Study On Preparation And Properties Of TiO₂/PU-EP Composites

Thermosetting epoxy resin are widely used in aerospace, military,electronics, construction, etc., because it has outstanding thermal properties,mechanical properties and electrical insulation properties. In the field of polymerresin are dominant, the comprehensive performance of epoxy resin were putforward higher requirements with the development of high and new technology.PU-EP precursor was prepared by epoxy as matrix, methyl tetrahydrophth-alic anhydride as the curing agent, polyurethane as toughening agent. PU-EP wasused as organic pure polymers, nano-TiO₂is modified by the silane couplingagent （KH-550, KH-560and KH-570） and titanium acid ester201（TCA201） forinorganic filler, and TiO₂/PU-EP composite material was prepared, Its purpose isto enhance the mechanical properties and thermal stability of the compositematerials, improve the comprehensive properties of composites.The micromorphology of pure TiO₂and TiO₂modified by different couplingagent was observed by FT-IR, SEM and TEM, the results showed that surface ofTCA201-TiO₂have more active group, particle was loose, particle interactionscould abate, dispersed more evenly.Aggregation structure and energy spectrum analysis of TCA201-TiO₂/PU-EP composite were studied by SEM, AFM. The tensile properties of thecomposite materials were studied by electronic universal tensile testing machine,The viscoelastic of composite was analyzed by DMA. Thermal performance ofcomposite was tested by TGA, The dielectric performance of composite materialwas studied by the pressure tester and dielectric spectrometer. The resultsindicated that nano-TiO₂evenly dispersed in the PU-EP matrix. Betweenpolyurethane with soft chain and epoxy resin with an active group were crossedlinked network through the chemical bonds. The "island structure"could be seenfrom the microscopic structure of cross linked.The shear strength of composite material was enhanced firstly and then weakened with the increase of the nano-TiO₂content and reaches the maximum27.14MPa for the mass fraction of3wt%.That was increased by22.6wt%than PU-EP（22.13MPa）. The glass transitiontemperature of composites was20℃-86.3℃, the glass transition to the rubberystate is86.3℃-100.7℃, The glass transition temperature was92.4℃, Thethermal decomposition temperature of the composite was increased firstly andthen decreased, when addition of the inorganic nanometer TiO₂is3wt%, thermaldecomposition temperature reached the maximum397.82℃, that was improvedby17.48℃than that of PU-EP. The dielectric constant and dielectric loss factorof TiO₂/PU-EP composite monotone rise with the increasing of nano-TiO₂addingquantity, Volume resistivity and surface resistivity showed drab downward trendcompared to PU-EP, The breakdown field strength of TiO₂/PU-EP composite waslower than PU-EP. The dielectric constant of the composite was4.27, Thedielectric loss of the composite was0.02, The volume resistivity of thecomposites was6.31×10¹³·m, The surface resistivity of composite was9.96×10¹⁵·m², The breakdown field of composite was14.0319kV/mm, whenthe content of TiO₂was3wt%.