Preparation And Properties Of Polyphthalonitrile/H-BN Nanocomposites And Polyphthalonitrile Copolymers

Polyphthalonitrile is a novel class of high-performance thermosetting resin prepared from the addition-type polymerization between adjacent nitrile groups on the phthalonitrile monomer.In recent years,polyphthalonitrile materials have attracted more and more attention for its excellent thermal and thermo-oxidative stability,moisture resistance,flame retardancy,and mechanical properties.However,the polyphthalonitrile resin also has some disadvantages of high brittleness and low intrinsic thermal conductivity,which greatly limit its applications.New resins have been synthesized from the point of view of molecular design to overcome the shortcomings of polyphthalonitrile.The composite is expected to not only maintain some excellent properties of the matrix material,but also make up the defects of materials.So it is important and highly feasible to selectively add inorganic fillers to prepare nanocomposites.The characteristics of small particle size,large specific surface area,and good insulativity provide better conditions for improving the properties of polymer matrix.The boron nitride with hexagonal lattices(h-BN)possesses high thermal conductivity and excellent thermal stability.Therefore,it is an ideal nano-filling material for composites.The main research work of this paper is summarized as follows:(1)Polyphthalonitrile/BN nanocomposites were prepared by using catechol-based phthalonitrile resin as matrix and h-BN nanoparticles as filler materials for the first time to improve the toughness and thermal conductivity.The silane coupling agent(KH550)was used to modify the surface of BN to enhance the repulsive force between particles and to enhance adhesion with the matrix,and the thermal conductivity mechanism of nanocomposites was investigated.The thermal conductivities of composites reached 0.79W/(m?K),which was 3.6 times as much as that of the neat resin,and conformed to the Cheng-Vachon model by fitting the measured values into several heat conduction models.The three-point bending test showed that the toughness and strength were improved at the same time and toughening mechanism was explored by using scanning electron microscope.The h-BN nanoparticles can not only improve the thermal conductivity of the resin but also enhance its mechanical properties.III(2)The phthalonitrile monomers based on poly(aryl ether sulfone)oligomers were successfully synthesized by using bisphenol A,bis(4-chlorophenyl)sulfone and 4-nitrophthalonitrile.The number of repeat units equalled 9.25 which can be calculated by using the ~1H NMR spectrum.A series of polyphthalonitrile copolymers were prepared by uniformly blending oligomeric monomers with catechol-based phthalonitrile through an aqueous mixing method.The results showed that with the increase of the ratio of the oligomeric monomer,the melting temperature of the blended monomer decreased and the crosslinking reaction temperature gradually increased.The storage modulus of copolymers is higher than that of catechol-based polyphthalonitrile and the maximum increase is 537MPa.