Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843, USA.
ACS Appl Mater Interfaces. 2012 Mar;4(3):1643-9. doi: 10.1021/am2017915. Epub 2012 Mar 1.
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.
通过可再生材料的层层（LbL）组装制备的薄膜表现出优异的氧气阻隔和阻燃性能。带正电荷的壳聚糖（CH）在两种不同的 pH 值（pH 3 和 pH 6）下与阴离子蒙脱石（MMT）纳米片层配对。在高 pH 值下制备的薄膜组装体更厚，因为如果聚合物电荷密度低。一个 30 层（CH pH 6-MMT）纳米涂层（100nm 厚）将厚度为 0.5mm 的聚乳酸薄膜的氧气透过率降低了四个数量级。当暴露于来自丁烷火炬的直接火焰时，相同的涂层系统仅用 10 层（30nm 厚）就完全阻止了柔性聚氨酯泡沫的熔融。锥形量热法证实，与未涂层的对照相比，这种涂层泡沫的峰值放热率降低了多达 52%。这些环境友好型纳米涂层可能有助于新型食品包装或替代环境持久性阻燃化合物。
