Search results for "COMPOSITE"
showing 10 items of 4584 documents
Mesoporous silicon carbide via nanocasting of Ludox® xerogel
2016
Porous SiC with uniformly sized 12 nm and 22 nm spherical mesopores was synthesized from nanocomposites of polycarbosilane (PCS) preceramic polymer and xerogels of Ludox® SiO2 nanoparticles as templates. The influence of PCS type (Mw 800 and 2000 Da), PCS : SiO2 ratio, pyrolysis temperature 1200–1400 °C, and addition of Ni complex to the preceramic composite was studied with respect to the SiC porous morphology, crystalline structure and chemical properties. We found that the pore walls of Ni-free por-SiC are composed of relatively large (20 nm) crystallites embedded inside a poorly crystalline SiC/SiC1+x phase. Increasing the pyrolysis temperature resulted in an increase of the large cryst…
Nanoclays for Conservation
2019
Within the conservation of artworks materials, this chapter describes innovative strategies based on clay nanoparticles that are promising for protective coating, surface cleaning, and consolidation. We present the preparation of polymer/montmorillonite nanocomposites, which are revealed as efficient protective coatings for highly porous stones, marbles, and bread-made artifacts. Anticorrosive films for metal substrates have been obtained by polymer filling with laponite and halloysite nanotubes (HNTs) containing corrosion inhibitors into their lumen. The dispersion of hydrophobically modified HNTs into chitosan matrix drives to fabricate biofilms with surface cleaning capacity. Rust stains…
Influence of the modification, induced by zirconia nanoparticles, on the structure and properties of polycarbonate
2013
Melt compounding was used to prepare polycarbonate (PC)–zirconia nanocomposites with different amounts of zirconia. The effect of the zirconia loading, in the range of 1–5 wt.%, on the structure, mechanical properties and thermal degradation kinetics was investigated. The zirconia nanoparticle aggregates were well dispersed in the PC matrix and induced the appearance of a local lamellar order in the polycarbonate as inferred by SAXS findings. This order could be a consequence of the intermolecular interactions between zirconia and the polymer, in particular with the quaternary carbon bonded to the methyl groups and the methyl carbon as inferred from the NMR results. The presence of zirconia…
Polyethylene glycol/clay nanotubes composites
2012
Nanocomposites of poly(ethylene) glycol (PEG) 20000 filled with clay nanotubes (HNTs) were prepared. The thermal properties obtained from thermogravimetry and differential scanning calorimetry were correlated to the morphology imaged by scanning electron microscopy. Low amounts of HNTs generate compact structure while large amounts of HNTs create craters and voids. The decrease of polymer degradation temperature in the presence of large amount of nanoclay (ca. 80 wt%) is a consequence of the morphology at the mesoscale range. The thermal opposite effect observed in the HNTs low regime (up to ca. 20 wt%) is due to the gas entrapment into the nanoparticles lumen. The quantitative analysis of …
Polyisoprene-carbon black nanocomposites as tensile strain and pressure sensor materials
2004
Abstract Electrically conductive polymer composites (ECPC) are shown as prospective large-size flexible pressure and stretch sensors for detecting of dangerous deformations and vibrations of vehicle parts. Reversible change of resistance dependent on stretch and pressure is obtained in electro-conductive polymer nanocomposites. At certain concentrations of carbon nano-particles a change of electrical resistance by more than four orders is observed at 40% relative stretch. The maximum sensitivity of nanocomposites is observed in the vicinity of the transition of electro-conductive percolation. Nanocomposites exhibit a very weak semiconductor-like temperature dependence of resistance. The ten…
Towards completely miscible PMMA nanocomposites reinforced by shear-stiff, nano-mica
2014
Abstract Optimizing the reinforcement of polymers with nanoplatelets requires optimization of the aspect ratio and the moduli of the filler while providing a complete stress transfer. Employing a novel shear-stiff, nano-mica with large aspect ratio, we focus on maximizing the interfacial interaction between filler and matrix. External surfaces of the nano-mica were selectively modified by a polycationic macro-initiator and two PMMA-polymer brushes of length below and above critical entanglement length, respectively, and the mechanical properties of the three PMMA nanocomposites were measured. The multiple electrostatic anchoring groups of the macro-initiator not only provide reliable adhesi…
Effect of elongational flow on morphology and properties of polymer/CNTs nanocomposite fibers
2010
Carbon nanotubes (CNTs) have been attracting increasing interest for the fabrication of polymer-based nanocomposites because of their excellent properties. Traditional methods for the preparation of polymer/CNTs nanocomposites are in situ polymerization, solution blending, and melt mixing. The achievement of a good CNT dispersion and a percolation network is important in order to obtain better mechanical and electrical properties. However, the rheological behavior of polymer/CNTs systems, in particular regarding the extensional flow, has not been much investigated so far. In this work we present, for the first time, rheological data in non-isothermal extensional flow and an investigation on…
Effect of stress and temperature on the thermomechanical degradation of a PE-LD/OMMT nanocomposites
2014
Thermomechanical degradation of nanocomposites is a topical issue that has not been fully investigated as demonstrated by the low number of papers available in the literature regarding this spe- cific aspect. In particular, with regards to low density polyethylene/clay nanocomposites, the degrada- tion behavior is very complex since it involves the degradation paths of both the polymer matrix and the organomodified nanoclay. In the present work, the effects of mechanical stress and temperature on the thermomechanical behavior of PE-LD/organomodified clay nanocomposites and the degradation paths were investigated by rheological, FT-IR and mechanical methods. The results have shown that the t…
EVA copolymer based nanocomposites: rheological behavior under shear and isothermal and non-isothermal elongational flow
2006
Abstract Nanocomposites are a very promising new class of polymer composites that exhibit an interesting combination of chemical, physical and mechanical properties. Only small amounts of nanofiller are sufficient to generate great variation of many properties. This work focuses on the rheological properties of poly[ethylene- co -(vinyl acetate)] (EVA copolymer) based nanocomposites in shear and in isothermal and non-isothermal elongational flow. The nanocomposites, at two different filler contents, were prepared in two different extruders and intercalates were obtained for all the samples. The twin-screw compounder is more efficient. The change of rheological properties, both in shear and …
Recycling and Thermomechanical Degradation of LDPE/Modified Clay Nanocomposites
2013
The special features of polymer nanocomposites are continually gaining interest both in academia and in industry. The latter is especially experiencing an increase in interest towards this class of polymer composites, and this is leading to the first concerns about their reprocessing and reciclability. Here, a systematic study on the behavior of LDPE/Cloisite 15A systems upon reprocessing in a single-screw extruder is described, focusing on rheological, mechanical, and morphological properties changes. The investigated systems show a very complex thermomechanical degradation behavior, with the degradation of the clay modifier and different degradation paths involving the polymer matrix; all…