Liu Ya, Guan Yanjin, Zhai Jiqiang, Zhang Lei, Chen Fengjiao, Lin Jun
Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061, China.
Polymers (Basel). 2023 Feb 27;15(5):1204. doi: 10.3390/polym15051204.
The isothermal crystallization properties of polypropylene/graphite nanosheet (PP/GN) nanocomposites under supercritical N were systematically studied by a self-made in situ high-pressure microscope system. The results showed that the GN caused irregular lamellar crystals to form within the spherulites due to its effect on heterogeneous nucleation. It was found that the grain growth rate exhibits a decreasing and then increasing trend with the enhancement of N pressure. Using the secondary nucleation model, the secondary nucleation rate for spherulites of PP/GN nanocomposites was investigated from an energy perspective. The increase in free energy introduced by the desorbed N is the essential reason for the increase in the secondary nucleation rate. The results from the secondary nucleation model were consistent with those acquired through isothermal crystallization experiments, suggesting that the model can accurately predict the grain growth rate of PP/GN nanocomposites under supercritical N conditions. Furthermore, these nanocomposites demonstrated good foam behavior under supercritical N.
通过自制的原位高压显微镜系统，系统地研究了聚丙烯/石墨纳米片（PP/GN）纳米复合材料在超临界氮气条件下的等温结晶性能。结果表明，由于石墨纳米片（GN）对异相成核的影响，其导致球晶内形成不规则片晶。研究发现，随着氮气压力的升高，晶粒生长速率呈现先降低后升高的趋势。利用二次成核模型，从能量角度研究了PP/GN纳米复合材料球晶的二次成核速率。脱附氮气引入的自由能增加是二次成核速率增加的根本原因。二次成核模型的结果与等温结晶实验结果一致，表明该模型能够准确预测超临界氮气条件下PP/GN纳米复合材料的晶粒生长速率。此外，这些纳米复合材料在超临界氮气条件下表现出良好的发泡行为。
