Effect of functionalized multiwalled carbon nanotubes on the coefficient of thermal expansion of bismaleimide-triazine resins (BT resins)

This paper reports that the functionalized multiwalled carbon nanotube (f-MWCNTs), produced by an oxidative method with a mixture of HNO₃ and H₂SO₄, can lead to enhanced glass transition temperature (T_g) and a significant reduction of the coefficient of thermal expansion (CTE) of the BT resin. The composites containing f7-MWCNTs with high functionalization degree present enhanced T_g. The CTE of composites decreased from an initial value of 67.0 ppm/°C for the neat BT resin to 49.9 ppm/°C with small loading (1.0 wt%) of f7-MWCNTs, which equals to the that of the composite filled with 7.0 wt% of the pristine MWCNTs. The strong enhancement of T_g and lower CTE could be attributed to the low intrinsic CTE of MWCNTs, excellent distribution of f-MWCNTs, and strong interface coupling to matrix materials. The obtained results are important for obtaining high-performance composites in the next generation of integrated circuits, three-dimensional (3D) integration, and semiconductor packages.