title: Getting in shape: molten wax drop deformation and solidification at an immiscible liquid interface.
abstract: The controlled production of non-spherical shaped particles is important for many applications such as food processing, consumer goods, adsorbents, drug delivery, and optical sensing. In this paper, we investigated the deformation and simultaneous solidification of millimeter size molten wax drops as they impacted an immiscible liquid interface of higher density. By varying initial temperature and viscoelasticity of the molten drop, drop size, impact velocity, viscosity and temperature of the bath fluid, and the interfacial tension between the molten wax and bath fluid, spherical molten wax drops impinged on a cooling water bath and were arrested into non-spherical solidified particles in the form of ellipsoid, mushroom, disc, and flake-like shapes. We constructed cursory phase diagrams for the various particle shapes generated over a range of Weber, Capillary, Reynolds, and Stefan numbers, governed by the interfacial, inertial, viscous, and thermal effects. We solved a simplified heat transfer problem to estimate the time required to initiate the solidification at the interface of a spherical molten wax droplet and cooling aqueous bath after impact. By correlating this time with the molten wax drop deformation history captured from high speed imaging experiments, we elucidate the delicate balance of interfacial, inertial, viscous, and thermal forces that determine the final morphology of wax particles.
authors.affiliation: Mechanical Engineering, University of Washington, Seattle, WA 98195, United States.
authors.forename: Shilpa N
authors.initials: SN
authors.lastname: Beesabathuni
authors.affiliation: Corporate Engineering, The Procter & Gamble Company, OH 45069, United States.
authors.forename: Seth E
authors.initials: SE
authors.lastname: Lindberg
authors.affiliation: Corporate Engineering, The Procter & Gamble Company, OH 45069, United States.
authors.forename: Marco
authors.initials: M
authors.lastname: Caggioni
authors.affiliation: Corporate Engineering, The Procter & Gamble Company, OH 45069, United States.
authors.forename: Chris
authors.initials: C
authors.lastname: Wesner
authors.affiliation: Mechanical Engineering, University of Washington, Seattle, WA 98195, United States; Micro/Bio/Nanofluidics Unit, Okinawa Institute of Science and Technology, Japan. Electronic address: amy.shen@oist.jp.
authors.forename: Amy Q
authors.initials: AQ
authors.lastname: Shen
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D004548:Elasticity; D010577:Petrolatum / Q000737:chemistry*; D044367:Phase Transition; D013500:Surface Tension; D013696:Temperature; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D000473:Alkanes; D014867:Water; D010577:Petrolatum; C007932:n-hexadecane
keywords: Deformation; Liquid–liquid interface; Molten wax drop; Non-spherical particles; Solidification