Processing-Structure-Property Relationships in Polymer/Boron Nitride Nanotube Composite Fibers for Electronic Packaging Applications.

Boron nitride nanotubes are promising materials for polymeric composites due to their electrical insulation and thermal conductivity properties. In this work, boron nitride nanotubes (BNNTs) are dispersed in a polymer solution that is then spun and drawn to make polymeric fibers with aligned bundles of long BNNTs. These polymer/BNNT fibers are then studied to determine the relationship among processing, structure, and properties. A sonication-centrifuge procedure was conducted to preserve longer BNNTs within the polymer structure and improve the alignment of BNNTs within the fiber. Herein, changes in the internal structure of PAN/BNNT fiber are mapped, highlighting the importance of the dry-jet wet spinning air gap and cold and hot drawing stages to achieve high orientation of BNNTs and a higher draw ratio of 25x. These fibers can be used to produce thermally conductive, electrically insulating composites, which have significant applications in electronics. This approach is scalable and can also be used to produce high-performance neat BNNT fibers.