Preparation And Modification Of Nanographite Flakes And Their Application In Polyurethane Composites

Nanographite flakes, a rising nanomaterials, possess a unique two-dimensional structure and excellent mechanical, thermal, and electrical properties. Because of their exceptional physical properties, chemical tunability, and potential for applications, there is intense interest in studying of nanogrphite flakes. The transformation of electromagnetic field energy into thermal energy in polar materials, here, using microwave-assisted method, which changes the direction of dipoles of GO by following the direction of the electromagnetic field, transforming the applied microwave energy into thermal energy, microwave expanding and reducing GO(wGO) was produced. EDS, TGA, FT-IR, XRD, Raman spectrum, elementary analysis, TEM and AFM were used either to prove the reduction of the microwave, or to characterize the structure and morphology of the wGO. In addition, the change in particle size distribution and specific surface area of GO and wGO as well as their dispersing performance in the solvents were analyzed. The octadecyl isocyanate modified GO(iGO) was prepared attributing to the derivation of both hydroxvl and carboxyl functional groups via formation of carbamate esters and amides. FT-IR, TGA. XRD and Raman spectrum were applied to analysis the changes of surface chemical groups and structure. Bsides. laser particle size analysis, SEM, AFM and solvent dispersing performance were used to characterize the microcosmic structure of iGO and the effect of modification. Composites of polyurethane elastomer(TPU) with wGO were prepared via in-situ polymerization. The micro phase structure and dynamic performance of composites as well as the dispersing situation of wGO in TPU were characterized by FT-IR. XRD. DSC. DMA or SEM. respectively. Meanwhile, the physical performance enhancement of wGO/TPU nanocomposites was also analyzed. The main research results are as follows:(1) Research shows that the content of oxygen in wGO was significantly reduced and the oxygen polar functional groups on the surface was decomposited under microwave, indicating that microwave have a reduction to GO. What’s more, microwave also has an exfoliating effect and augments the intercalating space of GO. making the particle size smaller and specific surface area larger.(2)Analysis shows that octadecyl isocyanate was covalently bonded to the surface of GO. changing its polarity. And iGO can be sufficiently wetted and stablely dispersed in organic solvent, preventing particle aggregation in a lone time. The configuration of carbon atoms in iGO laminar layer didn’t change after the isocyanate modification, but the layer spacing increase to1.23nm comparing to GO’s.(3)Results show that the nanographite flakes were uniformly dispersed in the composite. Compared with the pristine TPU, the tensile strength is increased by116.1%when the wGO content is3%, and the thermal conductivity is increased by81.6%when the wGO content is5%. Moreover, the percolation threshold of the composite is about2%, making the electrical conductivity improved by106. The internal microphase mixability of wGO/TPU nanocomposites is reduce, causing a higher microphase separation degree. In addition, The nanocomposites possess a higher storage modulus at room temperature.