Synthesis And Application Study Of Graphene-like MoS₂/graphene Composites

Bismaleimide?BMI?resin,a class of resin system which is derived from the polyimide resins,exists a lot of rigid groups in its molecular chain structure,such as imide rings and aromatic rings,and has high flexural strength and modulus,good heat resistance,wave transparent and friction performance.The forming process of BMI is similar to that of epoxy resin.BMI is widely used in primary and secondary load-bearing parts in machinery,aerospace,electronics and other areas,also can be used as resin matrix of advanced composite material.At the same time,BMI resin exists the disadvantages of low impact strength,poor solubility,high curing temperature,curing brittleness,easily being broken and so on.All these disadvantages limit the applications of BMI resin,so the modification of BMI is requisite.Graphene,thanks to the unique two-dimensional honeycomb lattice structure and physicochemical properties,has a wide range of applications in the field of materials science,electronic science,biomedicine,catalyst carrier and tribology.However,due to the strong van der Waals force in the layers of graphene,resulting in the poor dispersibility in the solvents and poor compatibility with other materials,seriously restrictinging the applications of graphene.MoS₂ is a typical kind of layered transition metal sulfides with two S atom layers and one Mo atom layer that constitute the “sandwich” structure.Bulk MoS₂ can be exfoliated into the lamellar structure that similars to graphene,and synergistic effect can be achieved between the exfoliated graphene like MoS₂ and graphene.The compatibility in structure and morphology can optimize their friction performance.The study found that the modification of graphene can improve the dispersion in solvents and the compatibility with polymer composites,but the current methods more or less decrease the heat resistance of graphene.Therefore,in this paper,the MoS₂/graphene composites are produced from graphene-like MoS₂ and graphene,and two modification methods are used to modify the as-prepared composite: covalent modification by using silane coupling agent and noncovalent modification by using home-made polyphosphazene polymers.Finally,the modified particles are added into BMI resin to prepare the composites with excellent mechanical properties,friction properties,and thermal performance.The main research contents are as follows:1.Graphene-like MoS₂ was prepared by a low-energy ball milling and ultrasonic method,and composed with graphene oxide to produce GO/MoS₂ nanocomposite particles which was further surface modified by silane coupling agent ?-aminopropyltriethoxysilane,namely NH₂-r GO/MoS₂.Finally,NH₂-r GO/MoS₂ was added to BMI resin to prepare nanocomposites.The effects of NH₂-r GO/MoS₂ contents on the impact and flexural strengths of NH₂-r GO/MoS₂/BMI nanocomposites were studied.When the filler content was 0.6 wt%,the impact strength and flexural strength of the NH₂-r GO/MoS₂/BMI composites reached the maximum: 18.4 k J/m2 and 161.4 MPa,respectively,increased of 40.5% and 32.3% compared to 13.1 k J/m2 and 122.0 MPa of pure BMI resin,respectively.But with the addition of NH₂-r GO/MoS₂,the impact strength and flexural strength decreased gradually,indicating that the NH₂-r GO/MoS₂ has the function of reinforcing and toughening.In addition,the tribological properties of the composites with different NH₂-r GO/MoS₂ contents were studied.After the addition of NH₂-r GO/MoS₂,the friction coefficient and the volume wear rate of the composites decreased obviously.When the added amount of NH₂-r GO/MoS₂ are 0.4 wt% and 0.6 wt%,the friction coefficient of NH₂-r GO/MoS₂/BMI reached 0.20,decreased by 56.5% compared to 0.46 of pure BMI resin,the volume wear rate of NH₂-r GO/MoS₂/BMI reached 2.89×10-6 mm3/?N·m?,decreased by 82% compared to 16.35×10-6 mm3/?N·m?of pure BMI resin.But with the further addition of NH₂-r GO/MoS₂,the friction coefficient and volume wear rate increased.The study also found that the addition of NH₂-r GO/MoS₂ enhanced the thermal stability of NH₂-r GO/MoS₂/BMI composites.2 rGO/MoS₂ composites were noncovalent modificated by PZD to produce PZD/r GO/MoS₂.PZD/r GO/MoS₂/BMI composites with different PZD/r GO/MoS₂ contents were produced from PZD/r GO/MoS₂ as reinforcement and BMI resin as resin matrix.The mechanical properties,friction properties,and thermal performance were investigated in the same conditions.When the mass fraction of PZD/r GO/MoS₂ was 0.6 wt%,the impact strength and flexural strength of the PZD/r GO/MoS₂/BMI system reached the maximum,15.98 k J/m2 and 179.32 MPa,respectively,increased of 21.25% and 46.86% compared to the pure BMI resin,respectively.When PZD/r GO/MoS₂ dosage was 0.4 wt%,the friction coefficient of PZD/r GO/MoS₂/BMI was 0.06,decreased by 56.5% compared to that of the pure BMI,the wear volume rate of 0.4 wt% PZD/r GO/MoS₂/BMI composite was 1.80×10-6 mm3/?N·m?,decreased by 89% compared to that of the pure BMI.The study also found that the addition of PZD/r GO/MoS₂ enhanced the thermal stability of BMI resin,and PZD/r GO/MoS₂/BMI composites showed better thermal performance than NH₂-r GO/MoS₂/BMI composites.The reseach results showed that the as-prepared PZD/r GO/MoS₂ composites have better mechanical properties,friction properties,and thermal performance than NH₂-r GO/MoS₂/BMI composites.