New polymeric nanocomposites were prepared by covalent bonding of nanosized octahedral silsesquioxane particles containing reactive glycidyl group to polyamidoimides containing a carboxy group in the pendant chain. The influence of temperature, molecular weight of the polymer, and reaction time on the covalent bonding of polyhedral oligomeric silsesquioxane (POSS) nanoparticles was revealed. The effect of the POSS nanoparticle incorporation on the structure, dielectric and deformation-strength properties, and heat resistance of the new polymeric nanocomposites was examined. 相似文献
Summary: Octaaminophenyl polyhedral oligomeric silsesquioxane (OapPOSS) was used as a crosslinking agent together with 4,4′‐methylenebis‐(2‐chloroaniline) to prepare polyurethane networks containing POSS. Fourier transform infrared spectroscopy (FT‐IR), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) were employed to characterize the POSS‐reinforced polyurethane. The POSS‐containing PU networks displayed enhanced glass transition temperatures (Tgs) and the storage moduli of the networks of the glassy state and rubber plateaus were also observed to be significantly higher than that of the control polyurethane although only a small amount of POSS was incorporated into the systems. The results can be ascribed to the significant nanoscale reinforcement effect of POSS cages on the polyurethane matrix. TGA results showed the thermal stability was also improved with incorporation of POSS into the system.
Dynamic mechanical spectra of PU and PU nanocomposites containing POSS. 相似文献
A series of polyhedral oligomeric silsesquioxane/epoxy nanocomposites (POSS/EP) containing 0 wt%, 5 wt%, 10 wt% and 15 wt% content of POSS were prepared. Mechanical properties were used as the index to show the effect of POSS on the thermo-oxygen degradation resistance of epoxy resin. And the thermo-oxygen degradation mechanism was investigated by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Results showed that the incorporation of POSS into epoxy networks enhanced the thermo-oxygen resistance of epoxy. POSS led to the formation of inert layer on the surface of materials which could protect the internal structure from decomposition. As a result, the retention of mechanical properties of EP/POSS hybrids increased with the POSS content increasing. 相似文献
Polyhedral oligomeric silsesquioxane (POSS)-reinforced epoxy nanocomposites were prepared by reacting commercially available diglycidyl ether of bisphenol-A (DGEBA) and tetraglycidyl diamino diphenyl methane (TGDDM) epoxy resins with 1,1-bis(3-methyl-4-glycidyloxyphenyl)cyclohexane (Cy-Ep) separately and reinforced with POSS nanocluster. POSS (OAPS)-reinforced hybrid Cy-Ep-epoxy resin castings were characterized for their mechanical and morphological properties. The data obtained from mechanical studies indicated that the incorporation of nano OAPS into Cy-Ep modified hybrid systems results in improved stability. Among the epoxy systems studied, the TGDDM-based hybrid epoxy system exhibited higher values of tensile and flexural properties than that of the DGEBA hybrid epoxy system, whereas the impact strength of the DGEBA system was higher than that of the TGDDM system. The dispersion of POSS was confirmed by scanning electron microscopy and visual observation studies. 相似文献
Two types of the epoxy-POSS nanocomposites were prepared and their electrical/dielectric and thermomechanical properties were determined. The mono- and octa-epoxyfunctionalized POSS (POSS,E1 and POSS,E8) were covalently incorporated in the epoxy network matrix DGEBA-3,3′-dimethyl-4,4′-diaminocyclohexylmethane (Laromin C260) as pendant units or as polyhedral junctions, respectively. While the POSS junctions are well dispersed in the hybrid network DGEBA-Laromin-POSS,E8, the pendant POSS aggregate to form large crystalline POSS domains.The properties of the nanocomposites correlate with the morphology. The nanocomposites with inhomogeneously dispersed large aggregates of pendant POSS,E1 show poor properties, including low Tg and thermal stability, and the high dielectric loss factor at higher temperatures. On the contrary, the well homogeneous nanocomposites containing POSS,E8 dispersed units display improved electrical properties in the range of 1–10 wt.% POSS. The hybrid exhibits the high resistivity (1 × 1015 Ω m) and polarization index pi1 characterizing electrical relaxation, as well as the low dielectric loss factor tan δ, mainly at temperatures above 50 °C. Moreover, the material shows improved thermo oxidative stability and enhanced thermomechanical behavior. Consequently, this nanocomposite was proved to be a prospective insulation material particularly for a high temperature electrotechnical application. In contrast to electrical properties being the best at a low POSS content, the thermomechanical properties, such as rubbery modulus and Tg, are gradually improving with increasing POSS content due to growing crosslinking density. 相似文献
Summary: This investigation presents a simultaneous and convenient approach to produce a high‐performance polyimide with a low dielectric constant by introducing the octa‐acrylated polyhedral oligomeric silsesquioxane (methacrylated‐POSS) into a polyimide matrix to form polyimide semi‐interpenetrating polymer network (semi‐IPN) nanocomposites. The differential scanning calorimetry (DSC) and Fourier‐transform infrared (FT‐IR) results indicate that the self‐curing of methacrylated‐POSS and the imidization of polyamic acid (PAA) occurs simultaneously. The morphology of a semi‐IPN structure of polyimide/POSS‐PI/POSS nanocomposites with POSS nanoparticles embedded inside the matrix is elucidated. The POSS particles are uniform and are aggregated to a size of approximately 50–60 nm inside the polyimide matrix. The interconnected POSS particles are observed at high POSS content. The structure is highly cross‐linked, so the PI/POSS nanocomposites have an enhanced glass transition temperature. The high porosity of the PI/POSS nanocomposites markedly reduces the dielectric constant of PI because of the nanometer‐scale porous structure of POSS.
FT‐IR spectra of the various compounds of A) methacrylate‐POSS before curing, B) methacrylate‐POSS after curing, C) PAA containing 15 wt.‐% POSS, and D) PI/POSS containing 15 wt.‐% POSS. 相似文献
<正>Low-dielectric-constant poly(acetoxystyrenezhi-co-octavinyl-polyhedral oligomeric silsesquioxane)(PAS-POSS) organicinorganic hybrid nanocomposite was successfully synthesized via one-step free radical polymerization and characterized by FTIR,high-resolution ~1H NMR,~(29)Si NMR,DSC,TGA,AFM,spectroscopic elhpsometry and dielectric constants measurements. The results show T_g and T_(dec) were elevated dramatically due to the incorporation of inorganic POSS cores.Spectroscopic ellipsometry and dielectric constants measurement display the incorporation of POSS into PAS homopolymer can apparently reduce the dielectric constant of materials due to the increase of relative porosity of the hybrid nanocomposites. 相似文献
Abstract A novel polyhedral oligomeric silsesquioxane/polymethyl methacrylate (POSS/ PMMA) hybrid nanocomposite was synthesized by using potassium persulfate and sodium dodecyl sulfate as the initiator and emulsifier, respectively. The structures of prepared nanocomposites were characterized with X-ray photoelectron spectroscopy, laser particle size analysis, and X-ray diffraction. The thermal properties of the POSS/PMMA nanocomposites were studied by differential scanning calorimetry, and thermogravimetric analysis. The results indicate that POSS could be incorporated into the PMMA matrix at molecular lever and the incorporation of POSS molecules can improve the thermal stability of PMMA. [Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the following free supplemental files: Additional figures] 相似文献
The novel poly-benzoxazinyl functionalized polyhedral oligomeric silsesquioxane macromonomer (BZ-POSS), containing 7.6 benzoxazine groups per molecule on average was synthesized from octaaminophenylsilsesquioxane, p-cresol and paraformaldehyde. BZ-POSS was well miscible with bisphenol A-based benzoxazine (BBZ) melt. By ring-opening copolymerization of BBZ and BZ-POSS under condition similar to that used for polymerizing neat BBZ, the transparent and uniform BBZ/BZ-POSS organic-inorganic hybrid nanocomposites were prepared. The nano-scale dispersion of POSS cores in the nanocomposite was verified by powder X-ray diffraction and transmission electron microscopy studies. Dynamic mechanical analyses and thermal gravimetric analysis indicated that thermal stabilities, cross-link densities and the flame retardance of the nanocomposites were increased in comparison with neat PBBZ resin, although only small amounts of inorganic POSS cores were incorporated into the systems. Structural analyses of BZ-POSS and BBZ/BZ-POSS nanocomposites are discussed herein. 相似文献