Graphene nanosheets (GNS) with and without surface functionalization were used as the reinforcements to prepared the composites with thermoplastic polyester elastomer (TPEE) by melting mixing. The results show that the presence of GNS improves modulus, yield and tensile strengths of TPEE, and the surface functionalization of GNS further improves its reinforcing effect because of enhanced interfacial interactions. However, the elongation levels also increase in the presence of GNS, which indicates the increased elastoplasticity and viscoplasticity of system. This is because the discrete hard poly(butylene terephthalate) domains of TPEE are enriched on the surface of GNS and form ‘ball bearing’ structure in composites, leading to increased deformation ability of soft continuous poly(tetramethylene glycol) of TPEE during large-scale deformation. Thus, the composites show more amounts of tensile cycles with shorter true strain plateau associated with onset of chain disentangling during cyclic tensile tests. This ‘bearing ball’ effect, however, is not evident in small-scale viscoelastic deformation because the presence of GNS restrains creep of TPEE. In this case, the impeding effect of GNS on the deformation of TPEE chain coils is the dominant role. This work provides useful information on structure design and control of the GNS filled thermoplastic elastomer composites.

http://www.sciencedirect.com/science/article/pii/S0266353816303049