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Flame Retardant Properties and Thermal Stability of Polylactic Acid Filled with Layered Double Hydroxide and Rice Husk Ash Silica
Journal of Polymers and the Environment ( IF 4.7 ) Pub Date : 2020-01-20 , DOI: 10.1007/s10924-020-01658-2
Chuenkhwan Tipachan , Rakesh K. Gupta , Sushant Agarwal , Somjai Kajorncheappunngam

Polylactic acid (PLA) samples containing a layered double hydroxide modified with sodium dodecyl sulfate (PKL_DS), silica from rice husk ash (SiRHA) and a combination of the two nanofillers were prepared by both solvent casting and a more practical approach involving dry blending of constituents and their melting in a mixing tank followed by compression molding. The morphology of the nanocomposite films was investigated using transmission electron microscopy (TEM) and X-ray diffraction (XRD), and it was confirmed that the nanocomposite structures were intercalated. Additionally, SEM pictures of surfaces of nanocomposite films suggest that PKL_DS was well dispersed throughout the PLA matrix, and the films were essentially featureless except at the highest concentration examined. In the case of SiRHA, there was filler aggregation at low concentration, while holes and cavities were clearly visible at higher concentrations. The addition of PKL_DS to films containing SiRHA ameliorated these effects, and ultimately a dense structure was obtained. From TGA results, it was determined that only the addition of SiRHA significantly improved the thermal stability of PLA. The flammability performance of PLA nanocomposites was investigated using limiting oxygen index (LOI) and UL-94V type measurements. A maximum LOI value of 32.8% could be achieved for PLA nanocomposites containing 10 wt% PKL_DS and 5 wt% SiRHA. This was 78% higher than the LOI of neat PLA alone. Furthermore, PLA containing 10 wt% PKL_DS and 3–5 wt% SiRHA attained a V-0 rating on UL-94 type tests with anti-dripping behavior. It was found that there was synergism between PKL_DS and SiRHA, and this was very effective in improving the flame retardant performance of PLA. That this performance came about without having to completely exfoliate the nanofillers is a remarkably useful result.



中文翻译:

层状双氢氧化物和稻壳灰二氧化硅填充聚乳酸的阻燃性能和热稳定性

聚乳酸(PLA)样品通过溶剂浇铸和更实用的方法(包括干法共混)制备,其中包含用十二烷基硫酸钠(PKL_DS)改性的层状双氢氧化物,稻壳灰中的二氧化硅(SiRHA)以及两种纳米填料的组合。成分及其在混合罐中的熔融,然后压模。使用透射电子显微镜(TEM)和X射线衍射(XRD)研究了纳米复合膜的形态,并且证实了纳米复合结构被插入。此外,纳米复合膜表面的SEM图片表明PKL_DS很好地分散在整个PLA基质中,并且除了在最高浓度下检测外,这些膜基本上没有任何特征。对于SiRHA,低浓度时有填料聚集,而高浓度时明显可见孔洞。向包含SiRHA的薄膜中添加PKL_DS可以改善这些效果,最终获得致密的结构。从TGA结果,确定仅添加SiRHA显着改善了PLA的热稳定性。使用极限氧指数(LOI)和UL-94V型测量研究了PLA纳米复合材料的可燃性。对于包含10 wt%PKL_DS和5 wt%SiRHA的PLA纳米复合材料,最大LOI值可以达到32.8%。这比纯PLA的LOI高78%。此外,含有10 wt%PKL_DS和3-5 wt%SiRHA的PLA在具有抗滴落行为的UL-94型试验中达到了V-0等级。发现PKL_DS与SiRHA之间存在协同作用,这对于提高PLA的阻燃性能非常有效。无需完全剥落纳米填料即可获得这种性能,这是非常有用的结果。

更新日期:2020-01-20
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