Search results for "Ethylene"
showing 10 items of 2589 documents
Single-pump bi-dimensional LC applied to the characterization of derivatized fatty alcohol ethoxylates.
2010
A column selection valve and a 6-port 2-position injection valve were combined to implement bi-dimensional LC in a system driven by a single pump. The system was applied to the separation of linear fatty alcohol ethoxylates with 12-18 carbon atoms in the hydrocarbon moiety, previous derivatization with diphenic anhydride. Separation on the first separation dimension (C(1)) was carried out with a propyl-diol column and an acetonitrile/aqueous ammonium acetate gradient. Fatty alcohol ethoxylate hydrocarbon series (oligomers with the same number of carbon atoms in the alkyl chain but differing in the number of ethylene oxide units) were resolved without distinguishing the oligomers within the …
Preparation of monodisperse polyethylene oxides by gel permeation chromatography of discontinuous polymer-homologous series
1970
Abstract Starting from triethylene glycol, monodisperse polyethylene oxides of a molecular weight (MW) up to 2000 (degree of polymerisation (DP) During the first step the ditosylate of triethylene glycol is reacted with the sodium alkoxide of the same diol at room temperature. The condesation product (polymer homologues of triethylene glycol) was separated by molecular distillation and yielded the pure oligomers nonaethylene glycol (DP = 9, MW 414) and pentadecaethylene glycol (DP = 15, MW = 678), as proved by gel chromatography. During the next step the polymer homologues of nonaethylene glycol were synthesised in a similar way. The pure oligomers hepteicosa (DP = 27, MW = 1207) and pentat…
Theory-based improvements of continuous polymer fractionation demonstrated for poly(carbonate)
1992
For the first time, a quantitative theoretical analysis (liquid/liquid phase equilibria treated by means of the continuous thermodynamics) of the operating characteristics of continuous polymer fractionation (CPF) was performed. The results of these calculations were compared with data published for CPF of polyethylene. It turned out that the efficiency of the conventional CPF corresponds to approximately two theoretical plates only. For this reason, several improvements, suggested by theoretical considerations, were realized experimentally, for which purpose the system dichloromethane/diethylene glycol/bisphenol-A polycarbonate was chosen. The pulsating sieve-bottom column was replaced by …
Gas chromatography of homologous esters
1985
Abstract The retention behaviour of C 1 C 18 n -alkyl esters of butanoic 2-, 3- and 4-chlorobutanoic acids was examined isothermally at several temperatures on SE-30 and OV-351 capillary columns. Retention increments showing the effects of each position of chlorine substitution are presented. The considerable enhancement of terminal chlorine substitution is discussed together with the corresponding behaviour of the monochloropropanoate esters.
Influence of the physical state of water on the barrier properties of hydrophilic and hydrophobic films.
2000
Water transfer through different films, as a function of the physical state of water in contact with the film, the relative humidity difference, and the water vapor pressure difference, was investigated. The films were two synthetic packagings (hydrophobic polyethylene and hydrophilic cellophane) and an edible film. The physical state of water affects water sensitive films, such as cellophane, inducing a higher liquid water transfer due to interactions with the polymer. For hydrophobic polymers, such as polyethylene, neither the physical state of water nor the relative humidity has an influence on the water permeability. In complex system, such as an edible film composed of hydrophilic part…
Enantioselektive Trifluoracetylierung mit Hilfe chiraler Polyamide
1980
(S)-Poly(2-aminobutyric acid) (1) [(S)-poly(imino-1-methyl-3-oxotrimethylene)] was transformed into its N-trifluoroacetyl derivative 4. The IR spectra and the circular dichroism of both substances were compared. In addition, (S)-poly[N-(1-phenylethyl)acrylamide] (2) ((S)-poly-[1-(1-phenylethylaminocarbonyl)ethylene]) was trifluoroacetylated leading to polymer 5. 4 was found to react as trifluoroacetylating agent with L-1-phenylethylamine (L-3) twice as fast as it reacts with D-3. Accordingly, the reaction of 4 with D,L-3 leads preferentially to the L-form of N-(1-phenylethyl)trifluoroacetamide with optical yields up to 6%. The reaction of 5 with D,L-3 affords the D-form of N-(1-phenylethyl)…
Effect of extrusion and photoxidation on polyethylene/clay nanocomposites
2009
Polyethylene (a 1:1 blend of m-LLDPE and z-LLDPE) double layer silicate clay nanocomposites were prepared by melt extrusion using a twin screw extruder. Maleic anhydride grafted polyethylene (PEgMA) was used as a compatibiliser to enhance the dispersion of two organically modified monmorilonite clays (OMMT): Closite 15A (CL15) and nanofill SE 3000 (NF), and natural montmorillonite (NaMMT). The clay dispersion and morphology obtained in the extruded nanocomposite samples were fully characterised both after processing and during photo-oxidation by a number of complementary analytical techniques. The effects of the compatibiliser, the organoclay modifier (quartenary alkyl ammonium surfactant) …
Synthesis of Precision Poly(1,3-adamantylene alkylene)s via Acyclic Diene Metathesis Polycondensation
2019
[Image: see text] Fully saturated, aliphatic polymers containing adamantane moieties evenly distributed along the polymer backbone are of great interest due to their exceptional thermal stability, yet more synthetic strategies toward these polymers would be desirable. Herein, we report for the first time the synthesis of poly(1,3-adamantylene alkylene)s based on α,ω-dienes containing bulky 1,3-adamantylene defects precisely located on every 11th, 17th, 19th, and 21st chain carbon via acyclic diene metathesis polycondensation. All saturated polymers revealed excellent thermal stabilities (452–456 °C) that were significantly higher compared to those of structurally similar polyolefins with al…
Vitamin C Loaded Polyethylene: Synthesis and Properties of Precise Polyethylene with Vitamin C Defects via Acyclic Diene Metathesis Polycondensation
2020
A polyethylene-like polymer with an in-chain vitamin C group was synthesized by olefin metathesis polymerization. Here, we describe both the synthesis and a comprehensive physical characterization. Because of the olefin metathesis synthesis, the vitamin C groups are equidistantly arranged in the polyethylene (PE) main chain. Their separation was adjusted to 20 CH2 units. After hydrogenation, a semicrystalline polymer is obtained that is soluble in polar solvents. Because of its size and steric effect, the vitamin C acts as a chain defect, which is expelled from the crystal lattice, yielding a lamellar crystal with a homogeneous thickness corresponding to the interdefect distance. The physic…
Effective conductivity in association with model structure and spatial inhomogeneity of polymer/carbon black composites
1996
The relationship between effective conductivity and cell structure of polyethylene/carbon composites as well as between effective conductivity and spatial distribution of carbon black are discussed. Following Yoshida's model both structures can, in a way, be said to be intermediate between the well known Maxwell-Garnett (MG) and Bruggeman (BR) limiting structures. Using TEM photographs on composites with various carbon blacks we have observed that the larger is Garncarek's inhomogeneity measure H of two-dimensional (2D) representative distribution of the carbon black, the smaller is the effective conductivity of the composite.