Creep behaviour of elastomeric nanocomposites by flat punch indentation: Influence of graphene modification and content

Creep can be understood as the resistance of a material to a continuous stress and represents an important property for engineering design. The creep behaviour of a series of nanocomposites with electromechanical applications based on a thermoplastic elastomer, poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS), and small amounts of graphene has been explored using cylindrical flat punch depth-sensing indentation. Special attention is paid to the influence of the nature of the polymer brushes (polyethylene or polystyrene) attached to the graphene surface. Common methodologies for indentation creep analysis are critically examined and brought together to provide a comprehensive picture of creep deformation. It is found that graphene significantly reduces the creep rate and this is most significant under viscoplastic deformation than in the linear viscoelastic regime. Most interesting, polyethylene branches reduce visco-elastic-plastic flow in a more effective manner and this is attributed to the selective interaction of the filler with the matrix chains.Financial support from MINECO (Ministerio de Economía y Competitividad), Spain, under grants MAT2013-47898-C2-1-R, MAT2013- 47898-C2-2-R and MAT2017-88382-P is gratefully acknowledged