Abstract: The structure of graphene nanosheets (GNPs) was studied using Raman spectroscopy, TEM, and SEM. The thermal conductivity and mechanical properties of polybutylene terephthalate (PBT) with different carbon fillers (GNPs, carbon fibers, carbon black) were compared. Compared with spherical and rodlike fillers, the sheetshaped GNP resulted in a lower percolation threshold. It found that Y Agari model was in good agreement with the experimental data. Addition of 1 % GNPs made the impact, tensile, and flexural strengths of the composites increased 15 %, 9.6 %, and 16 %, respectively.

Key words: poly（butylene terephthalate）, graphene nanosheet, morphology, thermal conductive property, mechanical property