title: Lightweight, highly compressible, noncrystalline cellulose capsules.
abstract: We demonstrate how to prepare extraordinarily deformable, gas-filled, spherical capsules from nonmodified cellulose. These capsules have a low nominal density, ranging from 7.6 to 14.2 kg/m(3), and can be deformed elastically to 70% deformation at 50% relative humidity. No compressive strain-at-break could be detected for these dry cellulose capsules, since they did not rupture even when compressed into a disk with pockets of highly compressed air. A quantitative constitutive model for the large deformation compression of these capsules is derived, including their high-frequency mechanical response and their low-frequency force relaxation, where the latter is governed by the gas barrier properties of the dry capsule. Mechanical testing corroborated these models with good accuracy. Force relaxation measurements at a constant compression rendered an estimate for the gas permeability of air through the capsule wall, calculated to 0.4 mL μm/m(2) days kPa at 50% relative humidity. These properties taken together open up a large application area for the capsules, and they could most likely be used for applications in compressible, lightweight materials and also constitute excellent model materials for adsorption and adhesion studies.
authors.affiliation: School of Chemical Science and Engineering, Department of Fibre and Polymer Technology and ‡School of Chemical Science and Engineering, Wallenberg Wood Science Centre (WWSC), KTH Royal Institute of Technology , SE-100 44 Stockholm, Sweden.
authors.forename: Christopher
authors.initials: C
authors.lastname: Carrick
authors.forename: Stefan B
authors.initials: SB
authors.lastname: Lindström
authors.forename: Per Tomas
authors.initials: PT
authors.lastname: Larsson
authors.forename: Lars
authors.initials: L
authors.lastname: Wågberg
mesh_terms: D002214:Capsules / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry*; D008422:Materials Testing
chemical_list: D002214:Capsules; D002482:Cellulose