▎ 摘　　要

NOVELTY - Nanocomposite compositions based on expandable thermoplastic polymers comprises: a) a polymeric matrix produced by polymerization of a base containing at least one polymerizable monomers; b) an expanding agent (1-10 wt.%), embedded in the polymer matrix; c) an athermanous filler (0.004-15 wt.%), containing nano-scaled graphene plates with a thickness (orthogonal to the graphene sheet) of not greater than 150 nm, an average dimension (length, width, or diameter) of not greater than 10 mu m and a surface area of greater than 50 m2/g. USE - As nanocomposite composition for producing expanded extruded sheets of vinyl aromatic thermoplastic polymers, such as polyethylene (claimed). ADVANTAGE - The composition has improved thermal insulation capacity. The nano-scaled graphene plates has a thickness (orthogonal to the graphene sheet) of not greater than 150 nm, an average dimension (length, width, or diameter) of not greater than 10 mu m and a surface area of greater than 50 m2/g. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) expanded articles obtained with the nanocomposite compositions, having a density of 5-50 g/l and a thermal conductivity of 25-50 mW/mK; (2) expanded extruded sheets of thermoplastic polymers containing a cellular matrix having a density of 10-200 g/l, an average cell dimension of 0.01-1 mm and containing the athermanous filler (0.004-15 wt.%), calculated with respect to the thermoplastic polymer, comprising the nano-scaled graphene plates with a thickness (orthogonal to the graphene sheet) of not greater than 150 nm, an average dimension (length, width, or diameter) of not greater than 10 micrometers and a surface area of greater than 50 m2/g; (3) preparing (P1) compositions of expandable vinyl aromatic thermoplastic polymers, in beads or granules, involving polymerizing in aqueous suspension at least one vinyl aromatic monomer, possibly together with at least one polymerizable co-monomer in a quantity of up to 50 wt.%, in the presence of the athermanous filler comprising the nano-scaled graphene plates with a thickness (orthogonal to the graphene sheet) of not greater than 150 nm, an average dimension (length, width, or diameter) of not greater than 10 mu m and a surface area of greater than 50 m2/g and at least in the presence of a peroxide radical initiator system and an expanding agent added before, during or at the end of the polymerization; (4) preparing (P2) in mass the compositions of expandable thermoplastic polymers, in granules or beads, involving in series: i) mixing a thermoplastic polymer in granules/pellets or in powder form or already in the molten state, having an average molecular weight (Mw) of 50000-300000, with the athermanous filler comprising the nano-scaled graphene plates with a thickness (orthogonal to the graphene sheet) of not greater than 150 nm, an average dimension (length, width, or diameter) of not greater than 10 mu m and a surface area of greater than 50 m2/g and with the totality or a part of possible other additives; ii) optionally, if not already in the molten state, bringing the polymeric mixture to a temperature higher than the melting point of the thermoplastic polymer; iii) incorporating in the molten polymer, the expanding agent and possibly the remaining portion or the totality of the other additives; iv) mixing the polymeric composition thus obtained by means of static or dynamic mixing elements; and v) granulating the composition thus obtained in a device which comprises a die, a cutting chamber and a cutting system; and (5) production (P3) of the expanded extruded sheets of thermoplastic polymers, involving: a1) mixing a thermoplastic polymer in pellets or granules or beads and at least the athermanous filler comprising the nano-scaled graphene plates with a thickness (orthogonal to the graphene sheet) of not greater than 150 nm, an average dimension (length, width, or diameter) of not greater than 10 micrometers and a surface area of greater than 50 m2/g; b) heating the mixture (a1) to a temperature of 180-250 degrees C so as to obtain a molten polymer which is subjected to homogenization; c1) adding to the polymeric melt, at least one expanding agent and possibly the other further additives, for example the flame-retardant system; d1) homogenizing the polymeric melt which englobes at least the expanding agent; e1) homogeneously cooling the polymeric melt (d1) to a temperature of not greater than 200 degrees C and not less than the glass transition temperature (Tg) of the resulting polymeric-composition; and f1) extruding the polymeric melt through a die in order to obtain a polymeric expanded sheet.