The tensile properties of polypropylene (PP) composites filled separately with three kinds of graphene
nano-platelets (GNPs) with different size were measured using a universal materials tester at room
temperature and rate of extension of 50 mm/min. It was found that the values of the Young's modulus of
the composites increased, the values of the tensile yield strength and tensile fracture of the composites
increased slightly while the values of the tensile elongation at break decreased with increasing the GNPs
weight fraction. The reinforcement of the composites could be attributed to the relatively big interfacial
area and good interfacial adhesion between the matrix and the GNPs.