Durability of a lightweight construction material made with dune sand and expanded polystyrene

The partial/total substitution of ordinary aggregates by other unused local materials in order to produce new lightweight concretes/mortars is an interesting alternative that can solve technical, economical and environmental problems. On the other hand, the replacement of cement by other binders in the elaboration of concretes and mortars can also provide other properties and benefits more important and more interesting. In this context, previous works have been undertaken and have shown the possibility and the effectiveness of the use of expanded polystyrene aggregates and dune sands on the physicomechanical properties of plaster mortars, especially in term of lightness and thermal insulation. Our current concern is to know: how this composite will behave in certain aggressive environments. Therefore, the main objective of the present work is to study the effect of some chemical environments on the behaviour of a plaster mortar based on dune sands and expanded polystyrene beads. For this study, three different environments have been envisaged: demineralised water (as reference), sulphuric acid solution and magnesium sulphate solution. The obtained results showed that although the surface of the studied samples seems to be degraded, in their interior, the material appears more homogeneous and compact with relatively a good adhesion sand/plaster and EPS/plaster. The presence of the acid or the sulphate in water does not increase the water effect; besides, the acid considerably improves its effect in compression.     

支化聚苯乙烯的合成及其与ABS的共混

以对氯甲基苯乙烯(CMS)、苯乙烯、2,2′-联吡啶(Bpy)和CuCl组成过渡金属催化原子转移自由基聚合制备支化聚苯乙烯(BPS)。研究了少量BPS的引入对丙烯腈-丁二烯-苯乙烯共聚物(ABS)熔体流动性能和热性能的影响。以Bpy/CuCl作为络合催化剂,CMS和苯乙烯可顺利自缩合乙烯基聚合合成BPS。在ABS中加入少量的BPS后,共混物的拉伸强度小幅提高,耐热性能基本保持不变,而熔体黏度降低7%～18%,改善了ABS的加工性能。     

Polystyrene/polybutadiene blends: An analysis of the phase‐inversion region and cophase continuity and a comparison with theoretical predictions

Blends of polystyrene and polybutadiene were prepared by melt mixing. The melt rheology behavior of the blends was studied with a capillary rheometer. The morphology of the blends was examined with scanning electron microscopy. The levels of continuity and cocontinuity were studied by both morphology and dissolution techniques. The region of phase inversion was observed at 50 wt % polystyrene. Various theoretical models were applied to determine the region of cophase continuity and to locate the point of phase inversion. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1007–1016, 2003     

The study of polystyrene blends: The relationship of phases and structure in blends of polystyrene with ethylene–propylene diene monomer rubber and its grafted copolymer

Pressed films of blends of polystyrene (PS) with ethylene–propylene diene monomer rubber (EPDM) or grafted copolymer of styrene (St) onto EPDM (EPDM-g-St) rubber were examined by small-angle X-ray scattering (SAXS), and scanning electron microscope (SEM). Small-angle X-ray scattering from the relation of phase was analyzed using Porod's Law and led to value of interface layer on blends. The thickness of interface layer (σ_b) had a maximum value at 50/50 (PS–EPDM-g-St) on blends. The radius of gyration of dispersed phase (domain) and correlation distances a_c in blends of PS–EPDM-g-St were calculated using the data of SAXS. The morphology and structure of blends were investigated by SEM. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 805–810, 1998     

Sulfur release from coal in fluidized-bed reactor through pyrolysis and partial oxidation with low concentration of oxygen

Yima (YM) and Datong (DT) raw coal were pyrolyzed in a fluidized bed reactor under 0.6%O₂-N₂, 1.1%O₂-N₂ and 2.1%O₂-N₂ atmosphere, and a flue gas analyzer was used to check the SO₂ in pyrolysis gas. The product of sulfur removal and char yield is suggested to measure the efficiency of sulfur removal. For YM coal, sulfur removal generally has increasing trend with the increase of oxygen concentration in atmosphere. The char yield of YM coal has no remarkable decrease when the oxygen content is lower than 1.1%. However, in 2.1%O₂-N₂ less char yield is obtained. For DT coal more sulfur is removed in 0.6%O₂-N₂ than in N₂, and at the same temperature more SO₂ is released with increasing oxygen content. It is suggested that the atmospheres used selectively break the C-S bonds other than C-C bonds. Pyrolysis of coal in fluidized-bed reactor under low concentration of oxygen atmosphere is a promising method to greatly remove sulfur, and not remarkably decrease the char yield.     

Characterization by dilute solution and rheological methods of polystyrene and poly(methyl methacrylate) produced with a tetrafunctional peroxide initiator

Polystyrene (PS) and poly(methyl methacrylate) (PMMA) samples produced by the bulk homopolymerization of styrene and methyl methacrylate with a tetrafunctional peroxide initiator (JWEB50) are characterized in detail by various solution and rheological methods. For comparison purposes, “linear” PS and PMMA samples were produced under similar conditions with a monofunctional initiator (TBEC). The four sample types were characterized by size exclusion chromatography (SEC) setups to determine molecular weight, radius of gyration, and intrinsic viscosity distributions. Contraction factors were calculated and indicated evidence of branching for polystyrene produced with JWEB50 while no such effects were observed with PMMA. The rheological behavior of the samples was subsequently investigated by performing oscillatory shear and creep experiments. Compared to the “linear” material, samples produced with JWEB50 exhibited a reduction in zero‐shear viscosity that was attributed to long‐chain branching. Retardation spectra were calculated based on creep data and converted to dynamic compliances that were then combined with the oscillatory data. This provided master curves spanning a much wider frequency range than could be obtained experimentally. Examination of various viscoelastic functions showed evidence of long‐chain branching for both polystyrene and poly(methyl methacrylate) samples produced with JWEB50. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1340–1355, 2007     

Synthesis of cationic hemicellulosic derivatives with a low degree of substitution in dimethyl sulfoxide media

A series of water‐soluble cationic 2‐hydroxylpropyltrimethylammonium hemicellulosic derivatives with low average degrees of substitution (DS's) were prepared by the incorporation of the cationic moiety 2,3‐epoxypropyltrimethylammonium chloride (ETA) onto the backbone of hemicelluloses in the presence of NaOH as a nucleophilic catalyst in homogeneous dimethyl sulfoxide (DMSO) media. The dependence of the homogeneous reaction on the different affecting factors was investigated. The average DS was calculated from the N/C ratio in the products and from the weight gain. The degree of substitution determined by the nitrogen content (DS_N) values up to 0.25 in a one‐step synthesis of the etherified hemicelluloses could be controlled by the adjustment of the amount of solvent used and the molar ratio of NaOH or ETA to the anhydromonomer units in the hemicelluloses. The structure of the cationic hemicellulosic derivatives formed was determined by Fourier transform infrared spectroscopy and further confirmed with solution‐state ¹³C‐NMR spectroscopy. In comparison, no significant degradation of the hemicellulosic derivatives occurred during the etherification of the polymers in the homogeneous DMSO system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Initiation of chain and thermal explosions by the reactor surface. Criterion for the participation of branching chains in a thermal explosion

The combustion of hydrogen and silane is studied. It is established that the chain initiation reaction on quartz in the zone of hydrogen and silane combustion is manifested as an autocatalytic reaction which is able to initiate a chain explosion and participate in the initiation of a thermal explosion. It is shown that in the case of an oxyhydrogen gas, the assumption of a branching-chain nature of the third limit is inconsistent with Semenov’s law, which includes double exponential dependences of the chain reaction rate on time and temperature. A criterion for the participation of branching chains in complex processes is proposed based on the presence or absence of short delays of a thermal explosion (≈1 sec). According to the criterion, the explosion of an oxyhydrogen gas at atmospheric pressure with delays markedly exceeding 1 sec proceeds without the participation of branching chains and is consistently explained by the joint action of autocatalytic processes on the reactor wall and gas-phase processes. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 44–51, September–October, 2007.     

Functionalization at the double-bond region of jojoba oil. 8. Chemical binding of jojoba liquid wax to a polymer matrixvia an amine “spacer”

Jojoba wax was chemically bonded to a polymer matrixvia stable C-N covalent bonds. The polymer matrix was prepared by amination of several types of styrene-divinyl benzene or styrene-vinylbenzylchloride-divinylbenzene copolymers with diamines or polyethylene imines (polyamines). The jojoba wax was attached to the aminated polystyrene matrix by reacting an allyl-brominated derivative of jojoba with the matrix to form a C-N bond between the matrix and the jojoba wax. The amount of bound jojoba wax added to the polymer was in the range of 20–70% (w/w), depending on the type of polymer matrix and reaction conditions. The double-bond regions in the jojoba wax bonded to the matrix were preserved, and they were subsequently functionalized by phosphonation and sulfur-chlorination reactions.     

5万t／a食品级液体CO2生产装置运行总结

介绍了5万t／a食品级液体CO2生产装置的工艺流程和主要设备;简述了催化剂的选择和应用情况;分析了装置的生产运行情况及存在的主要问题;采取了相应的技改措施。     

Development of dual stage solvent fractionation as an approach to concentrate carotenoids from crude palm oil with high recovery: The potential use of molecular simulation as a pre-screening tool

Crude palm oil (CPO) is highly abundant in carotenoids. Previous findings found that dry fractionation can concentrate carotenoids from CPO but resulted in a significant loss of carotenoids. Therefore, the present study aimed to utilize solvent fractionation, which offers a better separation efficiency, to concentrate carotenoids from CPO with improved recovery. Computational study revealed a high binding affinity of phytonutrient towards unsaturated triacylglycerols (TAGs) species in olein fraction due to similar polarity. This prediction was further verified with evidence showing strong, positive correlation between the iodine value and carotenoids concentrations of fractionated oil. The difference in binding affinity of saturated and unsaturated TAG towards different solvents can be used as a guide for screening and selection of solvent suitable for recovery of phytonutrient during solvent fractionation. Subsequently, a lab-scale single- stage fractionation study disclosed that crystallization temperature of 15°C, oil to acetone ratio of 1:5 (w/v) for 4 h under agitation at 100 rpm produced olein with the highest carotenoid concentration (637 ppm) and recovery (94%). Subsequent double-stage fractionation successfully concentrated the carotenoids up to 125% with a recovery of >93%. Conclusively, solvent fractionation provides an effective way to concentrate valuable carotenoids from CPO while minimizing the lost.     

The conversion of methane to ethylene and ethane with near total selectivity by low temperature (< 610 ° C) oxydehydrogenation over a calcium-nickel-potassium oxide catalyst

The catalytic oxidative coupling of methane to C₂, C₃ and C₄ paraffins and olefins has been accomplished with close to 100% selectivity at methane conversions of about 10% per pass. Essentially no carbon oxides are formed and the mechanism appears to be a surface catalyzed reaction. Temperatures of < 600 ° C are used and the presence of steam is important. The catalyst comprises a ternary mixture of calcium, nickel and potassium oxides. Method of preparation and composition of the catalyst are critical for its performance. Presence of a carbidic carbon on the catalyst surface may be important.     

A review on the mechanical and electrical properties of graphite and modified graphite reinforced polymer composites

Carbon materials particularly in the form of sparkling diamonds have held mankind spellbound for centuries, and in its other forms, like coal and coke continue to serve mankind as a fuel material, like carbon black, carbon fibers, carbon nanofibers and carbon nanotubes meet requirements of reinforcing filler in several applications. All these various forms of carbon are possible because of the element's unique hybridization ability. Graphene (a single two-dimensional layer of carbon atoms bonded together in the hexagonal graphite lattice), the basic building block of graphite, is at the epicenter of present-day materials research because of its high values of Young's modulus, fracture strength, thermal conductivity, specific surface area and fascinating transport phenomena leading to its use in multifarious applications like energy storage materials, liquid crystal devices, mechanical resonators and polymer composites. In this review, we focus on graphite and describe its various modifications for use as modified fillers in polymer matrices for creating polymer-carbon nanocomposites.