Effect of hyperbranched polyethyleneimine grafting functionalization of carbon nanotubes on mechanical, thermal stability and electrical properties of carbon nanotubes/bismaleimide composites

Hyperbranched polyethyleneimine (PEI) grafted CNTs (CNTs-PEI) were used to reinforce bismaleimide (BMI) composites. The effect of CNTs-PEI on mechanical properties, thermal resistance and electrical conductivity of composites was investigated. Evaluation of mechanical properties showed that the mechanical properties of CNTs-PEI/BMI composites were higher than that of CNTs/BMI composites. A maximum increase of impact strength up to 44% compared with that of pure BMI was observed in CNTs-PEI/BMI composites. The flexural strength of CNTs-PEI/BMI composites reached the maximum of 205 MPa which was much higher than that of CNTs/BMI composites. Similar tendency on the flexural modulus of the composites was observed. The maximum Tg of CNTs/BMI composites and CNTs-PEI/BMI composites were 224 °C and 240 °C respectively. Electrical conductivity of CNTs-PEI/BMI composites increased by 14 magnitude compared with pure BMI, while only 8 magnitude increased in CNTs/BMI composites.