Polyurethane/polyhedral oligomeric sisesquioxane (PU/POSS) nanocomposites were syn-thesized via polymerization utilizing the compatibility between POSS nanoparticles and 4,4'-diphenyl methylene diisocyanate. Scanning electron microscope images and Fouriertransform infrared spectra revealed that POSS nanoparticles were dispersed in PU matrix.Thermal gravimetric analysis was employed to investigate the thermal decomposition be-havior of PU/POSS nanocomposites at elevated temperatures. Then fire performance wasevaluated by limiting oxygen index, underwriters laboratories 94 testing and char residue morphology. These results showed that the addition of POSS promoted the formation of char residues which were covered on the surface of polymer composites, leading to the im-provement of thermal stability and flame retardancy. 相似文献
In this study, high performance shape memory polyurethane (SMPU)/silica nanocomposites with different silica weight fraction including SMPU bulk, 3%, 4.5%, 6%, 7.5%, 10%, were prepared by sol‐gel process initiated by the solid acid catalyst of p‐toluenesulfonic acid (PTSA). Field emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM) observation show that the silica nanoparticles are dispersed evenly in SMPU/silica nanocomposites. Tensile test and dynamic mechanical analysis (DMA) suggest that the mechanical properties and the glass transition temperature (Tg) of the nanocomposites were significantly influenced by silica weight fraction. Thermogravimetric analysis (TGA) was utilized to evaluate the thermal stability and determine the actual silica weight fraction. The TGA results indicate that the thermal stability can be enhanced with the hybridization of silica nanoparticles. Differential scanning calorimetry (DSC) was conducted to test the melting enthalpy (ΔH) and the results suggest that the ΔH was markedly improved for the SMPU/silica nanocomposites. Thermomechanical test was conducted to investigate the shape memory behavior and the results show that the shape fixity is improved by hybridization of silica and good shape recovery can be obtained with the increasing of cycle number for all the samples. 相似文献
Different polymerizable ammonium surfactants were successfully synthesized via Michael‐addition and quaternarization reactions. Organoclays containing reactive methacrylate groups were prepared by the cationic exchange process. Intercalated nanocomposites were produced by UV initiated polymerization with 5 wt.‐% organophilic clay loading. DMTA tests and tensile analysis implied that a long chain polymerizable modifier could crosslink with the polymer matrix, and mechanical and tensile properties were enhanced dramatically about 80%. Water sorption was not elevated, which was determined by the polymer itself and the hydrophobicity of the modifier, although the water permeation was improved.
