Search results for "Ethylene"
showing 10 items of 2589 documents
Morphology of melt-crystallized linear polyethylene fractions and its dependence on molecular weight and crystallization temperature
1980
Replicas and thin-section electron microscopic studies were made of fractions of linear polyethylene covering the molecular weight range 2.78 × 104 to 6.0 × 106 for a variety of crystallizing conditions. Lamellar crystallites were found under all circumstances; and the supermolecular structure, or crystalline morphology, is in agreement with that previously reported from an analysis of the small-angle light-scattering patterns of the same samples under similar crystallization conditions. Details of the crystalline microstructure are also described, which range from truncated hollow pyramids which degenerate as the molecular weight or the undercooling are increased. From these results, it is…
Co-Assembly of A–B Diblock Copolymers with B′-type Nanoparticles in Thin Films: Effect of Copolymer Composition and Nanoparticle Shape
2014
The coassembly of A–B diblock copolymers with B′-type nanoparticles (i.e., nanoparticles that are slightly incompatible with the B domain) leads to hierarchical structures, where the block copolymer phase separates first and the nanoparticles create close-packed arrays within the B domains due to a slower, secondary phase separation process. Here we report the results of a comprehensive study, which focused on two aspects: the influence of the nanoparticle shape (spherical vs rod-like) and the effect of the volume composition of the blocks. Three polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) copolymers featuring similar molecular weights but differing in PS volume fraction were mi…
Comparative Study of Different Maleic Anhydride Grafted Compatibilizer Precursors toward LDPE/PA6 Blends: Morphology and Mechanical Properties
2005
The study deals with the effectiveness of maleic anhydride grafted styrene-b-ethylene-co-propylene copolymer (SEPMA) as compatibilizer precursor (CP) for blends of low density polyethylene (LDPE) with polyamide-6 (PA). The CP was produced by grafting MA onto SEP in the melt. The specific interactions between the CP and the blends components have been investigated through characterizations of the binary LDPE/CP and PA/CP blends. The compatibilizing efficiency of the MA-grafted SEP, as revealed by the thermal properties and the morphology of the compatibilized blends, has been shown to be excellent. The morphology, as well as the mechanical properties of the compatibilized with SEPMA 75/25 w/…
Morphology modification of a polyethylene/clay nanocomposite samples under convergent flow
2009
The morphology of PE/CL nanocomposite samples subjected to convergent flows is studied. Elongational flow – the typical flow involved in spinning and film-blowing processing operations – significantly increases with the reduction of the capillary diameter. The values of the convergent extensional stress (calculated by Cogswell's formula) for the PE/CL systems, for all the adopted capillary geometries, are greater than the calculated values for pure polyethylene. The applied convergent flow, at the entrance of the capillary, is able to change the clay morphology and consequently the final material properties on the PE/CL system with limited affinity between the matrix and organo-modified cla…
Morphology and mechanical properties of extruded ribbons of LDPE/PA6 blends compatibilized with an ethylene-acrylic acid copolymer
2003
Two grades of low density polyethylene (LDPE) were blended with polyamide-6 (PA) in the 75/25 and 25/75 wt/wt ratios and shaped into ribbons with a Brabender single screw extruder. An ethylene-acrylic acid copolymer (EAA) was used in the 2 phr concentration as a compatibilizer precursor (CP). The morphology of the ribbons and its evolution during high temperature annealing were investigated by scanning electron microscopy (SEM). The results confirmed that EAA does actually behave as a reactive compatibilizer for the LDPE/PA blends. In fact, in the presence of EAA, the interfacial adhesion is improved, the dispersion of the minor phase particles is enhanced and their tendency toward fibrilla…
Heats and Entropies of Reaction of Transition Metal Ions with Ethylenediamine
1960
THE heats of formation of complexes between ligands and metal ions are very important to further the ligand field-theory and check its implications. Until now, only the heats of hydration of the first transition group ions have been used for this purpose1 as the thermochemical data on the complexes formed by ligands other than water are very incomplete. The transition metal complexes of ethylenediamine, which have a very nearly octahedral configuration, could also be fruitfully studied in terms of ligand field-theory. Unfortunately only the thermal data on nickel (II), copper (II) and zinc (II) complexes are known2, and so the formation constants have been used instead of the values of enth…
CCDC 711699: Experimental Crystal Structure Determination
2010
Related Article: S.Fustero, P.Bello, B.Fernandez, C.del Pozo, G.B.Hammond|2009|J.Org.Chem.|74|7690|doi:10.1021/jo9013436
MDMA Administration and Heat Shock Proteins Response: Foreseeing a Molecular Link
2010
Molecular and cellular mechanisms of MDMA-induced toxicity have been extensively studied in a number of experimental models. Nevertheless, only few studies investigated the involvement of HSPs ("molecular chaperones") in MDMA organs toxicity. In the present minireview we highlight this subject analysing the results of these studies conducted especially on brain tissue. Despite of it seems obvious that HSPs overexpression is a protective reaction against MDMA treatment, the molecular mechanisms for exerting their action are far to be undiscovered. At the same time, we need of comprehensive studies concerning the whole range of Hsps/chaperones expressions in all organs after acute and chronic…
Liquid–liquid equilibria of the systems dipropyl ether+n-propanol+water and dipropyl ether+n-propanol+ethylene glycol at different temperatures
2007
Abstract In this work, experimental liquid–liquid equilibria (LLE) data of the dipropyl ether + n-propanol + water and dipropyl ether + n-propanol + ethylene glycol systems are presented. The LLE of both systems have been measured at 283.15 and 323.15 K. The equilibrium data presented are correlated using NRTL and UNIQUAC equations. The reliability of these models is tested by comparison with experimental results. Moreover, the solvent capabilities of water and ethylene glycol were compared, concluding that ethylene glycol is the best solvent to extract n-propanol.
Mode of action of herbicidal derivatives of aminomethylenebisphosphonic acid. I. Physiologic activity and inhibition of anthocyanin biosynthesis
1996
N-Pyridylaminomethylenebisphosphonic acids constitute a class of promising herbicides. Since their mode of action at the cellular level is still poorly understood, we studied the influence of N-pyridylaminomethylenebisphosphonic acids on plant growth, at the whole plant and undifferentiated tissue levels, using seedlings and cell suspension cultures of mono- and dicotyledonous species. These compounds exhibited strong herbicidal properties, being equipotent with the popular herbicide glyphosate. Since they also depressed buckweed anthocyanin biosynthesis, the shikimate pathway could represent a site of action of N-pyridylaminomethylenebisphosphonic acids.