Brainscape's Knowledge GenomeTM

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


See full index

CP 4544 FCSC > TOPIC 9A Colloidal Systems > Flashcards

TOPIC 9A Colloidal Systems Flashcards

1
Q

macroemulsion particle size

A

0.2-50 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

microemulsion particle size

A

0.01-0.2 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

emulsion type depends on

A

nature of emulsifying agent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

type of emulsifier for O/W

A

hydrophilic (high HLB 8-18)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

type of emulsifier for W/O

A

hydrophobic (low HLB 3-6)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

type of emulsifier for W/Si

A

hydrophobic (low HLB) 3-6)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

advantages of O/W emulsion (4)

A

● good skin spreadability and penetration with active hydration by water
● non-greasy, light feel, easily removable
● cooling effect (water evaporation)
● easy to formulate and low cost

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

disadvantages of O/W emulsion (3)

A

● not as effective for dry skin bc less emolliency and nourishment delivered
● not water-resistant
● lesser active concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

advantages of W/O emulsion (3)

A

● most effective for dry skin bc more emolliency and nourishing purposes
● water-resistant
● precisely tailored to needs with wide choice of ingredients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

disadvantages of W/O emulsion (4)

A

● greasy, oily, tacky feel
● not washable with water
● less stable due to lack of double layer effect
● more expensive ingredients, harder to manufacture and clean up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

clear micro-emulsions are called solubilised systems because …

A

macroscopically they behave like true solutions
they have globule radius within 10-50 nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

three (3) tests for emulsion types

A
  1. dilution test
  2. dye test
  3. conductivity measurement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

dilution test

A

water added slowly into emulsion
● if distributed uniformly, water is cont. phase (O/W)
● if separate out as a layer, water is dispersed phase (W/O)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

dye test

A

malachite (green, water-soluble) and sudan III (red, oil-soluble) dyes added
● if readily coloured by green, water is cont. phase (O/W)
● if readily coloured by red, oil is cont. phase (W/O)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

conductivity measurement

A

apply small electrical charge between 2 terminals immersed in emulsion connected to light bulb
● if bulb glows, water is cont. phase (O/W)
● if bulb does not glow, oil is cont. phase (W/O)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

characteristics of effective emulsifiers (3)

A

● good surface activity
● able to form condensed interfacial film
● rate of adsorption to interface comparable to emulsion forming time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

rules (2) in choosing emulsifier

A
  1. RHLB-HLB matching: RHLB (required HLB) should approximate HLB value
  2. surfactant blends
    ● blends give better interface coverage = better stability
    ● blends from same parent chain = best synergy
    ● chemical type of surfactant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

why pair emulsifiers

A

allows more surfactants to pack at oil-water interface and lower interfacial tension for more stable emulsion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

chemical type of surfactant is related to

A

attraction of lipophilic group in emulsifier to lipophilic material with which emulsifier is being used

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

emulsifiers with unsaturated alkyl chains eg. oleyl chains have an increased affinity for …

A

oils with unsaturated bonds eg. vegetable oils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

emulsifiers with saturated alkyl chains have an increased affinity for …

A

oils with saturated bonds eg. mineral oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

four (4) stages in emulsifier selection

A
  1. select required HLB range by calculating RHLB value for oil-phase components
  2. select emulsifier systems and consider chemical type
  3. select blending ratio to match HLB
  4. prototyping stage: make a series of formulations varying total emulsifier dosage (using same blending ratio)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

two (2) steps in emulsification process

A
  1. rapid breaking of internal phase into droplets by agitation
  2. stabilisation of droplets
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

for hot process, why must oil and water phases be heated to same temperature (what happens if not)

A

to ensure stability
● if not, emulsifiers / co-emulsifiers may solidify when it meets lower temperature and precipitate out
● results in particulates in formulation and affects stability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

high energy method (hot process) of emulsification (O/W macroemulsion) (5)

A
  1. both oil and water phases heated to around 75-80 deg C
  2. oil mixed into water
  3. energy supply breaks down both phases and disperses oil into water in fine droplets
  4. (opt) homogenisation for 1-3 min to achieve finer droplets
  5. cool down under slower speed to eliminate air entrapment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

physical parameters affecting droplet size distribution, viscosity, and emulsion stability (6)

A

● agitation speed and time
● location of emulsifier
● quantity of total emulsifiers used
● method of incorporation of phases
● rate of addition
● temperature of each phase and rate of cooling after mixing phases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what to watch out for with agitation speed and time

A

long enough for sufficient breakdown into smaller droplets but avoid over-agitation during and after emulsion formation as it may cause coalescence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

three (3) options to incorporate emulsifier in formulation

A

● all emulsifiers in oil phase
● divide 2/3 in oil phase and 1/3 in water-phase
● high HLB in water-phase, low HLB in oil-phase (most common)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

smaller droplets need _____ total dosage of emulsifiers

A

higher dosage of emulsifiers

(to ensure sufficient encapsulation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

two (2) methods of incorporation of phases for O/W emulsion

A
  1. standard: addition of internal oil phase to external water phase
  2. phase inversion by volume technique: add water to oil first (lesser mechanical action)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

advantage (1) of phase inversion technique

A

allows formation of smaller droplets with lesser mechanical action

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

limitation (1) of phase inversion technique

A

production equipment limitation

33
Q

important thing to note about rate of addition of water phase into W/O emulsions

A

water phase must be added slowly for better stabilisation of emulsion

34
Q

common temperature heated to in hot process

A

75-80 deg C

35
Q

how does cooling rate (hot process) affect emulsion

A

gradual cooling gives time for better alignment of emulsifier; sudden cooling can result in low viscosity

36
Q

what is phase inversion

A

phenomenon where phases of W/O dispersion interchange spontaneously from W/O to O/W

37
Q

two (2) approaches to phase inversion

A
  1. by volume
  2. by temperature (typically for ethoxylated non-ionic emulsifiers)
38
Q

what happens near / at inversion point for phase inversion by volume

A

water droplets begin to coalesce and emulsion inverts upon any small further addition, entrapping oil phase

39
Q

where does viscosity peak during phase inversion by volume

A

inversion point

40
Q

phase inversion by temperature emulsification can be used when

A

● O/W emulsion
● stabilised by ethoxylated non-ionic surfactant

41
Q

phase inversion by temperature emulsification process (4)

A
  1. when temp increases, water solubility of O/W emulsifier decreases = CMC and HLB decreases
  2. when temp increases beyond cloud point, emulsifier precipitates, causing separation with now insoluble emulsifier and water into oil phase
  3. low-viscosity W/O emulsion is formed containing water droplets in continuous oil phase
  4. during cooling stage, HLB of O/W emulsifier increases as water solubility increases back. once phase inversion temperature is attained, W/O inverts back to O/W
42
Q

what is phase inversion temperature?

A

PIT is the temperature at which the emulsion inverts from water-in-oil to back to oil-in-water. It is the temperature at which the hydrophilic and lipophilic properties of the emulsifier are in balance and is therefore also called HLB temperature.

43
Q

what is observed at phase inversion temperature

A

viscosity increases

44
Q

advantage of phase inversion by temperature emulsification method

A

smaller droplet O/W emulsion formed

45
Q

what to note for phase inversion by temperature method

A

must heat to ABOVE phase inversion temperature so it can cool down to phase inversion temperature

46
Q

process (3) for determining phase inversion temperature experimentally

A
  1. weigh 200g of emulsion in beaker and heat it at 1°C / min
  2. adjust stirring speed to get a 1cm deep vortex
  3. record the temperature at which vortex disappears
47
Q

how does phase inversion temperature affect stability

A

PIT is inversely proportional to rate of droplet coalescence
(so if PIT is high, rate of coalescence is low = more stable!)

48
Q

ideal PIT

A

20 deg C higher than storage temperature

49
Q

properties of W/Si emulsion (2)

A

● silicone emulsifiers only (high or low shear)
● water phase added slowly into oil phase

50
Q

why is low shear emulsifier preferred for W/Si emulsions

A

lesser energy required for dispersion

51
Q

what to note for formulating with silicone emulsifiers (2)

A

● silicone emulsifiers are nonionic
● silicone emulsifiers have optimum range for silicone oil content

52
Q

cetyl dimethicone copolyol (Abil EM 90) (silicone emulsifier) optimum oil-phase content range

A

22-35%

53
Q

Lauryl PEG-10 Tris(trimethylsiloxy)silylethyl Dimethicone (Dowsil ES-5300) optimum oil-phase content range

A

min. 5% (can take high level of water phase to form HIPE)

54
Q

properties of W/O emulsion

A

● oil phase is mixture of oil and silicones
● emulsifier can be silicone or non-silicone

55
Q

for W/O, increasing water phase ratio will (2)

A

● increase viscosity
● decrease gloss

56
Q

how to increase viscosity of W/O cream (3)

A

● increase water phase ratio
● incorporating occlusive emollients eg. petrolatum, DISM, DISD
● incorporate emulsion stabilising waxes eg. hydrogenated castor oil, beeswax, hydrocarbon waxes

57
Q

examples of occlusive emollients (3)

A

● petrolatum
● DISM
● DISD

58
Q

what should be added to stabilise W/Si or W/O (2)

and exceptions!

A

● 2-5% w/w glycerine
● 0.5% w/w NaCl or MgSO4 (heptahydrate)

except for
● Dowsil 5225C and ES5300: 1-2% w/w NaCl
● EasyNov no need NaCl

59
Q

key ingredients of hyper internal phase emulsion (HIPE) using geltrap technology (2)

A

● non-silicone W/O emulsifier (EasyNov)
● Sepiplus 400 (emulsifier + thickener for water phase)

60
Q

advantage of HIPE emulsion

A

rich sensory feel without heavy or greasy afterfeel

61
Q

how to increase viscosity of HIPE (geltrap) (2)

A

● increase dispersion speed
● replace lower viscosity oils with higher viscosity oils

62
Q

what is liquid crystal emulsion (LCE) (3)

A

● O/W emulsion
● 3D association structures that stabilise emulsions
● can refract and reflect polarised light and hence exhibit birefringence under polarised light microscope (looks like cabbage)

63
Q

impact of increasing surfactant concentration on LCE

A

formation of larger aggregates (liquid crystals)

64
Q

lamellar gel network effect on stability of emulsion (2)

A

● barrier to coalescence and prevents emulsion breakdown
● when liquid crystals extend from surface of droplets to bulk of external phase, viscosity increases

65
Q

advantages of liquid crystal emulsion (2)

A

● enhanced stability
● prolonged moisturisation effect

66
Q

how does liquid crystal emulsion provide prolonged moisturisation effect (2)

A

● structure of LCE is similar to skin = enhanced affinity with skin
● offers better absorption and counters water evaporation

67
Q

how to achieve liquid crystal emulsion in formulation (3 ingredients)

A

● nonionic emulsifier pair
● fatty alcohol (co-emulsifier)
● fatty acid (optional co-emulsifier)

68
Q

ingredient: Brij S2

A

low HLB nonionic emulsifier

69
Q

ingredient: Brij S721

A

high HLB nonionic emulsifier

70
Q

ingredient: Lubrizol Chemonic OE-2

A

low HLB nonionic emulsifier

71
Q

ingredient: Lubrizol Chemonic OE-20

A

high HLB nonionic emulsifier

72
Q

ingredient: Glucate SS

A

low HLB nonionic emulsifier

73
Q

ingredient: Glucamate SSE

A

high HLB nonionic emulsifier

74
Q

things to note during heating and cooling to form LCE (3)

A

● water and oil phase should be heated to same temperature and must be fully melted
● maintain temperature for 10-15 min after mixing
● gradual cooling down

75
Q

key benefits of LCE in cosmetic formulation (6)

A

● increased stability against coalescence and creaming
● prolonged skin hydration
● varying skin feel due to structuration of emulsion
● enhanced water resistance
● controlled release of actives
● pH flexibility and salt tolerance (since emulsifiers are nonionic)

76
Q

benefits of multiple emulsions (2)

A

● controlled / sustained release of actives
● protection of sensitive actives from external phase

77
Q

process of preparation of W/O/W emulsion (4)

A
  1. prepare primary W/O emulsion: add water phase dropwise to oil phase with lipophilic (low HLB, W/O) emulsifier.
  2. homogenise at high shear rate (8000-10000 rpm)
  3. pour primary W/O emulsion into another aqueous solution containing hydrophilic (high HLB, O/W) emulsifier
  4. homogenise at low shear (to obtain larger droplet)
78
Q

problems with multiple emulsion (2)

A

● settling, coalescence bc of large droplets
● phase separation

CP 4544 FCSC (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions