Search results for " press"
showing 10 items of 4213 documents
Processing and properties of blends with liquid crystal polymers
1990
Experimental data on the processing behavior and on the rheological and mechanical properties of blends with a liquid crystal polymer as one component are presented. The blends with low amounts of LCP show easier processability and lower viscosity than the thermoplastic matrix. The elastic modulus is also improved. The reduction of viscosity has been attributed to the lower pressure entry, due to the formation of fibrils and to the immiscibility of the two phases.
Entropic Unmixing in Nematic Blends of Semiflexible Polymers.
2020
Binary mixtures of semiflexible polymers with the same chain length, but different persistence lengths, separate into two coexisting different nematic phases when the osmotic pressure of the lyotropic solution is varied. Molecular Dynamics simulations and Density Functional Theory predict phase diagrams either with a triple point, where the isotropic phase coexists with two nematic phases or a critical point of unmixing within the nematic mixture. The difference in locally preferred bond angles between the constituents drives this unmixing without any attractive interactions between monomers.
Isobornyl Methacrylate as a Reactive Solvent of Polyethylene
2004
Solutions containing 15 wt, -% of a low-molar-mass polyethylene (PE) in isobornyl methacrylate (IBoMA), containing 0, 5 or 10 wt.-% of 1,4 butanediol dimethacrylate (BDDMA) as crosslinker, were polymerized using either benzoyl peroxide (BPO), at 80°C, or dicumyl peroxide (DCPO), with a thermal cycle attaining 150°C, as initiators. Phase separation of an amorphous PE-rich phase took place when carrying out the reaction at temperatures higher than the PE melting temperature. Partial crystallization of PE was observed when cooling to room temperature. Depending on the initial amount of BDDMA, the fraction of PE that was phase separated varied between 57 and 66% of the initial amount, with crys…
Sorption of n-hexane in amorphous polystyrene
2014
Sorption properties of pure n-hexane vapor in amorphous polystyrene (PS) were studied at 298 K by thermogravimetry under controlled vapor pressure. Two sorption-desorption cycles were performed by varying the relative pressure between 0 and 0.91. Mixing of PS with n-hexane resulted in a strong plasticization, which was evidenced by quite significant depression in the glass transition temperature of the polymer as shown by differential scanning calorimetry. Maximum quantity of n-hexane sorbed in the PS at 298 K and at a pressure close to saturation was about 12.4 wt %. The thermogravimetry yielded an isotherm with a strong hysteresis loop, explanation of which was hypothesized with the help …
Determining sulfur-containing amino acids by capillary electrophoresis: A fast novel method for total homocyst(e)ine human plasma
1999
A high-performance capillary electrophoresis (HPCE) method based on laser-induced fluorescence detection is presented here. It enables the determination of sulfur-containing amino acids within 15 min. Fluorescence of sulfur-containing amino acids in plasma is linear over a range of 50-150 micromol/L for L-methionine, 5-100 micromol/L for L-homocysteine, and 50-200 micromol/L for L-cysteine. For homocysteine, we were able to detect 1 fmol injected, equivalent to a plasma concentration of 10 nmol/L. A similar sensitivity is present for cysteine, an even lower one being found for methionine. The intra- and interassay relative standard deviations are < 1%. High-performance liquid chromatography…
Über die verschiedenen mittelwerte des molekulargewichts und die uneinheitlichkeit von naturkautschuk und synthetischem cis-polyisopren
1969
An Naturkautschuk und einem cis-Polyisopren von annahernd gleichem [η]-Wert wurden Molekulargewichtsbestimmungen durch Diffusion-Sedimentation, Osmose und Lichtstreuung gemacht. Aus den Mittelwerten Mn (osmotisch) und Mw (Lichtstreuung) wird die molekulare Uneinheitlichkeit bestimmt. Bei etwa gleichem Mw (2·106) ist das osmotische Molekulargewicht Mn bei Naturkautschuk 3,0·105 und beim synthetischen cis-Polyisopren 6,2·105. Auserdem macht sich beim Naturkautschuk ein nur schwer entfernbarer Anteil von Mikrogelen bemerkbar. Da die Tragheitsradien und die Wechselwirkungsparameter mit den Losungsmitteln fur Natur- und Synthesekautschuk sich nur wenig unterscheiden, konnen technologische Unters…
Green extraction approach for the recovery of polyphenols from Croatian olive leaves (Olea europea)
2017
Abstract Pressurized liquid extraction (PLE) is shown as an innovative green technology for the effective extraction of the various phytochemicals from food by-products, therefore the aims of this study were to evaluate the application of PLE to engineer green extracts of Croatian olive leaves ( Olea europaea , cv. Oblica) for potential industrial production (functional foods/pharmaceuticals). PLE was conducted under various cycle numbers (1, 2), temperature (60, 80, 100 °C) and static times (5, 10, 15 min). Obtained extracts were characterized in terms of: (i) total polyphenols (TP); (ii) total flavonoids (TF); hydroxycinnamic acids (HCA); and (iv) flavonols (FLA). Response surface methodo…
The effects of non-thermal processing on carotenoids in orange juice
2009
New non-thermal technologies are emerging, such as pulsed electric fields (PEF) and high hydrostatic pressure (HHP), in order to provide a response to the need for greater nutritional and sensory quality in some manufactured foods in which the characteristics of freshness are especially affected by thermal treatments. The effect of non-ther - mal processing (PEF, 30 kV/cm, 100 µs and HHP, 4000 bars, 5 min) and pasteurisation (90°C, 20 s) on carotenoids of orange juice was studied. The total carotenoid concentration in the pasteurised juice (1195.4 ± 31.6 µg/100 ml) decreased significantly in comparison with the fresh juice (1367.2 ± 64.7 µ g/100 ml), and the decrease was less in the juice t…
Capillary electroendoosmotic chromatography of peptides
2000
This review focuses on the current state of peptide separation by capillary electroendoosmotic chromatography (CEC). When carried out under optimised conditions, peptide separation by CEC methods represents an orthogonal and complementary technique to micro-HPLC (micro-HPLC) and high-performance capillary zone electrophoresis (HPCZE). The origin of the selectivity differences that can be achieved with these three separation techniques (CEC, micro-HPLC and HPCZE), respectively are discussed, and the current limits of performance with CEC methods documented. Peptide separations by CEC methods with n-alkyl bonded silicas or mixed-mode phases are also illustrated. The development of different v…
Pressure effect studies on spin crossover systems
2005
Abstract In the present review article we discuss the results of investigations of the influence of hydrostatic pressure (up to 1.2 GPa) on the spin transition behaviour in coordination compounds of 3d transition metal ions. The systems under investigation are mononuclear spin crossover compounds of iron(II) and chromium(II), dinuclear complexes of iron(II) exhibiting coexistence of intramolecular anti-ferromagnetic coupling and thermal spin crossover, and 1D, 2D and 3D polynuclear spin crossover complexes of iron(II). It is demonstrated that the application of hydrostatic pressure serves as a tool for modifying the ligand field strength in a controlled manner.