Chitin, extracted from crustacean shells, is the second most abundant polysaccharide after cellulose. Alkaline deacetylation of chitin produces chitosan (CH), which is soluble in acidic aqueous solutions because of the protonation of its amino groups at pH &lt; 6. In addition to its solubility, chitosan is biodegradable, biocompatible, and benign. Thin films prepared via a layer-by-layer (LbL) assembly were prepared with cationic CH and 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 nanocoating (∼100 nm thick) reduces the oxygen permeability of a 0.5-mm-thick polylactic acid film by four orders of magnitude. In an effort to create an environmentally-friendly flame retardant, ten bilayers of pH 6 chitosan (CH), as the cationic layer, and pH 10 montmorillonite (MMT) as the anionic layer, were deposited on flexible polyurethane foam (30 nm thick and added 4 wt%). When cut open after direct flame from a propane torch for 10 seconds, white undamaged foam was revealed under a thin black char layer. In related work on foam, vermiculite (VMT) clay was layered with CH, followed by layers of an intumescent system comprised of CH and APP (or polysodium phosphare [PSP]). This ‘stacked’ FR system (i.e., intumescent layers on top of clay layers) reduced the foam’s peak heat release rate by 66%. Just two clay layers provide enough support to the foam during heating to allow intumescence to occur prior to collapse, creating our best result to-date. These environmentally-benign nanocoatings are useful for food packaging or as a replacement for environmentally persistent antiflammable compounds.

Biopolymer-based multilayer nanocoatings that exhibit high gas barrier and flame retardant behavior

252nd National Meeting (2016)

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