▎ 摘　　要

A simple and fast method to prepare high-performance graphene to improve polyolefin performance is highly desirable to fulfil the technical requirements of modern society. In this paper, flake graphite was the main raw material used to prepare thick sheet graphene (TSG). (NH4)(2)PtCl6, H3PO4 and H2SO4 were added to flake graphite to prepare TSG by a hydrothermal method and a high-temperature expansion method. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) results show that the TSG adopted a worm-like structure with large open voids and significantly increased layer spacing, specifically a lamellar structure. TSG/polyolefin composites were prepared by the melt blending method. The XRD results show that melt intercalation of TSG in polyolefin was realized under the action of shear force. When the TSG content was 0.1%, the tensile strength (17.1 MPa), impact strength (58.0 kJ center dot m(-2)) and bending modulus (144.3 MPa) of linear low-density polyethylene (LLDPE) increased by 10.4%, 21.0% and 6.6%, respectively. When the TSG content was 0.1%, the tensile strength (19.9 MPa) and bending modulus (278.9 MPa) of polypropylene random copolymer (PPR) increased by 7.7% and 16.7%, respectively. Differential scanning calorimetry (DSC) test results show that the addition of TSG can effectively increase the crystallinity of polyolefin, and the crystallinity of LLDPE and PPR reached 31.5% and 50.4%, respectively. At the same time, the SEM test results show that the addition of TSG can effectively improve the polyolefin profile.