Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

S1 Pharmaceutics > Powder Flow > Flashcards

Powder Flow Flashcards

1
Q

Why is powder flow important ?

A
  • powders are building blocks for many solid dosage forms
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What can powder flow directly affect ?

A
  • can affect manufacturing efficiency
  • dosage form weight
  • drug dose uniformity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the 2 driving forces for powder flow ?

A
  • gravity
  • mechanical agitation (external forces)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the 2 resistive forces for powder flow ?

A
  • cohesion / adhesion
  • friction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Gravitational force

A
  • F = m x g
  • F = gravitational force
  • m = mass of the particle
  • g = particle acceleration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Mechanical agitation

A
  • external forces to induce powder motion and to affect its flow behaviour
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is cohesion ?

A
  • attractive forces between 2 chemically similar surfaces (e.g particle + particle )
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are adhesion and cohesion a result of ?

A
  • van der waals forces
  • electrostatic interactions
  • mechanical interlocking
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is adhesion ?

A
  • attractive forces between 2 chemically different substances (e.g particle + equipment )
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Van der Waals forces

A
  • induced dipole - induced dipole interactions
  • greater if particles are larger + closer together
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is tribocharging ?

A
  • surface statics develop due to friction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where does the tribocharging effect take place during the flow of powder in a device ?

A
  • takes place at the contact between the grains + at the contact between the grains and the device
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does mechanical interlocking occur ?

A
  • rough surface textures
  • sharp edges
  • angular shapes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does mechanical interlocking affect particle movement ?

A
  • particles with irregular complementary shape lock together
  • so they strongly resist further movement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How can you reduce mechanical interlocking ?

A
  • make particles more spherical by granulation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is friction + how does it affect particle movement at contact surfaces ?

A
  • present at contact surfaces where at least one surface is in motion
  • acts in opposite direction versus direction of movement, thus inhibiting particle movement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

5 particle properties that affect powder flow ?

A
  • size
  • shape
  • density
  • surface texture
  • moisture content
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does size of particle affect powder flow ?

A
  • as particle size decreases, flow is reduced
  • due to greater adhesion forces
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How does shape of particle affect particle flow ?

A
  • optimal flow provided by spherical particles
  • because there is no interlocking
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How does density of particle affect powder flow ?

A
  • influence gravity + surfaces forces
  • denser particles have better flow
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How does surface texture affect powder flow ?

A
  • smooth surfaces increase powder flow
  • more rough surface = more particle adhesion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How does moisture content affect particle flow ?

A
  • higher amount of moisture = greater risk of adhesion and cohesion
  • reduces particle flow
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Optimal particle properties for powder flow ?

A
  • large size
  • spherical shape
  • small surface area (large particles)
  • high density
  • moderate moisture content
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Do smaller particles have a large or small surface area ?

A
  • small particles have large surface area
25
Q

Effects of large surface area

A
  • greater surface free energy
  • more bonding interactions
  • more cohesive
  • greater resistive forces
  • poorer flowability
26
Q

Why is spherical particle shape better for powder flow ?

A
  • has the smallest surface area of any particles shape
  • less likely to mechanically interlock with another particle
27
Q

Effects of spherical particles shape

A
  • smaller specific surface area
  • lower surface free energy
  • fewer bonding interactions
  • less cohesive
  • smaller resistive forces
  • better flowability
28
Q

What is packing geometry ?

A
  • position of solid particles relative to one another
29
Q

What is packing fraction ?

A
  • volume fraction of solid particles (k)
30
Q

What is porosity ?

A
  • volume fraction of air (e = 1- k)
31
Q

What does high porosity mean ?

A
  • more air between particles
32
Q

What is bulk density ?

A
  • density of solid particles plus entrapped air when the powder is allowed to settle naturally under gravity
  • bulk density = mass / bulk volume
33
Q

What is tapped density ?

A
  • density of solid particles with minimal amount of entrapped air, after consolidation using a pharmacopeial method
  • tapped density = mass / tapped volume
34
Q

What does particle density (true density) refer to?

A
  • refers to the density of the solid material in a particle excluding air or pores
  • assuming the particle is non-porous.
35
Q

Characteristics of a denser particle ?

A
  • greater mass at same volume
  • greater gravitational force
  • lower specific surface area
  • smaller resistive forces
  • better flowability
36
Q

Arrange bulk density, tapped density, and true density in increasing order ?

A
  • Bulk density < Tapped density < True density.
37
Q

What role does moisture play as a binder in powders ?

A
  • moisture acts as a binder, helping particles adhere to each other (cohesion ) + surfaces (adhesion)
38
Q

What does moderate moisture form ?

A
  • forms liquid bridges between particles
39
Q

How does moisture affect lubrication in powders ?

A
  • provides lubrication by reducing friction between particles
  • improves flow
40
Q

What problems can arise with dry particles ?

A
  • more likely to experience friction + generated by statics
41
Q

What does moderate moisture content provide a balance between ?

A
  • between lubrication + cohesion
42
Q

Mass flow

A
  • first in, first out
  • good flowability
43
Q

Funnel flow

A
  • last in, first out
  • arching, ratholing
  • poor flowability
44
Q

What are some powder flow problems ?

A
  • caking
  • wall build up
  • funnelling
  • plugging
45
Q

4 methods for testing powder flow ?

A
  • flow rate
  • density ratios
  • angle of repose
  • shear cell
46
Q

What causes a powder to flow out of a funnel ?

A
  • due to gravity
47
Q

What is method 1 for measuring powder flowability ?

A
  • measure amount of powder discharged over a fixed duration
48
Q

What is method 2 for measuring powder flowability ?

A
  • measure the time taken to discharge a fixed amount of powder
49
Q

Equation for calculating flow rate ?

A
  • flow rate = amount of powder discharged / discharge duration
50
Q

How does cohesion affect powder flow ?

A

more cohesive powder :
- flows less readily
- takes longer to flow through an orifice
- lower flow rate

51
Q

What 2 factors is flow rate influenced by ?

A
  • hopper shape
  • orifice shape
52
Q

How does orifice diameter affect flow rate ?

A
  • increased diameter = increased flow rate
53
Q

How does height of powder in hopper effect flow rate ?

A
  • has no effect when height is greater than orifice diameter
54
Q

How do you measure powder flowability using density ratios ?

A
  • measure degree of volume reduction upon powder consolidation
  • standardised set of parameters (number of taps, drop of height )
55
Q

What is the angle of repose ?

A
  • angle between slope and horizontal
56
Q

What does steepness of the slope represent ?

A
  • represents equilibrium of driving and resistive forces
57
Q

How does cohesion affect angle of repose ?

A
  • causes particles to pile up (stop flowing)
  • increases angle of repose
58
Q

How does gravity influence the angle of repose ?

A
  • cause particles to roll down the slope (flow)
  • reduces angle of repose
59
Q

What does higher angle of repose mean ?

A
  • poor flowability

S1 Pharmaceutics (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions