Design,Preparation And Performance Of Halogen-Free-Resistant Phosphazene-Based Epoxy Resin And Bifunctional Phase-Change Energy-Storage Materials

Environment pollution and resources shortage are two urgent problems faced by human society, which results in the sustainable development become a general principle for strategic consensus of global development and guilding of social and economic development. As a result, the development of green chemistry, exploit of environmentally friendly materials and renewable energy, and improving energy efficiency have become one of the most important responsibility for scientist and attracted much attention. This research based on green chemistry and regarded the novle materials in the field of sustainable development which included environmental-friendly with high performance and renewable energy as the starting point. The main content includes two parts: synthesis of halogen-free resistant phosphazene-based functional epoxy material and preparation of bifunctional phase-change microcapsules for improving solar energy utilization efficiency.Molecular and structural design, synthesis and process development,performance characterization, and mechanism of reaction were investigated which are challenged the difficult problem of "green chemisry”.In chapter II to IV, three different molecular structures of phosphazene-based functional epoxy materials included cyclolinear-,cyclospiro- and linear- were designed and synthesized. The chemical structure of final product was characterized by Nuclear Magnetic Resonance spectroscopy and Fourier Transform Infrared Spectroscopy(FTIR). Three kinds of phosphazne-based compound were cured with conventional epoxy resin and then the thermosets were prepared, and their non-isothermal and isothermal curing behaviors were investigated.Thermal stability of the epoxy thermosets was analyzed by differential scanning calorimeter (DSC) and thermal gravimetric analyzer (TGA), and the flame retardancy was investigated by limiting oxygen index and vertical combustion test. The results demonstrated that the thermosets not only maintained a high thermal stability, but also exhibited excellent flame-retardant properties. The flame-retardant mechanism study examined by scanning electron microscope (SEM), FTIR and solid-state NMR, and the results showed that solid and gas phase flame-retardant mechanism were included. Phosphazene structure colud effectively enhance the formation of phosphorus-rich char and releasing some nonflammable gases during the combustion of the resulting thermoset.The formed char layer and releasing nonflammable gases could act as an insulation layer to shield the materials and dilutile the oxygen in air, and then achieved the excellent flame resistance. These results demonstrated that three kinds of molecular structure for phosphazene-based functional epoxy materials not only presented halogene-free resetant properties, but also showed an improvement in mechanical property, thermal resistance and stability than traditionally functional epoxy resin.In chapter V, the microencapsulated phase-change materials with bifunctionality for solar thermal energy storage and solar photocatalysis was prepared, and their structure design, synthesis, performance and related mechanism were investigated. The microcapsules were tailored by encapsulating an n-eicosane phase-change material into CdS/SiO2 through interfacial polycondensation and in-situ precipitation. The morphology and microstructure of microcapsules were investigated by SEM and transmission electron microscope (TEM), and their chemical structure were analyzed by FTIR, energy dispersive X-ray (EDX) and X-ray diffraction (XRD). The phase-change behaviors and thermal stability of phase-change microcapsules were characterized by DSC and TGA. Meanwhile, the energy storage properties, optical performance and thermal regulating performance of phase change materials were also investigated. These results showed that an excelent solar energy storage and good photocatalytic degradation of organic dye of methylene blue under the nature light after microencapsulated phase change materials with cadmium sulfide. Furthermore, n-eicosane@SiO2@CdS achieved a photoluminescence characteristic and good reversibility;In the VI chapter, the organic phase-change materials encapsulated by TiO2 for the enchancement of solar thermal energy storage and solar photocatalysis were prepared, and their preparation design, performance and related mechanism were investigated. The microcapsule system presented a spherical and core-shell structural morphology, where graphene nanosheets were attached to the microcapsule surfaces through hydrogen bonding. The microcapsule system achieved phase-change enthalpies over 160 J/g, and their thermal conductivity was also improved due to the introduction of graphene nanosheets. This study confirmed that the introduction of graphene nanosheets was effective way not only improve the structural stability and serving durability of the microcapsule system, but also to enhance its photocatalytic activity by promoting the electrons transfer and charges separation of TiO2.In chapter VII, the structure design, synthesis technology and performance for organic phase-change materials encapsulated by TiO2 were investigated, and the key research was focused on their formation mechanism. The microencapsulated n-eicosane with amorphous Ti02 was synthesized also through hydrolysis reaction by raw material of tetrabutyl titanate in the first place. And then different morphology and crystalline titanium dioxide of n-eicosane@Ti02 phase change microcapsules were acquired by the change additive amount and order of NH4F and NaOH solution. The SEM and TEM results showed that the microcapsules phase change materials with morphology of microtube, microtube-octahedron and octahedron were successfully synthesized. XRD results indicated that these three different microstructures of microtube, microtube-octahedron and octahedron correspond to TiO2 (B)-form, TiO2 (B)-brookite-form and brookite-form crystals, respectively. The phase change behaviors and thermal stability of microcapsule samples with different morphology were investigated. The infrared thermography, rapid heating and cooling process testing results indicated that the morphology of octahedron microcapsules achieved best energy-storage and thermal regulating performance. Meanwhile, the photocatalytic activity of microcapsules was investigated by UV photodegradation of rhodamine B.Three kinds of bifunctional phase-change microcapsuels designed and developed form chapter V to VII not noly enhanced the solar thermal energy and solar photochemistry unlitization efficiency for traditional phase-change materials, but also provided important scientific basis for multiphase and multi-component phase-change energy-storage materials function and structure design. Moreover, the study of synthesis and bifunctional effect mechanism provided a key theroretical guidance for the development and ultization of new energy multifunctional materials.These three kinds of phase-change energy-storage materials achieved a different bifunctional or multifunctional characteristic compared with traditional phase-change materals, which showed a boraden application prospect in the field of solar ultilization efficiency for further improvement.