The effect of clay type and of clay–masterbatch product in the preparation of polypropylene/clay nanocomposites

Clay containing polypropylene (PP) nanocomposites were prepared by direct melt mixing in a twin screw extruder using different types of organo‐modified montmorillonite (Cloisite 15 and Cloisite 20) and two masterbatch products, one based on pre‐exfoliated clays (Nanofil SE 3000) and another one based on clay–polyolefin resin (Nanomax‐PP). Maleic anhydride‐grafted polypropylene (PP‐g‐MA) was used as a coupling agent to improve the dispersability of organo‐modified clays. The effect of clay type and clay–masterbatch product on the clay exfoliation and nanocomposite properties was investigated. The effect of PP‐g‐MA concentration was also considered. Composite morphologies were characterized by X‐ray diffraction (XRD), field emission gun scanning electron microscopy (FEG‐SEM), and transmission electron microscopy (TEM). The degree of dispersion of organo‐modified clay increased with the PP‐g‐MA content. The thermal and mechanical properties were not affected by organo‐modified clay type, although the masterbatch products did have a significant influence on thermal and mechanical properties of nanocomposites. Intercalation/exfoliation was not achieved in the Nanofil SE 3000 composite. This masterbatch product has intercalants, whose initial decomposition temperature is lower than the processing temperature (T ～ 180°C), indicating that their stability decreased during the process. The Nanomax‐PP composite showed higher thermal and flexural properties than pure PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of hydrophilic copolymers of maleimide derivatives with 2‐hydroxyethyl methacrylate: electrochemical and thermal behavior

BACKGROUND: The high‐technology industries have been the driving force in the development of new synthetic polymers that combine thermal stability with specific functional properties. In this study p‐chlorophenylmaleimide, p‐hydroxyphenylmaleimide and p‐nitrophenylmaleimide (R‐PhMI) with 2‐hydroxyethyl methacrylate (HEMA) were synthesized by free radical polymerization to obtain hydrophilic polymers, in order to study the effect of the p‐chloroaryl, p‐hydroxyaryl or p‐nitroaryl group on the copolymer composition, electrochemical behavior and thermal properties. RESULTS: The thermal behavior was correlated with the copolymer composition and functional groups, maleimide derivatives, on the copolymers. Thermal decomposition temperature (TDT) and glass transition temperature (T_g) were influenced by the functional groups of R‐PhMI moiety on the copolymer. The polymers showed an electrochemically irreversible reduction process under the conditions tested. CONCLUSION: Poly[(p‐chloromaleimide)‐co‐(2‐hydroxyethyl methacrylate)] copolymer shows a higher TDT than poly[(p‐hydroxymaleimide)‐co‐(2‐hydroxyethyl methacrylate)] or poly[(p‐nitromaleimide)‐co‐(2‐hydroxyethyl methacrylate)] (NPHE). T_g decreases in going from nitro to hydroxyl to chloro groups. The NPHE copolymer shows a lower stability, losing weight at 200 °C. The NPHE copolymer shows a well‐defined reduction wave which is similar to those of the other copolymers and it also shows an additional quasi‐reversible reduction wave corresponding to the nitrobenzene group. Copyright © 2009 Society of Chemical Industry     

Boron removal by liquid‐phase polymer‐based retention technique using poly(glycidyl methacrylate N‐methyl D‐glucamine)

The removal of boron was analyzed by liquid‐phase polymer based retention (LPR) technique using washing and enrichment method. The extracting reagents were water‐soluble polymers (WSPs) containing quaternary ammonium salts and N‐methyl‐D ‐glucamine (NMG) groups. The removal experiments of boron using the washing method were conducted at 1 bar of pressure by varying pH, polymer:boron molar ratio, and concentrations of interfering ions (chloride and sulfate). The results showed higher retention capacity for boron (60%) at pH 10 with the polymer containing NMG group. The optimal polymer:boron molar ratio was 40 : 1. Selectivity experiments showed that the presence of interfering ions did not affect the boron removal capacity. The maximal boron retention capacity was determined by the enrichment method, obtaining a value of 12 mg B/g‐polymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Improving an autotuning engine for 3D Fast Wavelet Transform on manycore systems

This paper presents an enhanced auto-optimization method to run the 3D-Fast Wavelet Transform on different computing units in a system (GPU, MIC, CPU). The proposed method automatically selects a set of parameter values (block size, number of streams and number of threads) in order to reduce the total execution time, obtaining performances close to the optimal and decreasing the number of evaluations needed.     

Biostatic Behavior of Side Chain Charged Polycations and Polymer-Ag Complexes

Summary Poly[(3-methacryloylamino)propyl]trimethylammonium)chloride (PMF'TA), and poly (2-acrylamido-2-methyl-1-propane sulfonic acid) (PAPSA) were synthesized by radical polymerization. Three copolymers of (3-methacryloylamino)propyl] trimethylammonium chloride and 2-acrylamido-2-methyl-1-propane sulfonic acid P(MPTA-co-APSA) with different feed monomer mol ratios were also synthesized by radical polymerization. These polymer materials and the commercial poly(vinylpyrro1idone-co-2-dimethylaminoethyl methacrylate) quaternized P(VP-co- DMAEM) were purified by ultrafiltration membranes and subsequently their complexes with Ag(I) were prepared. Antibacterial activity of all these polymers, was investigated against Escherichia coli (6538P), and Staphylococcus aureus (ATCC 28922), using the National Comittee for Clinical Laboratory Standards method [1]. None of these compounds exhibited biocidal or biostatic action against E. coli, and only PMTA and P(VP-co-DMAEM) exhibited some action against S. aureus.     

Magnetic Dynamics in Condensed Oxygen: Recent Experimental Results

The spin dynamics in the condensed phases of ambient–pressure molecular oxygen (liquid, plastic–crystalline (–), magnetically disordered (–) and fully ordered –O ₂ ) iS investigated by means of the concurrent use of neutron scattering and muon–spin relaxation. Above the transition the magnetic dynamics is governed by fast paramagnetic fluctuations whose spectrum is determined from the S(Q,) dynamic structure factors accessible from inelastic neutron scattering. Such information is shown to provide a key to understand the non–trivial temperature dependence of longitudinal relaxation rates found in muon spin relaxation measurements. Recent neutron scattering measurements performed within the magnetically ordered –phase under high–resolution conditions reveal the presence of a low–energy excitation of magnetic origin, unnoticed in a previous polarized–neutron experiment, which corresponds to the continuation to longer wavevectors of the spin–wave mode detected in antiferromagnetic resonance (AFMR) experiments carried out by optical means.     

FlexSched: Efficient scheduling techniques for concurrent kernel execution on GPUs

The Journal of Supercomputing - Nowadays, GPU clusters are available in almost every data processing center. Their GPUs are typically shared by different applications that might have different...     

Cellular genetic algorithms without additional parameters

Cellular genetic algorithms (cGAs) are a kind of genetic algorithms (GAs) with decentralized population in which interactions among individuals are restricted to close ones. The use of decentralized populations in GAs allows to keep the population diversity for longer, usually resulting in a better exploration of the search space and, therefore, in a better performance of the algorithm. However, it supposes the need of several new parameters that have a major impact on the behavior of the algorithm. In the case of cGAs, these parameters are the population and neighborhood shapes. We propose in this work two innovative cGAs with new adaptive techniques that allow removing the neighborhood and population shape from the algorithm’s configuration. As a result, the new adaptive cGAs are highly competitive (statistically) with all the compared cGAs in terms of the average solutions found in the continuous and combinatorial domains, while finding, in general, the best solutions for the considered problems, and with less computational effort.