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Stage 2, Cycle 2 - PSFC2 > Powder flow > Flashcards

Powder flow Flashcards

1
Q

Why is Powder flow important ?

A
  • Tabletting
  • Granulation
  • Capusulation
    For transfer in the manufacturing process
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2
Q

State 3 types of transfer in the manufacturing process ?

A
  • Pneumatic transfer
  • Hydraulic transfer
  • Gravity or mechanically assisted feeding
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3
Q

Name 3 methods used for measurement of Powder flow

A

1) Hausner ratio
2) Carr index
3) Angle repose

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4
Q

State 6 consequences of poor powder flow

A

1) Uneven mix into food
2) Risk of degradation
3) No-uniformity of dose
4) Problems w/reproducibility of dosage forms (which require powder transfer)
5) Risk of capping and lamination (tabletting specific problem) (due to entrapped air w/in powders)
6) Increase in particle-die-wall friction and risk of dust contamination

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5
Q

What is Adhesion

A

Clinging of unlike molecules

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6
Q

What is Cohesion

A

Clinging of like molecules
due to: 1) VDW forces
- dependent on nature of particles
- VDW forces increases as particle size decreases

2) Moisture
(formed b/wn particles when above critical humidity)

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7
Q

Factors affecting powder flow

A
  • Resistance to flow; due to Adhesion/Cohesion
  • Particle size;
    < 10micrometre particles extremely cohesive
    < 50micrometre particles = irregular/no flow due to VDW
    > 50micrometre = free flowing

-Density of particles
(dense particles = less cohesive)

  • Particle shape
    (Spherical particles have less interparticulate contact than uniform/irregular shaped particles)
  • Particle size distribution
  • Particle surface
    (Electrostatic forces increases Cohesion)
  • Particle texture
    (Rough surfaces are more cohesive)
  • Humidity
    (Absorbed moisture on particle surface)
  • Processing conditions
  • Powder density
  • Powder porosity
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8
Q

Rearrangement of particle packing geometry can lead to 2 changes. Name them

A

1) Change in bulk volume

2) Change in powder density

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9
Q

Different geometric packing can be achieved with particles of the same shape. TRUE or FALSE

A

TRUE

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10
Q

What is Bulk density ?

A

The density of a powder sample

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11
Q

The volume of a powder sample includes ?

A

Particulate volume and Interparticulate pores

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12
Q

Define ‘Minimum bulk density’

A

The maximum vol occupied by powder

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13
Q

Define ‘Poured bulk density’ (Do)

A

Volume of powder measured after pouring into a cylinder

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14
Q

Define ‘Tapped bulk density’ (Df)

A

The maximum bulk density (in theory) that can be achieved w/out deformation of particles

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15
Q

Relative density (k) is also known as …

A

Packing fraction or Fractional solids content

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16
Q

What is the equation for bulk density

A

k = bulk density/true density

17
Q

What is meant by ‘Porosity of powder bed’ ?

A

The proportion of powder bed that is occupied by pores

18
Q

Name 2 things added to powder to improve formulation ?

A

1) Glidants (added to powder to improve flowability)

2) Anti-adherent properites

19
Q

Give 3 examples of Anti-adherent properties

A

1) Magnesium stearate
2) Colloidal silicon dioxide (helps reduce bulk density of powder bed)
3) Sodium bicarbonate (May improve flow of hygroscopic powder)

20
Q

Name 2 types of powder flow in a hopper

A

1) Mass flow

2) Core flow

21
Q

All material is in motion during discharge in Mass flow. TRUE or FALSE

A

TRUE

22
Q

In Mass flow, the whole bulk of powder moves downwards. TRUE or FALSE

A

TRUE

23
Q

Mass flow has a wall friction angle of about 20 degrees. TRUE or FALSE

A

TRUE

24
Q

During Core flow, some powders remain undisturbed. TRUE or FALSE

A

TRUE

25
Q

During Core flow, dead space occurs during discharge. TRUE or FALSE

A

TRUE

26
Q

State one difference b/wn Mass and Core flow

A
  • MASS flow; all material is in motion during discharge (move downwards)

whereas in CORE flow; some powders remain undisturbed (dead space occurs during discharge)

27
Q

Core flow has a wall friction angle of about 50 degrees. TRUE or FALSE

A

TRUE

28
Q

State 3 problems associated with Core flow

A

1) Flow from hopper can suddenly stop
2) On the other hand, sudden rapid discharge of powder can occur
3) Segragation of powder

29
Q

Particles just above

orifice flow freely. TRUE or FALSE

A

TRUE

30
Q

A ‘tongue’ is formed

above the orifice. TRUE or FASLE

A

TRUE

31
Q

At which angle of repose is powder considered to have ‘good flow’ ?

A

when angle of repose is <30degrees

32
Q

At which angle of repose is powder considered to have ‘problematic flow’ ?

A

when angle of repose is

> 40 degrees

33
Q

Tapped bulk density / Poured bulk density = ?

A

Hausner ratio

34
Q

When value of Hausner ratio is about 1.2, what does this suggest ?

A

The powder is free flowing

35
Q

When value of Hausner ratio is greater than 1.6, what does this suggest ?

A

The powder is Cohesive

36
Q

What equations can be in bulk density measurement ?

A

Tapped bulk density / Poured bulk density = Hausner ratio

and CARR INDEX

37
Q

The smaller the Carr index value, the better the powder flowability. TRUE or FALSE

A

TRUE

38
Q

Describe how to measure Tapped density according to the BP

A

Carry out 10,500 and 1250 taps and read the
corresponding volumes (V10, V500, V1250) to the
nearest mL

Stage 2, Cycle 2 - PSFC2 (11 decks)

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