▎ 摘　　要

NOVELTY - Composition containing graphene and graphene nanoplatelets durably dispersed in a solvent, comprises (a1) containing at least 1 wt.% of a vinyl aromatic polymer based on total weight of the solvent, and (b1) graphene and graphene nanoplatelets (GRS) at 0.001-10 wt.% by weight, based on total weight of the solvent. USE - The composition is useful in polymer composites or polymer nanocomposites or master-batch which is useful in expandable polymer composites or expandable polymer nanocomposites (all claimed) which are useful in electronic applications, for preparing polymer granules, manufacturing products or expanded polymer articles, expanded polymeric foams. ADVANTAGE - The composition provides polymer composites or polymer nanocomposites or master-batches having high mechanical performances, a high thermal resistance, antistatic capabilities, electromagnetic insulation properties, or having a high thermal conductivity; and articles and expanded polymeric foams having a high thermal insulation capacity, thermal resistance and high mechanical performances. DETAILED DESCRIPTION - Composition containing graphene and graphene nanoplatelets durably dispersed in a solvent, comprises (a1) containing at least 1 wt.% of a vinyl aromatic polymer based on total weight of the solvent, and (b1) graphene and graphene nanoplatelets (GRS) at 0.001-10 wt.% by weight, based on total weight of the solvent. The vinyl aromatic polymer is obtained by partial or total polymerization of the related vinyl aromatic monomer alone or in mixture up to 50 wt.% with further copolymerizable monomers, and with the condition that the sum of the possible content of the non-reacted monomers and of the content of the vinyl aromatic polymer formed is equal to at least 10 wt.% with respect to the total weight of the solvent. INDEPENDENT CLAIMS are also included for: (1) preparing the composition at least partially polymerized, containing graphene and graphene nanoplatelets durably dispersed in a solvent, starting from graphite material, comprising: (a) putting into contact the graphite material with a main solvent comprising at least 10 wt.% of a vinyl aromatic monomer alone or in mixture up to 50 wt.% with additional copolymerizable monomers, forming a starting composition; and (b) subjecting the starting composition to ultrasounds, characterized by a frequency spectrum of 18-1000 kHz, and a pressure greater than or equal to 2 bar absolute and in a container or sonication chamber where in contact with the composition a separated phase of fluid at the gaseous phase must not be present, and the process is characterized in that at least 1% of the vinyl aromatic monomer present in the main solvent is polymerized; (2) polymer composites or polymer nanocomposites or master-batch comprising the composition; and (3) expandable polymer composites or expandable polymer nanocomposites containing the composites or polymer nanocomposites or master-batch and at least an expanding agent.