. Allow powder to flow through a funnel onto a flat surface.
2. Measure the height of the powder pile (h) and the radius of its base (r).
3. Use the formula: Angle of Repose (θ) = tan⁻¹(h/r).
   A lower angle indicates better flow.

Q5. What is the difference between bulk density and tapped density?
A:

• Bulk density: The mass of powder in a unit volume, including voids between particles.
• Tapped density: The mass of powder in a unit volume after tapping to minimize voids.
  The ratio of tapped to bulk density gives insight into powder compressibility.

Q6. What is the compressibility index, and how is it calculated?
A:
The compressibility index (Carr’s Index) measures the tendency of a powder to consolidate:
Q7. What is the Hausner ratio, and how does it relate to powder flow?
A:
The Hausner ratio is the ratio of tapped density to bulk density:

• Hausner Ratio < 1.25: Good flow.
• Hausner Ratio > 1.25: Poor flow.

Q8. How does particle size distribution affect powder flow?
A:
A wide particle size distribution improves packing and reduces voids, enhancing flow. However, very fine particles may lead to cohesion and poor flow, while very large particles may cause segregation.

Q9. What role does moisture play in the flow properties of powders?
A:
Moisture increases cohesion between particles, leading to clumping and reduced flowability. This is why drying and controlling humidity are crucial in powder processing.

Q10. How do flow properties impact the tablet manufacturing process?
A:
Poor flow can lead to:

• Uneven die filling during compression.
• Variation in tablet weight and content uniformity.
• Processing delays or equipment blockages.