Stabilisation of water-in-oil emulsions to improve - eTheses ...

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HLB Theoretical and Analytical Calculation for each Emulsifier For the majority of non-ionic emulsifiers the HLB is purely an indication of the percentage weight of the hydrophilic portion of the emulsifier molecule multiplied by 1/5 for the purpose of convenience as indicated in Equation 2.1 (Pasquali, Taurozzi & Bregni, 2008). 5 Where the Hydrophilic Group is defined as hydroxyl, sorbitan or polyoxyethylene. 23 2.1 Although this formula works for most non-ionic emulsifiers, for those where the molecular formula is an approximation of the actual composition the method leads to considerable errors. In these cases values are best obtained by means of analytical data using Equation 2.2 (Pasquali, Taurozzi & Bregni, 2008): 20 1 2.2 Where = Saponification number of the ester and = Acid number of the recovered acid.
2.7 Emulsion stability & instability Whilst it is well documented that the role of an emulsifier is to lower the interfacial tension between the oil and the water phase by forming a mechanically cohesive interfacial film around the droplets thus aiding in the droplet fragmentation during emulsification and preventing subsequent coalescence, very little is mentioned about (the need for) stabilisation, both transient (during emulsion formation) and long-term (shelf-life). During emulsification, transient droplet stability is of paramount importance in order to reduce re-coalescence during processing (Darling & Birkett, 1987), which in turn determines the final droplet size distribution. The stability of an emulsion is important in understanding its formation, as its stability is the endpoint or measurement of the entire process (Fingas & Fieldhouse, 2004). There are five main mechanisms that can contribute to emulsion instability: (1) creaming and sedimentation (Binks, 1995); (2) flocculation (Binks, 1995; Dickinson, Ritzoulis & Povey, 1999); (3) Ostwald ripening (Dickinson, Ritzoulis & Povey, 1999); (4) coalescence (Boode & Walstra, 1993; Goff, 1997); and (5) phase inversion (Dickinson, Ritzoulis & Povey, 1999; Rousseau, 2000). Ideally all of the factors need to be minimised or prevented in order to produce a stable emulsion cosmetic lipstick. Creaming and sedimentation (Binks, 1995) is separation due to the differences in density between the two phases under the influence of gravity, leading to phase separation where either a cream or a sediment layer is produced. The creaming and sedimentation rate is proportional to the difference in density of the two phases and can therefore be minimised by using phases with similar densities (relative ρ ≈ 1). This would be impossible to achieve as the wax and oil phase would always have a lower density than the aqueous phase. However the high viscosity crystalline wax within the continuous phase would form a solid matrix around the dispersed water 24
Page 1 and 2: Stabilisation of water-in-oil emuls
Page 3 and 4: Abstract The stabilisation of water
Page 5 and 6: Contents 1 Introduction ...........
Page 7 and 8: 4.7.1 Penetrometer Test ...........
Page 9 and 10: Figures Fig. 1.1. The global cosmet
Page 11 and 12: Fig. 5.18. DSC Thermograms for the
Page 13 and 14: Fig. 5.36. Changes in the viscoelas
Page 15 and 16: Table. 5.6. Emulsion based Lipstick
Page 17 and 18: Symbols α Alpha β Beta β’ Beta
Page 19 and 20: provide additional moisture for the
Page 21 and 22: 1.1 Layout of the Thesis This Thesi
Page 23 and 24: more than 2 to 3 applications daily
Page 25 and 26: O HO O C H 3 CH 3 O OH O O O Molecu
Page 27 and 28: C H 3 HO O OH Molecular Formula = C
Page 29 and 30: C H 3 C H 3 Molecular Formula = C 6
Page 31 and 32: the long chains. Due to its structu
Page 33 and 34: and subsequent infections. This can
Page 35 and 36: In order to attain a state of minim
Page 37 and 38: which there is an excess of opposit
Page 39: By applying the HLB system, one wil
Page 43 and 44: (Voorhees, 1992; Dickinson, Ritzoul
Page 45 and 46: chains are in free rotation and pre
Page 47 and 48: (a) (b) (c) Fig. 2.7. Double chain
Page 49 and 50: prevented by the addition of crysta
Page 51 and 52: 2.9 Microbial stability & Origin of
Page 53 and 54: There are a number of important fac
Page 55 and 56: which of course is an important con
Page 57 and 58: ideal for assessing not only the de
Page 59 and 60: 3 Materials 3.1 Waxes & Emulsifiers
Page 61 and 62: With the continuous phase being oil
Page 63 and 64: melting point range in order to mai
Page 65 and 66: The moulds were then placed in a fr
Page 67 and 68: Table. 4.2. IFT Procedure settings
Page 69 and 70: 4.4 Emulsion Lipstick Preparation F
Page 71 and 72: The water was transferred directly
Page 73 and 74: emulsions were taken in triplicate
Page 75 and 76: d0,0; number-weighted mean (e.g. NM
Page 77 and 78: 4.7 Texture Profile Analysis - TA T
Page 79 and 80: 4.7.2 Compression Test The second m
Page 81 and 82: 4.7.3 Rheology Rheological non-dest
Page 83 and 84: critical micelle concentration (CMC
Page 85 and 86: Interfacial Tension (mN/m) 10 CMC -
Page 87 and 88: Sorbitan Hydrophilic portion (Water
Page 89 and 90: HO O O O O Water droplet O O O O HO
Page 91 and 92:
5.3.2 Wax selection for Simplified
Page 93 and 94:
5.3.3 Thermo-physical Characteristi
Page 95 and 96:
Heat Flow Endo/Exo (mW) 2% PGPR DSC
Page 97 and 98:
Heat Flow Endo/Exo (mW) 2% Span 80
Page 99 and 100:
Table. 5.3. Thermo-physical charact
Page 101 and 102:
Relative frequency Emulsion Stabili
Page 103 and 104:
drainage and rupture. In spite of t
Page 105 and 106:
Table. 5.4. Emulsion based Lipstick
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
the emulsification process along wi
Page 113 and 114:
Fig. 5.29. 30 wt% water content wit
Page 115 and 116:
Fig. 5.33. Cryo-SEM micrograph of H
Page 117 and 118:
no doubt give rise to a much denser
Page 119 and 120:
Table. 5.9. Texture profile penetro
Page 121 and 122:
Table. 5.10. Compression firmness d
Page 123 and 124:
Although no emulsions were prepared
Page 125 and 126:
G' & G'' (Pa) x 10 5 Viscoelastic p
Page 127 and 128:
Table. 5.11. Viscoelastic moduli, G
Page 129 and 130:
potentially reduce microbial spoila
Page 131 and 132:
Appendix The following Figures; 5.9
Page 133 and 134:
Heat Flow Endo/Exo (mW) 5 4 3 2 1 0
Page 135 and 136:
Heat Flow Endo/Exo (mW) 2.0 1.5 1.0
Page 137 and 138:
References Adamczyk, S., Lázaro, R
Page 139 and 140:
Dweck, A. C., & Burnham, C. A. M. (
Page 141 and 142:
Kobayashi, H., & Tagami, H. (2004).
Page 143 and 144:
Pourreza, N., & Rastegarzadeh, S. (
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