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Pharm Y2S2 > Comminution > Flashcards

Comminution Flashcards

1
Q

Define comminution.

A

Reduction of solid particles to lower average particle size

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2
Q

What size classification are granules?

A

Up to 2mm

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3
Q

What size classification is a coarse powder?

A

> 350um

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4
Q

What size classification is a medium/fine powder?

A

100-350um

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5
Q

What size classification is a fine powder?

A

50-100um

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6
Q

What size classification is a very fine powder?

A

10-50um

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7
Q

What size classification is a micronised powder?

A

<10um

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8
Q

What is a disadvantage of using a sieve for particle size analysis?

A

Limited information about shape or size range

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9
Q

What is a disadvantage of using microscopy for particle size analysis?

A

Not representative

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10
Q

What is a disadvantage of using laser diffraction for particle size analysis?

A

Must consider interaction with the solvent

Particles assumed to be spheres

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11
Q

Define milling.

A

Transformation of approximate normal particle size distribution into a finer bimodal population

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12
Q

What effect does prolonged milling have?

A

Forms a unimodal population

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13
Q

What happens when particle sizes are reduced to 1-5um?

A

Particle-particle forces predominate and agglomeration can occur

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14
Q

What are the features of cutting methods?

A

Series of knives/blades on rotor
High shear rates
Screen acts to retain particles larger than a specified size

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15
Q

What are the features of compression methods?

A

Material passes through rollers, one is mechanically driven

Series of rollers can be used to achieve smaller particles

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16
Q

What are the features of impact methods?

A

Filled to 80% with steel balls

Body of the mill vibrates

17
Q

Give examples of size separation methods.

A

Sieving
Sedimentation
Cyclone
Elutriation

18
Q

Give examples of agitation methods.

A

Oscillation
Mechanical vibratioon
Gyration

19
Q

What is crack propagation?

A

Localised stress producing strains in particles that lead to ruptures/cracking

20
Q

At low temperatures, what happens to materials?

A

Transition from plastic to brittle behaviours

21
Q

How is energy lost?

A 
Elastic/plastic deformation
Deformation initiating cracks
Interaction with mechanics
Heat
Vibration
22
Q

What is the Moh’s scale?

A

Qualitative determination of hardness

23
Q

What methods can be used to determine hardness qualitatively?

A

Brinell and Vickers

24
Q

What is the range of attrition?

A

1-100um

25
Q

What is the range of hammer milling?

A

30-10000um

26
Q

What is the range of vibration milling?

A

1-1000um

27
Q

What is the range of roller milling?

A

600-200000um

28
Q

What is the range of end runner milling?

A

20-100000um

29
Q

What is the range of cutting?

A

100-100000um

30
Q

What is the range of fluid energy milling?

A

1-100000um

31
Q

What is the range of pin milling?

A

10-9000um

32
Q

What is the range of ball milling?

A

1-200um

Pharm Y2S2 (26 decks)

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