Morphological analyses of nanocomposites based on TPU and polyhedral oligomeric silsesquioxanes (POSS) was performed using different techniques (transmission electron microscopy, small‐ and wide‐angle X‐ray scattering, differential scanning calorimetry) as a function of molecular weight of poly(ethylene glycol) (PEG) and PEG/POSS mol ratio. A strong interdependence in crystallisation behaviour between the two (POSS and the soft segments of TPU) specified to be able to crystallise in TPU/POSS was found. The mechanical properties determined by using recording microindentation techniques at room temperature were significantly improved by POSS for two material formulations.
A zirconium hybrid polyhedral oligomeric silsesquioxane derivative (Zr–POSS–bisDOPO) is synthesized by the corner-capping and Kabachnik–Fields reactions. It is characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR), and then used as a flame retardant in diglycidyl ether of bisphenol A (DGEBA) to endow epoxy resin (EP) with flame retardancy. The flame retardancy, thermal stability, and mechanical properties of the cured EP/Zr–POSS–bisDOPO composites are investigated. The results show that when Zr–POSS–bisDOPO is added by 5–7 wt%, the EP/Zr–POSS–bisDOPO composites pass the UL-94 V-0 rating test. In addition, they have a better flame-retardant effect than pure EP. The combination of Zr atom embedded in the Si O cubic cage and the two phosphaphenanthrene substituent groups in one corner of cubic cage is expected to realize the Zr/Si/P ternary intramolecular hybrid synergistic effect and achieve the possibility of dispersing metal–POSS cages at a sub-micrometer-scale level into polymer matrix. It also proves that Zr–POSS–bisDOPO produces phosphorus-containing free radicals and terminates the chain reactions in gas phase. Meanwhile the Si O Si and Zr O units are retained in the solid phase, which promote the char formation and enhance the flame retardancy. This kind of Zr-doped POSS will be helpful for developing the new metal–POSS hybrid flame-retardant and polymer composites. 相似文献
Summary: Hybrid polyester resins containing polyhedral oligomeric silsesquioxanes (POSS), and their polyurethanes were prepared using reactive POSS as a substitution for partial diol monomer. They were investigated by FT‐IR, rheometry, dynamic mechanical analysis, wide‐angle X‐ray diffraction, contact‐angle measurement, atomic force microscopy, and thermogravimetric analysis, respectively. The results showed that the hybrid polyester‐POSS resins had a shear thinning behavior, and the more the POSS was embedded, the stronger the shear thinning behavior, and the higher the viscosity. Incorporation of POSS could increase the glass transition temperature and thermal stability and decrease the surface free energy of the polyurethanes. When the POSS content was relatively high, the POSS molecules in hybrid polyurethane‐POSS had a strong self‐assembling ability to form nanocrystalline domains.
