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form and tech > powder flow - prac > Flashcards

powder flow - prac Flashcards

1
Q

why must powder flow be good

A

if not insignificant weight variation

potentially cause product failure

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2
Q

what is powder flowability

A

ability of powder to flow with ease and consistency

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3
Q

how to measure flowability

A

no single test
- its not an inherent property but
trait derived and affected by combination of factors

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4
Q

what are the factors affecting powder flowability

A

physical properties of the powder affecting flow

  • environment
  • equipment used to handle process or store the powder
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5
Q

what is the angle of repose

A

angle relative to the horizontal base of the conical pile produced when a powder material is poured onto a horizontal surface

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6
Q

what is the angle of repose related to

A

density, surface area and coefficient of friction of the material

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7
Q

what is the apparatus used to measure the angle of repose

- name of the tester and what it comprises of

A

eg is copley powder flow tester

comprises of

  • funnel
  • base spout shuttered by a stopper
  • cylindrical base for a free standing powder cone to form
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8
Q

what is the angle of repose used to indicate

A

provides a measure of powder flow

- can predict the performance of powder when transferred

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9
Q

list the angle of repose and the flow properties

A 
angle : 
25-30 - excellent 
31-35  - good 
36-40  - fair , aid not needed 
41-45   - passable, may hang up
46-55  - poor, must agitate , vibrate 
56-65  - very poor 
> 66     - very, very poor
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10
Q

purpose of lubricants

A

improve flowability

reduce sticking and friction between tablet and compaction tool surfaces

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11
Q

popular lubricant and what type of lubricant is it

A

mg stearate

boundary lubricant

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12
Q

disadvantage of mg stearate

A

can cause detrimental effects on tablet hardness and dissolubility
- commonly seen with hydrophobic substances

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13
Q

steps in measuring angle of repose

A
  1. ensure funnel is vertically upright
  2. fix funnel stem tip about 30mm above graph paper
  3. empty all the lactose powder provided into the black mixing container
  4. for the first determination, pour some powder over the graph paper to “season” the graph paper by spreading the powder over the paper with a spatula. then return the powder back into the container and dust away any remaining powder. place the graph paper below the funnel.
  5. pour the powder into the funnel to form a free standing cone of about 20mm
  6. assist the flow with a thin rod or wire if the powder does not flow freely through the funnel
  7. switch on the inclinometer , place it flat and levelled on the graph paper, set it to “zero”
  8. tilt the inclinometer with bottom edge parallel to the slope of the cone,
    determine the angle of the cone formed using the inclinometer, in 2 opposite directions and record the angles in the results form. r
  9. move the retort stand forward to form another cone and repeat angle of repose measurements
  10. carefully empty out all of the remaining powder from the black mixing container and in the funnel onto the paper
    - place the empty mixing container onto the weighing balance and tare its weight. transfer the powder from the paper into the mixing container. record the weight of the powder collected.
  11. weigh out 0.2% w/w of lubricant on a small paper, add the weighed lubricant to the the black container containing lactose
  12. mix the powders in a figure of 8 formation for 3 minutes . repeat steps 5-8 to test powder flow.
  13. incrementally add magnesium stearate, mix and repeat the angle of repost measurement
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14
Q

materials needed for the experiment

A 
lactose powder, stock 
lubricant, stock 
empty mixing container and cover 
spatula or spoon 
weighing paper 
plastire wire twist tie or thin rod 
weighing balance ( for weighing lubricant and must be at least 3 decimal place balance )
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15
Q

what data to collect

A 
the weight of lactose 
amt of mgst added for the final conc 
angles of both sides for cone 1 
angles of both sides for cone 2 
average angle of the 4

plot of angle of repose vs lubricant conc

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16
Q

steps in using manual tablet press

A
  • use free flowing powder containing 1% w/w of mgst
  • pour excess amt of powder on the tableting table over the die
  • sweep the powder across the die cavity
  • lock pressure release valve ( turn towards you ) and pump til pressure gauge shows the desired force ( 1 bar _
  • release the piston pressure ( turn away from u )
  • eject the tablet by pulling the ejection lever
  • collect tablet
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17
Q

identify the parts of the manual tablet press

A
  • ejection lever on the left
  • hydraulic pressure gauge on top
  • pump handle on the right
  • pressure release valve on the right bottom
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18
Q

describe the methodology for measuring

hardness

A
  1. place the tablet between the platens of the hardness tester
  2. determine hardness
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19
Q

methodology for friability test

A

weight tablets
place into drum of friabilator
begin test, 100 revolutions
- collect tablets, dust them and determine weight of the tablets

20
Q

describe methodology for disintegration test

A

place the tablet in each of the 6 open ended transparent tubes in the basket-rack assembly of the disintegration tester

  • start tester
  • determine disintegration time of the tablet
21
Q

what is the dissolution test for

A

paddle most commonly used

  • for release studies
  • determine biopharm performance
22
Q

what is disintegration test for and what is dissolution test for

A

disintegration - ensure tablet breaks up

dissolution - ensure it dissolves

23
Q

which are biopharm tests

which are mechanical tests

A

weight , disintegration and dissolution
- biopharm

hardness and friability - mechanical

24
Q

what is the hardness test requirement

A

breaking force
tested across diameter or parallel to the longest axis
10 tablets
must specify the type apparatus and orientation

25
Q

friability how many tabs to use and whats the passing requirement

A

weight more than 650g take 10 tablets
if equal to or less than 650, take as near as possible to 6.5g

if damaged - fail
loss of 1% or less = pass
if > 1% repeat twice more and mean of 3 test shld be not greater than 1%

26
Q

passing requirement for disintegration test

A
  • all particles must pass thru the 10 min esh screen in time specific 15 mins , if any residue it must be soft mass withotu core
    if 1-2 fail repeat with additional 12 units , pass only if 16 or more of the 18 tested have disintegrated

28-32 cycles/min over 50-60 mm 37 deg +- 2 de

27
Q

reproduce the calculation steps of adding the lubricant incrementally

initial weight is 30g

A

final conc 0, 0.2, 0.5, 1, 2, 5

add 0.2, add 0.3, 0.5, 1 , 3

28
Q

causes of poor powder flow

A

interparticle friction
interlocking particles
surface forces

29
Q

cohesion vs adhesion

A

adhesion - similar cohesion is same

30
Q

what are some surface forces

A 
vdw 
moisture 
electric charge 
particle size 
contact sites 
time of contact 
crystalline bridges
31
Q

arching

A
  • arch shaped obstruction blocking flow due to interlocking particles forming an arch
    outlet must be 6-10x bigger than the max particle size
32
Q

ratholing

A

discharge occurs only in central flwo channel above th eoutlet
cohesive material outside the channel wont flow
- make the hopper more steep

33
Q

glidant for what and example

A

improve flowability
require certain conc of it

work by 1.
ball bearing effect - reduce irregulatiry/ rolling action
reduce interparticulate friction
r reduce surface charge

eg talc 1-5%
starch 5-10Z% - ball bearing effect
colloidal silica 0.5-3% - reduces firction

34
Q

angle of difference

A

angle of repose - angle of fall

angle of fall - for poor flowability
applu certain shoc and measure angle again
eg tap weight

35
Q

angle of spatula

A

powder heap formed on spatula
raise spatula and measure angle formed on spatula
qualitative assesmment of internal cohesive and frictional effect

36
Q

fixed funnel/free-standign cone vs fixed bed cone

A

fixed bed cone - has certain diameter

fixed height - H = H’+ h (in cone )

37
Q

angle of repose < 35 > 45

A

< 35 - free flowing
> 45 - poorly flowing
used for comparative flow

38
Q

precautions when measuring angle of repose

A 
no ibration 
ensure plane horizontal 
condition surface 
funnel type and diameter - no arching 
constant material moisture content 
controll ambient humidity 
no particle fragmentation 
accuracy of measuremtn +2%
39
Q

2 types of orifice flow

A

powder start flowign thru orifice , laser blocked and senses again when flow over
- get flow rate
popular for qc

2 types - volumetric or gravimetric ( more common )

40
Q

tapping studies

A 
sieve powder into cylinder 
remove excess, level 
weight
put on tapping machine 
tap to constant volume

greater the change after - poor flow
much rearrangment of particles
alot of void spaces, stickly/ cohesive with poor flow

41
Q

hausner ratio and carr index

A

hausner ratio - tapped density/bulk density
= final vol after tappping / quotient of weight of powder & vol of cylinder

carr indec = tapped - bulk density/ tapped density

smaller values good

42
Q

powder rheometer

A
  • used for eradicating powder history by moving blade up and down to disturb and gentry drop each particle in order to form a compact bed,
    remove excess air
  • ensure test results independant of history
  • forced or confined flow
  • measured during downward blade movement

low stress or unconfined flow , specific energy (SE)
- measure when bladee transverses from bottom to top of the vessel

43
Q

revolution powder tester

A

drum rotation
determine avalanche angle & avalanche flow characteristics
- can measure potential energy of powder every image also

44
Q

shear cell

A
  • used fo rpoor flowing powders
    ( if good flow use angle of repose )

shear cell splits horizontally forming shear plane between lower stat and upper movable plane
( apply amt of shear stress and try to split it and look @ amt of force needed to twist the powder )

45
Q

powder flow is related to

A

interparticulate adhesion and surface friction

46
Q

what eliminates operator variability

A

automation

47
Q

what do poor flowing powders require

A

flow measurement using shear cells

form and tech (9 decks)

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