This study investigates the role of polytetrafluoroethylene (PTFE) nanofibers on the peculiar micro and nano foaming behavior of polybutylene terephthalate (PBT) before and after crystallization. In-situ PBT/PTFE nanofibrillated composites were prepared by melt compounding in torque rheometer. A physical network of high aspect ratio PTFE nanofiber is formed as the result of the fibers splitting and entanglement demonstrated by scanning electron microscope (SEM). In molten PBT, the formation of the nanofiber networks significantly increases the melt viscoelastic properties and promotes cell nucleation. As a result, high expansion ratio foams with average cell size of 13 μm were achieved in the melting PBT, which has some guiding significance for the formation of microcellular foam in extrusion foaming process. In addition, the crystallization process and crystallization morphology were investigated by differential scanning calorimeter (DSC), polarizing microscope (POM) and SEM. The crystallization kinetics of PBT were promoted due to the more crystallization nucleation interface provided by the high specific surface area of PTFE nanofibers. In the crystallization process of PBT/PTFE nanofibrillated composites, the PBT molecular chain first crystallized along the surface of PTFE nanofiber to form shish-kebab crystalline structure, and then the PBT molecular chain away from PTFE nanofibers crystallized. Consequently, the shish-kebab crystalline structure and the two-step crystallization induced formation of the peculiar oriented micro and nano cells. The research could present a facile and flexible method to regulate the cell morphology and expand the application of PBT foam.

本研究调查了聚四氟乙烯 (PTFE) 纳米纤维对聚对苯二甲酸丁二醇酯 (PBT) 在结晶前后的特殊微和纳米发泡行为的作用。通过在扭矩流变仪中熔融复合制备原位 PBT/PTFE 纳米原纤化复合材料。扫描电子显微镜 (SEM) 显示，由于纤维分裂和缠结，形成了高纵横比 PTFE 纳米纤维的物理网络。在熔融 PBT 中，纳米纤维网络的形成显着增加了熔体粘弹性并促进了细胞成核。结果，在熔融 PBT 中获得了平均泡孔尺寸为 13 μm 的高膨胀比泡沫，这对挤出发泡过程中微孔泡沫的形成具有一定的指导意义。此外，采用差示扫描量热仪(DSC)、偏光显微镜(POM)和扫描电镜对结晶过程和结晶形貌进行了研究。由于 PTFE 纳米纤维的高比表面积提供了更多的结晶成核界面，因此促进了 PBT 的结晶动力学。在PBT/PTFE纳米纤丝复合材料的结晶过程中，PBT分子链首先沿PTFE纳米纤维表面结晶形成shish-kebab晶体结构，然后远离PTFE纳米纤维的PBT分子链结晶。因此，烤羊肉串的晶体结构和两步结晶诱导了特殊取向的微米和纳米细胞的形成。