title: Particles at Oil-Air Surfaces: Powdered Oil, Liquid Oil Marbles, and Oil Foam.
abstract: The type of material stabilized by four kinds of fluorinated particles (sericite and bentonite platelet clays and spherical zinc oxide) in air-oil mixtures has been investigated. It depends on the particle wettability and the degree of shear. Upon vigorous agitation, oil dispersions are formed in all the oils containing relatively large bentonite particles and in oils of relatively low surface tension (γla < 26 mN m(-1)) like dodecane, 20 cS silicone, and cyclomethicone containing the other fluorinated particles. Particle-stabilized oil foams were obtained in oils having γla > 26 mN m(-1) where the advancing air-oil-solid contact angle θ lies between ca. 90° and 120°. Gentle shaking, however, gives oil-in-air liquid marbles with all the oil-particle systems except for cases where θ is <60°. For oils of tension >24 mN m(-1) with omniphobic zinc oxide and sericite particles for which advancing θ ≥ 90°, dry oil powders consisting of oil drops in air which do not leak oil could be made upon gentle agitation up to a critical oil:particle ratio (COPR). Above the COPR, catastrophic phase inversion of the dry oil powders to air-in-oil foams was observed. When sheared on a substrate, the dry oil powders containing at least 60 wt % of oil release the encapsulated oil, making these materials attractive formulations in the cosmetic and food industries.
authors.affiliation: †Surfactant and Colloid Group, Department of Chemistry, University of Hull, Hull HU6 7RX, U.K.
authors.forename: Bernard P
authors.initials: BP
authors.lastname: Binks
authors.affiliation: †Surfactant and Colloid Group, Department of Chemistry, University of Hull, Hull HU6 7RX, U.K.
authors.forename: Shaun K
authors.initials: SK
authors.lastname: Johnston
authors.affiliation: ‡Shiseido Research Center, Shin-Yokohama, 2-2-1 Hayabuchi, Tsuzuki-Ku, Yokohama 224-8558, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Sekine
authors.affiliation: †Surfactant and Colloid Group, Department of Chemistry, University of Hull, Hull HU6 7RX, U.K.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Tyowua
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D001546:Bentonite / Q000737:chemistry; D000077215:Clay; D004655:Emulsions / Q000737:chemistry*; D017611:Fluorine Compounds / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D009821:Oils / Q000737:chemistry*; D010316:Particle Size; D013185:Squalene; D013499:Surface Properties; D014867:Water / Q000737:chemistry*; D015034:Zinc Oxide / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D004655:Emulsions; D017611:Fluorine Compounds; D009821:Oils; D014867:Water; D001546:Bentonite; D013185:Squalene; D015034:Zinc Oxide; D000077215:Clay
keywords: dry oil; liquid oil marbles; oil foam; omniphobicity; surface energy