Search results for "Composites"
showing 10 items of 1905 documents
Halloysite nanotubes as polyolefin fillers
2015
Artykuł stanowi przegląd najnowszej literatury dotyczącej nanokompozytów poliolefinowych napełnianych nanorurkami haloizytowymi (HNT). Omówiono wpływ dodatku HNT na osnowę poliolefinową, ze szczególnym uwzględnieniem morfologii oraz właściwości mechanicznych nanokompozytów poliolefina/HNT. Modyfikowane HNT wykazywały wysoki stopień rozproszenia w osnowie poliolefinowej, dzięki czemu powodowały poprawę właściwości mechanicznych poliolefinowych nanokompozytów napełnianych nanorurkami haloizytowymi. Połączenie korzystnych właściwości poliolefin, ekonomicznych metod ich przetwórstwa oraz unikatowych w³aoeciwooeci HNT pozwoli na szersze rozpowszechnienie nanokompozytów wytworzonych z ich udziałe…
Effect of the orientation and rheological behaviour of biodegradable polymer nanocomposites
2014
Abstract The recent increasing interest towards biodegradable polymers has favoured the investigation on these systems, showing also their limits. On the other hand, the success achieved by nanocomposites has fostered the search for new systems where the polymer matrix is biodegradable. The final properties can depend on a number of factors, including the biodegradable polymer used as well as the nanosized filler, their mutual compatibility, the filler dispersion and the processing conditions. In this work, nanocomposites based on a starch-derived matrix and three different lamellar silicates were prepared, and the effects of the elongational flow on the dispersion, the improvement of inter…
The synergy between the CsPbBr3 nanoparticle surface and the organic ligand becomes manifest in a demanding carbon–carbon coupling reaction
2020
We demonstrate here the suitability of CsPbBr3nanoparticles as photosensitizers for a demanding photoredox catalytic homo- and cross-coupling of alkyl bromides at room temperature by merely using visible light and an electron donor, thanks to the cooperative action between the nanoparticle surface and organic capping. Fil: Rosa-Pardo, Ignacio. Instituto de Ciencia Molecular; España. Universidad de Valencia; España Fil: Casadevall, Carla. Barcelona Institute Of Science And Technology. Institut Català D'investigació Química.; España Fil: Schmidt, Luciana Carina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigac…
Spin-crossover iron(ii) complex showing thermal hysteresis around room temperature with symmetry breaking and an unusually high T(LIESST) of 120 K.
2019
We report a Fe(II) complex based on 4′,4′′ carboxylic acid disubstituted dipyrazolylpyridine that shows a spin-crossover close to room temperature associated to a crystallographic phase transition and the LIESST effect with a high T(LIESST) of 120 K.
Glass transition of polymer melts: Test of theoretical concepts by computer simulation.
2003
Abstract Polymers are good glass formers and allow for the study of melts near the glass transition in (meta-)stable equilibrium. Theories of the glass transition imply such an equilibrium and can, hence, be tested by the study of polymer melts. After a brief summary of the basic experimental facts about the glass transition in polymers, the main theoretical concepts are reviewed: mode coupling theory (MCT), entropy theory, free-volume theory, the idea of a growing length describing the size of cooperative regions, etc. Then, two basic coarse-grained models of polymers are described, which have been developed aiming at a test of these concepts. The first model is the bond-fluctuation model …
Influence of Molar Mass Distribution on the Compatibility of Polymers
1996
Abstract Phase equilibria were calculated by means of a new method (direct minimization of the Gibbs energy of mixing) for polymer blends consisting of monodisperse polymer A and polydisperse polymer B. The results obtained for a Schulz-Flory distribution of B (molecular nonuniformity U = (M w/M n) −1 = 1 and 100 components of model B) agree quantitatively with that of computations on the basis of continuous thermodynamics. The influence of U B on the miscibility of A and B in 1:1 mixtures was studied for constant M w of B, quantifying the incompatibility of the polymers by the length of the tie lines. The outcome of these calculations demonstrates that the typical effect of an augmentation…
On the handedness of helical aggregates of C3 tricarboxamides: a multichiroptical characterization
2015
A complete chiroptical characterization of the supramolecular polymers formed by tricarboxamides (S)-1 and (R)-1 is performed using ECD, VCD and CPL dichroic techniques. The helical aggregates show an intense CPL signal and their absolute P- or M-configuration is assigned with the help of theoretical calculations.
Improving the properties of polypropylene–wood flour composites by utilization of maleated adhesion promoters
2007
Polymer composites filled with natural organic fillers have gained a significant interest during the last few years, because of several advantages they can offer compared with properties of inorganic-mineral fillers. However, these composites (based, in most cases, on polyolefins) often show a reduction in some mechanical properties. This is mainly due to the problems regarding dispersion of the polar filler particles in the non-polar polymer matrix and their interfacial adhesion with polymer chains. In this work, polypropylene-wood flour composites were prepared and the effect of the addition of a maleated polypropylene was investigated. The two materials were compounded by an industrial c…
Insight in NLO Polymer Material Behavior from Langevin Dynamic Modeling of Chromophore Poling
2011
Calculation of chromophore polar order, i.e. the polarization of nonlinear optically (NLO) active polymers poled by external field, is challenging. One possible solution is to reproduce the orientation polarization of chromophores under external field using Langevin dynamics (LD) molecular modeling. The present work investigates the influence of chromophore dipole moment, density and field extent on NLO efficiency and polarization/relaxation dynamics. Results of simulations convince us, that the method is applicable for modeling real NLO polymers. In the spotlight of this investigation we would like to describe a NLO polymer as a “ferrofluid” where chromophores are active particles or elect…
Stochastic dynamics of polymer brushes under shear deformation
1998
The dynamical properties of polymer brushes under shear deformation have been studied by computer simulation. Both the local and the global dynamic properties at various shear rates have been calculated. The distribution of orientational and translational mobilities of the different monomers along the chain have been obtained. It was shown that the local mobility of the brushes changes very slowly with increasing of shear rates up to the largest rates. Increase in grafting density leads to an increasingly step like dependence of the correlation times as a function of shear rate.