Search results for "Ethylene"
showing 10 items of 2589 documents
The role of organoclay in promoting co-continuous morphology in high-density poly(ethylene)/poly(amide) 6 blends
2008
The effect of organically modified clay on the morphology, rheology and mechanical properties of high-density polyethylene (HDPE) and polyamide 6 (PA6) blends (HDPE/PA6 ¼ 75/25 parts) is studied. Virgin and filled blends were prepared by melt compounding the constituents using a twin-screw extruder. The influence of the organoclay on the morphology of the hybrid was deeply investigated by means of wide-angle X-ray diffractometry, transmission and scanning electron microscopies and quantitative extraction experiments. It has been found that the organoclay exclusively places inside the more hydrophilic polyamide phase during the melt compounding. The extrusion process promotes the formation o…
Thermo-Mechanical Degradation of LDPE-Based Nanocomposites
2007
Thermo-mechanical degradation of LDPE-based nanocomposites was studied by mainly investigating the rheological properties. For all of the investigated processing conditions, the viscosity of the nanocomposites was higher than that of the pure-LDPE matrix, but on increasing the severity of the mixing conditions, the difference between the viscosity of the nano-filled polymer and that of the pure LDPE decreased. The X-ray traces of the nanocomposites suggest that intercalation has been achieved during the melt, when less-severe processing conditions were used. At severe processing conditions (longer mixing time, high temperature and shear stress) the thermo-mechanical degradation was accelera…
Thermomechanical degradation of polyethylene/polyamide 6 blend-clay nanocomposites
2014
Abstract Polymer nanocomposites are gaining a growing interest both in the academia and in the industrial field, because of some specific properties they can assure. However, the rise in the attention from the industry is also leading to concerns about their processing, which can involve issues which are not present in traditional polymers processing; furthermore, additional issues can arise when nanocomposites are based on a polymer blend rather than a single polymer. In this work, a systematic study on thermomechanical degradation and reprocessing behaviour of LDPE/PA6/Cloisite 15A systems has been performed. The characterization was based on rheological, mechanical and morphological anal…
Selective localization of organoclay and effects on the morphology and mechanical properties of LDPE/PA11 blends with distributed and co-continuous m…
2010
A study was made on the effect of small amounts of organically modified clay on the morphology and mechanical properties of blends of low-density polyethylene and polyamide 11 at different compositions. The influence of the filler on the blend morphology was investigated using wide angle X-ray diffractometry, scanning and transmission electron microscopy and selective extraction experiments. The filler was found to locate predominantly in the more hydrophilic polyamide phase. Although such uneven distribution does not have a significant effect on the onset of phase co-continuity of the polymer components, it brings about a drastic refinement of the microstructure for the blends both with dr…
Compatibilization of a polyethylene/polyamide 6 blend nanocomposite
2014
Polymer blends of incompatible components need to be compatibilized to give rise to a blend with good properties. At the same way, polymer/clay nanocomposites show the same problem because of different chemical nature of the polymer matrix and of the clay. Compatibilization is then necessary if an incompatible polymer blend is filled with an organomodified clay. In this work a polyethylene/polyamide 6 blend filled with an organomodified clay has been compatibilized with a maleic anyhidride grafted SEBS (styrene-ethylene-butylene-styrene) copolymer and a glicidylmethacrylate-ethylene copolymer. The results show that compatibilization improves the mechanical properties in terms of elongation …
Ethylene-vinyl Acetate Thermoplastic Copolymers Filled with Multiwall Carbon Nanotubes: Effect of Hydrothermal Ageing on Mechanical, Thermal, and Ele…
2013
A range of properties of two commercial thermoplastic ethylene-vinyl acetate (EVA) copolymers, Elvax 420 and Elvax 450, neat and as melt-mixed composite filled with 15 wt.-% of multi-wall carbon nanotubes (MWCNTs), are studied in the “as produced” state and after hydrothermal ageing. Addition of MWCNTs into the neat copolymers introduces the functionality of electrical conductivity and significantly improves their mechanical properties, while thermal characteristics are slightly affected by the presence of carbon nanotubes. A remarkable increase of the elastic modulus (150%) and stress at failure (50%) in stress–strain experiments as well as creep resistance (40%) of the nanocomposites in c…
Self-assembly of small gold colloids with functionalized gold nanorods.
2007
We present a general strategy to stabilize gold nanorod suspensions with mono- and bifunctional polyethylene glycol (PEG) and to attach a controlled number of nanoparticles or biomolecules. Characterization by gel electrophoresis, transmission electron microscopy (TEM), and optical dark-field microscopy show the specific binding of functionalized nanorods to their target while avoiding nonspecific binding to substrates, matrices, and other particles. Such nanorods are well suited for self-assembly of nanostructures and single-molecule labeling.
Olefin Polymerisation Catalysts
2002
Polyolefins, which are products of polymerisation of unsaturated hydrocarbons of the olefin series, have a molecular weight in the range from several thousands to several millions. Depending on the type of monomer and method and mechanism of polymerisation the resulting polyolefins may differ in their structure and molecular weight. They can be used in many applications, for example as constructional plastics and in packaging, fibres, rubbers, and also as additives to control the viscosity of motor oils(1). As regards their scale of production polyolefins occupy the top position among mass-produced polymers(2).
The effect of TMEDA on the kinetics of the anionic polymerization of methyl methacrylate in tetrahydrofuran using lithium as counterion
2000
The kinetics of the anionic polymerization of methyl methacrylate in presence of N,N,N', -tetramethylethylenediamine (TMEDA) in THF are investigated using 1,1-diphenyl-hexyllithium as initiator in a temperature range between -20°C and 0°C in a flow-tube reactor. The rate constants of propagation determined in the presence of TMEDA are compared to those obtained in the absence of a chelating agent. For propagation, the reaction order with respect to active centers is found to be 0.5 in both cases which indicates that the chelation of the lithium cation does not effectively perturb the aggregation of the enolate ion pair. Both the rate constants of propagation via non-aggregated ion pairs, k …
A DFT study of the Huisgen 1,3-dipolar cycloaddition between hindered thiocarbonyl ylides and tetracyanoethylene
2004
Abstract The mechanism for the 1,3-dipolar cycloaddition between the hindered thiocarbonyl ylide 1 and tetracyanoethylene 2 has been studied at the B3LYP/6-31G ∗ level. Formation of the [3+2] cycloadduct 4 takes place through a stepwise mechanism that is initiated by the nucleophilic attack of the thiocarbonyl ylide 1 to the ethylene derivative 2 to give a zwitterionic intermediate IN . The subsequent cyclization of IN yields a seven-membered cyclic ketene imine 6 , which equilibrates with the thermodynamically more stable [3+2] cycloadduct 4 . The computed free energies are in agreement with the experimental outcomes.