Novel clay-carbon tube composites were synthesized by catalytic decomposition of acetylene over iron-catalyst centers supported on montmorillonite surfaces by ion-exchange. TEM and SEM micrographs show the growth of carbon tubes rooted to the clay surfaces, while the iron-nanoparticles (which catalyze the formation of carbon-nanotubes) are detected and characterized by Mössbauer spectroscopy, mainly as ferromagnetic cementite (Fe3C). In the hybrid materials the clay retains its exchange properties making possible the preparation of clay-carbon nanotube derivatives that are valuable for various technological applications. 相似文献
A novel phosphorus-containing hyperbranched macromonomer (PHM), successfully synthesized via Michael addition polymerization of tri(acryloyloxyethyl) phosphate (TAEP) with n-butylamine (BA), was blended with epoxy acrylate resin (EA) to prepare UV curable flame retardant coatings. The study of thermal degradation of these coatings revealed that PHM can catalyze the degradation of EA, contributing to the formation of thermally stable char layer. The residues of EA3 (which contains 45 wt.% PHM) at various temperatures were analyzed by X-ray photoelectron spectroscopy (XPS) and the results displayed that the formation of phosphorus-carbon structure can well protect the carbonaceous char from thermal-oxidative degradation at 800 °C. Besides, the investigation of the flammability illustrated that the addition of PHM increased the limiting oxygen index (LOI) value and reduced the peak heat rate release (HRR) and total heat release (THR). 相似文献
Ethylene vinylacetate (EVA) copolymer-based nanocomposites with maleic anhydride-grafted ethylene-vinylacetate (EVAgMA) and
organically modified clay (o-clay) were prepared in a twin screw extruder by following a two-step melt compounding method.
EVAgMA/o-clay masterbatches with various clay contents up to 50 wt% were examined, after which the masterbatch with the highest
clay content was melt compounded with EVA for the preparation of EVA/o-clay nanocomposites containing specific amounts of
clay. Further morphological dispersion of the clay particles by highly polar EVA and shearing was confirmed in the EVA/o-clay
nanocomposites by X-ray diffraction (XRD) and transmission electron microscopy (TEM). These morphologies led to increased
thermal properties in air as well as a considerable decrease in heat release rate (HRR). EVA/o-clay/MDH nanocomposites were
also prepared using a high clay-bearing masterbatch to confirm the synergistic flame retardancy of clay as a co-additive in
EVA/MDH composites. EVA/o-clay/MDH nanocomposites prepared by substituting o-clay for MDH showed significantly lower and wider
HRR during combustion compared to EVA/MDH composite. 相似文献
Layers from delaminated colloidal dispersions of two structurally different layered solids-octylamine-intercalated graphite oxide and cetyltrimethylammonium-intercalated smectite - could be costacked to obtain smectite clay/graphite oxide composites. The layers of the two parent solids were randomly stacked together in these composites. On thermal decomposition the graphite oxide sheets in the composites are reduced to graphene sheets resulting in clay/graphene composites. The composition is not uniform in these composites, which have many smectite-rich and carbon-rich regions. The clay component of the clay/graphene composites could be leached out to obtain exfoliated graphite. 相似文献
Halloysite nanotube (HNT) was etched by hydrochloric acid, and epigallocatechin gallate (EGCG) was loaded into the etched HNT (HH) to prepare loaded antioxidant (HH-E) for polylactic acid (PLA) with improved thermal-oxidative stability. The loading process was confirmed by TGA and FT-IR, and the loading capacity was 16.15%. The presence of EGCG on the surface of etched HNT was further confirmed by nitrogen adsorption and TEM. The effect of loaded EGCG on thermal-oxidative stability of PLA was characterized by the change in OOT values of PLA after the aging process under 140°C. The results showed that HH-E increased OOT values of PLA from 231.2°C to 293.6°C at first, indicating that HH-E provided PLA with excellent thermal-oxidative stability. Furthermore, as can be seen from the trend of OOT changing over aging time, during the 14 days aging process, OOT values of PLA composites with HH-E decreased more slowly than that of PLA composites with EGCG alone, endowing PLA with sustainable thermal-oxidative stability. Further kinetic analysis showed that the apparent activation energy of the degradation process (Ea) of PLA composites with HH-E changed less than that of PLA composites with EGCG alone, which showed that the loading system provided PLA better sustainable stability. Moreover, the isothermal crystallization process of modified PLA was characterized by DSC and POM. The results showed that HH-E provided heterogeneous crystal nucleus for PLA, reducing the half crystallization time (t0.5) and improvement of crystallization rate for PLA. These results prove that HH-E exhibited excellent performance in improving the thermal stability and crystallization property of PLA, showing multifunctional characterization. 相似文献
The kinetics of the thermal-oxidative decomposition of expandable polystyrene (EPS) was studied by a conventional thermogravimetric
technique in various concentrations of oxygen from 0 to 21%. A kinetic model that accounts for the effects of oxygen concentration
was proposed to describe the thermal-oxidative decomposition of EPS. The thermogravimetric analysis curve and its derivative
have been analyzed by using differential and integral methods with modification of the Friedman and Coats-Redfern methods.
The activation energy, the pre-exponential factor, and the reaction order for unreacted material and oxygen concentration
have been determined. When oxygen was present, the activation energy was reduced significantly. 相似文献
In this article, based on the surface chemical treatment of carbon fiber, a clay coating process was developed for the surface modification of the carbon fiber to obtain a controlled interface between carbon fiber and polyetherimide (PEI) matrix in the composites system. SEM, XPS spectrum and contact angle measure reveal that the clay coating can improve the surface roughness of the carbon fiber surface for a favorable wettability with the matrix, which can also improve the interfacial adhesion of the composites. Experimental results show that the interlaminar shear strength (ILSS) and the three-point bending (TPB) of the composites reinforced by the carbon fiber coated with the clay have been enhanced. 相似文献
New low‐melting organic–inorganic glassy polymers containing phosphorus and silicon are synthesized by the reaction between phenylphosphonic acid and methyltrichlorosilane or methyltriethoxysilane. They possess both low‐softening points and high onset decomposition temperatures, which are favorable for preparing flame retardant composites. Although the glass by itself is sensitive to water, the composites are not significantly affected in that way. For glass/clay/epoxy composites glass transition temperature (Tg) as well as storage modulus increase with the glass amount. The glasses improve flame retardancy significantly due to flame inhibition and the formation of fire residue working as protection layer during burning. The total heat evolved is reduced by 23–28% for using 5–15 wt.% glass and the maximum HRR even by 58–48%. The latter effect decreases with increasing glass amount due to an adulterate residue deformation. The combination of glass and clay is proposed as a possible route to enhance flame retardancy.
Polymeric nano‐composites are prepared by melt intercalation in this study. Nano‐clay is mixed with either a polymer or a polymer blend by twin‐screw extrusion. The clay‐spacing in the composites is measured by X‐ray diffraction (XRD). The morphology of the composites and its development during the extrusion process are observed by scanning electron microscopy (SEM). Melt viscosity and mechanical properties of the composites and the blends are also measured. It is found that the clay spacing in the composites is influenced greatly by the type of polymer used. The addition of the nano‐clay can greatly increase the viscosity of the polymer when there is a strong interaction between the polymer and the nano‐clay. It can also change the morphology and morphology development of nylon 6/PP blends. The mechanical test shows that the presence of 5–10 wt.% nano‐clay largely increases the elastic modulus of the composites and blends, while significantly decreases the impact strength. The water absorption of nylon 6 is decreased with the presence of nano‐clay. The effect of nano‐clay on polymers and polymer blends is also compared with Kaolin clay under the same experimental conditions. 相似文献
Polymer layered‐silicate (clay) nanocomposites have not only the unique advantage of reduced flammability, but also improved mechanical properties. This is a key advantage over many flame retardants, which reduce flammability but also reduce the mechanical properties of the polymer. In our efforts to further understand the mechanism of flame retardancy with polymer‐clay nanocomposites, we investigated the effect of the clay, the loading level and polymer melt viscosity on the flammability of polystyrene‐clay nanocomposites. The nanoscale dispersion of the clay in the polymer was analysed by wide‐angle X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Cone calorimetry and gasification studies were used to evaluate the flammability of these nanocomposites. There were major reductions in peak heat release rates (HRRs), and increased carbonaceous char formation, for these nanocomposites. It was determined that while the viscosity of the PS nanocomposite played a role in lowering the peak HRR, the clay loading level had the largest effect on peak HRR. Finally, it was found that clay catalysed carbonaceous char formation, and the reinforcement of the char by the clay was responsible for the lowered flammability of these nanocomposites. Published in 2002 by John Wiley & Sons, Ltd. 相似文献