In situ synthesis of MWCNT-graft-polyimides: thermal stability, mechanical property and thermal conductivity

Herein, MWCNT-graft-polyimides (MWCNT-g-PIs) were prepared by the in situ grafting method. Strengthening the interfacial interaction between MWCNTs and polyimide chains decreased their interfacial thermal resistance (RC). In contrast to the RC of 10% MWCNT/PIs, the RC of 10% MWCNT-g-PI decreased by 16.7%. Hence, MWCNT-g-PIs possessed higher thermal conductivity than MWCNT/polyimides (MWCNT/PIs). Meanwhile, the Tg values of all the samples (MWCNT/PIs and MWCNT-g-PIs) were greater than 399 °C (by DMA). Compared with MWCNT/PIs, 5% and 10% MWCNT-g-PIs showed enhancement in thermal stability in air. The storage modulus retentions were greater than 63% at 200 °C and 45% at 300 °C. Also, 5% and 10% MWCNT-g-PIs maintained the high tensile strength of pure PI, and the tensile modulus increased up to 2.59 GPa on increasing the loading amount of MWCNTs. This study sheds light on improving the thermal conductivity of polyimides effectively at relatively low loadings.