Construction of carbon nanotubes/bismaleimide composite films with superior tensile strength and toughness

Abstract Carbon nanotubes (CNTs) have been considered as promising reinforcements for various composites due to their excellent mechanical properties. However, preparation of high-performance CNT/resin composites still suffers from bad dispersion, low fraction, and poor alignment of CNTs and their weak bonding with the resin matrix. Herein, we report an effective strategy towards preparing CNT/Bismaleimide (BMI) composite films with excellent mechanical properties. Firstly, from floating catalytic spray pyrolysis, CNTs are deposited on a water soluble substrate as a thin film to maintain their original microstructures. The films are then stacked layer by layer and pulled in tension with the substrate dissolved in water. The pristine stacked films are immersed in BMI solutions of different concentrations and stretched to different strains for simultaneous CNT reorientation and resin infiltration. The films are finally pressed at low temperature for resin permeation and redistribution and high temperature for resin curing. The determining factors such as the alignment and mass fraction of CNTs and the distribution of BMI resin in the composite film can be easily tailored. Benefiting from the resultant excellent CNT alignment, high CNT content (61.4 wt%), and uniform distribution of the resin between CNTs, the composite film can achieve excellent mechanical properties, including a tensile strength of 4.18 GPa, elongation at break of 4.35%, Young's modulus of 145 GPa, and toughness of 94.2 J cm−3. Such a strength and toughness are superior to those for the CNT composites published in the literature so far.