Microcellular Foaming of Poly(lactic acid)/Silica Nanocomposites in Compressed CO2: Critical Influence of Crystallite Size on Cell Morphology and Foam Expansion

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• 作者：Guoying Ji ; Wentao Zhai ; Dongpo Lin ; Qian Ren ; Wenge Zheng ; Dong Won Jung
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2013
• 出版时间：May 15, 2013
• 年：2013
• 卷：52
• 期：19
• 页码：6390-6398
• 全文大小：785K
• 年卷期：v.52,no.19(May 15, 2013)
• ISSN：1520-5045

文摘

During the solid state foaming, the CO₂ saturated poly(lactic acid) (PLA) sample at 5 MPa and 20 掳C has a high crystallinity of 23.2%, and the prepared PLA foams exhibits low foam expansion and nonuniform cell structure. This study presents an interesting effect of nanosilica addition on the cell morphology and expansion ratio of PLA foams. It was found that the presence of nanosilica increased the induced crystallinity of PLA up to 29.7% at 5 MPa. The resultant PLA/silica foams exhibited significant and concurrent increase in cell structure uniformity and cell density: the cell density increased about 5鈥?0 times, the expansion ratio increased 1.4鈥?.1 times, and the crystallinity of foams increased 1.3 times, compared to pure PLA foams. Further investigation suggested that the formation of the tiny crystallite size and the well dispersed nanosilica aggregates were thought as the main reasons to explain the interesting effect of nanosilica addition on the foaming behavior of PLA.