Epoxy resin nanocomposites with different contents of multiwalled carbon nanotubes (MWNTs) are prepared. The interaction between MWNTs and the epoxy resin matrix and the microstructure and mechanical properties of the composites are systematically investigated by Fourier‐transform infrared (FTIR) spectroscopy, transmission electron microscopy, scanning electron microscopy, and positron annihilation technology. FTIR spectra reveal that two kinds of hydrogen bonds exist at the interface for the nanocomposites modified by amine, one between the epoxy group on the side chain and the NH group, and the other between the epoxy group on the alicycle and the NH group. Compared to unmodified MWNT composites, the modified MWNT composites possess better mechanical properties, which are attributed to stronger interfacial interaction resulting from an efficient load transfer from matrix to MWNTs. Positron annihilation lifetime spectroscopy is used to characterize the microstructure of the epoxy/MWNT composites. The subtransition and glass transition temperatures are determined by finite‐term positron lifetime analysis and the variation of the free‐volume size as a function of temperature. Shifts of structure transition temperatures of the composites are observed with increasing MWNT weight content. Interestingly, the continuous lifetime analysis reveals the existence of two long‐lived lifetime components above the glass transition temperature, which may be attributed to the formation of local ordered regions related to the packing density of chains. 相似文献
Summary: Electro‐active shape‐memory composites were synthesized using conducting polyurethane (PU) composites and multi‐walled carbon nanotubes (MWNTs). Surface modification of the MWNTs (by acid treatment) improved the mechanical properties of the composites. The modulus and stress at 100% elongation increased with increasing surface‐modified MWNT content, while elongation at break decreased. MWNT surface modification also resulted in a decrease in the electrical conductivity of the composites, however, as the surface modified MWNT content increased the conductivity increased (an order of 10−3 S · cm−1 was obtained in samples with 5 wt.‐% modified‐MWNT content). Electro‐active shape recovery was observed for the surface‐modified MWNT composites with an energy conversion efficiency of 10.4%. Hence, PU‐MWNT composites may prove promising candidates for use as smart actuators.
The electro‐active shape‐recovery behavior of PU‐MWNT composites. The pictured transition occurs within 10 s when a constant voltage of 40 V is applied. 相似文献
The in situ bulk polymerization method was applied to synthesize composites of multiwalled carbon nanotubes (MWNTs) and polystyrene
(PS) under ultrasonication to open π-bonds in the MWNTs. Morphology of the composite products was studied by both scanning
electron microscopy (SEM) and transmission electron microscopy (TEM). Thermal properties and molecular weight of the PS synthesized
in the presence of the MWNTs were examined by thermogravimetric analysis (TGA) and gel permeation chromatography (GPC), respectively.
The MWNTs were observed to play an important role as initiator consumers during the polymerization reaction. Electrical conductivity
of a film-type sample of the PS/MWNT nanocomposite was found to increase with increased amount of MWNTs added, following the
percolation theory. 相似文献