255
J. Cosmet. Sci., 74.5, 255–274 (September/October 2023)
*Address all correspondence to Alicia Roso, alicia.roso@airliquide.com.
A paper was presented at the SCC76 annual meeting December 14, 2022, in Los Angeles, with the title “High
Internal Phase (HIP) Gel-in-Oil Emulsions: Optimization of Composition and Preparation Factors.”
Critical Factors to Obtain Stable High Internal Phase (HIP)
Gel-in-Oil Emulsions
LIMING SUN, ALICIA ROSO AND CARLA PEREZ
Seppic Chemical Specialities Co. Ltd., Shanghai, China (L.S., C.P.)
Seppic Research &Innovation, Castres, France (A.R.)
Accepted for publication September 19, 2023.
Synopsis
The interest of the high internal phase (HIP) gel-in-oil concept for the development of emulsions with original
aesthetic qualities was highlighted some years ago. Manufactured using a sustainable cold process, these
emulsions were characterized by a fresh skin contact and triggered similar emollience to classical emulsions
and cream gels with half the oil concentration. However, the factors governing the emulsion structure have
not been thoroughly clarified. Composition factors (i.e., the essential structural materials and concentration
of the internal gel phase) and the preparation procedure (i.e., emulsification mode and agitation procedure)
have been investigated on a standard HIP gel-in-oil emulsion. Their influence on the creation, structure, and
stability of gel-in-oil emulsions was determined by conventional observations, stability tests, and rheology
experiments, from low to high shear conditions (rotational controlled stress/strain rheometer). Limitations and
critical factors such as characteristics of the gel phase and a required dose of emulsifier were highlighted. An
emulsification mixing procedure with medium shear using an anchor provided the best results. In addition,
conventional conductivity monitoring combined with rheology experiments detected early indicators of the
risk of destabilization soon after manufacturing. Precise recommendations to obtain stable HIP gel-in-oil
emulsions, characterized by highly stable elastic structure, could be defined.
INTRODUCTION
HIGH INTERNAL PHASE EMULSIONS: OVERVIEW AND RECENT CONTEXT
High internal phase emulsions (HIPEs) are rare formulations containing a volume of the
dispersed phase exceeding the close packing limit of spheres, above around 74%,1 stabilized
by surfactants or amphiphilic solid particles (high internal phase Pickering emulsions:
HIPPEs) or combining both materials.
In recent years, HIPPEs, including water-in-oil (W/O), have been used as templates
to manufacture a wide spectrum of functional porous materials based on cellulose,
polyurethane, silica, polystyrene–acrylate copolymers, polystyrene composites, polymethyl
J. Cosmet. Sci., 74.5, 255–274 (September/October 2023)
*Address all correspondence to Alicia Roso, alicia.roso@airliquide.com.
A paper was presented at the SCC76 annual meeting December 14, 2022, in Los Angeles, with the title “High
Internal Phase (HIP) Gel-in-Oil Emulsions: Optimization of Composition and Preparation Factors.”
Critical Factors to Obtain Stable High Internal Phase (HIP)
Gel-in-Oil Emulsions
LIMING SUN, ALICIA ROSO AND CARLA PEREZ
Seppic Chemical Specialities Co. Ltd., Shanghai, China (L.S., C.P.)
Seppic Research &Innovation, Castres, France (A.R.)
Accepted for publication September 19, 2023.
Synopsis
The interest of the high internal phase (HIP) gel-in-oil concept for the development of emulsions with original
aesthetic qualities was highlighted some years ago. Manufactured using a sustainable cold process, these
emulsions were characterized by a fresh skin contact and triggered similar emollience to classical emulsions
and cream gels with half the oil concentration. However, the factors governing the emulsion structure have
not been thoroughly clarified. Composition factors (i.e., the essential structural materials and concentration
of the internal gel phase) and the preparation procedure (i.e., emulsification mode and agitation procedure)
have been investigated on a standard HIP gel-in-oil emulsion. Their influence on the creation, structure, and
stability of gel-in-oil emulsions was determined by conventional observations, stability tests, and rheology
experiments, from low to high shear conditions (rotational controlled stress/strain rheometer). Limitations and
critical factors such as characteristics of the gel phase and a required dose of emulsifier were highlighted. An
emulsification mixing procedure with medium shear using an anchor provided the best results. In addition,
conventional conductivity monitoring combined with rheology experiments detected early indicators of the
risk of destabilization soon after manufacturing. Precise recommendations to obtain stable HIP gel-in-oil
emulsions, characterized by highly stable elastic structure, could be defined.
INTRODUCTION
HIGH INTERNAL PHASE EMULSIONS: OVERVIEW AND RECENT CONTEXT
High internal phase emulsions (HIPEs) are rare formulations containing a volume of the
dispersed phase exceeding the close packing limit of spheres, above around 74%,1 stabilized
by surfactants or amphiphilic solid particles (high internal phase Pickering emulsions:
HIPPEs) or combining both materials.
In recent years, HIPPEs, including water-in-oil (W/O), have been used as templates
to manufacture a wide spectrum of functional porous materials based on cellulose,
polyurethane, silica, polystyrene–acrylate copolymers, polystyrene composites, polymethyl
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