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PHA6124 LEC Manufacturing Pharmacy > Particle Size Reduction > Flashcards

Particle Size Reduction Flashcards

- info from table not included in the deck - no need to memorize size reduction range; focus on the method daw sabi ni maam

1
Q

[TRUE OR FALSE] size reduction aids in efficient processing of solid particles by facilitating powder mixing or the production of suspension

A

TRUE

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2
Q

[true or false]
Some special functions of size reduction, such as exposing cells prior to extraction or reducing the bulk volume of a material to improve transportation efficiency

A

true

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3
Q

Influence of Material Properties on size reduction

A
  1. crack propagation and toughness
  2. surface hardness
  3. energy requirements of size reduction process
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4
Q

size reduction or comminution

A

crack propagation and toughness

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5
Q

[TRUE OR FALSE] Stress of material is concentrated at the middle of a crack

A

FALSE - tip of a crack

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6
Q

ease of comminution depends on _____________ or ____________ of the material and their relationship with crack initiation and propagation

A

brittleness or plasticity

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7
Q

crack is Propagated through regions of a material that possess the most ______ or ______, and is related to the strain energy in specific regions

A

flaws or discontinuities

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8
Q

German mineralogist

A

Mohs

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9
Q

Mohs scale

A

describe the hardness of a material

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10
Q

more quantitative measure of surface hardness was devised by

A

Brinell

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11
Q

[TRUE OR FALSE] Harder materials are more difficult to comminute and can lead to abrasive wear of metal mill parts, causing product contamination

A

TRUE

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12
Q

materials with large elastic components (e.g., rubber) are extremely soft which makes it (easy/difficult) to size reduce

A

difficult to size reduce

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13
Q

what is described by its position in a scale devised by a German mineralogist called Mohs

A

Surface Hardness

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14
Q

Materials such as rubber which are soft under ambient conditions, waxy substances such as stearic acid which soften when heated, and “sticky” materials such as gums are capable of _________ large amounts of energy through elastic and plastic deformation without _______ initiation and propagation.

A

absorbing; crack

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15
Q

polymeric material, which resists comminution at ambient or elevated temperatures, can be more easily size reduced by lowering the temperature below the __________ of material

A

glass transition point of the material

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16
Q

glass transition point of the material allows it to go from _______ to _______

A

plastic to brittle behavior

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17
Q

Moisture content of feed material below 5% is suitable for _______ and greater than 50% if _________ is to be carried out

A

dry grinding; wet grinding

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18
Q

Moisture content ______ is suitable for dry grinding and ________ if wet grinding is to be carried out

A

below 5%; greater than 50%

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19
Q

Table of materials

A

Mohs’ Scale

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20
Q

at the top of Mohs’ scale

A

diamond

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21
Q

diamond Mohs hardness

A

> 7

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22
Q

at the bottom of Mohs’ scale

A

talc

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23
Q

talc Mohs hardness

A

<3

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24
Q

[true or false]
diamond can scratch anything below it

A

true

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25
Q

[true or false]
talc is so soft it can be scratched by anything below it

A

false
it can be scratched by anything above it

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26
Q

a very ________ amount of the energy put into a comminution operation actually effects size reduction

A

small

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27
Q

___% of total energy is consumed; the remainder being lost in many ways, including elastic deformation of particles, plastic deformation of particles without fracture, deformation of metal machine parts, interparticle friction, particle machine wall friction, heat, sound and vibration

A

2%

28
Q

Influence of Size Reduction and Size Distribution

A
  • Uneven milling
  • Particles agglomeration
29
Q

consists of a series of knives attached to a horizontal rotor which act against a series of stationary knives attached to the mill casing.

A

Cutting Methods

30
Q

During milling, size reduction occurs by fracture of particles between the 2 sets of knives, which have a clearance of a few mm.

A

Cutting Methods

31
Q

Screen is fitted in the base of the mill casing and acts to retain material in the mill until sufficient degree of size reduction has been effected.

A

Cutting Methods

32
Q

Useful in producing a coarse degree of size reduction of dried granulations prior to tableting and fibrous crude drugs such as roots, peels, or barks prior to extraction

A

Cutting Methods

33
Q

can be carried out on a small scale using a mortar and pestle

A

Compression Methods

34
Q

End runner and edge runner mills are mechanized forms of mortar and pestle

A

Compression Methods

35
Q

Size reduction by compression can be carried out on a small scale using a ____________

A

mortar and pestle

36
Q

mechanized forms of mortar and pestle type compression comminution

A

End runner and edge runner mills

37
Q

a weighted pestle is turned by the friction of material passing beneath it as the mortar rotates under power

A

end runner mill

38
Q

has the pestle equivalent mounted horizontally and rotating against a bed of powder, so that size reduction occurs by attrition as well as compression

A

Edge runner mill

39
Q

size reduction in Edge runner mill occurs by attrition as well as compression (such techniques are (rarely/often) used in pharmaceutical production)

A

rarely

40
Q

It uses 2 cylindrical rolls mounted horizontally and rotated about their long axis

A

roller mills

41
Q

Hammer mills (50-8000 um); Vibration Mills (1- 1000 um) are under what method

A

Impact Methods

42
Q

During milling the whole body of the milling is vibrated and size reduction occurs by repeated inpaction

A

vibration mills

43
Q

in vibration mills, the body is filled to approximately ___% total volume with porcelain or steel balls

A

80%

44
Q

balls used in vibration mills are made of _____ or ______

A

porcelain or steel

45
Q

consist of a series of four or more hammers, hinged on a central shaft which enclosed within a rigid metal case

A

Hammer mills

46
Q

in vibration mills, balls are of (different/same) sizes

A

same

47
Q

Produce size reduction of solids in suspensions, pastes or ointments

A

Attrition Methods

48
Q

what method:
2 or 3 porcelain or metal rolls are mounted horizontally with an adjustable gap, which can be as small as 20 um. The rollers rotate at different speeds so that the material is sheared as it passes through the gap and is transferred from the slower to the faster roll, from which it is removed by means of a scraper

A

Attrition Methods

49
Q

in attrition method, how many porcelain or metal rolls are mounted horizontally with an adjustable gap

A

2 or 3

50
Q

in attrition method, rolls are mounted horizontally with an adjustable gap, which can be as small as ______.

A

20 um

51
Q

in attrition method, The rollers rotate at (same/different) speeds so that the material is sheared as it passes through the gap

A

different

52
Q

in attrition method, The rollers rotate at different speeds so that the material is sheared as it passes through the gap and is transferred from the (slower to the faster roll/faster to slower roll), from which it is removed by means of a scraper

A

slower to the faster roll

53
Q

what method:
Ball mills (1-200 um); pin mills (10-10,00 um); fluid energy mills (1-50,000 um)

A

Combined Impact and
Attrition Methods

54
Q

consist of hollow cylinder mounted such that it can be rotated on its horizontal longitudinal axis. Mills usually contain balls with many different diameters owing to self attrition.

A

Ball mills

55
Q

in ball mills, (small/large) balls tend to break down the coarse feed materials

A

large

56
Q

in ball mills, (small/large) balls help to form the fine product by reducing void spaces between balls

A

small

57
Q

acts by particle impaction and attrition. It is also known as jet mill

A

Fluid energy milling

58
Q

fluid used in Fluid energy milling is usually _______

A

air

59
Q

what technique
A fluid, usually air, is injected as high pressure jet through nozzles at the bottom of the loop.

A

Fluid energy milling

60
Q

in fluid energy milling, high velocity of the air gives rise to _______ into which solid particles are fed. The high kinetic energy of the air causes the particles to impact with other particles with sufficient momentum for fracture to occur

A

zones of turbulence

61
Q

(true/false)
Fluid energy milling involves low velocity fluid like air

A

false
high velocity

62
Q

2 discs with closely spaced pins rotate against one another at high speeds.

A

Pin mills

63
Q

pin mills technique is influence by _______

A

centrifugal force

64
Q

(2) alternative techniques for combined impact and attrition method

A

Fluid energy milling and pin mills

65
Q

alternative technique for impact method

A

vibration mills

66
Q

alternative technique for compression method

A

roller mills

PHA6124 LEC Manufacturing Pharmacy (4 decks)

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