Fabrication of Hollow Polyimide Microspheres with Controllable Sizes

Lightweight and excellent thermal stability hollow polyimide (PI) microspheres play an important role in high-end engineering applications such as aerospace, marine use among others. Herein, a simple approach is proposed to scalable fabrication of hollow PI microspheres with controllable sizes by powder foaming method combined with gradient heating strategy. The diameter of PI microspheres ranges from 295.5 to 1479.6 µm with a wall thickness of ≈7.78 µm. Interestingly, the diameter of PI microspheres exhibits a good correlation with the size of polyester ammonium salt (PEAS) particles. The hollow PI microspheres demonstrate excellent heat resistance with a bulk density ranging from 56.9 to 132.2 kg m –3 . Furthermore, PI microspheres could be readily converted into carbon microspheres without destroying their original integrity, which shows potential applications in preparing multifunctional composites. The proposed method is easily scalable which can be adopted to fabricate hollow PI microspheres at large quantities for industrial applications.