title: Clay-chitosan nanobrick walls: completely renewable gas barrier and flame-retardant nanocoatings.
abstract: Thin films prepared via a layer-by-layer (LbL) assembly of renewable materials exhibit exceptional oxygen barrier and flame-retardant properties. Positively charged chitosan (CH), at two different pH levels (pH 3 and pH 6), was paired with anionic montmorillonite (MMT) clay nanoplatelets. Thin-film assemblies prepared with CH at high pH are thicker, because if the low polymer charge density. A 30-bilayer (CH pH 6-MMT) nanocoating (~100 nm thick) reduces the oxygen permeability of a 0.5-mm-thick polylactic acid film by four orders of magnitude. This same coating system completely stops the melting of a flexible polyurethane foam, when exposed to direct flame from a butane torch, with just 10 bilayers (~30 nm thick). Cone calorimetry confirms that this coated foam exhibited a reduced peak heat-release rate, by as much as 52%, relative to the uncoated control. These environmentally benign nanocoatings could prove beneficial for new types of food packaging or a replacement for environmentally persistent antiflammable compounds.
authors.affiliation: Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843, USA.
authors.forename: Galina
authors.initials: G
authors.lastname: Laufer
authors.forename: Christopher
authors.initials: C
authors.lastname: Kirkland
authors.forename: Amanda A
authors.initials: AA
authors.lastname: Cain
authors.forename: Jaime C
authors.initials: JC
authors.lastname: Grunlan