Preparation And Study On The Structrue And Properties Of High Performance Epoxy Resin And Epoxy Composites

There is a close relationship between the structure and properties of materials; therefore, it has long been a hot topic in materials science about the preparation of advanced materials with multi-functional properties through ingenious molecular design, on the basis of well characterization and understanding about the microstructure of materials as well as the corresponding mechanism of formation. In this thesis, multi-scale solid-state NMR techniques, combined with several other characterization techniques, were employed to investigate the microphase separation, interphase structure, dynamics of different components and the mechanisms for the formation of different microphases in the epoxy resin/block copolymer (ER/BCP) blends. Meanwhile, we synthesized advanced epoxy resin and polyurethane/epoxy composites by adopting the idea of the bionic designs inspired by biomaterials.(1) A variety of multi-scale solid-state NMR techniques were used to characterize the heterogeneous structure and dynamics of the interphase and cross-linked network in nanostructured epoxy resin/block copolymer (ER/BCP) blends, focusing on the role of ER-miscible blocks containing poly(ε-caprolactone)(PCL) or poly(ethylene oxide)(PEO) blocks having different intermolecular interactions with ER.1H spin-diffusion experiments indicated that the interphase thickness of PEO-containing blends is obviously smaller than that of PCL-containing blends. High-resolution1H fast MAS spin-exchange experiments revealed detailed interfacial mixing between ER and BCPs for the first time, and two different types of interphase structure were found.1H fast MAS DQ filter experiment provided a fast and convenient way of characterizing interphase composition, including immobilized BCPs and partially cured or local damaged ER networks. The driving force for the interphase formation and miscibility in PCL-containing blends was successfully determined by high-resolution13C CPMAS experiments, demonstrating that the formation of hydrogen bonds between PCL and ER, and competing hydrogen bonding interactions, were also found when ER was blended with PEO-b-PCL (EOCL). A new calculation method was proposed to quantitatively determine the distribution of different blocks in the interphase and dispersed phase for PCL-containing blends in combination with13C CPMAS and1H spin-diffusion experiments.13C T1spin-lattice relaxation experiment provided a quantitative determination of the amount of local destroyed network in the interphase. Furthermore, it was found that the incorporation of BCPs induced unexpected enhanced rigidity of cross-linked network. On the basis of NMR results, we proposed a model to describe the unique structure and dynamics of the interphase and cross-linked network as well as their underlying formation mechanism in ER/BCP blends.(2) The self-healing ability of biomaterials has attracted much attention of scientists, and many efforts have been put on developing advanced materials with this ability. Herein, a precise molecular structure was designed to prepare the thermally reversible epoxy resin (DAERs). Furan and maleimide functional groups were incorporated onto the side chains of DAERs, and thus DAERs possessed high mechanical performance, good heat-resistance and recyclability owing to the reversible covalent cross-linked sites on side chains, which were well characterized by DSC, in-situ solid state NMR, DMA and some other techniques.(3) Inspired by nature, such as the self-healing ability of biomaterials, hierarchical structure in spider silk and organic-inorganic hybrid properties in shells, cross-linked polyurethane/epoxy resin composites (DAPUERs) were prepared through incorporating maleimide and furan functional groups onto the side chains of linear segmented polyurethane and rigid epoxy resin, respectively. DAPUERs exhibited good thermal remendability and recyclability based on reversible Diels-Alder (DA)/retro-DA reactions, and their mechanical properties were optimized by changing soft segment structure, and incorporating inorganic nano-clay. Thus, reversible cross-linked composites showed good mechanical performance, solution-/heat-resistance and recyclability, as well as expected microscopic molecular structures, which were determined by DSC, DMA, TEM and in-situ solid state NMR. It can be well expected that such multi-step design method for preparation of DAPUER materials, combining special molecular structures, micro structures and organic-inorganic hybrid into one material, will provide new insights into preparing novel advanced materials.