Study On The Synthesis And Properties Of Benzoxazine/T₇POSS Composites

As a novel developing material, Organic-inorganic hybrids have attracted much attention recently, owing to their possession of toughness, well processing, low cost of organic polymer and high strength, high heat resistance of inorganic material. Polyhedral oligomeric silsesquioxane (POSS) is a hybrid of organic-inorganic components, including condensed and incompletely condensed structure. It has an inorganic (SiO1.5)n core, which is surrounded by organic groups. The inorganic core provides it with high thermal stability, while the organic groups endow it with good compatibility with the organic matrix, as a result, interreaction of the interface of organic and inorganic components are increased and comprehensive capabilities of materials are improved. However, lots of factors have affected POSS synthesis, and the synthetic technologies have been still not mature, which restrict the further study and development of POSS. Therefore, it is necessary to study the synthetic conditions and influencing factors.Tri-hydroxyl incompletely condensed POSS (T7POSS) was synthesized by the hydrolysis and condensation of phenyltrialkoxyarylsilane monomer in this paper. Optimum synthetic conditions were determined after yields and GPC analysis used to evaluate the effects of experimental parameters on the synthesis reaction. The conpounds were charactered by FTIR、29SiNMR、MS、GPC、XRD, which showed the incompletely condensed cage structure of T7POSS.Isothermal differential scanning calorimetry (DSC) was used to study the curing behavior of bisphenol-A type benzoxazine and BZ/T7POSS hybrid resins. The results showed that the cure reaction of benzoxazine could be catalyzed by the weak acidic function Si-OH on T7POSS. The initiative curing temperature of hybrid resins was declined, curing exothermic enthalpy was enhanced, curing reaction temperature range was broadened after adding T7POSS to BZ.Curing kinetics of BZ and BZ/T7POSS hybrid resins was studied by the nonisothermal DSC. The apparent activation energies and reaction order of both systems were obtained by Kissinger and Ozawa equation and curing kinetic equation was calculated. The result showed that the apparent activation energy of hybrid resin was declined and reaction order was increased after adding T7POSS.Uniform hybrid resins were prepared by blending of T7POSS and thermosetting BZ resin, which were cured afterward to obtain organic-inorganic hybrid PBZ/T7POSS composites in which T7POSS was dispersed uniformly. Thermal and dynamic mechanical capability of cured composites were studied, which showed that the glass transition temperature, dynamic storage modulus were improved sharply and thermal stability was elevated after adding T7POSS comparing to BZ resin.