Todd Ostergaard – Dow Corning Corporation, United States Scott Hawkins – Lipo Technologies Inc., United States Stephen Greenberg Ph.D – Lipo Chemicals Inc., United States
The cosmetic industry, for many years, has focused on providing products to consumers that prevent premature ageing of the skin and that promote a younger, healthier appearance.
Delivery system platforms vary dramatically and the choice of the “right” platform relies heavily on the cosmetic formulator’s application parameters and the expertise of the delivery system provider.
Encapsulation technology overview
Micro-/millicapsules are composed of a polymeric skin, wall or matrix enclosing a liquid, solid or gaseous core. The capsule wall is typically inert to the substance it contains. It generally possesses sufficient strength to allow for normal handling without rupture and the shell or matrix is sufficiently thin to permit a high core volume to polymer ratio. The contents of the capsule are typically kept within the wall until released by some means that serve to break, crush, melt, dissolve, rupture or remove the capsule shell. Micro-/millicapsule technology encompasses many processes; these processes are varied and are based on scientific principles that deal with polymerisation, surface energy and reaction kinetics. Although microencapsulation has a basis in the science of physical and chemical processes, the application and manufacture of microcapsules continues to remain more an art form than a science. The following will provide a general technology overview of the processes employed to produce microencapsulated materials. These will include coacervation, polymer precipitation, extrusion/ spheronisation, adsorption/absorption and thermosetting matrix systems.
Complex coacervation
This method involves the complexation of a positively charged colloid in an aqueous environment with a negatively charged colloid in order to induce a polymer rich phase. This phase can then be induced to deposit on a hydrophobic substrate based on its borderline solubility in the liquid being employed. Following adsorption onto the substrate, the coacervate is then chemically cross-linked to form the finished microcapsule which has a hard outer shell. Gelatin is the primary (positively charged) component in this type of microencapsulation system and the complex coacervation process is carried out in a dilute solution containing the gelatin as well as a negatively charged colloid.
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