Preparation, Structure And Properties Of High Performance Polymer Nanocomposites

High-performance polymer composite material, with its exceptionally good high specific modulus, high strength, and excellent high temperature performance, versatility, becomes the major material of defense and space programs, and plays an important influence in national economy, especially the aircraft, sports goods, textile machinery and ground transportation tools. As all the industries continues to improve, the consumption and requirement on properties of composite materials increased with time. In order to provide the technical rationale for the development of high-performance composite materials, research in the basic sciences and engineering needs further.For this purpose, Benzoxazine (Ba) and Poly ether ether ketone (PEEK) were selected as representations of high-performance thermoset and thermoplastic polymers as the base material in this paper. By modificating the excellent dispersion properties and matrix compatibility of graphene nano-fillers, nano-sized multifunction modification on the high-performance polymer matrix becomes more effective. The prepared high-performance polymer nanocomposites are carried out the research on material design, preparation technology, the relationship of structure and properties and modification mechanism to provide theoretical basis for nano-modified high-performance polymers.(1) Graphene with different reduction level were synthesised by redox. FTIR, EDS, TGA, DSC test results showed that, after42h reduction, oxygen-containing functional groups gradually replaced and the oxygen content lowers6.22%, and thermal performance significantly enhanced with the initial decomposition temperature raised from55℃to221℃. The microscopic dispersion morphology was observed by SEM and AFM. With the increasing level of reduction, exfoliated graphene sheets stack firstly reduced and then increased to aggregate, and the average size decreased90%. Dispersion performance was tested by UV-vis absorption spectra and digital camera.The results showed that after24h reduction, the graphene showed the best dispersion, with the maximum of absorption peak wavelength and absorption.And the dispersion performance increasee firstly and deteriorated further with the increasing reduction level,under different dispersion conditions like,different solvents, stewing time and concentrations.According to the analysis of characterization results, the effective force of oxygen-containing functional groups on the graphene layer surface,which can also discribed as a value of electrostatic force under unit slice area of the oxygen-containing functional groups may get to the maximum after24h reduction. It cauesd the optimum dispersion properties of graphene in an aqueous solution.(2) Nano-modified thermosetting resins, polybenzoxazine/modified graphene (PBa/iGO) Nano Composite materials were prepared by Ultrasonic melt blending method. DSC showed that the curing temperature of benzoxazine can be efficiently decreased with the addition of graphene oxide(GO),which can favour the industry curing process. FTIR, DSC were induced to characterize the chemical instruction change as well as the behavior of curing progress. SEM was used to characterize the microstructure of section before and after curing, and it can be observed that iGO were uniformly dispersed and had an good intermiscibility with bulk material.TGA、 DMA were also induced to characterize the thermal properties. It indicated that With the addition of iGO, Tg almost constant, while the thermal stability incrsed.It meant the addition of iGO had little effect on the activity of chains and molecular cross-linking degree.With nano modification,tensile strength increased111.77%,Young’s modulus increased from1517.23MPa to1453.86, and fracture toughness highly increased263.2%with only0.1wt%additon of iGO. Which were significantly enhance effect when compare with the addtion of equivalent amount nmodified RGO.According to the analysis of characterization results, the unformly dispersion and matrix compatibility of iGO had a significant effect on the toughening effect promoting. And toughening mechanisms are mainly the nano-sized nail anchor crack, crack deflection and packing graphene sheets aside curl absorption.(3) Nano-modified thermoplastic resin by sonication and rotary evaporation process to get pre-intercalated structure of graphene sheets and monomers, and then PEEK/RGO composites were prepared under in-situ condensation. XRD, DSC, TGA and other tests have shown that with the increase content of RGO, PEEK molecular weight decreased, crystallization temperature reduced, crystal structure unchanged during the in situ polycondensation process. With0.1wt%addtion of RGO, the crystallinity degree increased8%, and further added RGO hindered segmental motion to decrease crystallinity. Introduced RGO reduced polymer molecular weight, but with their own relatively excellent thermal properties and dispersion, melting point unchanged, and the initial decomposition temperature substantial increased to increase the overall thermal performance of the composite material. Friction performance testing showed that, the coefficient of friction (COF) of PEEK/RGO-0.5wt%fell from0.161to0.078and wear rate decreased80.19%. Combined SEM images of the samples after friction properties test, a preliminary wear resistance improving mechanism of RGO on PEEK was studied. With the addtion of RGO, surface hardness and thermal properties of PEEK icreased, which effectively suppressed the friction surface to soften and break down the wear process. And the relative displacement between the layers of RGO played a solid lubrication, which protect the friction surface of movable PEEK film, hence wear performance of PEEK can be effectively improved.Improvement of preparation process and modification of nanofiller improve the problems of nanoscale dispersion in the matrix, and enhance the interaction between the polymer matrix and nano filler, which more substantially improved the properties of the polymer for more rigorous demanding.