Part Size Reduction Flashcards
What is comminution?
Process that applies mostly to powders
Why does particle size need to be carefully controlled?
Maintain therapeutic range
= particle size influences dissolution, flowability + ect
What happens if you have smaller particles?
BAD
Poorer flowability = larger specific SA
What happens if you have smaller particles?
GOOD
Packed tighter together
= decreased porosity
= increased bulk density
= better for transport
What does particle size dictate?
Deposition site of inhaled particles
Why is it bad if have larger specific SA?
Interact more
= more cohesive
= flow poorly
What does the Noyes-Whitney equation show?
Dissolution rate to SA
What happens to dissolution rate if there is a larger specific SA?
Faster dissolution
= increased bioavailability
What is milling?
Fracturing large particles into smaller ones by applying mechanical stress
Describe what happens in cutter mill
Particles cut between rotating + stationary knives
Screen retains particles until desired size achieved
Describe what happens in hammer mill
Hammer radiates from central rotating shaft
Hammers hit particles at high velocity to cause brittle facture in most materials
Describe what happens in runner mill
Edge runner mill grinds on rotating wheel
End runner mill grinds under flat base of rotating wheel
Describe what happens in roller mill
2 rollers rotate against each other, or on roller rotates around stationary
Particles crushed as drawn through gap between rollers
Speed differential effect sheering
Describe what happens in ball mill
Hollow rotating drum filled with mill balls
Mill balls lifted up against mill wall by centrifugal force
Mill balls cascade back down when dynamic angle of expose exceeded
Describe what happens in vibration mill
Vibration mill filled with milling balls
Vibration causes impact between particles + mill balls
DOESN’T ROTATE
